Dialdehyde carboxymethyl cellulose cross-linked chitosan for the recovery of palladium and platinum from aqueous solution

Reactive and Functional Polymers 141 (2019) 145–154

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Dialdehyde carboxymethyl cellulose cross-linked chitosan for the recovery of palladium and platinum from aqueous solution

T

⁎

Tsegaye Girma Aserea,b, , Stein Minckea, Karel Folensa,c, Flore Vanden Busschea,d, Linsey Lapeiree, Kim Verbekene, Pascal Van Der Voortd, Dejene A. Tessemaf, Gijs Du Lainga, Christian V. Stevensa a

Department of Green Chemistry and Technology, Ghent University (UGent), Coupure Links 653, 9000 Ghent, Belgium Department of Chemistry, Jimma University, P. O. Box 378, Jimma, Ethiopia c Center for Microbial Ecology and Technology (CMET), Faculty of Bioscience Engineering, Coupure Links 653, 9000 Ghent, Belgium d Department of Chemistry, Ghent University, Krijgslaan 281 S3, 9000 Ghent, Belgium e Department of Materials, Textiles and Chemical Engineering, Ghent University, Technologiepark Zwijnaarde 46, 9052 Zwijnaarde, Belgium f Department of Chemistry, Welkite University, Gubrei Wabe Bridge 5, Southern Nations, Nationalities and Peoples' Region, Welkite, Ethiopia b

A R T I C LE I N FO

A B S T R A C T

Keywords: Platinum Palladium Chitosan Carboxymethyl cellulose Resource recovery

Platinum (Pt) and palladium (Pd) have widespread applications, such as in catalysts, jewelry, fuel cells, and electronics because of their favorable physical and chemical properties. Recovery of Pt and Pd from secondary sources is of great concern due to the increased market demand and limitation of the natural reserves of these precious metals. The aim of this research is to achieve recovery of Pt and Pd ions from dilute aqueous solution using dialdehyde of carboxymethyl cellulose (DCMC) crosslinked chitosan (Ch-DCMC). The DCMC was prepared by periodate oxidation of carboxymethyl cellulose (CMC). Both the DCMC and Ch-DCMC were characterized before and after Pt or Pd adsorption using Fourier-transformed infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM). The effect of cross-linking ratios of chitosan and DCMC (1:1, 1:0.8, 1:0.5, 1:0.25 and 1:0.1) on the Pt and Pd recovery was studied. The optimal cross-linking ratio was found to be 1:0.25 (chitosan: DCMC) with maximum adsorption capacity of 80.8 mg/g Pt and 89.4 mg/g Pd. High selectivity for Pt and Pd compared to base metals and common anions was achieved.

1. Introduction Platinum group metals (PGMs) are only limited available in nature and the quantities found in the earth's crust are below 10 mg/kg. Their mineral ores are mainly located in South Africa, Russia, Canada and Zimbabwe [1]. The elements have a wide range of applications owing to their desirable physical and chemical properties [2]. For example, PGMs are used as catalysts in petrochemical industries and exhaust gas treatment of automobiles, in jewelry, fuel cells, and electronic components. Although their availability is limited, making the commodities expensive [3,4], a large amount of these metals is still discharged after use, so they may eventually accumulate in the environment [5–7]. Such release of PGMs, without appropriate treatment and recovery, is on the one hand considered as a significant loss of resources for our society and, on the other hand, can also pollute the environment. The recovery of precious metals from secondary sources is an increasing concern in

recent years due to the increasing market demand and limited natural reserves of these metals being available [2]. However, their selective recovery from waste streams is also still challenging due to their complex chemistry and similar behavior [8]. Several methods exist for the recovery of PGMs from aqueous solutions, such as ion exchange [9], chemical precipitation [10], solvent extraction [11,12], membrane filtration [13,14], and adsorption [15–17]. Comparing to other methods, adsorption seems to be the most suitable method for the recovery of elements from dilute waste streams due to its low cost, high efficiency and minimal generation of secondary waste [18]. A number of adsorbents have been developed and tested for the recovery of precious metals, including activated carbon [19], polyacrylonitrile-based adsorbents [20], alginate and algal-based sorbents [21,22], chemically modified-microalgal residues [23], glutaraldehyde cross-linked chitosan [15], 1,10-phenanthroline-2,9-dicarbaldehyde cross-linked chitosan, [2,2′-bipyridine]-5,5′-

⁎ Corresponding author at: Laboratory of Analytical Chemistry and Applied Ecochemistry, Department of Green Chemistry and Technology, Ghent University (UGent), Coupure Links 653, 9000 Ghent, Belgium. E-mail addresses: [email protected], [email protected] (T.G. Asere).

https://doi.org/10.1016/j.reactfunctpolym.2019.05.008 Received 24 January 2019; Received in revised form 9 May 2019; Accepted 15 May 2019 Available online 16 May 2019 1381-5148/ © 2019 Published by Elsevier B.V.

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A)

OCH2COOH

OCH2COONa O OH

O

NaIO4

O

HO

O

n

CMC

O

O

n

DCMC

B) O

OH O

O HO

NH2

HO O

O

OH NH O OH

O HO

O

O

HO O

O

N

OH

n1

Chitosan

DCMC

+

NH O n1

HOOCH2CO O

OH O

O HO

NH

HO O

O

O

NH2 O OH

O

n3

OH

n2

O

O HO

Chitosan

NH

N HO O

O

O

O

OH n2

Scheme 1. Periodate oxidation of (A) CMC to DCMC and (B) crosslinking of chitosan using DCMC.

link chitosan because of its lower cost, and because it can be easily produced from renewable sources through the oxidation of carboxymethyl cellulose (CMC). Accordingly, it is assumed that DCMC-crosslinked chitosan is more economic and environmentally sustainable. It was well documented that the oxidation of CMC by periodate (Scheme 1 A) leads to a selective cleavage of the C2–C3 bond of the 1,4-glucan unit of CMC to yield a 2,3-dialdehyde carboxymethyl cellulose (DCMC) without significant side reactions occurring [48,49]. The chemical structure of DCMC and DCMC cross-linked chitosan (Ch-DCMC) before and after adsorption of Pt and Pd was investigated. The efficiency of Ch–DCMC to remove Pt and Pd from aqueous acidic solutions was evaluated, as well as the selectivity in the presence of base metal ions and common anions.

