Maximum Removal Efficiency Of Cr Research Articles

Phycoremediation of As(III) and Cr(VI) by Desmodesmus subspicatus: Impact on growth and biomolecules (carbohydrate, protein, chlorophyll and lipid) - A dual mode investigation.

Microalgae are under research focus for the simultaneous production of biomolecules (e.g., carbohydrates, proteins, pigments and lipids) and bioremediation of toxic substances from wastewater. The current study explores the capability of indigenously isolated microalgae (Desmodesmus subspicatus) for the phycoremediation of As(III) and Cr(VI). Variation of biomolecules (carbohydrate, protein, lipid and chlorophyll) was investigated during phycoremediation. D. subspicatus survived up to the toxicity level of 10mg/L for As(III) and 0.8mg/L for Cr(VI). A 70% decline in carbohydrate accumulation was observed at 10mg/L of As(III). An increased content of proteins (+ 28%) and lipids (+ 32%) within the cells was observed while growing in 0.5 and 0.2mg/L of As(III) and Cr(VI) respectively. A decrease in carbohydrate accumulation was noted with increasing Cr(VI) concentration, and the lowest (- 44%) was recorded at 0.8mg/L Cr(VI). D. subspicatus showed an excellent maximum removal efficiency for Cr(VI) and As(III) as 77% and 90% respectively.

Synthesis and two-step KOH based activation of porous biochar of wheat straw and waste tire for adsorptive exclusion of chromium (VI) from aqueous solution; thermodynamic and regeneration study

Biochar derived from Wheat Straw (WS), Waste Tire (WT), and their combination of 1:1 (WS/WT) was processed through different chemical activation methods i.e., wet (molar solution of KOH) and dry processes (physical mixing of biochar and KOH). The synthesized adsorbents were characterized by SEM-EDS, FTIR, BET, XRD and Point of Zero charge (PZC). Efficient adsorbent was selected based on the results of characterization and removal efficiency for chromium (VI). Among the synthesized adsorbents, the wheat straw-based biochar, activated by 1:3 proportion of KOH in dry process (WSKOHdry 1:3) showed maximum removal, possessed well developed porous structure and the largest specific surface area (529.48 m2/g). The adsorbent WSKOHdry 1:3 achieved maximum removal efficiency of Cr (VI) at optimum conditions i.e., pH 2, contact time 120 min, adsorbent dosage 2 g/L and temperature 25 °C. The kinetic study indicates that the removal of Cr (VI) by WSKOHdry 1:3 followed pseudo-second order kinetic model and Elovich kinetic model. Moreover, the Freundlich Isotherm model presented better fitting of the experimental data of Cr (VI) adsorption. The maximum Langmuir adsorption capacity (qmax) of WSKOHdry 1:3 at 25 °C was 96.082 mg/g. The thermodynamic analyses revealed that Cr (VI) uptake is endothermic (+ΔH) and spontaneous (−ΔG) in nature. Furthermore, electrostatic attraction, complexation, ion exchange, and reduction to chromium (III) were involved in the removal of Cr (VI) by WSKOHdry 1:3. Hence, the results proposed that WSKOHdry 1:3 exhibited great potential for Cr (VI) adsorption.

Synthesis, Optical Characterization, and Adsorption of Novel Hexavalent Chromium and Total Chromium Sorbent: A Fabrication of Mulberry Stem Biochar/Mn-Fe Binary Oxide Composite via Response Surface Methodology

