- Email: [email protected]
Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins
Accepted Manuscript Title: Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins Authors: Huosheng Li, Yongheng Chen, Jianyou Long, Daqian Jiang, Juan Liu, Sijie Li, Jianying Qi, Ping Zhang, Jin Wang, Jian Gong, Qihang Wu, Diyun Chen PII: DOI: Reference:
S0304-3894(17)30184-X http://dx.doi.org/doi:10.1016/j.jhazmat.2017.03.020 HAZMAT 18436
To appear in:
Journal of Hazardous Materials
Received date: Revised date: Accepted date:
16-10-2016 7-3-2017 9-3-2017
Please cite this article as: Huosheng Li, Yongheng Chen, Jianyou Long, Daqian Jiang, Juan Liu, Sijie Li, Jianying Qi, Ping Zhang, Jin Wang, Jian Gong, Qihang Wu, Diyun Chen, Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins, Journal of Hazardous Materials http://dx.doi.org/10.1016/j.jhazmat.2017.03.020 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins
Huosheng Li a, Yongheng Chen a, b,*, Jianyou Long b, Daqian Jiang e, Juan Liu a, c, Sijie Li a, Jianying Qi d, Ping Zhang b, Jin Wang c, Jian Gong b, c, Qihang Wu a, Diyun Chenc
a
Collaborative Innovation Center of Water Quality Safety and Protection in Pearl River
Delta, Guangzhou University, Guangzhou 510006, PR China b
Guangzhou University Key Laboratory of Water Safety and Protection in Pearl River
Delta, Ministry of Education, Guangzhou 510006, PR China c
School of Environmental Science and Engineering, Guangzhou University,
Guangzhou 510006, PR China d
South China Institute of Environmental Science, Ministry of Environmental Protection,
Guangzhou, PR China e School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, United States *
Corresponding author: Yongheng Chen, Collaborative Innovation Center
of Water Quality Safety and Protection in Pearl River Delta, Guangzhou University, Guangzhou 510006, PR China Phone: +86 020 393 66505 Email: [email protected] (Y. Chen)
1
Highlights
Simultaneous removal of Tl and Cl- by modified anion exchange resins was effective. Tl removal was based on the exchange of chlorocomplex formed under saline conditions. The operation had a broad flow rate and pH range. Elution and regeneration of the resins suggest good potential for practice application.
Abstract Simultaneous removal of thallium (Tl) and chloride from a highly saline industrial wastewater was investigated using modified anion ion exchange resins. The removal of thallium was mainly driven by the exchange of Tl-chlorocomplex (TlCl4 -) formed in the oxidation of thallous (Tl (I)) to thallic ion (Tl (III)) by hydrogen peroxide (H2O2) under saline conditions. Over 97% of thallium and chloride removal was achieved using the modified resins, with a wide optimal conditions found to be H2O2 dosage 1.0-25.0 mL/L, pH 1.6-4.3, and flow rate 0.5-4.7 mL/L. The modified resins had an exchange capacity of 4.771 mg Tl/g dry resins for thallium and 1800 mg Cl/g dry resins for chloride. Stable regeneration could be achieved with the modified resins: over 97% of thallium and 90% of chloride can be eluted using Na2SO3 solution and alternating hot (60℃) H2SO4 and cold (25℃) water, and over 98% removal of thallium and chloride was achieved after five consecutive regeneration cycles. 2
Keywords: Heavy metal; thallium; chloride; resins; industrial wastewater
1. Introduction Thallium (Tl), classified as one of the 13 USEPA priority metals, is an extremely toxic heavy metal [1-3]. It is reported to be highly bioaccumulative [4] and more toxic to living organisms than mercury and cadmium [5]. As a unique catalyst, Tl is gaining increasing application in the production of high-tech products including certain alloys, optical lenses, semiconductors, high temperature superconductor and low temperature thermometers [5, 6]. Significant anthropogenic discharge of Tl is often found in coal combustion, cement production, mining, metal refining and smelting industry [7]. Tl has two dominating oxidation states, namely mono (Tl(I)) and tri-valence (Tl(III)), in the aquatic environment [7, 8]. Tl (I) is quite stable and mobile in the aquatic media, while Tl(III) is highly reactive and can be readily reduced by common reducing agents or easily hydrolyzed in alkaline or neutral solutions [9]. It should be noted that Tl(III) can be stabilized by complexation with chloride[10, 11] and certain organics such as diethylenetriaminepentaacetic acid (DTPA) [9] and ethylenediaminetetraacetic acid (EDTA) [12], forming anion ions and being dissolved in the aqueous solution.
Due to the high toxicity of both states of Tl, pollution control for Tl is of significant importance during industrial activities. Adsorption of Tl using various chemical and biological materials, including MnO2 [13], polyacrylamide [14], TiO2 [15], ferrihydrite 3
[16], carbon nanotubes [17], sawdust [6] and microalga [18], has been shown effective in the removal of Tl. Oxidation combined with precipitation using lime or caustic have also been proven successful for Tl removal [19, 20]. Ion exchange can be an effective method for removal of Tl and other metals including uranium, chromium and platinum [20]. Solvent extraction of Tl(III) using certain organic extractant in HCl media is a good means for enrichment and recovery of Tl [10].
Despite previous success, Tl removal from hydrometallurgical wastewater such as the zinc refinery wastewater, still remains a challenge. In zinc refining wastewater, besides the high concentration of heavy metals, chloride is usually present with high concentration, often over 10000 mg/L [21]. Chloride could form chlorocomplex (tetrachlorothallate (III) anion, TlCl4 -) with Tl(III) during the wastewater treatment process [10], significantly impairing the adsorption and precipitability of Tl(III). High concentrations of chloride may also cause a host of other wastewater treatment problems, such as pipe corrosion [22] and false chemical oxygen demand (COD) measurements. Methods for simultaneous Tl and chloride removal still need to be developed, as most aforementioned adsorption methods are ineffective in chloride removal.
In this work, ion exchange coupled with an oxidation process was studied for simultaneous removal of Tl and chloride. Ion exchange resins, Dowex A-1 and Chelex4
100, have been used for removal of Tl(III) under acidic condition, but its application on Tl removal has not been extensively investigated [20]. This study proposed that via coupling modifying the ion exchange resins and coupling the ion exchange process with oxidation of Tl(I), simultaneous removal of Tl and chloride could be achieved (Reaction 1-5): R2SO4+2Cl-→2RCl+SO42-
(1)
Tl++2Cl-→TlCl2 -
(2)
Tl3++4Cl-→TlCl4-
(3)
R2SO4+2TlCl2-→2R(TlCl2)+SO42-
(4)
R2SO4+2TlCl4-→2R(TlCl4)+SO42-
(5)
Different operating conditions, including pH, dosage of oxidant (H2O2), and flow rate, were studied to identify the optimal conditions. The elution and regeneration capability of the ion exchange resins was also tested.
2. Materials and methods 2.1 Wastewater, reagents and solutions The industrial wastewater was obtained from a zinc industry company located in Jiangxi Province, China. Its composition is listed in Table 1. It is shown that this acidic wastewater (pH 5.8±0.20) contains a variety of heavy metals and high concentrations of chloride, thallium, sodium, potassium, zinc, and cadmium. The Tl in the wastewater was mostly in the form of Tl(I) (Supplementary Information, Figure S1 and Table S1). 5
Although it was free of organic compounds and suspended matters, the high strength at this magnitude poses a great difficulty in the wastewater treatment. During the experiments, the industrial wastewater was stored at ambient temperatures (25-29℃) and used directly without any pretreatment.
All the chemicals and reagents used were of analytical grade, and directly used without further purification (except the resins). The raw resins (212×7 (717), Yonghua, Jiangsu, China) used were gel-type spherical beads that were composed of polystyrene divinylbenzene as matrix structure and quaternary amine as functional groups (Figure. S2). Deionized water was used to prepare the acid and base solutions. In some cases, tap water was used to wash the resins and to prepare the sulfuric acid and sodium hydroxide solutions for pretreatment of the resins, depending on the goal of the experiments.
2.2 Pretreatment and modification of resins The resins were pretreated and modified as follows. They were sequentially washed with deionized (or tap water) water, 1.0M NaOH solution, deionized (or tap water) water, 0.75M H2SO4 solution, deionized (or tap water) water each for 30 min. The volume of the water or solutions used was 8 mL water/ g wet resins. The purpose of this modification was to transform the interlayer anion to sulfate. The resulted wet resins were kept in a closed vessel in the dark before use, and could be stable at least 6
for one month. To measure the dry weight of resins, the wet resins were dried in an oven at 60℃ overnight and weighed using a digital electronic balance (Sartorius BSA224S, Germany).
2.3 Procedures for exchange of thallium and chloride Glass columns (24mm in diameter and 250mm in height, Figure. S3) equipped with a valve of polytetrafluoroethylene (PTFE) were used for all ion exchange experiments. Before weighing of the resins, the water of wet resins in the vessel was drained with a pipette. For packing the columns, the pre-weighed wet resins (8 g) were washed into the columns with deionized water that was then drained through. Prior to ion exchange experiment, hydrogen peroxide (H2O2) solution (30%, w/w) was used for oxidation of thallium in the industrial wastewater. Spiking samples with designated amounts of oxidized wastewater were added to the columns and then passed through at various flow rate controlled by adjusting the opening of the PTFE valve. Interference of bubbles was avoided by expelling them with a fine tube (3.2 mm in diameter). The treated samples were filtered with syringe filters (0.45µm) and acidified before measurements of water quality. Each test was conducted at least in triplicate. The experiments were performed at room temperature (25-29℃).
Impact of different operating conditions were studied, including pH (1.6, 2.4, 3.3, 4.3, 5.9, 6.7, 7.6, 8.5 and 10.0) of resins, flow rate (0.5, 0.8, 1.2, 4.7, 8.0, 11, 16 mL/min) 7
and oxidant dosage (0, 1.0, 2.5, 5.0, 10, 25, 50, 100 mL/L), on the retention of thallium and chloride were determined. During these experiments, the resins and wastewater used were 8 g and 16 mL, respectively. The adsorption capacity of the resins was tested using a progressively increasing volume (2.1, 4.2, 8.3, 16.7, 33.3, 66.7, 133.3, 266.7, 533.3, 1066.7 and 2133.3 mL wastewater/g resins) of wastewater.