dicarbaldehyde cross-linked chitosan and glutaraldehyde cross-linked chitosan grafted with 8-hydroxyquinoline-2-carbaldehyde [24], L-lysine modified cross-linked chitosan [17,25], ion-imprinted chitosan fiber [18], tannins cross-linked Lagerstroemia speciosa [26], glycine modified cross-linked chitosan resin [27], chitosan flakes [28], etc. Nowadays, the demand is increasing for environmentally benign and readily available bio-based adsorbents with high sorption capacity for the removal and recovery of precious metal ions. Chitosan and its derivatives are among the most widely investigated biosorbents [22,27]. Chitosan is a polysaccharide, composed of β-D-glucosamine and Nacetyl-β-D-glucosamine residues with a 1,4-linkage [8]. Chitosan is a non-toxic and biodegradable biopolymer which is made by partial deacetylation of chitin, and is the most abundant polysaccharide next to cellulose. Commercially, chitosan is produced from exoskeleton shellfish processing waste. The structure of chitosan is given in Scheme 1. Chitosan has been used in various industries including biomedical [29], cosmetic [30], food [31,32], and wastewater treatment [33,34]. Recently, chitosan based adsorbents get more attention in recovery of precious metals from industrial waste streams [17]. Chitosan is characterized by the presence of many amino and hydroxyl groups which enable it to take up metal ions through different mechanisms such as ion-exchange or chelation, depending on the pH of the solution and speciation of the metals [35,36]. There are several reports proving that chitosan is a suitable bio-sorbent for the removal of heavy metal ions [27,37,38], radionuclides [39], dyes [40,41], and precious metals [24,28] from wastewater. However, chitosan is soluble in acidic conditions and has poor mechanical properties for practical applications. Hence, chitosan has been cross-linked [8,25,42], functionalized [36,43], coated or immobilized on a solid surface [44,45], hybridized with inorganic materials [46], etc. to enhance its efficiency, chemical stability, and mechanical strength. Industrial effluents contain very low concentrations of PGMs, while they contain strong acids and high concentrations of base metals [47]. Hence, in order to use chitosan for the recovery of platinum and palladium, a cross-linking step is usually required to ensure its chemical stability. Previously, several cross-linking agents have been used, such as epichlorohydrin, glutaraldehyde, etc. However, in the present work, dialdehyde carboxymethyl cellulose (DCMC) has been selected to cross-

2. Materials and methods 2.1. Materials Chemicals used were sodium salt of carboxymethyl cellulose (CMC, medium viscosity, VWR international BVBA, Leuven, Belgium), chitosan powder (low molecular weight (50–190 kDa), 75–85% deacetylated, Sigma-Aldrich), sodium periodate (98.8+ % ACS reagent, New Jersey, USA), PdCl2 (59% Pd, Merck, Darmstadt, Germany), K2PtCl6 (Pt 39.6%, Alfa Aesar, Thermo Fischer (kandel), GmbH, Germany), Ni (NO3)2.6H2O (min, 99%, Merck, Darmstadt, Germany), Zn(NO3)2·6H2O (> 99%, Merck, Darmstadt, Germany), Fe(NO3)3·9H2O (Merck, Darmstadt, Germany), Cu(NO3)2·2.5H2O (99–102%, Chem-Lab, Belgium), thiourea (> 99% Chem-Lab, Belgium), NaOH (Merck, Darmstadt, Germany), ethanol (VWR International BVBA, Leuven, Belgium), and deionized water. All chemicals were analytic grade reagents and used without further purification. 2.2. Oxidation of CMC The oxidation of CMC was carried out following the method used by Li et al. [48]. In brief, about 1.0 g CMC was dissolved in 20 mL deionized water in a flask at 40 °C. Then, the flask was wrapped with aluminum foil and 10 mL of NaIO4 (0.11 g/L) solution was added to the 146

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where C0 and Ct (mg/L) are the initial Pt or Pd concentration and the concentration at time t (min), respectively, V is the solution volume (L) and m (g) is the adsorbent mass.

CMC solution under stirring. The pH was adjusted to ~3.0 using 1 M H2SO4 solution and the stirring was continued for 4 h. Subsequently, the oxidized product, dialdehyde carboxymethyl cellulose (DCMC) (Scheme 1), was precipitated by pouring the solution into an excess amount of ethanol. It was then recovered and cross-washed with distilled water and ethanol until all iodic compounds were removed. Then, the product was dried at 60 °C for 12 h and stored in a vial until use.

2.5.1. Kinetics Kinetics of adsorption is one of the important characteristics that define the efficiency of sorption. It describes the solute uptake rate governing the contact time of the sorption reaction. To explore the adsorption kinetics of Pt and Pd ions onto the Ch-DCMC, the experimental kinetic data of Pt(IV) and Pd(II) adsorptions were fitted into a non-linear pseudo-first-order (PFO) kinetic model (Eq. 4) and a pseudosecond-order (PSO) kinetic model (Eq.5):

2.3. Determination of the aldehyde content The aldehyde content (AC) of DCMC was determined following the procedure used by Li et al. [48] and Jiang et al. [49]. Dried 0.5 g DCMC was dissolved in 25 mL distilled water. The pH of the solution was adjusted to 5.0 with 1 M NaOH. Then, a 20 mL 0.72 M hydroxylamine hydrochloride (pH ≈ 5.0) solution was added into the DCMC solution and the mixture was stirred at 40 °C in an oil bath for 4 h. Subsequently, 1.0 M NaOH was used to titrate the hydrochloric acid generated in the mixture and the consumption of NaOH solution was recorded as Vc (L). The same concentration of the CMC solution (pH ≈ 5.0) was used as a blank and its NaOH consumption was recorded as Vb (L). The amount of aldehyde in the DCMC was calculated using Eq. 1.

AC =

MNaOH (Vc – Vb) 2 m 211

qt = q e (1 − exp−K1t ) qt =

qt = kp t 0.5 + c

where MNaOH is 1.0 M, m is the dry weight of DCMC sample, and 211 is the average molecular weight (g/mol) of the repeating units in DCMC. Experiments were performed in duplicate.

qe =

(7)

1

(8)

where Ce (mg/L) is the concentration of Pt(IV) or Pd(II) in the aqueous phase at equilibrium; Qmax (mg/g) is the maximum adsorption capacity based on the Langmuir equation; b (L/mg) is the Langmuir constant; KF (mg1–1/n L1/n/g) is the adsorption coefficient based on the Freundlich equation; 1/n is the adsorption intensity based on the Freundlich equation. 2.5.3. Selectivity studies The effect of co-existing metal ions (Co(II), Cu(II), Ni(II), Zn(II), and Fe(III)) on Pd(II) and Pt(IV) adsorption were studied at fixed Pd(II) and Pt(IV) initial concentrations of 50 mg/L and adsorbent dose of 1.0 g/L while varying the metal ions concentration from 25 to 100 mg/L. The metal ions were prepared from their respective nitrate salts (Co (NO3)2.6H2O; Cu(NO3)2.2.5H2O; Ni(NO3)2.6H2O; Zn(NO3)2.6H2O; and Fe(NO3)3.9H2O). The effect of competing anions (100 mg/L, 250 mg/L and 500 mg/L of NO3−, HCO3−, SO42−, and PO43−) was evaluated in the 50 mg/L solution of Pd(II) or Pt(IV) at optimum conditions. Solutions of nitrate, bicarbonate, sulfate and phosphate anions were prepared from their respective sodium salts.

