Simultaneous sorption of dyes and toxic metals from waters using synthesized titania-incorporated polyamide

Accepted Manuscript Simultaneous sorption of dyes and toxic metals from waters using synthesized titania-incorporated polyamide

Islam Ali, Saddam A. AL-Hammadi, Tawfik A. Saleh PII: DOI: Reference:

S0167-7322(18)32710-7 doi:10.1016/j.molliq.2018.08.081 MOLLIQ 9526

To appear in:

Journal of Molecular Liquids

Received date: Revised date: Accepted date:

24 May 2018 10 August 2018 11 August 2018

Please cite this article as: Islam Ali, Saddam A. AL-Hammadi, Tawfik A. Saleh , Simultaneous sorption of dyes and toxic metals from waters using synthesized titaniaincorporated polyamide. Molliq (2018), doi:10.1016/j.molliq.2018.08.081

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ACCEPTED MANUSCRIPT Simultaneous sorption of dyes and toxic metals from waters using synthesized titania- incorporated polyamide

Islam Ali 1, Saddam A. AL-Hammadi 2, Tawfik A. Saleh 1 * Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261,

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Saudi Arabia

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Dhahran 31261, Saudi Arabia

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Department of Chemical Engineering, King Fahd University of Petroleum & Minerals,

(966) 13 860 4277

Phone # (966) 13 860 1734

http://faculty.kfupm.edu.sa/CHEM/tawfik/publications.html

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Home Page:

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Fax:

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*Correspondence to: E-mail address: [email protected] ; [email protected]

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Abstract

Interfacial polymerization of trimesoyl chloride (TMC) and 1,3- phenylene diamine (MPD) was

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simultaneously combined with the in-situ formation of TiO2 from TiCl4 using urea. The titaniapolyamide nanocomposite (TPN) was characterized by using X-ray diffraction, Fourier transform

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infrared spectroscopy, N2-physisorption analysis and a scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. The TPN was evaluated as an adsorbent for the removal of

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dyes. It showed high efficiency for the removal of several dyes in the order: methylene blue > bromo phenol > methyl orange > congo red > rhodamine B. The dosage, contact time, and temperature which are the main factors that affect adsorption efficiency, were optimized. Among isotherm models, the experimental adsorption results fitted well with the Langmuir model with a maximum adsorption capacity of 43 mg/g. Kinetic experiments were conducted to describe the equilibrium rate. The model of the pseudo-second-order adequately fitted the experimental data with a correlation coefficient R2 of 0.998. Thermodynamic studies were performed to evaluate the performance of TPN at various temperatures. Thus, parameters including free energy (ΔGo),

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ACCEPTED MANUSCRIPT enthalpy (ΔHo) and the entropy (ΔSo) were calculated. The influence of the interference on adsorption was investigated in the presence of metals including Ni, Hg, As, Cu, and Cr. Interestingly, with ≈100% removal of the dye, TPN showed a rapid simultaneous uptake of the toxic metals as well.

Keywords: Interfacial polymerization; in-situ titania formation; wastewater treatment;

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nanocomposites; toxic metals.

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1. Introduction

Wastewater contaminated with dyes and toxic heavy metals is a serious environmental problem

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caused both by industrial and everyday activities. Synthetic dyes are difficult to biodegrade due to their stability. Several industries such as plastics, paper textiles, and cosmetics use a large variety of

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dyes to change the color of their products [1, 2]. This process leads to a discharge of effluents containing toxic dyes that can cause ecological problems [3, 4]. Effluents from textile industries are

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a significant contributor to water pollution because dyes undergo biological and chemical changes in which dissolved oxygen leads to the destruction of aquatic life. Moreover, the products of the

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degradation of certain dyes may be toxic and carcinogenic. Therefore, the treatment of textile effluents before their disposal into the receiving water is important to save the environment.

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There are different methods for removal of dyes from industrial wastewater like adsorption, coagulation, flotation, electrochemical techniques, biological treatments, and oxidation [5-7].

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However, most types of dyes, such as neutral red, are soluble in aqueous solutions making many conventional treatment methods ineffective for the removal of dyes from wastewater [8, 9]. One of

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the most effective methods is adsorption which is highly efficient, readily available and easy to handle [10, 11]. Adsorption is widely used and is a well-known process of separation for dealing with certain types of chemical pollutants, particularly those that are not removed by the biological treatments of wastewater [12, 13]. Compared with other techniques, adsorption shows superior efficiency for the removal of pollutants due to its ease of operation, high efficiency, insensitivity to toxic pollutants and its simplicity [14, 15]. Several types of adsorbents used for different applications are being developed and some of these have been commercialized [5–10].