The ability of elution and regeneration of the resins was also tested. A series of sodium sulfite (Na2SO3) solutions 0.125, 0.25, 0.500 M) and HNO3 (1, 2, 4 M) were used as eluents for Tl(III), while a series of H2SO4 solutions (1, 2, 4 M) and water were used as eluents for chloride. Regeneration of resins was performed with 1.0M NaOH and then 1.0M H2SO4 and finally deionized water each for 30min. For analysis of X-ray photoelectron spectroscopy (XPS), the resins that had performed ion exchange were collected in beakers, and then air dried in a super-clean cupboard (Biocap 391, Erlab, France).
The capacities for retention of Tl and chloride are calculated as follows (Equation 6). 𝑞𝑒 =
(𝐶0 −𝐶)𝑉
(6)
𝑚
Where C0 and C are the initial and final Tl (or Chloride) concentrations of the studied solutions (mg/L), respectively, m is the mass (mg) of dry resins, and V is the solution volume (L).
8
2.4 Analytical methods An atomic absorption spectrometer (Thermo Scientific, USA) furnished with corresponding metal (except Tl) hollow-cathode lamps and air-acetylene flame was used for measurements of metals and sulfate. Inductively coupled plasma-mass spectrometry (NexION 300, PerkinElmer Inc., USA) was applied for all measurements of Tl. A chloride meter (Bante 931, Jiangsu, China) equipped with chloride ion selective electrode was used to determine the concentration of chloride. An X-ray photoelectron spectroscopy instrument with monochromatic Al Kα radiation (hv=1486.6 eV, Kratos Axis Ultra, Japan) was used to identify the element and compounds of the resins. In order to obtain sufficient signal of XPS spectra, high concentration of synthetic Tl wastewater was also used for the XPS analysis. Correction of the deviation of the binding energy (BE) owing to the relative surface charging was performed with the C 1s level at BE of 284.6 eV as an internal standard [23]. The fitting of all XPS spectra was conducted using the software XPSPEAK4.1.
3. Results and discussion 3.1 Tl and chloride retention under different operating conditions 3.1.1 Effect of H2O2 dosage It is shown that the addition of H2O2 substantially improved the removal of Tl. Without addition of H2O2, the effluent Tl concentration was over 3000 µg/L, approximately 47% of the Tl input; with the addition of H2O2, the effluent Tl concentration was lower than 9
100 µg/L at dosage over 25 mL/L (Figure. 1). Further increase in H2O2 dosage did not lead to complete removal of Tl, suggesting that a portion of Tl was not present in chlorocomplex (TlCl4-) or remained only in Tl(I) (Table S1). In practice, the dosage of H2O2 should not be higher than 5 mL/L when taking the cost into account. These results confirm that hydrogen peroxide, is capable of oxidizing Tl (I) to Tl (III) in acidic aqueous solutions [24, 25], which will help form the Tl(III)-chlorocomplex under highly saline conditions. The use of H2O2 can be broadly applicable, as most of the dissolved Tl in wastewater is Tl(I) [26].
The retention of chloride was efficient at over 85%, without the addition of H2O2, suggesting that the exchangeable group sulfate on the resins was able to effectively replace with the chloride (Equation 1) in wastewater even without presence of H 2O2. The spike of sulfate (over 30000mg/L) in the effluent indeed indicates the occurrence of the ion exchange of sulfate with chloride (Table S2).
3.1.2 Effect of pH of resins The pH of solution (or resins) is an important factor for capture of metals via ion exchange method [12, 27]. It is demonstrated that Tl removal was effective at pH range of 1.6 to 10.0, with optimum removal at acidic range of 1.6-4.3 (Figure. 2). The effluent pH of all treated wastewater increased with the increase in the pH of resins, but was still acidic (1.8-6.5). Under acidic conditions, the heavy metals in the industrial 10
wastewater remained in dissolved form and did not cause clogging problems. It is noted that the Tl retention efficacy at higher pH range from 5.9 to 10.0 was less effective than that at the acidic condition. The partition coefficient (kd) of the resins for Tl was found to decrease with the increasing pH value (Table S3). This may be attributed to the fact that the Tl-chlorocomplex (TlCl4-) is more stable under acidic conditions [28]. Lin and Nriagu [27] reported that the Chelex-100 (Aldrich) resins had a high affinity (over 103.1) for Tl(III) under pH of 1, probably due to the formation of strong complexes of TlCl4 -. These resins are much more expensive and its application is primarily in the biomolecular field.
The removal pattern of chloride is slightly different from that of Tl (Fig 2). The best removal efficiency was achieved in the neutral and basic range, but reasonably good removal was still achieved under acidic conditions. This study reveals the stability and flexibility of this type of resins for removal of Tl and chloride. Given the operational simplicity, the pH of resins should be controlled in the acidic range, preferably below 2.0, which can be readily achieved in the pretreatment and modification methodology.
3.1.3 Effect of flow rate The flow rate (contact time) is also important for retention of analyte during ion exchange [12]. It is found that removal of Tl at the studied flow rate range of 0.5-16 mL/min was nearly consistent, though the best was found at 0.8-8.0 mL/min (Figure. 11
3). For chloride removal, the high flow rate (over 4.7 mL/min) significantly lowered the Cl removal (Fig 3). The shorter contact time led to an impaired efficiency of both Tl and chloride at higher flow rate. This phenomenon impact of shorter contact time was more evident for chloride, indicating that high loading chloride requires a long contact time for complete ion exchange. Although the ion exchange between sulfate and chloride is reversible, it was unidirectional and quite stable at the studied conditions. These results suggest that the flow rate should be kept between 0.8 and 8 mL/min for optimal retention of Tl and Cl. 3.1.4 Comparison between preparation with deionized water and tap water Both Tl and chloride removal were similar for resins pretreated with deionized water or tap water (Table 2). This suggests that the resins used are a good candidate for the simultaneous removal of Tl and chloride from saline wastewater. In practical applications, the resins can be pretreated and modified with tap water instead of deionized water, to reduce the cost and simplify the operation.
3.2 Capacity for Tl and chloride removal The capacity of the modified resins for retention of Tl and chloride was evaluated with a series of different volume of wastewater treated by a given amount of resins. It is evident that the capacity of the Tl retention increased with the increase in the volume of wastewater (Figure.4b), whereas the effluent quality became less efficient with more wastewater being treated (Figure.4a). This phenomenon is commonly seen in ion 12
exchange and adsorption experiments. The capacity of Tl retention in this study (maximum 4771µg/g) was similar to other study in which nano-TiO2 (maximum 4900µg/g) [15] was used for adsorption of Tl(III). Similarly, the capture of chloride onto the resins became obviously less effective (Figure.4a), whereas the calculated capacity became dramatically stronger. Lv et al. [22] reported a maximum capacity of 169.3 mg/g for chloride adsorption with a resin called ZnAl-NO3 layered double hydroxides. By contrast, the modified resins in this study had a much stronger capacity (maximum 1800 mg/g) for chloride removal at a dosage of 2133.3 mL/g. In fact, in terms of the effluent chloride concentration, it spiked significantly at the ratio of wastewater to resin greater than 4 mL/g. Therefore, the treated amount of wastewater should not be higher than 4 mL/g. The much lower concentration of Tl than chloride led to this substantial discrepancy (several orders of magnitude) in the capacity.
3.3 Elution and regeneration of resins The elution ability for Tl and chloride was tested using different solutions. It is found that the use of H2SO4 or HNO3 alone, even at concentration as high as 4 M, was not able to release the Tl from the resins (Table 3). Acid solution such as HNO3 is usually used as eluent for desorption of Tl [9, 27] from resins. The fact that high concentrations of H2SO4 or HNO3 alone did not release the Tl from the resins indicate the high affinity of the bonding between the resins and the Tl(III)-chlorocomplex anion.
13
The use of Na2SO3 was effective (~98% elution efficiency) in elution of Tl, since the Tl(III) (likely TlCl4-) was reduced to Tl(I) and consequently dissociated from the resins to the solution. This is consistent with other study that H2SO3 solution was used as an effective reducing agent for thallium speciation analysis [3]. The combination of Na2SO3 and HNO3 solution resulted in marginal improvements on the elution. The use of 0.125M Na2SO3 solution was sufficient for elution of Tl, as a higher concentration of Na2SO3 did not lead to any enhancement of elution.
For chloride elution, the increase in concentration of acids brought about improvement on elution to some extent, however, operation with eluent at room temperature was not as effective as expected. Alternating hot (60 ℃) and cold (25 ℃) regime achieved improved elution of both Tl (99.5±2.16%) and chloride (98.4±2.41%). This may be related to the repeated expansion and contraction at alternating hot and cold conditions, which play a vital role in the dissociation of the bonding between the chloride and resins and thus desorption of chloride. Few literatures reported the combined elution of both chloride and thallium on the exhausted resins. The findings of this study point to a valuable means for removal of thallium from saline wastewater. After elution, the resins were regenerated by successively soaking in 1.0M NaOH solution, 1.0M H2SO4 and deionized water with the volume of 2 mL/g and for 30min. Results of five consecutive regenerations showed that steadily efficient removal and recovery of Tl and chloride were achieved, with the removal of Tl at over 98% and 14
chloride at over 90%, and the recovery of Tl at over 97% and chloride at over 98% (Figure 5). This indicates the excellent regeneration ability of these resins, which can be promising in the engineered applications.
3.4 Removal of other metals It is shown that after oxidation with H2O2, the composition of the wastewater remained nearly unchanged prior to ions exchange with the modified resins (Table 1 and Table 4). When the non-oxidized wastewater was treated by resins, not only Tl but also many other metals including Cd, Ca, Pd and Zn from the wastewater were partially removed (Table 4), probably due to complexation of these metals with chloride. It is interesting that for oxidized wastewater being treated by the resins, Tl removal was greatly improved while many other metals removal was not enhanced by oxidation (Table 4). This points to the formation of the Tl(III)-Cl anion complexes that were more stable and dominant than the Tl(I)-Cl anion ones under saline conditions [29]. The ion exchange by the modified anion resins can be applied to other stable metal-Cl complexes anions. In this study, the major focus was on the simultaneous removal of chloride and Tl from wastewater. By using an adequate dosage of resins, the chloride content can be substantially reduced and the Tl concentration can be lowered to a low level. The other metals (such as Zn) remained should be further treated, since a single treatment is usually inadequate for a high-strength type of wastewater.