Stock solutions of 1000 mg/L of Pt(IV) and Pd(II) were prepared from K2PtCl6 and PdCl2, respectively, in 1.1 M HCl solution [1]. A 50 mg/L Pt or Pd solution was prepared from the stock solutions. The pH was adjusted to 2.0 ± 0.1 and 10 mL of each solution was transferred into a 15 mL tube containing 0.01 g of the adsorbent. The mixture was shaken for a predetermined period and filtered through a 0.45μm membrane syringe filter (Machery-Nagel GmbH & Co., KG, Germany). Then, Pt and Pd concentrations in the filtrate were measured using ICP-OES (Varian Vista MPX, USA). All experiments were performed in duplicate. The relative amount of Pt or Pd adsorbed, A(%), and the amount of Pt or Pd adsorbed per unit mass of the adsorbent, qt (mg/g), at any time t (min) were determined using the equations (Eq. 2) and (Eq. 3), respectively.

(3)

Q max bCe (1 + bCe )

q e = KF Cen

2.5. Adsorption experiments

V qt = (C0 − Ct ) ⎛ ⎞ ⎝m⎠

(6)

2.5.2. Isotherms The adsorption behavior of a solute on the adsorbent at equilibrium at constant temperature can be described using an adsorption isotherm. Hence, the amount of Pt(IV) and Pd(II) adsorbed per unit mass of ChDCMC was correlated with the liquid-phase concentration at equilibrium using Langmuir and Freundlich adsorption isotherms as given in Eqs. (7) and (8).

About 1 g of chitosan in 40 mL acetic acid (1%) and 0.25 g of DCMC in 25 mL deionized water were dissolved, separately. Then, the DCMC and chitosan solutions were mixed and stirred gently for 5 h at 45 °C. The DCMC cross-linked chitosan (Ch-DCMC) was precipitated in acetone (Scheme 1B). Subsequently, it was filtered, rinsed with deionized water and grinded after being dried at 70 °C for 12 h. The fine particle size (0.075–0.425 mm) was used [50]. The effect of the DCMC amount on cross-linking of chitosan was evaluated using 0.1 g, 0.25 g, 0.5 g, 0.8 g or 1 g of DCMC and 1 g of chitosan. The optimized chitosan derivative (Ch-DCMC) was investigated by X-ray powder diffraction (Thermo Scientific ARL X'Tra diffractometer, operated at 40 kV, 30 mA using Cu Kα radiation (λ = 1.5406 Å)), FTIR spectroscopy (Shimadzu IR Affinity-1S), and SEM images (JEOL JSM-7600F FEG SEM apparatus) and compared with native chitosan.

(2)

(5)

where qt is the amount of Pt(IV) or Pd(II) adsorbed on Ch-DCMC (mg/g) at time t, kp (mg/(g.min0.5)) is the intra-particle diffusion rate constant.

2.4. Cross-linking of chitosan using DCMC

⎜

1 + K2q e t

where qe is the metals uptake in mg/g at equilibrium, qt is the uptake at any time t (mg/g), and k1 and k2 are the pseudo-first-order (L/min) and pseudo-second-order (g/mg min) rate constants, respectively [51]. To evaluate the diffusion mechanism of Pt and Pd onto Ch-DCMC, the adsorption kinetics were examined by applying the Weber and Morris intra-particle diffusion model [52] as given by Eq. (6).

(1)

C − Ct ⎞ × 100% A% = ⎛ 0 ⎝ C0 ⎠

(4)

K2q 2e t

2.5.4. Regeneration experiment Regeneration tests were carried out by using Ch-DCMC adsorbent, which was previously loaded with 50 mg/L Pt or Pd solution in a batch adsorption experiment as described above. Then, the Pt or Pd loaded adsorbent was subjected to desorption by adding 10 mL of 0.25 M thiourea solution in 15 mL centrifuge tubes and shaking the tubes at

⎟

147

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Fig. 1. SEM image of A) Chitosan (Ch), B) Ch-DCMC, C) Ch-DCMC-Pd, and D) Ch-DCMC-Pt.

crystallinity of chitosan is a key-parameter in the accessibility to internal sites for both water and metal ions. Many studies have shown that decreasing the crystallinity results in an improvement in metal ion sorption properties [58–60]. The aldehyde content of DCMC was approximated by measuring the amount of reactive aldehydes available for imine formation using Eq.1. The aldehyde content in DCMC was found to be 73%. Li et al. [48] also found about 81% of the total aldehyde present in DCMC. The rest of the aldehyde groups may be in the hemiacetal or acetal form that protects the aldehyde from further reactions. The formation of dialdehyde groups of DCMC was confirmed by FTIR analysis. Fig. 3 A shows the appearance of characteristic IR adsorption bands at 1726 cm−1 and 885 cm−1 in DCMC compared with the spectrum of CMC, which clearly indicated the formation of aldehyde groups in DCMC. Jiang et al. [49] also reported the appearance of an aldehyde characteristic peak at 1730 cm−1 upon oxidation of CMC. Generally, the absorbance at about 1740 cm−1 is characteristic of aldehyde groups, while the band around 880 cm−1 is assigned to the formation of hemiacetal bonds between the aldehyde groups and neighbor hydroxyl groups which is consistent with the reported FTIR spectra of DCMC [48]. The FTIR spectra show a single broad peak around 3286 cm−1 for Ch-DCMC, compared to two peaks at 3288 cm−1 and 3354 cm−1 for chitosan (Fig. 3 A). The two peaks for chitosan indicate NeH stretching of primary amines (and OeH stretching), whereas the single peak indicates OeH stretching and/or NeH stretching of secondary amines as a result of crosslinking. The latter confirms that some of the primary amines of chitosan are cross-linked by the aldehyde group of DCMC. The FTIR spectra of Ch-DCMC after Pd(II) and Pt(IV) adsorption are also recorded and presented in Fig. 3 B. A detailed peak assignment is given in the supporting information. As seen in Ch-DCMC before adsorption, the broad band around 3286 cm−1 shows the overlapping of OH or NH2 stretching vibration, because of the hydroxyl and free amino groups in the crosslinked chitosan [18]. The FTIR spectrum of ChDCMC confirms that the peaks at 2866 cm−1 and 1379 cm−1 are due to CH3 symmetric stretch and CH3 bending vibration, respectively. The peaks at 1637 cm−1 and 1546 cm−1 are attributed to the amide I and II (NeH bending vibration) bands, respectively. The band around 1024 cm−1 is attributed to the combined effects of CeN stretching vibration of primary amines and the CeO stretching vibration from the primary alcohol in chitosan [36]. The decrease in intensity of the amide II band after Pt and Pd adsorption indicates that the amine group participates in the Pd(II) and Pt(IV) adsorption. This observation is consistent with the mechanism suggested in section 3.4. From the FTIR spectra (Fig. 3 B), we can also conclude that the material is stable under acidic conditions after adsorption of Pt and Pd because all peaks remain present.