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ACCEPTED MANUSCRIPT The development of adsorbents which have excellent properties such as mechanical strength, rapid adsorption rate and a high capacity for adsorption, has attracted interest in wastewater treatment technology. Several adsorbents, including polymers with functional groups, have become very important due to their capacity for adsorption, particularly their reuse [16, 17]. Many types of adsorbents, polymers, activated carbon, clays and fly ash, have been reported with their efficiency in dyes and toxic metals removal [18, 19]. The important factors which should be considered when selecting adsorbents include the surface area and the number of active sites. The small diffusion

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resistance and surface nature of adsorbents make them valuable for practical use [20]. Due to their

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reduced costs, improved mechanical properties, stability, and chemical inertness, polymer

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composites have been used as promising adsorbents. Polymers have been used as flexible and elastomeric matrices that possess many physical properties such as strength, flexibility, high

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elasticity, bulk and controlled surfaces. The composites share the properties of both the inorganic particles and the polymers. Materials called multiphase which have one component constituent of nanoparticles in the nanoscale range (<100 nm) in at least one dimension are referred to as

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nanocomposites [21, 22]. To the best of the author's knowledge, the idea of simultaneous interfacial

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polymerization and in-situ formation of TiO2 has not been reported. Here, the interfacial polymerization of trimesoyl chloride (TMC) and 1,3- phenylene diamine (MPD)

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was simultaneously combined for the first time with the in-situ formation of TiO2 from TiCl4 using urea. The obtained novel TiO2- polyamide nanocomposite (TPN) was characterized to get insights

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into its structure and morphology. Dye polluted solutions were used to test the removal efficiency of TPN. Thus, dosage, contact time, and temperature were optimized. TPN showed excellent

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efficiency for the simultaneous removal of dyes and toxic metals, proving its usability in water

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treatment.

2. Experimental 2.1. Chemicals

The used chemicals, including titanium chloride (molecular weight of 189.68 g/mol and purity of 99 %), hexane (molecular weight of 86.18 g/mol and purity of 99 %), urea (molecular weight of 63.05 g/mol and purity of 98 %), and trimesoyl chloride, C9H3Cl3O3, (TMC) (molecular weight of 265.47 g/mol, and purity of 98 %) were purchased from Sigma Aldrich. 1,3 Phenylene diamine, C6H4(NH2)2, (MPD) (molecular weight of 108.14 g/mol and purity of 98%) was purchased from Fluka.

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ACCEPTED MANUSCRIPT 2.2. Synthesis of Materials The titania-polymer nanocomposite (TPN) was synthesized by in situ interfacial polymerization which was simultaneously combined with the in-situ formation of TiO2 from TiCl4 using urea. About 100 mL de-ionized water was used to dissolve 2 gm of 1, 3 phenylene diamine. 20 ml of TiCl4 was then added to the phenylene diamine solution. Then 1.5 g of urea was added and stirred for 10 min. On the other side, 50 ml hexane was used for dissolving 0.2 g of trimesoyl chloride by sonication.

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This solution was added dropwise to the previous mixture under continuous stirring. After that, the

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complete mixture was kept under stirring for about 24 h, then it was heated at 70 oC for 3 h. The

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obtained composite was filtered and washed to remove any unreacted components. For the purpose of comparison, both pure titania and pure polyamide were also prepared. The

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polyamide was prepared by following the same steps without adding TiCl4. While titanium oxide was prepared by the following steps; TiCl4 of volume 50 ml was added slowly to distilled water (200

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ml) in an ice bath, after that the beaker was transferred to room temperature. The beaker was kept under stirring for 30 min and the urea (1.5 g) was dissolved in water and then added. The bath

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temperature increased to 150 Co which was maintained. Urea was added to the solution to enhance the formation of hydroxides. The solution became white colloidal without precipitation, then the

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solution reaction was left to settle, cool and finally washed 3 times with distilled water [23-26].

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2.3.Characterization and analysis

A scanning electron microscope (SEM) was used to describe the morphology of TPN. An X-Max

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detector fitted with energy-dispersive X-ray spectroscopy (EDX) was used for the elemental analysis. X-ray mapping was used to illustrate the distribution of titania on the surface of the TPN.