15
3.5 Analysis of XPS spectra The resins used for adsorption of the industrial wastewater were analyzed by XPS spectra in order to gain more insight into the intrinsic reaction during the ion exchange process. In this test, 0.5g resins were used for treatment of 32 mL industrial wastewater. In the XPS spectra, the peaks of S 2p (BE of 161.0 and 166.0eV) appeared in all modified resins, indicating that sulfate was successful bonded during the modification, and that sulfate was in excess and remained on the resins although they were exchanged with chloride at this loading (Figure 6a). The peaks of Cl 2p (BE of 196.6 and 196.7, Figure 7) imply the existence of the compound poly(vinylbenzyltrimethylammonium chloride) [30, 31], which is an important group of the product after replacement of sulfate with chloride by the functional groups (poly(vinylbenzyltrimethylammonium sulfate)) from the modified resins. Other peaks of Cl 2p (197.7, 197.8, 198.8 and 199.4eV, Figure 7) were attributed to chloride-related compounds [31]. Due to the low proportion of Tl (0.08% for non-oxidation and 0.15% for oxidation, calculated based on the element peaks of O 1s, N 1s, C 1s, Cl 2p, s 2p and Tl 4f) on the resins, the Tl 4f spectra were very vague. To obtain sufficient XPS signal of Tl, a high load of synthetic Tl solution (0.5g resins for 100mL synthetic Tl(I) and Tl(III) of each 400mg Tl and each 1mol/L HCl) was also used to investigate the Tl speciation during the oxidation and ion exchange process. The high Tl load adsorption tests did show clear peaks of Tl 4f (Figure S4). For Tl(III), the Tl 4f 7/2 peak can be split to two sub-peaks (BE of 118.1and 117.6 eV), whereas it can be fitted into two distinctively different sub-peaks 16
for Tl(I) (BE of 117.7and 116.1 eV) (Figure 8). So far, no XPS spectra of TlCl4 - or related Tl-chlorocomplex are available. The spectra of pure chemicals of TlNO3 and Tl(NO3)3 were similar, and are ineffective in explaining the conversion of Tlchlorocomplex. The Tl(III)-chlorocomplex (BE of 118.1eV) might be half reduced to Tl(I) (BE of 117.6 eV) in air and this might explain the two sub-peaks with nearly equal area. The T(I) (BE of 117.7 eV) might be relatively stable, only marginally converted to an unknown Tl species. For resins without oxidation, Tl was also detected in these samples. This suggests that the resins used in this study was able to adsorb Tl(I), which is consistent with the results of the ICP-MS measurements.
4. Conclusions The modified anion ion exchange resin containing sulfate was effective in simultaneous removal of Tl and chloride from highly saline wastewater. The addition of hydrogen peroxide to form Tl(III)-chlorocomplex (TlCl4 -) as the anion was the key to obtaining high efficiency of Tl removal. The resins had a broad operating flow rate and should be operated at acidic condition (pH 1.6-4.3). To obtain good effluent quality, the ratio of the wastewater to resin should be controlled at less than 4 mL/g. The Tl adsorbed onto the resins can be eluted by 0.125 M Na2SO3 solution, while the chloride captured can be desorbed by alternating hot (60℃) 2M H2SO4 solution and cold (25℃) water. After five regeneration cycles, the resins still obtained significant removal of Tl and chloride from high strength wastewater. 17
Acknowledgements The research was supported by the Foundation for Fostering the Scientific and Technical Innovation of Guangzhou University, the Department of education of Guangdong Province (2015KQNCX115), the Guangzhou Education Bureau (1201630390), the Public welfare scientific fund of Environmental Protection Department (No.201509051), the Science and Technology Program of Guangzhou (201607010217), the Educational System Innovation Team Project of Guangzhou Education Bureau (13C02, 13xt02), the National Natural Science Foundation of China (41373118, 41573119, 41273100) and the high level university construction project (Regional water environment safety and water ecological protection). The authors thank the anonymous reviewers for improving the quality of our research.
18
References
[1] A. Voegelin, N. Pfenninger, J. Petrikis, J. Majzlan, M. Plotze, A.-C. Senn, S. Mangold, R. Steininger, J. Gottlicher, Thallium speciation and extractability in a thallium- and arsenic-rich soil developed from mineralized carbonate rock, Environmental science & technology, 49 (2015) 5390-5398. [2] L. Keith, W. Telliard, ES&T special report: priority pollutants: Ia perspective view, Environmental Science & Technology, 13 (1979) 416-423. [3] B.S. Twining, M.R. Twiss, N.S. Fisher, Oxidation of thallium by freshwater plankton communities, Environmental Science & Technology, 37 (2003) 27202726. [4] T.-S. Lin, J. Nriagu, X.-Q. Wang, Thallium concentration in lake trout from Lake Michigan, Bulletin of environmental contamination and toxicology, 67 (2001) 921-925. [5] V. Zitko, Toxicity and pollution potential of thallium, Science of the total environment, 4 (1975) 185-192. [6] S.Q. Memon, N. Memon, A.R. Solangi, J.-u.-R. Memon, Sawdust: A green and economical sorbent for thallium removal, Chemical Engineering Journal, 140 (2008) 235-240. [7] J.O. Nriagu, Thallium in the environment, John Wiley & Sons, New York, NY, ETATS-UNIS, 1998. [8] U. Karlsson, S. Karlsson, A. Duker, The effect of light and iron(II)/iron(III) on the distribution of Tl(I)/Tl(III) in fresh water systems, Journal of Environmental Monitoring, 8 (2006) 634-640. [9] P. Coetzee, J. Fischer, M. Hu, Simultaneous separation and determination of Tl (I) and Tl (III) by IC-ICP-OES and IC-ICP-MS, Water Sa, 29 (2004) 17-22. [10] N. Rajesh, M.S. Subramanian, A study of the extraction behavior of thallium with tribenzylamine as the extractant, Journal of Hazardous Materials, 135 (2006) 7477. [11] T.M. TRTIĆ, J.J. ČOMOR, Extraction of thallium with butyl acetate, Separation science and technology, 34 (1999) 771-779. [12] S. Dadfarnia, T. Assadollahi, A.M. Haji Shabani, Speciation and determination of thallium by on-line microcolumn separation/preconcentration by flow injection– flame atomic absorption spectrometry using immobilized oxine as sorbent, Journal of Hazardous Materials, 148 (2007) 446-452. [13] X. Huangfu, J. Jiang, X. Lu, Y. Wang, Y. Liu, S.-Y. Pang, H. Cheng, X. Zhang, J. Ma, Adsorption and Oxidation of Thallium(I) by a Nanosized Manganese Dioxide, 19
Water Air And Soil Pollution, 226 (2015). [14] Z.M. Senol, U. Ulusoy, Thallium adsorption onto polyacryamide-aluminosilicate composites: A Tl isotope tracer study, Chemical Engineering Journal, 162 (2010) 97-105. [15] L. Zhang, T. Huang, N. Liu, X. Liu, H. Li, Sorption of thallium (III) ions from aqueous solutions using titanium dioxide nanoparticles, Microchimica Acta, 165 (2009) 73-78. [16] K.M. Coup, P.J. Swedlund, Demystifying the interfacial aquatic geochemistry of thallium (I): New and old data reveal just a regular cation, Chemical Geology, 398 (2015) 97-103. [17] Y. Pu, X. Yang, H. Zheng, D. Wang, Y. Su, J. He, Adsorption and desorption of thallium (I) on multiwalled carbon nanotubes, Chemical Engineering Journal, 219 (2013) 403-410. [18] Z. Birungi, E. Chirwa, The adsorption potential and recovery of thallium using green micro-algae from eutrophic water sources, Journal of hazardous materials, 299 (2015) 67-77. [19] L. Rosengrant, R. Craig, Final Best Demonstrated Available Technology (BDAT) background document for P and U Thallium wastes, US EPA. Office of Solid waste, Washington, DC. EPA/530-sw-90-059R, National Technical Information Services PB90-234188l, (1990). [20] L.G. Twidwell, C. Williams-Beam, Potential technologies for removing thallium from mine and process wastewater: an annotation of the literature, European Journal of Mineral Processing and Environmental Protection, 2 (2002) 1-10. [21] Q. Wang, W. Qin, L. Chai, Q. Li, Understanding the formation of colloidal mercury in acidic wastewater with high concentration of chloride ions by electrocapillary curves, Environmental Science and Pollution Research, 21 (2014) 3866-3872. [22] L. Lv, P. Sun, Z. Gu, H. Du, X. Pang, X. Tao, R. Xu, L. Xu, Removal of chloride ion from aqueous solution by ZnAl-NO3 layered double hydroxides as anionexchanger, Journal of Hazardous Materials, 161 (2009) 1444-1449. [23] X.J. Li, D.L. Tang, F. Tang, Y.Y. Zhu, C.F. He, M.H. Liu, C.X. Lin, Y.F. Liu, Preparation, characterization and photocatalytic activity of visible-light-driven plasmonic Ag/AgBr/ZnFe2O4 nanocomposites, Materials Research Bulletin, 56 (2014) 125-133. [24] G. Kirkbright, P. Mayne, T. West, Photo-oxidation of thallium (I) with the production of hydrogen peroxide, Journal of the Chemical Society, Dalton Transactions, (1972) 1918-1920. [25] D. Li, Z. Gao, Y. Zhu, Y. Yu, H. Wang, Photochemical reaction of Tl in aqueous solution and its environmental significance, Geochemical Journal, 39 (2005) 113119. [26] B. Vink, The behaviour of thallium in the (sub) surface environment in terms of Eh and pH, Chemical geology, 109 (1993) 119-123. 20
[27] T.S. Lin, J.O. Nriagu, Thallium speciation in river waters with Chelex-100 resin, Analytica Chimica Acta, 395 (1999) 301-307. [28] Z. Marczenko, Spectrophotometric determination of elements, E. Horwood; Wiley, 1975. [29] S. Aldridge, A.J. Downs, The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities, John Wiley & Sons, 2011. [30] G. Beamson, D. Briggs, High resolution XPS of organic polymers, Wiley, 1992. [31] A.V. Naumkin, A. Kraut-Vass, S.W. Gaarenstroom, C.J. Powell, NIST X-ray Photoelectron Spectroscopy Database (Online version 4.1), 2016.