200 rpm in a horizontal shaker for 4 h at 20 ± 1 °C. Subsequently, the suspensions were filtered and the Pt or Pd concentration in the filtrate was measured using ICP-OES. The regenerated adsorbents were rinsed several times with deionized water and dried at 70 °C for 12 h, before being used again in subsequent adsorption cycles. 3. Results and discussion 3.1. Characterization of the adsorbent An increase of the viscosity was clearly visible after the addition of DCMC indicating cross-linking of chitosan. From the secondary electron (SE) images, it is clear that the morphology of native chitosan flakes (Ch) is different from that of the Ch-DCMC (Fig. 1) which confirms crosslinking of chitosan. The SEM morphology of Ch-DCMC (Fig. 1 C and D) after five adsorption-desorption cycles of Pt and Pd shows that the chitosan still remains intact in a large entity. This indicates that the Ch-DCMC adsorbent is quite stable under acidic conditions. X-ray powder diffraction (XRPD) analysis revealed that structural changes occurred during the modification steps of chitosan into ChDCMC. Fig. 2 compares the XRPD results of native chitosan and the modified chitosan (Ch-DCMC). Chitosan presented poor crystallinity, as indicated by the presence of a broad peak at 20° [53] (Fig. 2). When the cross-linking agent (DCMC) is added, it further decreases the intensity of this peak. Similar results were previously reported for chitosan crosslinked with different crosslinking agents [54–56]. The crystallinity associated with chitosan is due to the presence of many –OH and -NH2 groups in its structure that hold and maintain the polymeric chains stable through intra- and intermolecular hydrogen bonding. However, as the DCMC is introduced in the chitosan chain, a change in the crystalline arrangement could be expected, especially from loss of the hydrogen bonding [57]. The

3.2. Effect of DCMC ratio on removal of Pt and Pd Fig. 2. XRPD spectra of chitosan and crosslinked chitosan (Ch-DCMC).

As is shown in Fig. 4, the Ch-DCMC adsorbents produced with 148

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Fig. 3. FTIR spectra of A) Chitosan, CMC, DCMC, and Ch-DCMC and B) Ch-DCMC, Ch-DCMC-Pt, and Ch-DCMC-Pd.

adsorption can be attributed to the abundant availability of the active sites in the initial stage. Later on, the process becomes relatively slower, and equilibrium conditions are reached within < 120 min. However, a contact time of 300 min has been chosen for subsequent adsorption experiments to ensure that maximum adsorption occurs. To explore the kinetics of adsorption of Pt and Pd ions onto ChDCMC, the experimental kinetic data of Pt(IV) and Pd(II) adsorption were fitted to a non-linear PFO kinetic model (Eq. 4) and PSO kinetic model (Eq.5) (section 2.5.1). The parameters obtained from the two kinetic models for the adsorption of Pt(IV) and Pd(II) on Ch-DCMC are listed in Table 1. In the case of Pd(II), the data fitted better according to the pseudo-first-order model with a high determination coefficient (R2) of 0.9593. Recently, Nagireddi et al. [15] also reported that the kinetics of Pd removal by chitosan cross-linked by glutaraldehyde was best fitted to a pseudo-first-order model. On the contrary, the kinetic data of Pt(IV) were well fitted to the pseudo-second-order model with R2 value of 0.9777. Furthermore, the equilibrium of Pd(II) uptake calculated from the pseudo-first-order model (51.7 mg/g) and qe calculated from the pseudo-second-order model for Pt(IV) (47.8 mg/g) were very close to the experimental values of 51.2 and 47.4 mg/g for Pd(II) and Pt(IV), respectively. As shown in Fig. 5, the adsorption was very fast for both the adsorbates at the initial adsorption stage. The initial adsorption rates (V0, mg/g min) were calculated based on V0 = k2qe2, and the adsorption rate of Pt(IV) (4.57 mg/g min) was higher than that of Pd(II) (2.88 mg/g min). This may be attributed to the difference in speciation of Pd and Pt at pH 2. A high initial slope is favorable for industrial applications because a high sorption capacity can be obtained with low residual concentrations in a short period of time and low metal loss in the effluent [62]. The rate of adsorption is usually limited by diffusion processes where diffusion occurs through four consecutive steps: a) transport of the adsorbate from the bulk solution to the boundary layer of the adsorbent particle, b) film diffusion or external diffusion, c) intra-particle diffusion, and d) interaction of the adsorbate molecules with adsorption sites [63]. In general, the 1st and the 4th step are very fast in a well agitated system and the total rate of the adsorption process is determined by film and/or intra-particle diffusion. The plots of the intraparticle diffusion model for the adsorption of Pt and Pd on Ch-DCMC are given in Fig. 6. They indicate that the Pt and Pd adsorption process involves a very rapid stage that is dominated by diffusion solely, until all adsorbate ions were removed from solution. Therefore, mass transfer from the bulk to intra-particles and film control the overall adsorption of Pd(II) and Pt(IV) on Ch-DCMC.

Fig. 4. Effect of crosslinking ratio on Pt and Pd removal using DCMC crosslinked chitosan.

various DCMC ratios showed similar Pd(II) removal. However, the Pt (IV) removal increases as the ratio of chitosan to DCMC increases from 0.1 to 0.25. Further increase in the amount of DCMC compared to chitosan resulted in a decrease of Pt(IV) removal. Therefore, the 1: 0.25 ratio was considered as the optimum cross-linking ratio of chitosan using DCMC. In general, increasing the crosslinking ratio increases the stability of the chitosan in acidic media, improving the Pt/Pd removal as the crosslinked materials are more easy to separate from solution by filtration; however, it also decreases the number of free and available amino groups on the chitosan backbone and the accessibility to inner sites of the sorbent [61], resulting in a loss of Pt/Pd removal capacity. Moreover, the crosslinks involve a loss in the flexibility of the polymer chain. 3.3. Uptake kinetics Study of the kinetics describes the equilibration time required for most favorable adsorption. The effects of different contact times on the adsorption of platinum and palladium ions onto Ch-DCMC at a concentration of 50 mg/L Pt(IV) or Pd(II), pH 2 and constant temperature are presented in Fig. 5. It was observed that the amount of Pt and Pd ions adsorbed onto the adsorbent increases with contact time. Fast adsorption occurs in the beginning, which gradually becomes slower until no further increase in adsorption is observed. The initial rapid 149