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The X-ray powder diffraction (XRD) diffractogram was obtained using an X-ray diffractometer through radiation of Cu-Kα. The BET surface area was measured on a Micromeritics TriStar II Plus automatic analyzer using N2 adsorption-desorption at −196◦C. Prior to measurement, the sample was degassed at 150 ◦C for 3 h to remove impurities or moisture. The Brunauer, Emmett, and Teller (BET) method were used to calculate the surface area. A Thermo Scientific FTIR spectrometer was used to perform IR measurements with a deuterated triglycine sulfate detector. Spectra background corrections were done at a resolution of 2 cm-1 and 32 scans were made.

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ACCEPTED MANUSCRIPT A UV-vis spectrophotometer with optical quartz cuvettes was used to monitor the dyes concentrations. An Inductively Coupled Plasma Mass Spectrometer (ICP-MS ) was used to analyze the concentration of metal ions in the samples.

2.4.Adsorption evaluation A methylene blue (MB) dye solution with a concentration of 16 ppm was prepared. The initial pH of the solution was 6. Then, TPN was added and the contents were stirred for various periods and

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at different temperatures. Then, at different intervals, aliquots were collected and analyzed using

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UV-vis spectrophotometer at ʎ of 665 nm. The removal percentage of the dyes was then calculated.

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In this study, several factors were investigated such as the dosage effect, contact time, temperature and interference effect. For evaluating the dosage effect, the initial concentration of the dye was

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kept constant, 16 ppm. Different dosages of the TPN were used. Then experiments at different temperatures of 298, 318 and 338 K were done to describe the thermodynamic and kinetic

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parameters. The interference effect was studied using 20 mg of adsorbent in 16 ppm dye solution spiked with 1 ppm of metals including Ni, Cu, Pb, Se, As, Hg, Cd, and Cr. The removal percentage

(𝐶𝑖 − 𝐶𝑡 )𝑉 𝑊

(1)

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𝑞𝑡 =

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of the adsorbent is computed using equations 1 and 2:

(2)

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𝐶𝑖 − 𝐶𝑡 % 𝑎𝑑𝑠𝑜𝑟𝑏𝑒𝑛𝑡 𝑢𝑝𝑡𝑎𝑘𝑒 = ( ) × 100 𝐶𝑖

where, Ci and Ct represent concentrations of methylene blue (MB) (initial and final, respectively);

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V and W denote the volume of solution (L) and material weight (g). The capacity of adsorption at different times and equilibrium are expressed as qt and qe, respectively, where in the case of qe, the

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equilibrium concentration Ce is used instead of Ct. The analysis was done in triplicate and the average value was taken.

3. Results and discussion 3.1. Characterizations of the samples. From the XRD diffractogram, there are characteristic peaks of titania nanoparticles that can be observed at 2θ of 25.3ᵒ, 38.2ᵒ, 47.9ᵒ ,54.2ᵒ, 64.3ᵒand 77.1ᵒ, as shown in Fig. 1. Also, there is a characteristic peak of the polymer at 18.6ᵒ. Peaks at 2θ of 8.4ᵒ and 20.7ᵒ are related to the TPN 5

ACCEPTED MANUSCRIPT structure clarifying its crystalline nature [27-29]. From the results, the successful embedding of titanium oxide into the polyamide confirmed the formation of TPN. (20.7) (8.4)

(25.3)

(18.6)

(38.2)

(54.2)

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(47.9)

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(b)

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10

20

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Intensity (a.u)

(a)

30

40

50

(77.1)

(64.3)

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70

80

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2θ

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Fig. 1. The XRD diffractogram for (a) titania-Polyamide and (b) titania.

Fig. 2a illustrates the SEM image indicating the morphology of the sample in which the nanoparticles are embedded. The EDX describes the presence of elements which can be observed at

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0.277 for carbon, 0.392 for nitrogen and 0.525, 4.5 and 4.9 keV for titanium. The nitrogen peak is overlapped with the oxygen and titanium peaks. The spectrum clarifies a set of peaks for titanium

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represented by 15.87 wt% and 36.49 for Ti and O, respectively. This wt % indicates that titanium oxide is embedded successfully inside the polyamide. Fig. 2b depicts the X-ray mapping which

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shows the dispersion of titania nanoparticles within the polymer. As shown in the mapping images for titanium, there is a uniform distribution of the nanoparticles inside the composite. This was confirmed by the TEM image Fig. 2c, which shows the formation of titania particles within the polymer.