21
Figure Captions Figure 1 Effect of dosage of H2O2 on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n=4)
Figure 2 Effect of pH of resins on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 0.8 mL/min, H2O2 dosage of 5 mL/L, n=3)
Figure 3 Effect of flow rate on removal of Tl and chloride (8 g resins, 16 mL wastewater, pH of resins 1.6, H2O2 dosage of 5 mL/L, n=3)
Figure 4 Capacity of resins for removal of Tl and chloride: (a) effluent concentrations of Tl and chloride; (b) capacity of dry resins (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3)
Figure 5 Regeneration and elution of resins for removal of Tl and chloride: (a) Regeneration and (b) Elution (pH of resins 1.6, H 2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3; Ini. A means initial adsorption with resins, Ini. E means initial elution of resins; R means regeneration of resins, E means elution of resins).
Figure 6 XPS spectra of the raw resins, modified resins, modified resins for nonoxidized industrial wastewater and oxidized wastewater, pure TlNO 3 and Tl(NO3)3, 22
respectively.
Figure 7 XPS spectra of region of Cl 2p3/2 for resins treated with (a) oxidized industrial wastewater and (b) non-oxidized industrial wastewater.
Figure 8 XPS spectra of Tl 4f7/2 core level of resins treated with high Tl loading synthetic wastewater (a) Tl(III) and (b) Tl(I).
7000
1600
Tl concentration -
Cl concentration
1400
5000
1200
4000
1000
3208.2 800
2000
600
1000
400
-
3000
Cl (mg/L)
Tl concentration (g/L)
6000
142.5 174.9 57.6 115.9 89.4
0 0
1
2.5
5
10
25
73.2
69.0
50
100
200
Dosage of H2O2 (mL/L)
Figure 1 Effect of dosage of H2O2 on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n=4)
23
4000
Tl concentration Cl concentration 1200 2000
0 600 -2000 300
0
-
900
Effluent Cl (mg/L)
Effluent Tl concentration (g/L)
1500
-4000 1.6
2.4
3.3
4.3
5.9
6.7
7.6
8.5
10
The pH of resin
Figure 2 Effect of pH of resins on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 0.8 mL/min, H2O2 dosage of 5 mL/L, n=3)
24
500 2500
-
Cl concentration 400
2000 1500
-
300
Effluent Cl (mg/L)
Effluent Tl concentration (g/L)
Tl concentration
1000 200 500 100 0 0
-500 0.5
0.8
1.2
4.7
8
11
16
Flow rate (mL/min)
Figure 3 Effect of flow rate on removal of Tl and chloride (8 g resins, 16 mL wastewater, pH of resins 1.6, H2O2 dosage of 5 mL/L, n=3)
25
50000
Tl concentration Cl concentration
5000 40000
Effluent Cl (mg/L)
4000 30000 3000
-
Effluent Tl concentration (g/L)
(a) 6000
20000 2000 10000 1000 0 0 2.1
4.2
8.3 16.7 33.3 66.7 133.3 266.7 533.3 066.7 133.3 1 2
Dosage (mL wastewater/g resins)
(b) 7000
Tl capacity Cl capacity
6000
2100
1500
4000
1200
3000
900
2000
600
1000
300
0
-
Tl capacity (g/g)
5000
Cl capacity (mg/g)
1800
0 2.1
4.2
8.3 16.7 33.3 66.7 133.3 266.7 533.3 066.7 133.3 1 2
Dosage (mL wastewater/g resins)
Figure 4 Capacity of resins for removal of Tl and chloride: (a) effluent concentrations of Tl and chloride; (b) capacity of dry resins (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3) 26
110
110
100
100
90
90
Tl removal Cl removal
80
-
80
Cl removal (%)
Tl removal (%)
(a)
70
60
70 Ini. A
1st R
2nd R
3rd R
4th R
5th R
60
100
100
90
90
Tl recovery Cl recovery
80
-
80
Cl recovery (%)
Tl recovery (%)
(b)
70
70
60
60 Ini.E
1st E
2nd E
3rd E
4th E
5th E
Number of Elution
Figure 5 Regeneration and elution of resins for removal of Tl and chloride: (a) Regeneration and (b) Elution (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3; Ini. A means initial adsorption with resins, Ini. E means initial elution of resins; R means regeneration of resins, E means elution of resins).
27
O 1s
Tl 4f
Tl(NO3)3 C 1s Tl 5d
Tl(NO3)3
Intensity (Offset)
TlNO3 Oxidation No oxidation Modified resins Raw resins
TlNO3
O 1s
Tl 4f C 1s Tl 5d
Cl 2p S 2p
No oxidation
O 1s
Modified resins
O 1s
Raw resins
O 1s
1200
C 1s
O 1s
Oxidation
1000
C 1s Cl 2p S 2p
800
600
C 1s
C 1s
400
S 2p
Cl 2p
200
0
BE (eV)
Figure 6 XPS spectra of the raw resins, modified resins, modified resins for nonoxidized industrial wastewater and oxidized wastewater, pure TlNO3 and Tl(NO3)3, respectively.
28
3000
(a)
Intensity
2500
Raw Fitte d Ba c k g r o u d 1 9 7 .7 Pe a k 1 Pe a k 2 Pe a k 3 1 9 8 .8
Oxidation
1 9 6 .6
2000
1500
1000 2400
(b) 2200
Intensity
2000 1800
Raw 1 9 7 .8 Fitte d Ba c k g r o u d Pe a k 1 Pe a k 2 Pe a k 3 1 9 9 .4
No oxidation 1 9 6 .7
1600 1400 1200 1000 800 204
202
200
198
196
194
192
190
BE (eV)
Figure 7 XPS spectra of region of Cl 2p3/2 for resins treated with (a) oxidized industrial wastewater and (b) non-oxidized industrial wastewater.
29
(a)
5000
Intensity
4000
Raw Fitted Backgroud Peak1 Peak2
High Tl(III) loading
118.1
3000
117.6
2000
1000
0 Raw Fitted Backgroud Peak1 Peak2
(b)
High Tl(I) loading
117.7
4000
2000 116.1
0 121
120
119
118
117
116
115
114
BE (eV)
Figure 8 XPS spectra of Tl 4f7/2 core level of resins treated with high Tl loading synthetic wastewater (a) Tl(III) and (b) Tl(I).
30
Table 1 Compositions of the industrial wastewater (n a =3, unit: mg/L)
a
Ions
Range
Mean±SD b
Ions
Range
Mean±SD b
Na
1650-1708
1686±32
Cu
0.20-0.28
0.24±0.042
Mg
19-23
22±2.5
Cd
420-440
430±10
Mn
28-35
32±3.6
Ca
678-685
682±3.3
K
8250-8467
8367±109
Al
1.3-1.7
1.5±0.17
Fe
4.3-6.2
5.2±0.93
Tl
5.8-6.6
6.30±0.43
Ni
0.20-0.27
0.24±0.034
Zn
7100-7416
7267±159
Pd
8.2-8.4
8.3±0.11
Cl-
42600-53250
47333±5422
: n is the number of measurements.
b
: SD stands for the standard deviation.
31
Table 2 Comparison (deionized water (DIW) versus tap water (TW)) of performance of Tl and chloride removal (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n a =5) Cl- (mg/L)
Tl (µg/L) Items
a
DIW
TW
DIW
TW
Range
23.7-210.0
26.7-161.8
848-1459
870-1377
Mean
107.3
102.8
1005
1170
SD b
93.4
57.0
232
237
: n is the number of measurements.
b
: SD stands for the standard deviation.
32
Table 3 Recovery of Tl and chloride in the elution solution (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n a =3, Mean±SD b) Methods
Tl (%)
Cl- (%)
16mL 1M H2SO4
0.39±0.18
25.3±0.06
16mL 2M H2SO4
0.25±0.13
35.2±0.25
16mL 4M H2SO4
0.15±0.03
33.4±0.24
16mL 1M HNO3
0.18±0.04
32.0±0.98
16mL 2M HNO3
0.30±0.11
55.0±2.17
16mL 4M HNO3
0.14±0.03
63.9±0.22
16mL 0.1M Na2SO3
97.0±0.98
5.2±0.02
16mL 0.25M Na2SO3
92.3±4.94
7.1±0.06
16mL 0.5M Na2SO3
88.2±5.11
12.7±0.02
8mL 0.125M Na2SO3 +8mL 1M HNO3
96.7±3.86
12.9±0.09
8mL 0.250M Na2SO3 +8mL 2M HNO3
95.7±0.59
31.0±0.76
8mL 0.500M Na2SO3 +8mL 4M HNO3
92.7±4.06
43.8±2.17
8mL 0.125M Na2SO3 + 8mL 2M H2SO4 c
88.8±0.60
71.5±0.68
99.5±2.16
98.4±2.41
8mL 0.125M Na2SO3 + 8mL 2M H2SO4 c + 4mL water +4mL 2M H2SO4 a
c
: n is the number of measurements.
b
: SD stands for the standard deviation.
