Application of polypyrrole coated onto wood sawdust for the removal of carmoisine dye from aqueous solutions

In this research, the removal of carmoisine dye from aqueous solutions using polypyrrole coated onto sawdust (PPy/SD) has been investigated. The sorption experiments were performed using both batch and column systems. The effects of some important parameters such as pH, initial concentration, sorbent dosage, exposure time, and temperature on uptake of carmoisine dye were investigated. Based on the data obtained in batch system, it was found that maximum adsorption is occurred under acidic conditions. Complete removal was observed when a dye solution with the initial concentration of 100 mg L^?1 was treated by 1.0 g of the used adsorbent (PPy/SD) at pH value of 4 and room temperature. However, higher sorption was observed at elevated temperature. According to the kinetics study, it was found that the experimental data fitted very well the pseudo‐second‐order kinetic model (k₂ = 0.184 g mg^?1 min^?1). It was found that polypyrrole chemically coated on SD is an efficient system for the removal of carmoisine dye from aqueous solutions. Desorption of the dye‐loaded column was also possible by using dilute NaOH solution with high efficiency (～ 80%). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of polyaniline nanocomposite and its application for chromium removal from aqueous solution

The aim of this research was to investigate the sorption characteristics of polyaniline coated on sawdust (PAn/SD) for the removal of Cr(VI) ions from aqueous solutions. The sorption of Cr(VI) ions was carried out by the batch method. Characterization of PAn/SD was done by FTIR and SEM. The optimum conditions of sorption were found to be a PAn/SD dose of 0.6 g in 100 mL of Cr(VI) solution (50 mg/L), a contact time of 20 min, pH 2, and a temperature of 20°C, Increased temperature had a negative effect on the removal efficiency. Three equations, that is Morris–Weber, Lagergren, and pseudo‐second‐order, were tested to track the kinetics of the removal process. The kinetic data indicated that the adsorption process was described by the Morris–Weber equation. The Langmuir, Freundlich, and Dubinin–Radushkevick models were used with sorption data to estimate sorption capacity, intensity, and energy. The data were fitted with the Freundlich model. The thermodynamic parameters ΔH, ΔS, and ΔG were evaluated. They showed that the adsorption of Cr(VI) onto PAn/SD was feasible, spontaneous, and exothermic under the studied conditions. For desorption of Cr(VI) adsorbed onto PAn/SD, aqueous NaOH was used; with it, 85% of the adsorbed Cr(VI) could be desorbed. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Application of nanometer size of polypyrrole as a suitable adsorbent for removal of Cr(VI)

The objective of this work was to investigate the sorption characteristics of polypyrrole (PPy) for the removal of Cr(VI) from aqueous solutions. The sorption process was carried out by a dynamic batch method in order to determine the optimum conditions. For a sorbent dose of 0.6 g in 100 mL of a Cr(VI) solution, at a contact time of 15 min and a pH of 3, a removal efficiency of 84.5% was achieved. The Morris–Weber and Lagergren equations, as well as a pseudo‐second‐order equation were examined to explore the kinetics of the removal process. In addition, the Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were applied to estimate the capacity, intensity, and energy of the sorption process. It was found that increasing temperature showed a positive effect on the ion sorption efficiency. In summary, PPy was shown to be a suitable candidate for chromium(VI) ion removal from aqueous solutions at different concentrations. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers.     

Removal of toxic metal Cr(VI) from aqueous solutions using sawdust as adsorbent: Equilibrium, kinetics and regeneration studies