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(c)

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(b)

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(a)

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Fig. 2. SEM image of TPN and the EDX spectrum with a table of EDX elemental analysis (a);

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X-ray mapping of Ti and O in the TPN (b) and TEM image of the prepared TPN (c).

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The N2-physisorption analysis was performed to investigate the textural properties of TPN. Fig. 3 (a) depicts the BET isotherm plot which indicates that the isotherm belongs to type II with uniform surface energy and multilayer adsorption. The uptake of nitrogen at relatively low pressures gives an indication for the sample with a microporous structure. The mesoporous structure of TPN has been confirmed by a loop of hysteresis at a pressure that is relatively high. Other parameters obtained from the analysis were summarized in Table 1. The BET surface area of the TPN nanocomposite is shown to be 75 m²/g compared with 10 (m2/g) of the polymer. The pore size distribution indicated that the TPN material has a size in the range of 20- 100 nm, as shown in Fig. 3 (b).

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Fig. 3. BET data of TPN: (a) Nitrogen adsorption/desorption isotherms, (b) pore size distribution curve

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Table 1: The BET parameters of TPN and polyamide

TPN

polyamide

0.13 cm³. g-1

0.12 cm³. g-1

Micropore volume

0.14 cm³. g-1

0.15 cm³. g-1

Average pore diameter

94.4 Å

82 Å

Mesopore surface area

53.1 m². g-1

7 m². g-1

Micropore surface area

22.5 m². g-1

3 m². g-1

75 m². g-1

10 m². g-1

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Total pore volume

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Parameter

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BET surface area

Fig. 4 illustrates the FTIR spectra of polyamide and TPN composite. The broad band observed in the range of 3300-3500 cm-1 was attributed to N-H stretching vibration of 1,3 phenylenediamine. The peaks recorded at 2920 cm-1 and 2850 cm-1 were related to C-H stretching vibration. Another absorption band for C=O stretching vibration appeared at 1620 cm-1 [30].

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3.2. Evaluation of adsorption efficiency

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Fig. 4. FTIR spectra of (a) polyamide and (b) titania-polyamide (TPN).

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3.2.1. Evaluation of the adsorption of various dyes. The adsorption efficiency of the prepared TPN material was tested using different dyes. The dye

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solutions were prepared separately, and 20 mg TPN was added to each of them. The contact time was allowed until equilibrium was obtained. The concentration of the dye was determined by a UV-

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vis spectrophotometer. It was found that the performance of the TPN differs from one dye to another depending on the nature and the structural size of the dyes. The percentage removal of the dyes over

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the TPN was found to be in the following order of methylene blue > bromo phenol > methyl orange > congo red > rhodamine B, Fig. 5. For MB, the removal was ≈ 100 % so it was chosen for further investigation in this work. It should be also mentioned that the adsorption efficiency of TPN, titania, and polyamide was tested under the same conditions. TPN showed better efficiency than both titania and pure polyamide because TPN composite combines the properties and the functional groups of both titania and polyamide. This allows having more active sites for adsorption.

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Fig. 5. Scheme illustrating the colour changes of the dye solutions before and after the

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interaction with TPN; [ experimental conditions: adsorbent mass 20 mg, volume 20 mL of each

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dye solution, contact time 60 min, temperature 298 K].

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3.2.2. Contact Time

Different dosages of TPN (5, 10, and 20 mg) were added to dye solutions (30 mL each) having an initial concentration of 16 ppm. In these batch experiments, the dependence of the adsorption capacity on contact time at a room temperature of 298 K was evaluated. The fast dye adsorption rate with steep slopes indicates that the adsorption equilibrium was obtained within 20 min as shown in Fig. 6. This fast uptake makes the TPN promising for its use in real treatments.

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60

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20 mg 10 mg

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60

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0

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5 mg

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time (min)

Fig. 6: Effect of contact time on adsorption of MB with solutions containing different TPN masses

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[Experimental conditions; the amount of TPN: 5, 10 and 20 mg, medium volume: 30 mL,

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concentration of MB (16 ppm) and temperature: 298 K].

