Adsorption of hexavalent chromium from aqueous solution onto triethylenetetramine-functionalized cellulose aerogel

In this research, adsorption of chromium (VI) ions on wheat bran has been studied through using batch adsorption techniques. The main objectives of this study are to 1) investigate the chromium adsorption from aqueous solution by wheat bran, 2) study the influence of contact time, pH, adsorbent dose and initial chromium concentration on adsorption process performance and 3) determine appropriate adsorption isotherm and kinetics parameters of chromium (VI) adsorption on wheat bran. The results of this study showed that adsorption of chromium by wheat bran reached to equilibrium after 60 min and after that a little change of chromium removal efficiency was observed. Higher chromium adsorption was observed at lower pHs, and maximum chromium removal (87.8 %) obtained at pH of 2. The adsorption of chromium by wheat bran decreased at the higher initial chromium concentration and lower adsorbent doses. The obtained results showed that the adsorption of chromium (VI) by wheat bran follows Langmuir isotherm equation with a correlation coefficient equal to 0.997. In addition, the kinetics of the adsorption process follows the pseudo second-order kinetics model with a rate constant value of 0.131 g/mg.min The results indicate that wheat bran can be employed as a low cost alternative to commercial adsorbents in the removal of chromium (VI) from water and wastewater.

Chitosan‐coated perlite beads were prepared by drop‐wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The beads were characterized by SEM and EDS x‐ray microanalysis. The chitosan content of the beads was 23%, as determined by a pyrolysis method. Adsorption of hexavalent chromium from aqueous solutions on chitosan‐coated perlite beads was studied under both equilibrium and dynamic conditions. The effect of pH on adsorption was also investigated. The data were fitted to the Langmuir adsorption isotherm. The adsorption capacity of chitosan‐coated perlite was found to be 104 mg/g of adsorbent from a solution containing 5000 ppm of Cr(VI). On the basis of chitosan, the capacity was 452 mg/g of chitosan. The capacity was considerably higher than that of chitosan in its natural and modified forms, which was in the range of 11.3 to 78 mg/g of chitosan. The beads loaded with chromium were regenerated with sodium hydroxide solution of different concentrations. A limited number of adsorption‐desorption cycles indicated that the chitosan‐coated beads could be regenerated and reused to remove Cr(VI) from waste streams.

The adsorption of hexavalent chromium on Kaolinite and Illite was studied in order to evaluate their potential for the reduction of hexavalent chromium mobility and their possible application for the treatment of polluted sediment. The influence of various parameters affecting the adsorption of hexavalent chromium, such as the pH of aqueous solution, the ionic strength and the initial metal ion concentration were investigated. The optimal pH range corresponding to the hexavalent chromium adsorption maximum on the Kaolinite and Illite is 2 - 4 and 2 - 2.6, respectively. The results showed that hexavalent chromium sorption on Kaolinite and Illite was strongly influenced by the pH, the ionic strength and the initial metal ion concentration. Langmuir and Freundlich adsorption isotherms are employed to understand the nature of adsorption at room temperature. The characteristic parameters for each isotherm have been determined. This showed that the Freundlich isotherm model well described the equilibrium data. The data suggest that the charge of the clay mineral surface is one of the main factors controlling hexavalent chromium desorption at alkaline pHs.

Adsorption of hexavalent chromium on manganese nodule leached residue obtained from NH 3–SO 2 leaching

Microwave-assisted tetrabutyl ammonium-impregnated sulphate-crosslinked chitosan was synthesized for enhanced adsorption of hexavalent chromium. The adsorbent obtained was extensively characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray studies. Various isotherm models such as Langmuir, Freundlich and Dubinin–Radushkevich were studied to comprehend the adsorption mechanism of hexavalent chromium by the adsorbent. Maximum adsorption capacity of 225.9 mg g−1 was observed at pH 3.0 in accordance with Langmuir isotherm model. The sorption kinetics and thermodynamic studies revealed that adsorption of hexavalent chromium followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. A column packed with 1 g of adsorbent was found to give complete adsorption of Cr(VI) up to 900 mL of 200 mg L−1 solution which discerns the applicability of the adsorbent material for higher sample volumes in column studies. The effective adsorption results were obtained due to both ion exchange and ion pair interaction of adsorbent with hexavalent chromium. Greener aspect of overall adsorption was regeneration of the adsorbent which was carried out using sodium hydroxide solution. In the present study, the regenerated adsorbent was effectively reused up to ten adsorption–desorption cycles with no loss in adsorption efficiency.