In the present study, a low-cost adsorbent is developed from the naturally and abundantly available sawdust which is biodegradable. The removal capacity of Cr(VI) from aqueous solutions and from the synthetically prepared industrial effluent of electroplating and tannery industries is obtained. The batch experiments are carried out to investigate the effect of the significant process parameters such as initial pH, change in pH during adsorption, contact time, adsorbent amount, and the initial Cr(VI) concentration. The maximum adsorption of Cr(VI) on sawdust is obtained at an initial pH value of 1. The value of pH increases with increase in contact time and initial Cr(VI) concentration. The equilibrium data for the adsorption of Cr(VI) on sawdust is tested with various adsorption isotherm models such as Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan, Tempkin, Dubinin–Radushkevich and Generalized equation. The Langmuir isotherm model is found to be the most suitable one for the Cr(VI) adsorption using sawdust and the maximum adsorption capacity obtained is 41.5 mg g⁻¹ at a pH value of 1. The adsorption process follows the second-order kinetics and the corresponding rate constants are obtained. Desorption of Cr(VI) from sawdust using acid and base treatment exhibited a higher desorption efficiency by more than 95%. A feasible solution is proposed, for the disposal of the contaminant (acid and base solutions) containing high concentration of Cr(VI) obtained during the desorption process. The interference of other ions which are generally present in the electroplating and tannery industrial effluent streams on the Cr(VI) removal is investigated.     

Removal of chromium(VI) from aqueous solutions using polypyrrole-based magnetic composites

PPy/Fe₃O₄/AgCl composites were prepared via in situ polymerization for the removal of highly toxic Cr(VI). The structure and morphology of the prepared composites were characterized by the XRD, SEM, TEM, and VSM examinations. Up to 100 % removal was found with 1000 mg/L Cr(VI) aqueous solution at pH 2.0. The process of Cr(VI) ions’ adsorption was easy to reach equilibrium at higher temperatures. Adsorption results showed that Cr(VI) removal efficiency by the composites decreased with an increase in pH. Adsorption kinetics was described by the pseudo-second-order rate model. Isotherm data fitted well to the Langmuir isotherm model. Desorption experiment showed that the regenerated adsorption of PPy/Fe₃O₄/AgCl can be reused successfully for three times successive adsorption–desorption cycles without appreciable loss of its original capacity.     

Application of poly 3‐methylthiophene for removal of silver ion from aqueous solutions

This article deals with application of poly (3‐methyl thiophene) synthesized chemically on the surface of wood sawdust (termed as P3MTh/SD) and then was used for removal of silver ions (Ag⁺) from aqueous solution. The polymer was synthesized directly on the surface of sawdust, which has previously soaked in monomer solution using ferric chloride as chemical oxidant. The sorption experiments were performed on both batch and column systems under simple open circuit conditions. The effects of some important parameters such as pH, initial concentration, sorbent dosage, and exposure time on uptake of silver ion were investigated. The treatment of the data was also carried out using both Freundlich and Langmuir adsorption isotherms. To find out the possibility of the regeneration and reuse of the exhausted adsorbent, desorption studies were also performed. It was found that sawdust modified with polythiophene is an efficient system for uptake or recovery of the silver ions from aqueous solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Highly Efficient Dye Removal from Aqueous Solutions Using Simple Chemical Modification of Wood Sawdust

Abstract

This study examined the efficiency of oxidized wood meal for removal of methylene blue (MB) as a typical basic dye from aqueous waste streams. The adsorption process was performed using sawdust treated with KMnO₄, K₂Cr₂O₇, and H₂O₂ oxidants. Among the tested chemical oxidants, KMnO₄ was found to be more effective for modification of sawdust for dye uptake. Based on the breakthrough analysis, the highest column capacity of 227 mg g^?1 was obtained for the KMnO₄/SD. Sorption capacity of KMnO₄ treated sawdust for dye uptake was about seven times that of untreated sawdust (SD). The nature and morphology of adsorbents were characterized by SEM, XRD, and FTIR analysis. The adsorption behavior of KMnO₄/SD was found to be a strongly pH-dependent process and the maximum adsorption efficiency was obtained at pH 10. Dye-loaded KMnO₄/SD sorbent can be regenerated using low-cost chemicals.     