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3.2.3. Adsorption kinetics

Kinetic models of pseudo-second order and Lagergren's first order were used for examining the

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adsorption mechanisms. Linear equation (3) was used for the first order model [31]: (3)

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ln(𝑞𝑒 − 𝑞𝑡 ) = ln 𝑞𝑒 − 𝑘1 𝑡

Where the dye amount (mg. g-1) is adsorbed at equilibrium and t which are represented by qe and qt respectively, while the rate constant is represented by k1. qe and k1 values were obtained by plotting ln (qe - qt) versus t as shown in Fig. S1a and Table 2. The poor correlation coefficients (R2) and the disagreement between the calculated values of (qe, cal) and the experimental (qe, exp), gives an indication that the adsorption rate does not correlate with the first-order model. When studying the second-order rate of adsorption, the following equation (4) was used for that [32]:

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ACCEPTED MANUSCRIPT 𝑑𝑞𝑡 = 𝑘2 (𝑞𝑒 − 𝑞𝑡 )2 𝑑𝑡

(4)

Where the rate constant is represented by k2, qt and qe are the capacities of adsorption at time t and at equilibrium. The linear form of the pseudo-second-order is described as the following: 𝑡 1 𝑡 = + 𝑞𝑡 𝑘2 𝑞𝑒2 𝑞𝑒

(5)

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Where the rate constant value k2 is obtained from the plot of t/qt versus t as shown in Fig. S1b. There

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is an agreement between qe, exp and the qe, cal and the high correlation coefficient values clarified that

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the process of adsorption fitted to the pseudo-second-order model. This is an indication that the dye ions adsorption possibly occurred via a predominantly chemical interaction.

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Weber’s intraparticle diffusion model was used for fitting the adsorption results [3334], by using equation 6:

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qt  ki d t 1/ 2  C

(6)

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Where the rate constant of intraparticle diffusion is represented by a kid (mg. g-1• min1/2), and the intercept (mg. g-1) is C. As per the experimental data, the linearity varies to some extent when

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plotting qt versus t1/2 which indicates the rate-limiting step by intraparticle diffusion. As shown in Fig. S1c, the intraparticle diffusion is represented by linear portions.

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The external surface adsorption is the first stage and was completed within the first min. The second stage represents the intraparticle diffusion stage known as the rate determining step. This stage was

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observed in less than 20 min. The plot contains a third region where the interparticle diffusion begins to diminish. The linear line of the second stage didn’t intercept with the origin point because the

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final and initial stages of the adsorption process have a different mass transfer rate indicating that the interparticle diffusion wasn’t the only rate limiting step.

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ACCEPTED MANUSCRIPT Table 2. Kinetic parameters of dye adsorption on the TPN; Ci (16 ppm)

qe, exp (mg/g)

-1

qe, cal

(min )

(mg/g)

0.052

6.78

k2a

R2

qe, cal

0.0112

23.1

kidb

R2

(mg/g)

0.64

Intraparticle diffusion

C (mg/g)

0.998

0.163

1.36

R2

0.976

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22.7

k1

Pseudo-second order

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Lagergren's first order

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3.2.4. Adsorption Isotherms

A good analysis of adsorption capacities was conducted using isotherm models with fundamental

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physicochemical data. The Isotherm model of Langmuir is based on the idea of a homogenous

through it, as [34]:

(7)

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𝐶𝑒 1 𝐶𝑒 = + 𝑞𝑒 𝑘𝐿 𝑞𝑚 𝑞𝑚

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monolayer surface phase. The nature of the process, either chemical or physical, can be described

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Where kL (L.mg-1), qm (mg. g-1), qe (mg. g-1) and Ce (mg. L-1) clarify the sites of adsorption affinity; the theoretical monolayer adsorption capacity, the amount adsorbed of MB and its equilibrium

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concentration, respectively.