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Fig. 5. Effect of contact time on the removal of (A) Pt and (B) Pd at 1 g/L adsorbent dose, pH 2.0 ± 0.1 and initial element concentration of 50 mg/L, shaking time of 5 min to 24 h at 200 rpm at 20 ± 1 °C. Table 1 Parameters of the pseudo-first-order (PFO) kinetic model and pseudo-second order (PSO) kinetic model for Pt and Pd adsorption on Ch-DCMC. Parameter

qe,exp(mg/g) qe,cal(mg/g) k1(min−1) k2(g/(mg.min)) V0(mg/(g.min)) R2 χ2

Pt

Pd

PFO kinetic model

PSO kinetic model

PFO kinetic model

PSO kinetic model

47.42 46.32 0.052 – – 0.8698 10.74

47.42 47.79 – 0.002 4.57 0.9777 1.84

51.17 51.66 0.036 – – 0.9593 7.26

51.17 53.63 – 0.001 2.88 0.9047 17.02

Fig. 7. Effect of initial pH on the removal of Pt (pH 1–7) and Pd (pH 1–5) by ChDCMC at an adsorbent dose of 1 g/L and initial Pt/Pd concentration 50 mg/L, shaking at 200 rpm at 20 ± 1 °C.

with high concentrations of base metals [47], adsorption at lower pH is an advantage for selective precious metal ion recovery which can eliminate the adsorption of base metal ions. Previous reports also indicated that higher recoveries for precious metal ions using chemically modified chitosan were obtained at low pH (pH 1.0–4.0) [25,36,62,64]. The concentration of chloride ions was high enough to form chlorocomplexes because the Pd and Pt solutions were prepared in a high concentration of HCl (1.1 M). Consequently, Pd might be present as [PdCl4]2− and [PdCl3]2− while [PtCl4]2− and [PtCl6]2− might be the predominant Pt species [35,36]. These chloro-complexes of Pt and Pd then interact with the protonated amine groups of Ch-DCMC. The mechanism of precious metals recovery can involve electrostatic attraction, ion exchange, chelation and metal reduction, depending on the pH of the solution [27]. In acidic solutions, the amino groups are protonated and their availability for chelation of metal cations significantly decreases. Hence, the sorption of precious metals can possibly be explained by electrostatic attraction (Scheme 2) of anionic metal complexes, such as [PtCl6]2− and [PdCl4]2−, by protonated amine groups [27].

Fig. 6. Intra-particle diffusion plots of Pt(IV) and Pd(II) adsorption on ChDCMC.

3.4. Effect of pH The pH is a critical parameter for the design of an adsorption process because pH of the solution affects the material's surface charge and the speciation of metal ions and plays a critical role in the sorption of metal ions [21]. Therefore, the effect of pH on the adsorption of Pt(IV) and Pd(II) was studied individually by varying the pH of 50 mg/L initial metal concentration for a fixed adsorbent dosage of 1.0 g/L at 20 ± 1 °C. The results (Fig. 7) demonstrated that maximum adsorption occurred between pH 3.0 and 7.0 for Pt(IV) and between pH 3.0 and 5.0 for Pd(II). Pd(II) was tested only up to pH 5.0 as pH levels above 5 result in the precipitation of Pd(II). Furthermore, pH 2 was selected since at pH 3 and higher, large interference from base metals was observed during preliminary tests. As most wastewaters contain very low concentrations of precious metals (10–40 mg/L) and strong acids together

R-NH2 + HCl

RNH3+Cl-

2RNH3+Cl- + PtCl62-

(RNH3+)2PtCl62- + 2Cl-

2RNH3+Cl- + PdCl42-

(RNH3+)2PdCl42- + 2Cl-

Scheme 2. Possible mechanism of Pd(II) and Pt(IV) removal from aqueous acidic solution 150

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Fig. 8. Isotherms of equilibrium adsorption of A) Pt and B) Pd onto Ch-DCMC.

Values for adsorption capacity of other adsorbents presented in literature are given in Table 3. Crosslinking of chitosan significantly improved the adsorption capacity compared to chitosan flakes. Even though the Ch-GA showed higher adsorption capacity compared to DCMC, the synthetic crosslinking agent (GA) exhibits high cytotoxicity compared to an environmentally benign DCMC [49]. Therefore, DCMC could be an alternative crosslinking agent for chitosan for recovery of metals from aqueous solutions.

Table 2 Langmuir and Freundlich isotherm parameters of the adsorption of Pt and Pd on Ch-DCMC. Isotherm model

Parameters

Pt(IV)

Pd(II)

Langmuir

qmax (mg/g) b (L/mg) RL R2 χ2 KF((mg1–1/nL1/n)/g) n R2 χ2

80.83 0.46 0.008–0.176 0.9757 19.5 34.43 5.55 0.7811 175.9

89.38 2.01 0.002–0.048 0.9637 41.8 46.18 6.25 0.8042 206.6

Freundlich

3.6. Selectivity Common anions such as NO3−, HCO3−, SO42−, and PO43− at concentrations up to 500 mg/L do not show considerable interference on the adsorption of Pd and Pt (Fig. 9 A and B). However, the presence of Fe(III) ions slightly interferes with the recovery of Pt (Fig. 9 C). The uptake of coexisting metal ions, other than Pt or Pd, is almost negligible (Fig. 9 C and D). The main species of Pd and Pt ions are metal chloride anionic complexes ([PdCl4]2−and [PtCl6]2−) in acidic solutions [18]. However, the base metals, Cu, Zn, Fe, Co, and Ni, exist in their cationic forms in acidic solutions. The positively charged metal ions are repelled by the protonated amino groups of Ch-DCMC. Hence, the adsorption of Cu2+, Zn 2+, Fe3+, Co2+, and Ni2+ was negligible at pH ≤ 2. Only Fe3+ slightly interfered with the adsorption of Pt and Pd, which may be because of its ability to form chloride complexes in excess chloride ions in strongly acidic solution (pH ≤ 2) [18,65]. This result shows an excellent selectivity of Ch-DCMC for Pt(IV) or Pd(II) when co-existing with base metals in a solution.

3.5. Isotherm The adsorption behavior of a solute on an adsorbent at equilibrium at constant temperature can be described using an adsorption isotherm. The experimental data obtained for the adsorption of Pt(IV)and Pd(II) on Ch-DCMC plotted with Langmuir and Freundlich isotherm models (Fig. 8), and the isotherm constants are presented in Table 2. The amount of metal ions adsorbed at equilibrium per unit mass (qe) of the Ch-DCMC increased first with the increase of the equilibrium concentration of solutes (Ce), then almost reached plateau values, which indicates saturation of the active sites on Ch-DCMC. The Langmuir model gave the highest correlation coefficient values (R2) 0.9757 and 0.9637 (Table 2) and the qmax values were 80.8 mg/g and 89.4 mg/g for Pt(IV) and Pd(II) adsorbed on Ch-DCMC, respectively. The sorption capacity of Ch-DCMC at saturation of the monolayer was comparable for Pd(II) and Pt(IV). The observed qmax values are high enough to recover Pd and Pt from dilute waste solutions, in a single component system, using the Ch-DCMC adsorbent.