c
: Elution was conducted with H2SO4 solution of 60℃. 33
Table 4 Compositions of the industrial wastewater after treatment (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3, unit: mg/L) Resins-Treated
Non-
Resins-Treated
Oxidized
Oxidized Raw Wastewater Metals
oxidized Wastewater
Wastewater
Range
Mean ± SD
Range
Mean ± SD
Range
Mean ± SD
Na
1698~1708
1702±5.5
1556~1612
1583±28
1590~1601
1594±6.2
Mg
23~24
24±0.34
25~28
26±1.8
20~22
21±0.72
Mn
34~35
34±0.44
32~33
32±0.46
30~31
30±0.46
K
8350~8467
8400±60
7856~7923
7882±36
7700~7757
7724±30
Fe
4.3~6.2
5.2±0.92
6.0~7.3
6.6±0.69
6.8~6.9
6.8±0.091
Ni
0.20~0.27
0.24±0.035
0.15~0.17
0.16±0.010
0.21~0.24
0.23±0.015
Pd
8.3~8.4
8.36±0.051
0.35~0.43
0.39±0.041
0.35~0.37
0.36±0.010
Cu
0.20~0.28
0.24±0.042
0.19~0.22
0.20±0.016
0.19~0.20
0.20±0.010
Cd
431~443
438±5.9
20~21
21±0.25
22~23
23±0.16
Ca
659~685
674±14
342~351
347±4.8
308~310
309±1.2
Al
1.3~1.7
1.5±0.17
1.83~1.98
1.9±0.081
1.8~1.9
1.8±0.054
Tl
5.9~6.5
6.3±0.34
3.6~4.2
3.8±0.30
0.073~0.13
0.096±0.034
Zn
7283~7417
7333±73
4333~4401
4368±34
4180~4203
4189±13
Cl-
45895~48123
47194±1159
689~798
737±56
687~735
704±27
34
S0304-3894(17)30184-X http://dx.doi.org/doi:10.1016/j.jhazmat.2017.03.020 HAZMAT 18436
To appear in:
Journal of Hazardous Materials
Received date: Revised date: Accepted date:
16-10-2016 7-3-2017 9-3-2017
Please cite this article as: Huosheng Li, Yongheng Chen, Jianyou Long, Daqian Jiang, Juan Liu, Sijie Li, Jianying Qi, Ping Zhang, Jin Wang, Jian Gong, Qihang Wu, Diyun Chen, Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins, Journal of Hazardous Materials http://dx.doi.org/10.1016/j.jhazmat.2017.03.020 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins
Huosheng Li a, Yongheng Chen a, b,*, Jianyou Long b, Daqian Jiang e, Juan Liu a, c, Sijie Li a, Jianying Qi d, Ping Zhang b, Jin Wang c, Jian Gong b, c, Qihang Wu a, Diyun Chenc
a
Collaborative Innovation Center of Water Quality Safety and Protection in Pearl River
Delta, Guangzhou University, Guangzhou 510006, PR China b
Guangzhou University Key Laboratory of Water Safety and Protection in Pearl River
Delta, Ministry of Education, Guangzhou 510006, PR China c
School of Environmental Science and Engineering, Guangzhou University,
Guangzhou 510006, PR China d
South China Institute of Environmental Science, Ministry of Environmental Protection,
Guangzhou, PR China e School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, United States *
Corresponding author: Yongheng Chen, Collaborative Innovation Center
of Water Quality Safety and Protection in Pearl River Delta, Guangzhou University, Guangzhou 510006, PR China Phone: +86 020 393 66505 Email: [email protected] (Y. Chen)
1
Highlights
Simultaneous removal of Tl and Cl- by modified anion exchange resins was effective. Tl removal was based on the exchange of chlorocomplex formed under saline conditions. The operation had a broad flow rate and pH range. Elution and regeneration of the resins suggest good potential for practice application.
Abstract Simultaneous removal of thallium (Tl) and chloride from a highly saline industrial wastewater was investigated using modified anion ion exchange resins. The removal of thallium was mainly driven by the exchange of Tl-chlorocomplex (TlCl4 -) formed in the oxidation of thallous (Tl (I)) to thallic ion (Tl (III)) by hydrogen peroxide (H2O2) under saline conditions. Over 97% of thallium and chloride removal was achieved using the modified resins, with a wide optimal conditions found to be H2O2 dosage 1.0-25.0 mL/L, pH 1.6-4.3, and flow rate 0.5-4.7 mL/L. The modified resins had an exchange capacity of 4.771 mg Tl/g dry resins for thallium and 1800 mg Cl/g dry resins for chloride. Stable regeneration could be achieved with the modified resins: over 97% of thallium and 90% of chloride can be eluted using Na2SO3 solution and alternating hot (60℃) H2SO4 and cold (25℃) water, and over 98% removal of thallium and chloride was achieved after five consecutive regeneration cycles. 2
Keywords: Heavy metal; thallium; chloride; resins; industrial wastewater
1. Introduction Thallium (Tl), classified as one of the 13 USEPA priority metals, is an extremely toxic heavy metal [1-3]. It is reported to be highly bioaccumulative [4] and more toxic to living organisms than mercury and cadmium [5]. As a unique catalyst, Tl is gaining increasing application in the production of high-tech products including certain alloys, optical lenses, semiconductors, high temperature superconductor and low temperature thermometers [5, 6]. Significant anthropogenic discharge of Tl is often found in coal combustion, cement production, mining, metal refining and smelting industry [7]. Tl has two dominating oxidation states, namely mono (Tl(I)) and tri-valence (Tl(III)), in the aquatic environment [7, 8]. Tl (I) is quite stable and mobile in the aquatic media, while Tl(III) is highly reactive and can be readily reduced by common reducing agents or easily hydrolyzed in alkaline or neutral solutions [9]. It should be noted that Tl(III) can be stabilized by complexation with chloride[10, 11] and certain organics such as diethylenetriaminepentaacetic acid (DTPA) [9] and ethylenediaminetetraacetic acid (EDTA) [12], forming anion ions and being dissolved in the aqueous solution.
Due to the high toxicity of both states of Tl, pollution control for Tl is of significant importance during industrial activities. Adsorption of Tl using various chemical and biological materials, including MnO2 [13], polyacrylamide [14], TiO2 [15], ferrihydrite 3
[16], carbon nanotubes [17], sawdust [6] and microalga [18], has been shown effective in the removal of Tl. Oxidation combined with precipitation using lime or caustic have also been proven successful for Tl removal [19, 20]. Ion exchange can be an effective method for removal of Tl and other metals including uranium, chromium and platinum [20]. Solvent extraction of Tl(III) using certain organic extractant in HCl media is a good means for enrichment and recovery of Tl [10].
Despite previous success, Tl removal from hydrometallurgical wastewater such as the zinc refinery wastewater, still remains a challenge. In zinc refining wastewater, besides the high concentration of heavy metals, chloride is usually present with high concentration, often over 10000 mg/L [21]. Chloride could form chlorocomplex (tetrachlorothallate (III) anion, TlCl4 -) with Tl(III) during the wastewater treatment process [10], significantly impairing the adsorption and precipitability of Tl(III). High concentrations of chloride may also cause a host of other wastewater treatment problems, such as pipe corrosion [22] and false chemical oxygen demand (COD) measurements. Methods for simultaneous Tl and chloride removal still need to be developed, as most aforementioned adsorption methods are ineffective in chloride removal.
In this work, ion exchange coupled with an oxidation process was studied for simultaneous removal of Tl and chloride. Ion exchange resins, Dowex A-1 and Chelex4
100, have been used for removal of Tl(III) under acidic condition, but its application on Tl removal has not been extensively investigated [20]. This study proposed that via coupling modifying the ion exchange resins and coupling the ion exchange process with oxidation of Tl(I), simultaneous removal of Tl and chloride could be achieved (Reaction 1-5): R2SO4+2Cl-→2RCl+SO42-
(1)
Tl++2Cl-→TlCl2 -
(2)
Tl3++4Cl-→TlCl4-
(3)
R2SO4+2TlCl2-→2R(TlCl2)+SO42-
(4)
R2SO4+2TlCl4-→2R(TlCl4)+SO42-
(5)
Different operating conditions, including pH, dosage of oxidant (H2O2), and flow rate, were studied to identify the optimal conditions. The elution and regeneration capability of the ion exchange resins was also tested.
2. Materials and methods 2.1 Wastewater, reagents and solutions The industrial wastewater was obtained from a zinc industry company located in Jiangxi Province, China. Its composition is listed in Table 1. It is shown that this acidic wastewater (pH 5.8±0.20) contains a variety of heavy metals and high concentrations of chloride, thallium, sodium, potassium, zinc, and cadmium. The Tl in the wastewater was mostly in the form of Tl(I) (Supplementary Information, Figure S1 and Table S1). 5
Although it was free of organic compounds and suspended matters, the high strength at this magnitude poses a great difficulty in the wastewater treatment. During the experiments, the industrial wastewater was stored at ambient temperatures (25-29℃) and used directly without any pretreatment.
All the chemicals and reagents used were of analytical grade, and directly used without further purification (except the resins). The raw resins (212×7 (717), Yonghua, Jiangsu, China) used were gel-type spherical beads that were composed of polystyrene divinylbenzene as matrix structure and quaternary amine as functional groups (Figure. S2). Deionized water was used to prepare the acid and base solutions. In some cases, tap water was used to wash the resins and to prepare the sulfuric acid and sodium hydroxide solutions for pretreatment of the resins, depending on the goal of the experiments.
2.2 Pretreatment and modification of resins The resins were pretreated and modified as follows. They were sequentially washed with deionized (or tap water) water, 1.0M NaOH solution, deionized (or tap water) water, 0.75M H2SO4 solution, deionized (or tap water) water each for 30 min. The volume of the water or solutions used was 8 mL water/ g wet resins. The purpose of this modification was to transform the interlayer anion to sulfate. The resulted wet resins were kept in a closed vessel in the dark before use, and could be stable at least 6
for one month. To measure the dry weight of resins, the wet resins were dried in an oven at 60℃ overnight and weighed using a digital electronic balance (Sartorius BSA224S, Germany).
2.3 Procedures for exchange of thallium and chloride Glass columns (24mm in diameter and 250mm in height, Figure. S3) equipped with a valve of polytetrafluoroethylene (PTFE) were used for all ion exchange experiments. Before weighing of the resins, the water of wet resins in the vessel was drained with a pipette. For packing the columns, the pre-weighed wet resins (8 g) were washed into the columns with deionized water that was then drained through. Prior to ion exchange experiment, hydrogen peroxide (H2O2) solution (30%, w/w) was used for oxidation of thallium in the industrial wastewater. Spiking samples with designated amounts of oxidized wastewater were added to the columns and then passed through at various flow rate controlled by adjusting the opening of the PTFE valve. Interference of bubbles was avoided by expelling them with a fine tube (3.2 mm in diameter). The treated samples were filtered with syringe filters (0.45µm) and acidified before measurements of water quality. Each test was conducted at least in triplicate. The experiments were performed at room temperature (25-29℃).
Impact of different operating conditions were studied, including pH (1.6, 2.4, 3.3, 4.3, 5.9, 6.7, 7.6, 8.5 and 10.0) of resins, flow rate (0.5, 0.8, 1.2, 4.7, 8.0, 11, 16 mL/min) 7
and oxidant dosage (0, 1.0, 2.5, 5.0, 10, 25, 50, 100 mL/L), on the retention of thallium and chloride were determined. During these experiments, the resins and wastewater used were 8 g and 16 mL, respectively. The adsorption capacity of the resins was tested using a progressively increasing volume (2.1, 4.2, 8.3, 16.7, 33.3, 66.7, 133.3, 266.7, 533.3, 1066.7 and 2133.3 mL wastewater/g resins) of wastewater.
The ability of elution and regeneration of the resins was also tested. A series of sodium sulfite (Na2SO3) solutions 0.125, 0.25, 0.500 M) and HNO3 (1, 2, 4 M) were used as eluents for Tl(III), while a series of H2SO4 solutions (1, 2, 4 M) and water were used as eluents for chloride. Regeneration of resins was performed with 1.0M NaOH and then 1.0M H2SO4 and finally deionized water each for 30min. For analysis of X-ray photoelectron spectroscopy (XPS), the resins that had performed ion exchange were collected in beakers, and then air dried in a super-clean cupboard (Biocap 391, Erlab, France).