Fig. S2a shows the Ce/qe versus Ce plot, where the kL and Langmuir constant qmv values are

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obtained from the slope and intercept, shown in Table 3. The dimensionless equilibrium parameter RL is given in equation (8) [35]: 𝑅𝐿 =

1 1 + 𝐾𝐿 𝐶𝑜

(8)

Where the initial solute concentration is Co. RL is the equilibrium factor and indicates the adsorption, if RL = 1 linear, RL>1 unfavourable, 0 < RL< 1 favourable and RL = 0 irreversible. The adsorption favorability by the RL value of 0.13 was confirmed. The TPN adsorption capacity (qm) and other parameters are listed in Table 3. 13

ACCEPTED MANUSCRIPT Heterogeneous surfaces and their adsorption characteristics were illustrated by the Freundlich model considering the interactions of adsorbed molecules [36], as: 1

𝑞e = 𝐾f 𝐶𝑒𝑛

(9)

Kf (mg. g-1) represents the constant of the Freundlich isotherm and 1/n describes the capacity of adsorption and its intensity, respectively. The adsorbate concentration (mg. L-1) and the amount 1 ln𝐶e 𝑛

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ln𝑞e = ln𝐾f +

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adsorbed (mg. g-1) at equilibrium are represented by Ce and qe. The model is: (10)

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The plot ln qe versus ln Ce is used to calculate the values of KF and n as shown in Fig. S2b and included in Table 3. The nature of the adsorption processes is described by the n value where: 1/n

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<1 and > 1 imply a cooperative and a normal adsorption, respectively. The obtained results indicate the 1/n value of ≈ 0.22.

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A linear decrease in adsorption energy due to the interaction between adsorbent and adsorbate is assumed by the Temkin model and given as [37]: 𝑅𝑇 𝑅𝑇 ln 𝐾𝑇 + ln 𝐶𝑒 𝑏𝑇 𝑏𝑇

(11)

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𝑞𝑒 =

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Where bT represents the Temkin isotherm constant and shows the sorption heat (J/mol), while kT represents the binding constant of the Temkin isotherm equilibrium which describes the highest

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energy binding (L. g-1). T and R are representing the temperature (K) and gas constant, respectively. The isotherm constants are obtained by plotting the qe versus the ln Ce, as shown in

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Fig. S2c.

Table 3. Isotherm parameters of Langmuir, Freundlich, and Temkin for the dyes adsorption Langmuir qm

kL

(mg/g) (L/mg)

RL

Freundlich R2

1/n

n

kf ( mg/g)

14

Temkin R2

KT

bT

(L/g) (KJ/mol)

R2

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0.833

0.13

0.9606

0.22

4.59

3.13

0.9254

1.004

0.383

0.8775

3.2.5. Thermodynamic study Thermodynamic adsorption parameters such as free energy (ΔGo), enthalpy (ΔHo) and the entropy

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(ΔSo) can be determined to illustrate the process of adsorption and are evaluated using the following

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equations (12, 13, 14 and 15).

𝐸𝑎 − constant 2.303𝑅𝑇

(12) (13) (14) (15)

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log 𝑘2 =

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Kc =CAe/Ce ΔGo = −RT ln Kc ΔGo = ΔHo−TΔSo

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After carrying out the adsorption processes at three different temperatures of 298 K, 318 K, and 338 K, it was found that the removal rate decreases as the temperature of adsorption increases, as shown in Fig. 7. The Van’t Hoff equation is used to obtain the lnKc versus 1/T plot in the linear form gave

H 0 S 0  RT R

(16)

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ln Kc  

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the ΔHo and ΔSo values which can be used to compute the ΔGo using Eq. (14):

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The MB adsorption on TPN was found to be exothermic. The adsorption thermodynamic parameters were calculated. The ΔG⁰ values were in the range of -8.4 (KJ/mol ) for 298 K, -5.5 (KJ/mol ) for

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318 K and to -2.6 (KJ/mol ) for 348K. These values clarified the exothermic behavior for the process of adsorption. As the temperature increases, there is a decrease in the absolute values of ∆Go which indicates that the adsorption of the dye on TPN is an unfavorable process. On the other side, the negative value of enthalpy ∆Ho which is ≈ -51 kJ/mol shows the adsorption as an exothermic process, while the negative value of the entropy ∆So of -140 J/mol.K reflects the low affinity of the adsorbent toward the pollutant molecules at high temperature.

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(a)

80

% Removal

(i)

60 (ii)

40 (iii)

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20 0

20

40

60

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time (min)

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(b)

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Fig. 7: The plots of (a) MB percentage removal versus time at different temperature; (b) Plot of ln Kc versus 1/T]. [Experimental conditions; TPN amount: 20 mg, medium volume: 30 mL, concentration of MB (16 ppm) and temperature: (i) 298 K, (ii) 318 K, (iii) 338 K.