In this study, a new generation chromium sorbent, mulberry stem biochar/Mn-Fe binary oxide composite (MBC-MFC), was fabricated by chemical precipitation on carbonized mulberry stem according to response surface methodology (RSM) results. RSM was more convenient to figure out the optimized preparation condition of MBC-MFC theoretically for achieving a maximum removal efficiency of Cr(VI) and total chromium (TCr), compared to labor-intensive orthogonal experiments. The RSM results showed that Fe/Mn concentration (CFe; CMn), MBC activation temperature after soaking in KOH solution (T), and pH during precipitation of Fe-Mn oxide were three main factors to significantly affect the efficiency of MBC-MFC (p < 0.05) in Cr(VI) and TCr removal. With the selected condition (CFe = 0.28 mol/L; CMn = 0.14 mol/L; T = 790°C; pH = 9.0), MBC-MFC was synthesized with a large surface area (318.53 m2/g), and the point of zero charge values of MBC-MFC was 5.64. The fabricated MBC-MFC showed excellent adsorption performance of Cr(VI) and TCr in an aqueous solution. The maximum Cr(VI) and TCr removal capacity of MBC-MFC was 56.18 and 54.97 mg/g (T = 25°C, pH = 3.0, t = 48 h, and dosage = 0.10 g/50 ml), respectively, and the maximum Cr(VI) adsorption of MBC-MFC was 4.16 times that of bare MBC, suggesting the synergistic effects of Fe/Mn oxides and MB on the performance of MBC-MFC in Cr(VI) and TCr removal. The adsorption mechanism of MBC-MFC on chromium was mainly contributed by surface complexation and electrostatic attraction. Our study offers valuable outlooks to develop high-performance biochar-based sorbents for heavy metal removal and sustainable environmental remediation.

An extensive review on chromium (vi) removal using natural and agricultural wastes materials as alternative biosorbents.

Several conventional techniques for heavy metals decontamination for instance ion exchange, evaporation, precipitation and electroplating have been utilized in preceding years. Though these techniques have some drawbacks, adsorption using low-cost biosorbents is environmentally friendly. In this study, the potential of several natural and agricultural wastes as economical biosorbents for the reduction of Cr(VI) ions from polluted water has been reviewed. The application of adsorption models, as well as the impact of adsorption factors on heavy metals eradication, has been considered in this review. The study revealed that efficient reduction of Cr(VI) from water and wastewaters is highly dependent on the pH of the solution, shaking time, adsorbent type, initial concentration and temperature. The review of the relevant literature indicates that the maximum removal efficiency of Cr(VI) using the various low-cost adsorbents ranged from 50.0-100.0% with optimum pH and contact time ranging from 2.0-6.0 and 30.0-180.0min, respectively at room temperature (25.0 °C). Furthermore, considering all the studies reviewed, the pseudo-second-kinetics and Langmuir isotherm are the dominant models that best described the Cr(VI) equilibrium data. The thermodynamic parameters suggested that the biosorption of Cr(VI) on the biosorbents was spontaneous, realistic and endothermic at the temperature range of 30.0-45.0 °C. It is found that the natural and agricultural wastes as cheap biosorbents are feasible replacements to commercial activated carbons for metal-contaminated water treatment. However, gaps have been identified to improve applicability, regeneration, reuse and safe discarding of the laden adsorbents, optimization and commercialization of suitable agricultural adsorbents.

Biodegradable composite adsorbent of modified cellulose and chitosan to remove heavy metal ions from aqueous solution

Chromium (Cr), Lead (Pb) and Cadmium (Cd) have been conceded as one of the most perilous heavy metals which causes a prominent affliction on both environment and human health. In this study, chemical modification of biodegradable, eco-friendly materials such as cellulose and chitosan were carried out to prepare a composite adsorbent and established an optimized condition for adsorption of heavy metal ions such as Cr, Pb and Cd from contaminated aqueous wastes. α-cellulose was treated with HCl and H2SO4 to have better adsorption properties. On the contrary, modification of chitosan was carried out by acetaldehyde solution and acetic acid. Composite adsorbent was obtained as a mixture, comprising of modified cellulose and chitosan in a specific proportion (2g:1g). The surface characteristics of treated cellulose, chitosan and composite sample were evaluated by FTIR and SEM analysis. In addition, batch adsorption experiments were carried out to measure the influences of pH of the solution, adsorbent dosage and the initial concentration of metal ions. The maximum removal efficiency of Cr, Pb and Cd by composites was 56, 85 and 94%, respectively, at pH 4 when the metal concentration and adsorbent dosage were 60 ​ppm and 1.0 ​g ​L−1. The maximum adsorption of Cr, Pb and Cd by composites was 55, 80 and 91 ​mg ​g−1, respectively, at pH 4 when the metal concentration and adsorbent dosage were 120 ​ppm and 1.0 ​g ​L−1.