The capacities for retention of Tl and chloride are calculated as follows (Equation 6). 𝑞𝑒 =
(𝐶0 −𝐶)𝑉
(6)
𝑚
Where C0 and C are the initial and final Tl (or Chloride) concentrations of the studied solutions (mg/L), respectively, m is the mass (mg) of dry resins, and V is the solution volume (L).
8
2.4 Analytical methods An atomic absorption spectrometer (Thermo Scientific, USA) furnished with corresponding metal (except Tl) hollow-cathode lamps and air-acetylene flame was used for measurements of metals and sulfate. Inductively coupled plasma-mass spectrometry (NexION 300, PerkinElmer Inc., USA) was applied for all measurements of Tl. A chloride meter (Bante 931, Jiangsu, China) equipped with chloride ion selective electrode was used to determine the concentration of chloride. An X-ray photoelectron spectroscopy instrument with monochromatic Al Kα radiation (hv=1486.6 eV, Kratos Axis Ultra, Japan) was used to identify the element and compounds of the resins. In order to obtain sufficient signal of XPS spectra, high concentration of synthetic Tl wastewater was also used for the XPS analysis. Correction of the deviation of the binding energy (BE) owing to the relative surface charging was performed with the C 1s level at BE of 284.6 eV as an internal standard [23]. The fitting of all XPS spectra was conducted using the software XPSPEAK4.1.
3. Results and discussion 3.1 Tl and chloride retention under different operating conditions 3.1.1 Effect of H2O2 dosage It is shown that the addition of H2O2 substantially improved the removal of Tl. Without addition of H2O2, the effluent Tl concentration was over 3000 µg/L, approximately 47% of the Tl input; with the addition of H2O2, the effluent Tl concentration was lower than 9
100 µg/L at dosage over 25 mL/L (Figure. 1). Further increase in H2O2 dosage did not lead to complete removal of Tl, suggesting that a portion of Tl was not present in chlorocomplex (TlCl4-) or remained only in Tl(I) (Table S1). In practice, the dosage of H2O2 should not be higher than 5 mL/L when taking the cost into account. These results confirm that hydrogen peroxide, is capable of oxidizing Tl (I) to Tl (III) in acidic aqueous solutions [24, 25], which will help form the Tl(III)-chlorocomplex under highly saline conditions. The use of H2O2 can be broadly applicable, as most of the dissolved Tl in wastewater is Tl(I) [26].
The retention of chloride was efficient at over 85%, without the addition of H2O2, suggesting that the exchangeable group sulfate on the resins was able to effectively replace with the chloride (Equation 1) in wastewater even without presence of H 2O2. The spike of sulfate (over 30000mg/L) in the effluent indeed indicates the occurrence of the ion exchange of sulfate with chloride (Table S2).
3.1.2 Effect of pH of resins The pH of solution (or resins) is an important factor for capture of metals via ion exchange method [12, 27]. It is demonstrated that Tl removal was effective at pH range of 1.6 to 10.0, with optimum removal at acidic range of 1.6-4.3 (Figure. 2). The effluent pH of all treated wastewater increased with the increase in the pH of resins, but was still acidic (1.8-6.5). Under acidic conditions, the heavy metals in the industrial 10
wastewater remained in dissolved form and did not cause clogging problems. It is noted that the Tl retention efficacy at higher pH range from 5.9 to 10.0 was less effective than that at the acidic condition. The partition coefficient (kd) of the resins for Tl was found to decrease with the increasing pH value (Table S3). This may be attributed to the fact that the Tl-chlorocomplex (TlCl4-) is more stable under acidic conditions [28]. Lin and Nriagu [27] reported that the Chelex-100 (Aldrich) resins had a high affinity (over 103.1) for Tl(III) under pH of 1, probably due to the formation of strong complexes of TlCl4 -. These resins are much more expensive and its application is primarily in the biomolecular field.
The removal pattern of chloride is slightly different from that of Tl (Fig 2). The best removal efficiency was achieved in the neutral and basic range, but reasonably good removal was still achieved under acidic conditions. This study reveals the stability and flexibility of this type of resins for removal of Tl and chloride. Given the operational simplicity, the pH of resins should be controlled in the acidic range, preferably below 2.0, which can be readily achieved in the pretreatment and modification methodology.
3.1.3 Effect of flow rate The flow rate (contact time) is also important for retention of analyte during ion exchange [12]. It is found that removal of Tl at the studied flow rate range of 0.5-16 mL/min was nearly consistent, though the best was found at 0.8-8.0 mL/min (Figure. 11
3). For chloride removal, the high flow rate (over 4.7 mL/min) significantly lowered the Cl removal (Fig 3). The shorter contact time led to an impaired efficiency of both Tl and chloride at higher flow rate. This phenomenon impact of shorter contact time was more evident for chloride, indicating that high loading chloride requires a long contact time for complete ion exchange. Although the ion exchange between sulfate and chloride is reversible, it was unidirectional and quite stable at the studied conditions. These results suggest that the flow rate should be kept between 0.8 and 8 mL/min for optimal retention of Tl and Cl. 3.1.4 Comparison between preparation with deionized water and tap water Both Tl and chloride removal were similar for resins pretreated with deionized water or tap water (Table 2). This suggests that the resins used are a good candidate for the simultaneous removal of Tl and chloride from saline wastewater. In practical applications, the resins can be pretreated and modified with tap water instead of deionized water, to reduce the cost and simplify the operation.
3.2 Capacity for Tl and chloride removal The capacity of the modified resins for retention of Tl and chloride was evaluated with a series of different volume of wastewater treated by a given amount of resins. It is evident that the capacity of the Tl retention increased with the increase in the volume of wastewater (Figure.4b), whereas the effluent quality became less efficient with more wastewater being treated (Figure.4a). This phenomenon is commonly seen in ion 12
exchange and adsorption experiments. The capacity of Tl retention in this study (maximum 4771µg/g) was similar to other study in which nano-TiO2 (maximum 4900µg/g) [15] was used for adsorption of Tl(III). Similarly, the capture of chloride onto the resins became obviously less effective (Figure.4a), whereas the calculated capacity became dramatically stronger. Lv et al. [22] reported a maximum capacity of 169.3 mg/g for chloride adsorption with a resin called ZnAl-NO3 layered double hydroxides. By contrast, the modified resins in this study had a much stronger capacity (maximum 1800 mg/g) for chloride removal at a dosage of 2133.3 mL/g. In fact, in terms of the effluent chloride concentration, it spiked significantly at the ratio of wastewater to resin greater than 4 mL/g. Therefore, the treated amount of wastewater should not be higher than 4 mL/g. The much lower concentration of Tl than chloride led to this substantial discrepancy (several orders of magnitude) in the capacity.
3.3 Elution and regeneration of resins The elution ability for Tl and chloride was tested using different solutions. It is found that the use of H2SO4 or HNO3 alone, even at concentration as high as 4 M, was not able to release the Tl from the resins (Table 3). Acid solution such as HNO3 is usually used as eluent for desorption of Tl [9, 27] from resins. The fact that high concentrations of H2SO4 or HNO3 alone did not release the Tl from the resins indicate the high affinity of the bonding between the resins and the Tl(III)-chlorocomplex anion.
13
The use of Na2SO3 was effective (~98% elution efficiency) in elution of Tl, since the Tl(III) (likely TlCl4-) was reduced to Tl(I) and consequently dissociated from the resins to the solution. This is consistent with other study that H2SO3 solution was used as an effective reducing agent for thallium speciation analysis [3]. The combination of Na2SO3 and HNO3 solution resulted in marginal improvements on the elution. The use of 0.125M Na2SO3 solution was sufficient for elution of Tl, as a higher concentration of Na2SO3 did not lead to any enhancement of elution.
For chloride elution, the increase in concentration of acids brought about improvement on elution to some extent, however, operation with eluent at room temperature was not as effective as expected. Alternating hot (60 ℃) and cold (25 ℃) regime achieved improved elution of both Tl (99.5±2.16%) and chloride (98.4±2.41%). This may be related to the repeated expansion and contraction at alternating hot and cold conditions, which play a vital role in the dissociation of the bonding between the chloride and resins and thus desorption of chloride. Few literatures reported the combined elution of both chloride and thallium on the exhausted resins. The findings of this study point to a valuable means for removal of thallium from saline wastewater. After elution, the resins were regenerated by successively soaking in 1.0M NaOH solution, 1.0M H2SO4 and deionized water with the volume of 2 mL/g and for 30min. Results of five consecutive regenerations showed that steadily efficient removal and recovery of Tl and chloride were achieved, with the removal of Tl at over 98% and 14
chloride at over 90%, and the recovery of Tl at over 97% and chloride at over 98% (Figure 5). This indicates the excellent regeneration ability of these resins, which can be promising in the engineered applications.
3.4 Removal of other metals It is shown that after oxidation with H2O2, the composition of the wastewater remained nearly unchanged prior to ions exchange with the modified resins (Table 1 and Table 4). When the non-oxidized wastewater was treated by resins, not only Tl but also many other metals including Cd, Ca, Pd and Zn from the wastewater were partially removed (Table 4), probably due to complexation of these metals with chloride. It is interesting that for oxidized wastewater being treated by the resins, Tl removal was greatly improved while many other metals removal was not enhanced by oxidation (Table 4). This points to the formation of the Tl(III)-Cl anion complexes that were more stable and dominant than the Tl(I)-Cl anion ones under saline conditions [29]. The ion exchange by the modified anion resins can be applied to other stable metal-Cl complexes anions. In this study, the major focus was on the simultaneous removal of chloride and Tl from wastewater. By using an adequate dosage of resins, the chloride content can be substantially reduced and the Tl concentration can be lowered to a low level. The other metals (such as Zn) remained should be further treated, since a single treatment is usually inadequate for a high-strength type of wastewater.