3.2.6 Metals interference effect and recycling Industrial contamination contains many pollutants which are classified into organic and inorganic components. The process of dye adsorption may be affected by the presence of heavy metals, so it is necessary to investigate the influence of the components. Thus, the removal of MB was performed in the presence of several metals; As, Se, Cu, Pb, Hg, Cd, Cr, and Ni. Then, the dye concentration was analyzed using a UV-vis spectrophotometer and the metals were analyzed using ICP-MS. As 16

ACCEPTED MANUSCRIPT shown in Fig. 8, the results, indicated that the TPN adsorbed almost 98% the dye. In addition, metals like As, Se, Cu, Pb, and Hg were highly co-adsorbed by TPN. This indicates that the TPN has a high efficiency toward cationic species [38-43]. The analysis of the adsorbent after dye adsorption was conducted to understand the nature of the interaction. As shown in Figure 9, the morphology has not been changed significantly, however, the FTIR spectrum shown more bands as a result of dye adsorbent interaction. As the nitrogen is part of the methylene blue, the nitrogen mapping was conducted and the image indicated that the dye was dispersed on the TPN. The decrease in the

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affinity of adsorption of some metals could be due to the simultaneous removal of many metals along

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with the dye. There could be a metal-dye interaction as proposed in the mechanism shown in Fig.

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10. Thus, the electrostatic interactions cannot be the only adsorption force, and other complex and varying kinds of interactions could be involved in the adsorption. Possible mechanisms for the

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adsorption are proposed in, Fig. 10, including the π-π interaction and the electrostatic interaction. In addition, a complexation interaction between MB and metals could take place, which can be explained by the high adsorption of MB and the metal ions.

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The possibility to recycle the adsorbents, which is important to the industry, was also studied. The spent adsorbent was treated with acetone to dissolve dye and then was treated with a 1M solution of

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nitric acid to desorb the metals. The mixture then filtered and the collect TPN adsorbent was dried

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and reused for the adsorption of the dye and metals which showed almost the same performance with standard deviation, i.e. experimental errors of 5%. The filtrate containing the metals was treated

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Fig. 8: Simultaneous removal of MB dye and toxic metals by TPN.

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Fig. 9. Analysis of TPN after dye adsorption (a) FTIR spectrum, (b) SEM image, (c) mapping of nitrogen indicating the distribution of the dye on the TPN adsorbent.

Fig. 10. Analysis of TPN after dye adsorption (a) FTIR spectrum, (b) SEM image, (c) mapping of nitrogen indicating the distribution of the dye on the TPN adsorbent.

Conclusion 19

ACCEPTED MANUSCRIPT The simultaneous combination of the interfacial polymerization of trimesoyl chloride (TMC) and 1,3- phenylene diamine (MPD) with the in-situ formation of TiO2 from TiCl4 using urea was achieved. The combination of the titania with polyamide improved the properties of the TPN composite. The N2- physisorption analysis results indicated that the textural properties, like the surface area of TPN, were improved compared with that of polyamide. X-ray mapping showed the efficient distribution of the titania within the polymer structure. The TPN was evaluated for the adsorption of dyes and toxic metals. The TPN showed good removal of several dyes in the order of

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MB > bromo phenol > methyl orange > congo red > rhodamine B. Kinetic studies were performed

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to understand the adsorption mechanism. The kinetic studies indicated that the second-order fitted

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the experimental data. The thermodynamic studies indicated the applicability of the TPN at room temperature since by increasing the temperature the removal percentage decreased. Interestingly,

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TPN showed simultaneous removal of MB dye and toxic metals including Se, As, Cu, Pb, Hg, Cd, Cr, and Ni. The prepared TPN composite was demonstrated to be an efficient adsorbent for the

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simultaneous removal of dyes and toxic metals. Acknowledgments

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Authors would like to acknowledge the support and fund provided by King Fahd University of

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Petroleum & Minerals (KFUPM) through Project No. IN161011 under the Deanship of Research. References:

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sorptional–photocatalytic

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of

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selenotungstophosphate nanocomposite, Toxicological & Environmental Chemistry 97 (2015)

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526-537.

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ACCEPTED MANUSCRIPT Highlights

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For the first time, in-situ synthesis of titania- incorporated polyamide was achieved

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The composite showed excellent performance in simultaneous sorption of dyes and toxic metals

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The experimental results were fitted to adsorption isotherm with proposed mechanisms

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