Fabrication of copper coated polymer foam and their application for hexavalent chromium removal

The polymer foam coated with zero-valent copper (Cu⁰) was designed and prepared for the removal of hexavalent chromium (Cr(VI)) in water. Firstly, porous poly(tert-butyl acrylate) was fabricated by concentrated emulsion polymerization and then acrylic acid groups were generated on the surface of foam by hydrolysis reaction. Secondly, with the help of the large amount reactive carboxylic acid groups, polyethyleneimine (PEI) were chemically grafted onto the surface by the reaction between amine group and acrylic acid group. Finally, zero-valent copper was reduced by sodium borohydride (NaBH₄) and coated on the surface of polymer foam. Thus the copper functionalized porous adsorbent (Cu⁰–PEI–PAA) was constructed, and then applied for removing Cr(VI) from aqueous solution. The removal mechanism of Cr(VI) involved redox reaction by zero-valent copper and adsorption by amine groups, simultaneously. As a result, 99.5% of Cr(VI) could be removed within 2 h, and the maximum removal capacity for Cr(VI) of Cu⁰–PEI(1800)–PAA was 9.16 mg/g. Furthermore, the effect of initial concentration of Cr(VI), pH value, and temperature on the Cr(VI) removal was investigated. Therefore, the as-prepared zero-valent copper-loaded polymer foam could be an efficient and promising remediation material to remove Cr(VI) from wastewater.     

Preparation and properties of transparent and conducting nylon 6-based composite films

Highly transparent and conducting polypyrrole–(PPy–N) and polyaniline–nylon 6 (PAN) composite films could be easily obtained by immersing nylon 6 films containing pyrrole or aniline into an oxidant solution such as aqueous FeCl₃ solution or aqueous (NH₄)₂S₂O₈ solution containing HCl. The conductivity, transmittance, and mechanical properties of these composite films were affected by the preparative conditions. The maximum conductivity and transmittance of the PPy–N composite films were 10^?3 S/cm and about 75% at 550 nm, and in the case of the PA–N composite films, 10^?2 S/cm and 75%, respectively. The morphology of PPy–N and PA–N composite films depended on the polymerization conditions, which might be due to the difference in the polymerization speed of pyrrole or aniline in polymer matrices. These PPy–N and PA–N composite films exhibited good environmental stability and excellent mechanical properties. © 1994 John Wiley & Sons, Inc.     

Removal of Chromium(VI) and Chromium(III) from Aqueous Solution by Grainless Stalk of Corn

Abstract

Grainless stalk of corn (GLSC) was tested for removal of Cr(VI) and Cr(III) from aqueous solution at different pH, contact time, temperature, and chromium/adsorbent ratio. The results show that the optimum pH for removal of Cr(VI) is 0.84, while the optimum pH for removal of Cr(III) is 4.6. The adsorption processes of both Cr(VI) and Cr(III) onto GLSC were found to follow first-order kinetics. Values of k _ads of 0.037 and 0.018 min^?1 were obtained for Cr(VI) and Cr(III), respectively. The adsorption capacity of GLSC was calculated from the Langmuir isotherm as 7.1 mg g^?1 at pH 0.84 for Cr(VI), and as 7.3 mg g^?1 at pH 4.6 for Cr(III), at 20°C. At the optimum pH for Cr(VI) removal, Cr(VI) reduces to Cr(III). EPR spectroscopy shows the presence of Cr(V) + Cr(III)-bound-GLSC at short contact times and adsorbed Cr(III) as the final oxidation state of Cr(VI)-treated GLSC. The results indicate that, at pH ≈ 1, GLSC can completely remove Cr(VI) from aqueous solution through an adsorption-coupled reduction mechanism to yield adsorbed Cr(III) and the less toxic aqueous Cr(III), which can be further removed at pH 4.6.     

Experimental design and batch experiments for optimization of Cr(VI) removal from aqueous solutions by hydrous cerium oxide nanoparticles