15
3.5 Analysis of XPS spectra The resins used for adsorption of the industrial wastewater were analyzed by XPS spectra in order to gain more insight into the intrinsic reaction during the ion exchange process. In this test, 0.5g resins were used for treatment of 32 mL industrial wastewater. In the XPS spectra, the peaks of S 2p (BE of 161.0 and 166.0eV) appeared in all modified resins, indicating that sulfate was successful bonded during the modification, and that sulfate was in excess and remained on the resins although they were exchanged with chloride at this loading (Figure 6a). The peaks of Cl 2p (BE of 196.6 and 196.7, Figure 7) imply the existence of the compound poly(vinylbenzyltrimethylammonium chloride) [30, 31], which is an important group of the product after replacement of sulfate with chloride by the functional groups (poly(vinylbenzyltrimethylammonium sulfate)) from the modified resins. Other peaks of Cl 2p (197.7, 197.8, 198.8 and 199.4eV, Figure 7) were attributed to chloride-related compounds [31]. Due to the low proportion of Tl (0.08% for non-oxidation and 0.15% for oxidation, calculated based on the element peaks of O 1s, N 1s, C 1s, Cl 2p, s 2p and Tl 4f) on the resins, the Tl 4f spectra were very vague. To obtain sufficient XPS signal of Tl, a high load of synthetic Tl solution (0.5g resins for 100mL synthetic Tl(I) and Tl(III) of each 400mg Tl and each 1mol/L HCl) was also used to investigate the Tl speciation during the oxidation and ion exchange process. The high Tl load adsorption tests did show clear peaks of Tl 4f (Figure S4). For Tl(III), the Tl 4f 7/2 peak can be split to two sub-peaks (BE of 118.1and 117.6 eV), whereas it can be fitted into two distinctively different sub-peaks 16
for Tl(I) (BE of 117.7and 116.1 eV) (Figure 8). So far, no XPS spectra of TlCl4 - or related Tl-chlorocomplex are available. The spectra of pure chemicals of TlNO3 and Tl(NO3)3 were similar, and are ineffective in explaining the conversion of Tlchlorocomplex. The Tl(III)-chlorocomplex (BE of 118.1eV) might be half reduced to Tl(I) (BE of 117.6 eV) in air and this might explain the two sub-peaks with nearly equal area. The T(I) (BE of 117.7 eV) might be relatively stable, only marginally converted to an unknown Tl species. For resins without oxidation, Tl was also detected in these samples. This suggests that the resins used in this study was able to adsorb Tl(I), which is consistent with the results of the ICP-MS measurements.
4. Conclusions The modified anion ion exchange resin containing sulfate was effective in simultaneous removal of Tl and chloride from highly saline wastewater. The addition of hydrogen peroxide to form Tl(III)-chlorocomplex (TlCl4 -) as the anion was the key to obtaining high efficiency of Tl removal. The resins had a broad operating flow rate and should be operated at acidic condition (pH 1.6-4.3). To obtain good effluent quality, the ratio of the wastewater to resin should be controlled at less than 4 mL/g. The Tl adsorbed onto the resins can be eluted by 0.125 M Na2SO3 solution, while the chloride captured can be desorbed by alternating hot (60℃) 2M H2SO4 solution and cold (25℃) water. After five regeneration cycles, the resins still obtained significant removal of Tl and chloride from high strength wastewater. 17
Acknowledgements The research was supported by the Foundation for Fostering the Scientific and Technical Innovation of Guangzhou University, the Department of education of Guangdong Province (2015KQNCX115), the Guangzhou Education Bureau (1201630390), the Public welfare scientific fund of Environmental Protection Department (No.201509051), the Science and Technology Program of Guangzhou (201607010217), the Educational System Innovation Team Project of Guangzhou Education Bureau (13C02, 13xt02), the National Natural Science Foundation of China (41373118, 41573119, 41273100) and the high level university construction project (Regional water environment safety and water ecological protection). The authors thank the anonymous reviewers for improving the quality of our research.
18
References
[1] A. Voegelin, N. Pfenninger, J. Petrikis, J. Majzlan, M. Plotze, A.-C. Senn, S. Mangold, R. Steininger, J. Gottlicher, Thallium speciation and extractability in a thallium- and arsenic-rich soil developed from mineralized carbonate rock, Environmental science & technology, 49 (2015) 5390-5398. [2] L. Keith, W. Telliard, ES&T special report: priority pollutants: Ia perspective view, Environmental Science & Technology, 13 (1979) 416-423. [3] B.S. Twining, M.R. Twiss, N.S. Fisher, Oxidation of thallium by freshwater plankton communities, Environmental Science & Technology, 37 (2003) 27202726. [4] T.-S. Lin, J. Nriagu, X.-Q. Wang, Thallium concentration in lake trout from Lake Michigan, Bulletin of environmental contamination and toxicology, 67 (2001) 921-925. [5] V. Zitko, Toxicity and pollution potential of thallium, Science of the total environment, 4 (1975) 185-192. [6] S.Q. Memon, N. Memon, A.R. Solangi, J.-u.-R. Memon, Sawdust: A green and economical sorbent for thallium removal, Chemical Engineering Journal, 140 (2008) 235-240. [7] J.O. Nriagu, Thallium in the environment, John Wiley & Sons, New York, NY, ETATS-UNIS, 1998. [8] U. Karlsson, S. Karlsson, A. Duker, The effect of light and iron(II)/iron(III) on the distribution of Tl(I)/Tl(III) in fresh water systems, Journal of Environmental Monitoring, 8 (2006) 634-640. [9] P. Coetzee, J. Fischer, M. Hu, Simultaneous separation and determination of Tl (I) and Tl (III) by IC-ICP-OES and IC-ICP-MS, Water Sa, 29 (2004) 17-22. [10] N. Rajesh, M.S. Subramanian, A study of the extraction behavior of thallium with tribenzylamine as the extractant, Journal of Hazardous Materials, 135 (2006) 7477. [11] T.M. TRTIĆ, J.J. ČOMOR, Extraction of thallium with butyl acetate, Separation science and technology, 34 (1999) 771-779. [12] S. Dadfarnia, T. Assadollahi, A.M. Haji Shabani, Speciation and determination of thallium by on-line microcolumn separation/preconcentration by flow injection– flame atomic absorption spectrometry using immobilized oxine as sorbent, Journal of Hazardous Materials, 148 (2007) 446-452. [13] X. Huangfu, J. Jiang, X. Lu, Y. Wang, Y. Liu, S.-Y. Pang, H. Cheng, X. Zhang, J. Ma, Adsorption and Oxidation of Thallium(I) by a Nanosized Manganese Dioxide, 19
Water Air And Soil Pollution, 226 (2015). [14] Z.M. Senol, U. Ulusoy, Thallium adsorption onto polyacryamide-aluminosilicate composites: A Tl isotope tracer study, Chemical Engineering Journal, 162 (2010) 97-105. [15] L. Zhang, T. Huang, N. Liu, X. Liu, H. Li, Sorption of thallium (III) ions from aqueous solutions using titanium dioxide nanoparticles, Microchimica Acta, 165 (2009) 73-78. [16] K.M. Coup, P.J. Swedlund, Demystifying the interfacial aquatic geochemistry of thallium (I): New and old data reveal just a regular cation, Chemical Geology, 398 (2015) 97-103. [17] Y. Pu, X. Yang, H. Zheng, D. Wang, Y. Su, J. He, Adsorption and desorption of thallium (I) on multiwalled carbon nanotubes, Chemical Engineering Journal, 219 (2013) 403-410. [18] Z. Birungi, E. Chirwa, The adsorption potential and recovery of thallium using green micro-algae from eutrophic water sources, Journal of hazardous materials, 299 (2015) 67-77. [19] L. Rosengrant, R. Craig, Final Best Demonstrated Available Technology (BDAT) background document for P and U Thallium wastes, US EPA. Office of Solid waste, Washington, DC. EPA/530-sw-90-059R, National Technical Information Services PB90-234188l, (1990). [20] L.G. Twidwell, C. Williams-Beam, Potential technologies for removing thallium from mine and process wastewater: an annotation of the literature, European Journal of Mineral Processing and Environmental Protection, 2 (2002) 1-10. [21] Q. Wang, W. Qin, L. Chai, Q. Li, Understanding the formation of colloidal mercury in acidic wastewater with high concentration of chloride ions by electrocapillary curves, Environmental Science and Pollution Research, 21 (2014) 3866-3872. [22] L. Lv, P. Sun, Z. Gu, H. Du, X. Pang, X. Tao, R. Xu, L. Xu, Removal of chloride ion from aqueous solution by ZnAl-NO3 layered double hydroxides as anionexchanger, Journal of Hazardous Materials, 161 (2009) 1444-1449. [23] X.J. Li, D.L. Tang, F. Tang, Y.Y. Zhu, C.F. He, M.H. Liu, C.X. Lin, Y.F. Liu, Preparation, characterization and photocatalytic activity of visible-light-driven plasmonic Ag/AgBr/ZnFe2O4 nanocomposites, Materials Research Bulletin, 56 (2014) 125-133. [24] G. Kirkbright, P. Mayne, T. West, Photo-oxidation of thallium (I) with the production of hydrogen peroxide, Journal of the Chemical Society, Dalton Transactions, (1972) 1918-1920. [25] D. Li, Z. Gao, Y. Zhu, Y. Yu, H. Wang, Photochemical reaction of Tl in aqueous solution and its environmental significance, Geochemical Journal, 39 (2005) 113119. [26] B. Vink, The behaviour of thallium in the (sub) surface environment in terms of Eh and pH, Chemical geology, 109 (1993) 119-123. 20
[27] T.S. Lin, J.O. Nriagu, Thallium speciation in river waters with Chelex-100 resin, Analytica Chimica Acta, 395 (1999) 301-307. [28] Z. Marczenko, Spectrophotometric determination of elements, E. Horwood; Wiley, 1975. [29] S. Aldridge, A.J. Downs, The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities, John Wiley & Sons, 2011. [30] G. Beamson, D. Briggs, High resolution XPS of organic polymers, Wiley, 1992. [31] A.V. Naumkin, A. Kraut-Vass, S.W. Gaarenstroom, C.J. Powell, NIST X-ray Photoelectron Spectroscopy Database (Online version 4.1), 2016.
21
Figure Captions Figure 1 Effect of dosage of H2O2 on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n=4)
Figure 2 Effect of pH of resins on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 0.8 mL/min, H2O2 dosage of 5 mL/L, n=3)
Figure 3 Effect of flow rate on removal of Tl and chloride (8 g resins, 16 mL wastewater, pH of resins 1.6, H2O2 dosage of 5 mL/L, n=3)
Figure 4 Capacity of resins for removal of Tl and chloride: (a) effluent concentrations of Tl and chloride; (b) capacity of dry resins (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3)
Figure 5 Regeneration and elution of resins for removal of Tl and chloride: (a) Regeneration and (b) Elution (pH of resins 1.6, H 2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3; Ini. A means initial adsorption with resins, Ini. E means initial elution of resins; R means regeneration of resins, E means elution of resins).