3.7. Reusability The reusability is an important characteristic of a good adsorbent because it significantly decreases the product cost in an industrial

Table 3 Summary of reported adsorption capacities of Pt and Pd onto biomaterials. Adsorbent

Glutaraldehyde crosslinked chitosan Glutaraldehyde crosslinked chitosan copolymer resin Chitosan based hydrogels Microalgae residue Chitosan flakes Polyacrylonitrile-based sorbent Ion-imprinted chitosan fiber Cross-linked chitosan/montmorillonite membrane Thiourea-modified chitosan L-lysine modified crosslinked chitosan Ethylenediamine-modified magnetic cross-linking chitosan nanoparticles Ch-DCMC

pH

Dose (g/L)

– 0.6 0.25 1 6 1 0.4 0.5 3.33 3.33 0.5 1

2 8 2 – 2 1.5 2 2 2 2 2 2

151

Adsorption capacity (mg/g) Pt(IV)

Pd(II)

300 – 235 156 66.6 5.97 – – 129.9 129.3 171 80.8

180 166.7 190 212 62.5 7.78 324.6 193 112.4 109.5 138 89.4

References

[35,62] [15] [66] [23] [28] [20] [18] [46] [36] [25] [8] This study

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Fig. 9. Effect of anions and other metal ions on the removal of Pd (A and C) and Pt (B and D) by Ch-DCMC at pH 2.0 ± 0.1.

Fig. 10. Pt and Pd removal using Ch-DCMC in successive adsorption cycles at pH 2 following desorption.

agent of chitosan for recovery of Pt and Pd from acidic solutions. The high selectivity of Ch-DCMC for platinum and palladium, in the presence of other base metals and common anions, showed its efficiency in separation of platinum and palladium from other metals and anions in aqueous acidic solutions. The adsorbent can be recycled without losing much of its original efficiency. Therefore, there are good prospects for Ch-DCMC in practical applications for the recovery of Pt(IV) and Pd(II) from dilute, acidic solutions. Further study on selectivity for Pt over Pd and vice versa from solution that contains both metal ions, as well as monitoring of the adsorbent efficiency using a real waste stream is necessary before industrial application.

application. After Pt(IV) or Pd(II) adsorption on the Ch-DCMC adsorbent at pH 2.0, the saturated Ch-DCMC was desorbed using 0.25 M thiourea and washed with deionized water. The regenerated Ch-DCMC was then reused in a subsequent adsorption cycle. Regeneration was studied in 5 adsorption–desorption cycles. Even in the 5th adsorptiondesorption cycle, 92.5% Pt and 97.3% Pd were adsorbed and 92.0% Pt and 90.1% Pd were desorbed (Fig. 10). This indicates the high potential of the Ch-DCMC for regeneration after recovery of both Pt and Pd from aqueous solution. 4. Conclusion A novel dialdehyde of carboxymethyl cellulose (DCMC) cross-linked chitosan (Ch-DCMC) adsorbent was prepared and shows high efficiency in the removal of Pt(IV) and Pd(II) ions from acidic solutions. Ch-DCMC showed high Pt and Pd adsorption capacity, but lower than that of the Ch-GA. However, the cross-linker (GA) exhibits high cytotoxicity compared to DCMC. Therefore, DCMC could be a viable crosslinking

Acknowledgment The first author acknowledges the financial support given by Gent University, Belgium, through a Special Research Fund fellowship (BOF, scholarship code: 01W05414). 152