Hydrous cerium oxide (HCO) was synthesized by intercalation of solutions of cerium(III) nitrate and sodium hydroxide and evaluated as an adsorbent for the removal of hexavalent chromium from aqueous solutions. Simple batch experiments and a 2⁵ factorial experimental design were employed to screen the variables affecting Cr(VI) removal efficiency. The effects of the process variables; solution pH, initial Cr(VI) concentration, temperature, adsorbent dose and ionic strength were examined. Using the experimental results, a linear mathematical model representing the influence of the different variables and their interactions was obtained. Analysis of variance (ANOVA) demonstrated that Cr(VI) adsorption significantly increases with decreased solution pH, initial concentration and amount of adsorbent used (dose), but slightly decreased with an increase in temperature and ionic strength. The optimization study indicates 99% as the maximum removal at pH 2, 20 °C, 1.923 mM of metal concentration and a sorbent dose of 4 g/dm³. At these optimal conditions, Langmuir, Freundlich and Redlich–Peterson isotherm models were obtained. The maximum adsorption capacity of Cr(VI) adsorbed by HCO was 0.828 mmol/g, calculated by the Langmuir isotherm model. Desorption of chromium indicated that the HCO adsorbent can be regenerated using NaOH solution 0.1 M (up to 85%). The adsorption interactions between the surface sites of HCO and the Cr(VI) ions were found to be a combined effect of both anion exchange and surface complexation with the formation of an inner-sphere complex.     

Ion-crosslinked carboxymethyl cellulose/polyaniline bio-conducting interpenetrated polymer network: preparation,characterization and application for an efficient removal of Cr(VI) from aqueous solution

A simple, cheap, and environmentally friendly bio-conducting interpenetrated polymer blend network was prepared and introduced as a highly efficient system with suitable physical and mechanical properties for industrial removal of toxic Cr(VI) ions from aqueous solution. Carboxymethyl cellulose/polyaniline (CMC/PANI) interpenetrated network (IPN) blend was prepared by simple simultaneous ion-cross-linking of CMC and PANI chains using Al³⁺ cations. The CMC/PANI bio-conducting nanocomposite was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy equipped with an "energy dispersive X-ray spectroscopy" (SEM–EDX) technique. The CMC/PANI blend, ion-cross-linked by Al³⁺ cations, showed good stability and high surface area, proper for the removal of toxic Cr(VI) ions of the aqueous solution. Batch removal experiments were accomplished and the impression of effective variables including solution pH, initial concentration of Cr(VI) ions, contact time, and adsorbent dosage were checked and optimized. The outcome of our findings revealed that the removal of Cr(VI) ions by CMC/PANI nanocomposite IPN strongly depends on solution pH. The removal information was matched with the Langmuir adsorption isotherm model and the utmost monolayer adsorption capacity at pH 2 was 136.98 mg/g at 25 °C. The pseudo-second-order kinetics were operated and the thermodynamic parameters suggested spontaneous and exothermic nature of the adsorption process. Consequences indicated that CMC/PANI nanocomposite IPN could be an affective eco/environmentally friendly adsorbent for the removal of Cr(VI) ions from aqueous solutions.

     

Kinetics, thermodynamic and equilibrium study of Cr(VI) adsorption from aqueous solutions by NCL coal dust

The waste material NCL coal dust was used as adsorbent for removal of Cr(VI) from aqueous solutions under batch adsorption experiments. The maximum removal of 99.97% was recorded at pH 2. The time required to attain equilibrium was found to be 60 min. Adsorption kinetics was described by the Lagergren equation. The value of the rate constant of adsorption was found to be 0.0615 min^?1 at 16 mg dm^?3 initial concentration and 298 K. The applicability of the Langmuir and Freundlich equations for the present system was also tested at different temperatures: 298, 313, and 328 K. Both thermodynamic parameters and temperature dependence indicated the endothermic nature of Cr(VI) adsorption on coal dust. The results showed that NCL coal dust is a promising adsorbent for the removal of Cr(VI) from aqueous solutions.     

Removal of Chromium from Synthetic and Real Effluents Using Uncalcined MgAl-NO3 Layered Double Hydroxide: Column Study and Modeling

In this study, the sorption ability of MgAl-NO₃ layered double hydroxide prepared by coprecipitation method to remove Cr(VI) from aqueous solution was investigated in fixed-bed column. The sorbent was characterized by XRD, SEM, FTIR, BET surface area, and pH_zpc. The effects of bed height (2–5 cm), flow rate (5–20 mL/min), inlet Cr(VI) concentration (30–100 mg/L), and solution pH (3–8) on the breakthrough characteristics of the column were determined, and the optimum conditions were observed at 3.5 cm, 10 mL/min, 50 mg/L, and a pH of 6. Moreover, the performance of the sorbent to remove Cr(VI) from wastewater was also examined at optimum conditions. The results show high removal and good selectivity for Cr(VI) in wastewater containing large amounts of coexisting anions.     