In the current work, we have reported a cationic surfactant-modified Ethiopian kaolin for improved adsorption of Cr(VI) from aqueous solution. The raw kaolin was modified by treating with CTAB to enhance the adsorption properties. The crystal structure and vibrational analysis of CTAB–kaolin were investigated by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (p-XRD) techniques. The successful modification of kaolin by CTAB through intercalation and coating was investigated by XRD and FTIR. p-XRD confirms the raw kaolin obtained from Belesa, Tigo kebele is kaolinite mineral. The study has also focused on the application of kaolin–CTAB for adsorption of hexavalent chromium. The percent removal of Cr(VI) was investigated at different parameters such as pH, contact time, concentration of Cr(VI) and adsorbent dosage. CTAB–kaolin shows 99% removal of Cr(VI) at the adsorption equilibrium (time = 180 min, 100 mg CTAB–kaolin, 10 ppm/100 ml). The Langmuir and Freundlich isotherm models were used to investigate the adsorption process of chromium onto kaolin–CTAB composites. The equilibrium data obeyed Langmuir model than Freundlich, which shows that the adsorption process proceeds through monolayer adsorption and maximum adsorption capacity was found to be Qo = 22.72 mg/g. The pseudo-second-order kinetics model is found to be well fitted than Pseudo-first-order kinetics, which implies that the adsorption mechanism more favors electrostatic interaction between chromium and kaolin–CTAB composites. In conclusion, CTAB–kaolin was found to be a promising adsorbent for the efficient removal of Cr(VI) from the aqueous solution.

Activated carbon impregnated by zero-valent iron nanoparticles (AC/nZVI) optimized for simultaneous adsorption and reduction of aqueous hexavalent chromium: Material characterizations and kinetic studies

Adsorption of hexavalent chromium by metal organic frameworks from aqueous solution

Enhanced adsorption of hexavalent chromium from aqueous solutions on facilely synthesized mesoporous iron–zirconium bimetal oxide

High-capacity adsorption of hexavalent chromium from aqueous solution using magnetic microspheres by surface dendrimer graft modification

Heavy metals such as chromium, lead, arsenic and others are dense metals whose contamination of water may exterminate life on earth at the niche in industrial activities, foodstuffs or medicines and so on. Activated carbons are very helpful in removing heavy metal ions from aqueous solutions by adsorption, and have been investigated by many researchers so far. The practical relevance of activated carbon made from de oiled soya in the removal of hexavalent chromium ions through continuous adsorption mode is reported in this paper. A breakthrough plot was plotted in finding the effect of initial concentration and adsorbent bed height in the adsorption of hexavalent chromium through activated carbon of de oiled soya. The breakthrough time and saturation time increased as the concentration of the initial solution shot up from 40 mg/L to 60 mg/L. The saturation time was in an incremental mode when the thickness of the adsorbent bed height in a fixed bed was increased from 5cm to 7cm for 40 mg/L initial concentration of hexavalent chromium. The Adams-Bohart’s model was found to fit perfectly the fixed bed column in the removal of hexavalent chromium from aqueous solutions. The fabricated adsorbent worked well in detoxifying hexavalent chromium metal ion contaminated wastewater.

The batch removal of hexavalent chromium from aqueous solution by chitosan under different experimental conditions, such as the pH value and the initial hexavalent chromium ion concentration, was investigated. The adsorption of hexavalent chromium is highly pH-dependent, the results obtained in the present study indicating that the optimum pH for Cr(VI) ion removal was 4.0. The kinetics of the adsorption of Cr(VI) ions by chitosan were evaluated by the pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models, respectively. The results show that the pseudo-second-order kinetic model gave a good correlation (r2 = 0.9942) with the experimental data.

Adsorption of hexavalent chromium from aqueous solutions by bio-chars obtained during biomass pyrolysis

Magnetite nanoparticles and magnetite-pine cone nanocomposite were prepared and applied in the adsorption of hexavalent chromium from water. Pine cone powder stabilized the nanoparticles and acted as a support while simultaneously introducing functional groups which improved metal adsorption. The nanocomposite retained the nanoparticles magnetic properties while improving chromium adsorption efficiency. Adsorption of hexavalent chromium on both materials was pH and concentration dependent with the most efficient adsorption occurring at pH 2 and 75 mg/L. On both materials, chromium adsorption was spontaneous with Gibbs free energy values of −19.2 kJ mol −1 to −23.7 kJ mol −1 and −18.0 kJ mol −1 to −24.2 kJ mol −1 for nanoparticles and nanocomposite respectively between 298 K and 319 K. The changes in enthalpy and entropy were determined to be 44.4 kJ mol −1 , 212.7 J K −1 mol −1 and 78.3 kJ mol −1 , 323.3 J K −1 mol −1 for the prepared nanoparticles and nanocomposite respectively.

Adsorption of hexavalent chromium onto organic bentonite modified by the use of iron(III) chloride.