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Declaration of interest

[25] K. Fujiwara, A. Ramesh, T. Maki, H. Hasegawa, K. Ueda, Adsorption of platinum (IV), palladium(II) and gold(III) from aqueous solutions onto L-lysine modified crosslinked chitosan resin, J. Hazard. Mater. 146 (1–2) (2007) 39–50. [26] B.C. Choudhary, D. Paul, A.U. Borse, D.J. Garole, Recovery of palladium from secondary waste using soluble tannins cross-linked Lagerstroemia speciosa leaves powder, J. Chem. Technol. Biotechnol. 92 (7) (2017) 1667–1677. [27] A. Ramesh, H. Hasegawa, W. Sugimoto, T. Maki, K. Ueda, Adsorption of gold(III), platinum(W) and palladium(II) onto glycine modified crosslinked chitosan resin, Bioresour. Technol. 99 (9) (2008) 3801–3809. [28] H. Sharififard, M. Soleimani, F.Z. Ashtiani, Evaluation of chitosan flakes as adsorbent for palladium and platinum recovery from binary dilute solutions, Int. J. Glob. Warming 6 (2–3) (2014) 303–314. [29] R. Jayakumar, D. Menon, K. Manzoor, S.V. Nair, H. Tamura, Biomedical applications of chitin and chitosan based nanomaterials-a short review, Carbohydr. Polym. 82 (2) (2010) 227–232. [30] C. Anchisi, M.C. Meloni, A.M. Maccioni, Chitosan beads loaded with essential oils in cosmetic formulations, J. Cosmet. Sci. 57 (3) (2006) 205–214. [31] P.K. Dutta, S. Tripathi, G.K. Mehrotra, J. Dutta, Perspectives for chitosan based antimicrobial films in food applications, Food Chem. 114 (4) (2009) 1173–1182. [32] M.Z. Trevino-Garza, S. Garcia, M.D. Flores-Gonzalez, K. Arevalo-Nino, Edible active coatings based on pectin, pullulan, and chitosan increase quality and shelf life of strawberries (Fragaria ananassa), J. Food Sci. 80 (8) (2015) M1823–M1830. [33] L.N. Rao, Coagulation and flocculation of industrial wastewater by chitosan, Int. J. Eng. Appl. Sci. 2 (2015) 2394–3661. [34] H.A. Shawky, A.H.M. El-Aassar, D.E. Abo-Zeid, Chitosan/carbon nanotube composite beads: preparation, characterization, and cost evaluation for mercury removal from wastewater of some industrial cities in Egypt, J. Appl. Polym. Sci. 125 (2012) E93–E101. [35] M. Ruiz, A.M. Sastre, E. Guibal, Palladium sorption on glutaraldehyde-crosslinked chitosan, React. Funct. Polym. 45 (3) (2000) 155–173. [36] L.M. Zhou, J.H. Liu, Z.R. Liu, Adsorption of platinum(IV) and palladium(II) from aqueous solution by thiourea-modified chitosan microspheres, J. Hazard. Mater. 172 (1) (2009) 439–446. [37] B.J. McAfee, W.D. Gould, J.C. Nadeau, A.C.A. da Costa, Biosorption of metal ions using chitosan, chitin, and biomass of Rhizopus oryzae, Sep. Sci. Technol. 36 (14) (2001) 3207–3222. [38] M.I. Shariful, T. Sepehr, M. Mehrali, B.C. Ang, M.A. Amalina, Adsorption capability of heavy metals by chitosan/poly(ethylene oxide)/activated carbon electrospun nanofibrous membrane, J. Appl. Polym. Sci. 135 (7) (2018). [39] G.H. Wang, J.S. Liu, X.G. Wang, Z.Y. Xie, N.S. Deng, Adsorption of uranium (VI) from aqueous solution onto cross-linked chitosan, J. Hazard. Mater. 168 (2–3) (2009) 1053–1058. [40] W.H. Cheung, Y.S. Szeto, G. McKay, Enhancing the adsorption capacities of acid dyes by chitosan nano particles, Bioresour. Technol. 100 (3) (2009) 1143–1148. [41] M. Auta, B.H. Hameed, Chitosan-clay composite as highly effective and low-cost adsorbent for batch and fixed-bed adsorption of methylene blue, Chem. Eng. J. 237 (2014) 352–361. [42] E. Guibal, N.V. Sweeney, M.C. Zikan, T. Vincent, J.M. Tobin, Competitive sorption of platinum and palladium on chitosan derivatives, Int. J. Biol. Macromol. 28 (5) (2001) 401–408. [43] B.J. Wang, Y. Zhu, Z.S. Bai, R. Luque, J. Xuan, Functionalized chitosan biosorbents with ultra-high performance, mechanical strength and tunable selectivity for heavy metals in wastewater treatment, Chem. Eng. J. 325 (2017) 350–359. [44] T. Budnyak, V. Tertykh, E. Yanovska, Chitosan immobilized on silica surface for wastewater treatment, Mater. Sci. Medziagotyra 20 (2) (2014) 177–182. [45] H. Sharififard, F.Z. Ashtiani, M. Soleimani, Adsorption of palladium and platinum from aqueous solutions by chitosan and activated carbon coated with chitosan, Asia Pac. J. Chem. Eng. 8 (3) (2013) 384–395. [46] J. Liu, L.C. Zheng, Y.W. Li, M. Free, M.Z. Yang, Adsorptive recovery of palladium(II) from aqueous solution onto cross-linked chitosan/montmorillonite membrane, RSC Adv. 6 (57) (2016) 51757–51767. [47] X.H. Ju, K. Igarashi, S. Miyashita, H. Mitsuhashi, K. Inagaki, S.I. Fujii, H. Sawada, T. Kuwabara, A. Minoda, Effective and selective recovery of gold and palladium ions from metal wastewater using a sulfothermophilic red alga, Galdieria sulphuraria, Bioresour. Technol. 211 (2016) 759–764. [48] H.L. Li, B. Wu, C.D. Mu, W. Lin, Concomitant degradation in periodate oxidation of carboxymethyl cellulose, Carbohydr. Polym. 84 (3) (2011) 881–886. [49] X.L. Jiang, Z. Yang, Y.F. Peng, B.Q. Han, Z.Y. Li, X.H. Li, W.S. Liu, Preparation, characterization and feasibility study of dialdehyde carboxymethyl cellulose as a novel crosslinking reagent, Carbohydr. Polym. 137 (2016) 632–641. [50] T.G. Asere, K. Verbeken, D.A. Tessema, F. Fufa, C.V. Stevens, G. Du Laing, Adsorption of As(III) versus As(V) from aqueous solutions by cerium-loaded volcanic rocks, Environ. Sci. Pollut. Res. 24 (25) (2017) 20446–20458. [51] K.V. Kumar, Linear and non-linear regression analysis for the sorption kinetics of methylene blue onto activated carbon, J. Hazard. Mater. 137 (3) (2006) 1538–1544. [52] N. Viswanathan, C. Sairam Sundaram, S. Meenakshi, Development of multifunctional chitosan beads for fluoride removal, J. Hazard. Mater. 167 (1–3) (2009) 325–331. [53] J. Kumirska, M. Czerwicka, Z. Kaczynski, A. Bychowska, K. Brzozowski, J. Thoming, P. Stepnowski, Application of spectroscopic methods for structural analysis of chitin and chitosan, Marine Drugs 8 (5) (2010) 1567–1636. [54] S.P. Kuang, Z.Z. Wang, J. Liu, Z.C. Wu, Preparation of triethylene-tetramine grafted magnetic chitosan for adsorption of Pb(II) ion from aqueous solutions, J. Hazard. Mater. 260 (2013) 210–219. [55] E.C.N. Lopes, K.S. Sousa, C. Airoldi, Chitosan-cyanuric chloride intermediary as a

None. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.reactfunctpolym.2019.05.008. References [1] M.R. Gandhi, M. Yamada, K. Haga, A. Shibayama, Synthesis of pincer-type extractants for selective extraction of palladium from PGMs: an improved liquid-liquid extraction approach to current refining processes, Sci. Rep. 7 (2017). [2] T.H. Nguyen, C.H. Sonu, M.S. Lee, Separation of Pt(IV), Pd(II), Rh(III) and Ir(IV) from concentrated hydrochloric acid solutions by solvent extraction, Hydrometallurgy 164 (2016) 71–77. [3] T. Kimuro, M.R. Gandhi, U.M.R. Kunda, F. Hamada, M. Yamada, Palladium(II) sorption of a diethylphosphate-modified thiacalix [6] arene immobilized on amberlite resin, Hydrometallurgy 171 (2017) 254–261. [4] A. Fornalczyk, Industrial catalysts as a source of valuable metals, J. Achiev. Mater. Manuf. Eng. 55 (2) (2012) 864–868 Online]. [5] K. Ravindra, L. Bencs, R. Van Grieken, Platinum group elements in the environment and their health risk, Sci. Total Environ. 318 (1–3) (2004) 1–43. [6] A. Lim, M.H. Song, C.W. Cho, Y.S. Yun, Development of surface-modified polyacrylonitrile fibers and their selective sorption behavior of precious metals, Appl. Sci. Basel 6 (12) (2016) 1–12. [7] K. Folens, T. Van Acker, E. Bolea-Fernandez, G. Cornelis, F. Vanhaecke, G. Du Laing, S. Rauch, Identification of platinum nanoparticles in road dust leachate by single particle inductively coupled plasma-mass spectrometry, Sci. Total Environ. 615 (2018) 849–856. [8] L.M. Zhou, J.P. Xu, X.Z. Liang, Z.R. Liu, Adsorption of platinum(IV) and palladium (II) from aqueous solution by magnetic cross-linking chitosan nanoparticles modified with ethylenediamine, J. Hazard. Mater. 182 (1–3) (2010) 518–524. [9] A.N. Nikoloski, K.L. Ang, D. Li, Recovery of platinum, palladium and rhodium from acidic chloride leach solution using ion exchange resins, Hydrometallurgy 152 (2015) 20–32. [10] M.K. Jha, J.C. Lee, M.S. Kim, J. Jeong, B.S. Kim, V. Kumar, Hydrometallurgical recovery/recycling of platinum by the leaching of spent catalysts: a review, Hydrometallurgy 133 (2013) 23–32. [11] M.K. Jha, D. Gupta, J.C. Lee, V. Kumar, J. Jeong, Solvent extraction of platinum using amine based extractants in different solutions: a review, Hydrometallurgy 142 (2014) 60–69. [12] W. Yoshida, Y. Baba, F. Kubota, N. Kamiya, M. Goto, Extraction and stripping behavior of platinum group metals using an Amic-acid-type extractant, J. Chem. Eng. Japan 50 (7) (2017) 521–526. [13] P. Weerawat, V. Nattaphol, U. Pancharoen, Selective recovery of palladium from used aqua regia by hollow fiber supported with liquid membrane, Korean J. Chem. Eng. 20 (6) (2003) 1092–1096. [14] X. Li, C.C. Zhang, R. Zhao, X.F. Lu, X.R. Xu, X.T. Jia, C. Wang, L.J. Li, Efficient adsorption of gold ions from aqueous systems with thioamide-group chelating nanofiber membranes, Chem. Eng. J. 229 (2013) 420–428. [15] S. Nagireddi, V. Katiyar, R. Uppaluri, Pd(II) adsorption characteristics of glutaraldehyde cross-linked chitosan copolymer resin, Int. J. Biol. Macromol. 94 (2017) 72–84. [16] S. Bratskaya, Y. Privar, A. Ustinov, Y. Azarova, A. Pestov, Recovery of Au(III), Pt (IV), and Pd(II) using pyridylethyl-containing polymers: chitosan derivatives vs synthetic polymers, Ind. Eng. Chem. Res. 55 (39) (2016) 10377–10385. [17] P. Chassary, T. Vincent, E. Guibal, Metal anion sorption on chitosan and derivative materials: a strategy for polymer modification and optimum use, React. Funct. Polym. 60 (2004) 137–149. [18] S. Lin, W. Wei, X.H. Wu, T. Zhou, J. Mao, Y.S. Yun, Selective recovery of Pd(II) from extremely acidic solution using ion-imprinted chitosan fiber: adsorption performance and mechanisms, J. Hazard. Mater. 299 (2015) 10–17. [19] M. Wojnicki, E. Rudnik, R.P. Socha, K. Fitzner, Platinum(IV) chloride complex ions adsorption on activated carbon organosorb 10CO, Aust. J. Chem. 70 (7) (2017) 769–775. [20] M.H. Morcali, B. Zeytuncu, Investigation of adsorption parameters for platinum and palladium onto a modified polyacrylonitrile-based sorbent, Int. J. Miner. Process. 137 (2015) 52–58. [21] S.Y. Wang, T. Vincent, J.C. Roux, C. Faur, E. Guibal, Pd(II) and Pt(IV) sorption using alginate and algal-based beads, Chem. Eng. J. 313 (2017) 567–579. [22] S.Y. Wang, T. Vincent, J.C. Roux, C. Faur, E. Guibal, Innovative conditioning of algal-based sorbents: macro-porous discs for palladium sorption, Chem. Eng. J. 325 (2017) 521–532. [23] K. Khunathai, K. Inoue, K. Ohto, H. Kawakita, M. Kurata, K. Atsumi, H. Fukuda, S. Alam, Adsorptive recovery of palladium(II) and platinum(IV) on the chemically modified-microalgal residue, Solvent Extraction Ion Exch. 31 (3) (2013) 320–334. [24] S. Mincke, T.G. Asere, I. Verheye, K. Folens, F.V. Bussche, L. Lapeire, K. Verbeken, P. Van Der Voort, D.A. Tessema, F. Fufa, Functionalized chitosan adsorbents allow recovery of palladium and platinum from acidic aqueous solutions, Green Chem. 21 (2019) 2295–2306, https://doi.org/10.1039/C9GC00166B.

153

Reactive and Functional Polymers 141 (2019) 145–154

T.G. Asere, et al.

[56] [57]

[58]

[59] [60]

[61] C. Milot, J. McBrien, S. Allen, E. Guibal, Influence of physicochemical and structural characteristics of chitosan flakes on molybdate sorption, J. Appl. Polym. Sci. 68 (4) (1998) 571–580. [62] E. Guibal, A. Larkin, T. Vincent, J.M. Tobin, Chitosan sorbents for platinum sorption from dilute solutions, Ind. Eng. Chem. Res. 38 (10) (1999) 4011–4022. [63] S.K. Theydan, M.J. Ahmed, Adsorption of methylene blue onto biomass-based activated carbon by FeCl3 activation: equilibrium, kinetics, and thermodynamic studies, J. Anal. Appl. Pyrolysis 97 (2012) 116–122. [64] M.L. Arrascue, H.M. Garcia, O. Horna, E. Guibal, Gold sorption on chitosan derivatives, Hydrometallurgy 71 (1–2) (2003) 191–200. [65] C. Mack, B. Wilhelmi, J.R. Duncan, J.E. Burgess, Biosorption of precious metals, Biotechnol. Adv. 25 (3) (2007) 264–271. [66] D. Sicupira, K. Campos, T. Vincent, V. Leao, E. Guibal, Palladium and platinum sorption using chitosan-based hydrogels, Adsorpt. J. Int. Adsorption Soc. 16 (3) (2010) 127–139.

source to incorporate molecules-thermodynamic data of copper/biopolymer interactions, Thermochim. Acta 483 (1–2) (2009) 21–28. A. Khan, S. Badshah, C. Airoldi, Dithiocarbamated chitosan as a potent biopolymer for toxic cation remediation, Colloids Surf. B-Biointerfaces 87 (1) (2011) 88–95. M. Monier, D.A. Abdel-Latif, Y.G. Abou El-Reash, Ion-imprinted modified chitosan resin for selective removal of Pd(II) ions, J. Colloid Interface Sci. 469 (2016) 344–354. M.O. Machado, E.C.N. Lopes, K.S. Sousa, C. Airoldi, The effectiveness of the protected amino group on crosslinked chitosans for copper removal and the thermodynamics of interaction at the solid/liquid interface, Carbohydr. Polym. 77 (4) (2009) 760–766. X.H. Tang, X.M. Zhang, C.C. Guo, A.L. Zhou, Adsorption of Pb2+ on chitosan crosslinked with triethylene-tetramine, Chem. Eng. Technol. 30 (7) (2007) 955–961. L.F. Qi, Z.R. Xu, Lead sorption from aqueous solutions on chitosan nanoparticles, Colloids Surf. Physicochem. Eng. Aspects 251 (1–3) (2004) 183–190.

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