Removal of Cr(VI) from Aqueous Solution: Electrocoagulation vs Chemical Coagulation

Abstract

Hydrolyzed products of Al(III) have affinity below pH_zpc for oppositely charged mono and bi‐nuclear species of hexavalent chromium. This study investigates the comparative performance of electrocoagulation (EC) and chemical coagulation (CC) for the removal of Cr(VI) from aqueous solution. The highest removal of Cr(VI) achieved with EC was about 42% with 4.36 mA/cm² current density. Cathodic adsorption of chromium boosted up Cr(VI) removal during EC. Simultaneous electro‐ and chemical‐dissolution lead to high current efficiency of about 178%. Both the pH and the coagulant dosage have a significant impact on Cr(VI) removal in the pH ranges from 4.9 to 7.0. CC with alum and aluminum sulfate (AS) removed about 11% and 12% of Cr(VI). Co‐adsorption of divalent SO₄ ^2? ions with Cr(VI) is responsible for the lower removal observed with chemical coagulants. About 0.061 and 0.099 mole of SO₄ ^2? was adsorbed per mole Al in the precipitate in the pH range 4.9 to 7.0 with AS and alum. A higher coagulant dosage increases the removal of Cr(VI) but adversely affects the removal efficiency (Cr(VI) removed per unit of Al dosing). Cell current density (CD) has shown little effect on Cr(VI) removal and the pH elevation at the same charge density. Higher initial Cr(VI) concentration improves the removal efficiency as the species of Cr(VI) is acidic in solution and decreases the pH elevation rate.     

Removal of hexavalent chromium ion from aqueous solution using nanoscale zero-valent iron particles immobilized on porous silica support prepared by polymer template method

Porous silica supported nanoscale zero-valent iron was prepared by a polymer template method in order to effectively remove a hexavalent chromium ion (Cr(VI)) in an aqueous solution. It did not show a deterioration of Cr(VI) removal efficiency, which could be caused by the surface oxidation and agglomeration of nanoscale zero-valent iron (NZVI) particles. Porous silica by the polymer template method showed quite unique structure, which we named as quasi-inverse opal silica (QIOS), and it showed high surface area (375.4m²/g) and fine pore size (76.5 nm). NZVI immobilized on the surface of QIOS (NZVI@QIOS) was added to an aqueous Cr(VI) solution at 0.025 g/L, and it showed over 96% Cr(VI) removal efficiency. Such a high removal efficiency of Cr(VI) was maintained over two weeks after preparation (92% after 16 days). Morphology of porous silica supported nanoscale zero-valent iron was analyzed by TEM and FE-SEM. Identification of the reaction compounds produced by the reaction of Cr(VI) and zero-valent iron (Fe(0)) was made by the application of XPS.     

Preparation of highly conducting and spin-probed polypyrroles using coupled electrochemical-chemical synthesis in the presence of nitroxyl radicals

Summary A new method for the synthesis of conducting polypyrroles (PPy), based on chemical and combined electrochemical-chemical oxidation of pyrrole monomers in the presence of nitroxyl radical (TEMPOL-2,2,6,6-tetramethyl-4-hydroxy-1-oxy-piperidyl) as oxidation agent (in its oxidation state) and redox mediator respectively is described. The PPy films obtained are extremely porous and the electrical conductivity () of the resulting PPy samples ranges from 1 to 100 S cm^–1. PPy prepared in aqueous solutions has a lower conductivity 1 S cm^–1 as compared to the PPy prepared in acetonitrile solutions with conductivity of about 100 S cm^–1. The PPy films are quite compact and thick films (1 mm) can be pealed off from the electrode surface and pressed as a disc for further studies. Only after partial reduction of polypyrrole film the spin-probed PPy was obtained. The concentration of nitroxyl radicals incorporated in the polymer matrix can be changed using various degrees of polymer reduction. The anisotropic broadening of the observed ESR lines indicates a low mobility of incorporated nitroxyl radicals in the PPy matrix. The electronic interaction between the nitroxyl groups and the paramagnetic centers of the polymer chains, polarons, causes an ESR line broadening of polaron signal both on air (1.1 mT) and in vacuum (0.7 mT) as compared to unmodified PPy (0.2 mT on air, 0.05 mT in vacuum).     