Figure 6 XPS spectra of the raw resins, modified resins, modified resins for nonoxidized industrial wastewater and oxidized wastewater, pure TlNO 3 and Tl(NO3)3, 22
respectively.
Figure 7 XPS spectra of region of Cl 2p3/2 for resins treated with (a) oxidized industrial wastewater and (b) non-oxidized industrial wastewater.
Figure 8 XPS spectra of Tl 4f7/2 core level of resins treated with high Tl loading synthetic wastewater (a) Tl(III) and (b) Tl(I).
7000
1600
Tl concentration -
Cl concentration
1400
5000
1200
4000
1000
3208.2 800
2000
600
1000
400
-
3000
Cl (mg/L)
Tl concentration (g/L)
6000
142.5 174.9 57.6 115.9 89.4
0 0
1
2.5
5
10
25
73.2
69.0
50
100
200
Dosage of H2O2 (mL/L)
Figure 1 Effect of dosage of H2O2 on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n=4)
23
4000
Tl concentration Cl concentration 1200 2000
0 600 -2000 300
0
-
900
Effluent Cl (mg/L)
Effluent Tl concentration (g/L)
1500
-4000 1.6
2.4
3.3
4.3
5.9
6.7
7.6
8.5
10
The pH of resin
Figure 2 Effect of pH of resins on removal of Tl and chloride (8 g resins, 16 mL wastewater, flow rate 0.8 mL/min, H2O2 dosage of 5 mL/L, n=3)
24
500 2500
-
Cl concentration 400
2000 1500
-
300
Effluent Cl (mg/L)
Effluent Tl concentration (g/L)
Tl concentration
1000 200 500 100 0 0
-500 0.5
0.8
1.2
4.7
8
11
16
Flow rate (mL/min)
Figure 3 Effect of flow rate on removal of Tl and chloride (8 g resins, 16 mL wastewater, pH of resins 1.6, H2O2 dosage of 5 mL/L, n=3)
25
50000
Tl concentration Cl concentration
5000 40000
Effluent Cl (mg/L)
4000 30000 3000
-
Effluent Tl concentration (g/L)
(a) 6000
20000 2000 10000 1000 0 0 2.1
4.2
8.3 16.7 33.3 66.7 133.3 266.7 533.3 066.7 133.3 1 2
Dosage (mL wastewater/g resins)
(b) 7000
Tl capacity Cl capacity
6000
2100
1500
4000
1200
3000
900
2000
600
1000
300
0
-
Tl capacity (g/g)
5000
Cl capacity (mg/g)
1800
0 2.1
4.2
8.3 16.7 33.3 66.7 133.3 266.7 533.3 066.7 133.3 1 2
Dosage (mL wastewater/g resins)
Figure 4 Capacity of resins for removal of Tl and chloride: (a) effluent concentrations of Tl and chloride; (b) capacity of dry resins (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3) 26
110
110
100
100
90
90
Tl removal Cl removal
80
-
80
Cl removal (%)
Tl removal (%)
(a)
70
60
70 Ini. A
1st R
2nd R
3rd R
4th R
5th R
60
100
100
90
90
Tl recovery Cl recovery
80
-
80
Cl recovery (%)
Tl recovery (%)
(b)
70
70
60
60 Ini.E
1st E
2nd E
3rd E
4th E
5th E
Number of Elution
Figure 5 Regeneration and elution of resins for removal of Tl and chloride: (a) Regeneration and (b) Elution (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3; Ini. A means initial adsorption with resins, Ini. E means initial elution of resins; R means regeneration of resins, E means elution of resins).
27
O 1s
Tl 4f
Tl(NO3)3 C 1s Tl 5d
Tl(NO3)3
Intensity (Offset)
TlNO3 Oxidation No oxidation Modified resins Raw resins
TlNO3
O 1s
Tl 4f C 1s Tl 5d
Cl 2p S 2p
No oxidation
O 1s
Modified resins
O 1s
Raw resins
O 1s
1200
C 1s
O 1s
Oxidation
1000
C 1s Cl 2p S 2p
800
600
C 1s
C 1s
400
S 2p
Cl 2p
200
0
BE (eV)
Figure 6 XPS spectra of the raw resins, modified resins, modified resins for nonoxidized industrial wastewater and oxidized wastewater, pure TlNO3 and Tl(NO3)3, respectively.
28
3000
(a)
Intensity
2500
Raw Fitte d Ba c k g r o u d 1 9 7 .7 Pe a k 1 Pe a k 2 Pe a k 3 1 9 8 .8
Oxidation
1 9 6 .6
2000
1500
1000 2400
(b) 2200
Intensity
2000 1800
Raw 1 9 7 .8 Fitte d Ba c k g r o u d Pe a k 1 Pe a k 2 Pe a k 3 1 9 9 .4
No oxidation 1 9 6 .7
1600 1400 1200 1000 800 204
202
200
198
196
194
192
190
BE (eV)
Figure 7 XPS spectra of region of Cl 2p3/2 for resins treated with (a) oxidized industrial wastewater and (b) non-oxidized industrial wastewater.
29
(a)
5000
Intensity
4000
Raw Fitted Backgroud Peak1 Peak2
High Tl(III) loading
118.1
3000
117.6
2000
1000
0 Raw Fitted Backgroud Peak1 Peak2
(b)
High Tl(I) loading
117.7
4000
2000 116.1
0 121
120
119
118
117
116
115
114
BE (eV)
Figure 8 XPS spectra of Tl 4f7/2 core level of resins treated with high Tl loading synthetic wastewater (a) Tl(III) and (b) Tl(I).
30
Table 1 Compositions of the industrial wastewater (n a =3, unit: mg/L)
a
Ions
Range
Mean±SD b
Ions
Range
Mean±SD b
Na
1650-1708
1686±32
Cu
0.20-0.28
0.24±0.042
Mg
19-23
22±2.5
Cd
420-440
430±10
Mn
28-35
32±3.6
Ca
678-685
682±3.3
K
8250-8467
8367±109
Al
1.3-1.7
1.5±0.17
Fe
4.3-6.2
5.2±0.93
Tl
5.8-6.6
6.30±0.43
Ni
0.20-0.27
0.24±0.034
Zn
7100-7416
7267±159
Pd
8.2-8.4
8.3±0.11
Cl-
42600-53250
47333±5422
: n is the number of measurements.
b
: SD stands for the standard deviation.
31
Table 2 Comparison (deionized water (DIW) versus tap water (TW)) of performance of Tl and chloride removal (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n a =5) Cl- (mg/L)
Tl (µg/L) Items
a
DIW
TW
DIW
TW
Range
23.7-210.0
26.7-161.8
848-1459
870-1377
Mean
107.3
102.8
1005
1170
SD b
93.4
57.0
232
237
: n is the number of measurements.
b
: SD stands for the standard deviation.
32
Table 3 Recovery of Tl and chloride in the elution solution (8 g resins, 16 mL wastewater, flow rate 1.2 mL/min, resin pH 1.6, n a =3, Mean±SD b) Methods
Tl (%)
Cl- (%)
16mL 1M H2SO4
0.39±0.18
25.3±0.06
16mL 2M H2SO4
0.25±0.13
35.2±0.25
16mL 4M H2SO4
0.15±0.03
33.4±0.24
16mL 1M HNO3
0.18±0.04
32.0±0.98
16mL 2M HNO3
0.30±0.11
55.0±2.17
16mL 4M HNO3
0.14±0.03
63.9±0.22
16mL 0.1M Na2SO3
97.0±0.98
5.2±0.02
16mL 0.25M Na2SO3
92.3±4.94
7.1±0.06
16mL 0.5M Na2SO3
88.2±5.11
12.7±0.02
8mL 0.125M Na2SO3 +8mL 1M HNO3
96.7±3.86
12.9±0.09
8mL 0.250M Na2SO3 +8mL 2M HNO3
95.7±0.59
31.0±0.76
8mL 0.500M Na2SO3 +8mL 4M HNO3
92.7±4.06
43.8±2.17
8mL 0.125M Na2SO3 + 8mL 2M H2SO4 c
88.8±0.60
71.5±0.68
99.5±2.16
98.4±2.41
8mL 0.125M Na2SO3 + 8mL 2M H2SO4 c + 4mL water +4mL 2M H2SO4 a
c
: n is the number of measurements.
b
: SD stands for the standard deviation.
c
: Elution was conducted with H2SO4 solution of 60℃. 33
Table 4 Compositions of the industrial wastewater after treatment (pH of resins 1.6, H2O2 dosage of 5 mL/L, flow rate 1.2 mL/L, n=3, unit: mg/L) Resins-Treated
Non-
Resins-Treated
Oxidized
Oxidized Raw Wastewater Metals
oxidized Wastewater
Wastewater
Range
Mean ± SD
Range
Mean ± SD
Range
Mean ± SD
Na
1698~1708
1702±5.5
1556~1612
1583±28
1590~1601
1594±6.2
Mg
23~24
24±0.34
25~28
26±1.8
20~22
21±0.72
Mn
34~35
34±0.44
32~33
32±0.46
30~31
30±0.46
K
8350~8467
8400±60
7856~7923
7882±36
7700~7757
7724±30
Fe
4.3~6.2
5.2±0.92
6.0~7.3
6.6±0.69
6.8~6.9
6.8±0.091
Ni
0.20~0.27
0.24±0.035
0.15~0.17
0.16±0.010
0.21~0.24
0.23±0.015
Pd
8.3~8.4
8.36±0.051
0.35~0.43
0.39±0.041
0.35~0.37
0.36±0.010
Cu
0.20~0.28
0.24±0.042
0.19~0.22
0.20±0.016
0.19~0.20
0.20±0.010
Cd
431~443
438±5.9
20~21
21±0.25
22~23
23±0.16
Ca
659~685
674±14
342~351
347±4.8
308~310
309±1.2
Al
1.3~1.7
1.5±0.17
1.83~1.98
1.9±0.081
1.8~1.9
1.8±0.054
Tl
5.9~6.5
6.3±0.34
3.6~4.2
3.8±0.30
0.073~0.13
0.096±0.034
Zn
7283~7417
7333±73
4333~4401
4368±34
4180~4203
4189±13
Cl-
45895~48123
47194±1159
689~798
737±56
687~735
704±27
34