Application of polyaniline nanolayer composite for removal of tartrazine dye from aqueous solutions

In this research, polyaniline was synthesized chemically onto the surface of sawdust as a thin layer (termed as PAni/SD) and was then used for removal of tartrazine dye (a typical anionic azo dye) from aqueous solutions. Ammonium peroxodisulphate was used as chemical oxidant for polymerization of polyaniline directly on the surface of sawdust. The procedure involves sorption experiments were performed on both batch and column systems. The effects of some important parameters such as pH, initial concentration, sorbent dosage, exposure time and temperature on uptake of tartrazine dye were investigated. Adsorption studies have shown that pH of the tartrazine solution has influence on the dye removal capacity of PAni/SD. It was found that effective dye removal is occurred under neutral or acidic conditions. The treatments of the data were carried out using both Freundlich and Langmuir adsorption isotherms. Sorption/desorption studies showed that PAni/SD was fast, simple, inexpensive, highly efficient and potential re-usable adsorbent to remove tartrazine from aqueous solutions. Based on our kinetics and thermodynamic studies, it was found that sorption process was endothermic (ΔH > 0) and the experimental data fitted very well with pseudo second-order kinetic model.     

Synthesis and characterization of a surface imprinting silica gel polymer functionalized with phosphonic acid groups for selective adsorption of Fe(III) from aqueous solution

A Fe(III) ion‐imprinted silica gel polymer functionalized with phosphonic acid groups (IIP‐PA/SiO₂) was prepared with surface imprinting technique by using Fe(III) ion as template ion, grafted silica gel as support, and vinylphosphonic acid as functional monomer. The polymer was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, and thermogravimetric analysis. The synthesized imprinted silica gel polymer was used as a sorbent for Fe(III) adsorption. The adsorption properties, such as the effect of solution pH, adsorption kinetic, adsorption isotherm, adsorption selectivity as well as the regeneration of sorbent were studied. The results showd that the prepared sorbent (IIP‐PA/SiO₂) had a short adsorption equilibrium time (12 min) and high adsorption capacity (29.92 mg g^?1) for Fe(III) at the optimal pH of 2.0. The selectivity coefficients of the sorbent for Fe(III) in presence of Cr(III), M_n (II), and Zn(II) were 51.76, 27.86, and 207. 76, respectively. Moreover, the adsorption capacity of the prepared sorbent did not decrease significantly after six repeated use. Thus, the prepared ion‐imprinted silica gel polymer was a promising candidate sorbent for the selective adsorption of Fe(III) from aqueous solutions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45165.     

Optimization of an anode for arsenic(V) extraction

Electrochemical methods has led to the preparation of a poly(pyrrole)-modified steel electrode (SS/PPy) for testing and optimizing the polymer doping/undoping process for arsenic(V) removal. Potentiodynamic (cyclic voltammetry) electropolymerization optimal range was between −0.200 and 0.980 V vs SCE. On the other hand, the potentiostatic optimal working potential was 0.980 V. SS/PPy-modified electrode prepared under either of these optimum conditions displayed a doping/undoping process occurring at 0.700 and −0.200 V, respectively. Hence, As(V) extraction or removal was performed by incorporating the cation to SS/PPy applying a 0.700 V constant potential. Then, As(V) doped SS/PPy was transferred to another cell, in which the undoping potential (−0.200 V) was applied to remove the ion from the polymer matrix, completing thus the extraction cycle (EC). This way, for instance, with a SS of 10 cm² geometric area and potentiostatic deposition carried out for 10 min, arsenic removal rates over 77 % were attained for 10 EC of 60 s each. This outcome allows predicting a promising future for the method as As(V) extractor from aqueous solutions. Furthermore, the modified electrode exhibited acceptable conditions for developing a likely arsenic sensor, since a linear current vs As(V) concentration relationship exits, at least in the order of concentrations used herein (50–500 ppm).