Bio-sorption for effective removal of chromium(VI) from wastewater using Moringa stenopetala seed powder (MSSP) and banana peel powder (BPP)

Chromium is an extremely toxic metal in the form of Cr(VI) that causes severe environmental and health problems. Therefore, the aim of this study was to remove chromium ions from wastewater by using cost effective and environmentally friendly bio-sorbents; Moringa stenopetala seed powder (MSSP), and banana peel powder (BPP) and to evaluate its adsorption capacities as bio-sorbents. FT-IR characterization of the adsorbents showed that there was a change in the functional groups of the structure of both adsorbents before and after the adsorption that might be due to the adsorption processes taken place on the surface of adsorbent. Adsorption experiments were carried out as batch studies with different contact times, pH, adsorbent dose, initial metal ion concentration, and temperature. Results showed maximum removal efficiency for Cr(VI) at 120 min contact time, adsorbent dose of 20 g/L and pH 2 by MSSP and pH 4 by BPP. The percentage removal of Cr(VI) increased with increasing adsorbent dose (from 5 to 20 g/L) and contact time (from 60 to 120 min). Freundlich isotherm model showed a better fit to the equilibrium data than the Langmuir model. The kinetics of adsorption for chromium was well represented by pseudo-second order kinetic model and the calculated equilibrium sorption capacity of the model showed good agreement with the sorption capacity obtained from experimental results.

Magnetic graphene-based nanocomposites as highly efficient absorbents for Cr(VI) removal from wastewater.

Due to the merits of their high adsorption and convenient separation, magnetic graphene-based composites have become a promising adsorbent in terms of wastewater treatment. However, recycling and regeneration properties of magnetic graphene-based composites are still a conundrum, which remains to be resolved. Here, Fe3O4/reduced graphene oxide (RGO) (Fe3O4/RGO) nanocomposites were synthesized by one-step solvent-thermal reduction route and used as adsorbents for water purification. It was encouraging to find that the nanocomposites possessed many intriguing properties in removing of Cr(VI) ions, including high adsorption efficiency and excellent recycling and regeneration property. The results indicated that the magnetic separation process of the Fe3O4/RGO nanocomposites only took less than 5s and the maximum removal efficiency of Cr(VI) reached 99.9% under the optimum experimental conditions. Most significantly, the adsorption rate of Cr(VI) can still be as high as 98.13% after 10cycles and the single recycle quality of the nanocomposites can maintain at more than 80%. As a result, the Fe3O4/RGO nanocomposites could be a potential adsorbent for removing heavy metal ions effectively, especially in environmental protection and restoration.

Feasible and eco-friendly removal of hexavalent chromium toxicant from aqueous solutions using chemically modified sugarcane bagasse cellulose

The hexavalent chromium (Cr(VI)) reported severe threat to the environment and public health as it is considered potentially mutagenic and carcinogenic. This communication demonstrates a chemical modification process of sugarcane bagasse cellulose for the removal of Cr(VI) from aqueous solutions. Cellulose was extracted from sugarcane bagasse followed by succination to form cellulose succinate (CS), which was then reacted with acetic anhydride to form cellulose succinic anhydrides (CSA). The latter was then reacted with triethylenetetramine (TETA) to form CS-TETA (CST). The prepared CST was characterized by Fourier transform infrared spectrometry (FTIR), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), and Brunauer–Emmett–Teller (BET) analyzer. The maximum removal efficiency of Cr(VI) by CST reached nearly 100% after 180 min, which was obtained at pH 1.0. The adsorption process fit well with the pseudo-second-order kinetic model, while the rate constant was 9.13 × 10−3 g/mg min. The isothermal study showed that the results closely aligned with the Langmuir isotherm model and the maximum adsorption capacity was 12.4 mg/g.

Mechanism of Cr(VI) removal by magnetic greigite/biochar composites

This study synthesized magnetic greigite/biochar composites (MGBs) by a solvothermal method and tested their ability to remove Cr(VI) from heavy metal-polluted wastewater. X-ray diffraction (XRD), Fourier transformed infrared spectrometry (FT-IR) and scanning electron microscopy (SEM) revealed that magnetic greigite (Fe3S4) flakes were aggregated and anchored to the biochar surface, resulting in more active sites than pristine biochar. Maximum Cr removal efficiency and capacity of MGB-30 (greigite/biochar = 30%) at an initial Cr(VI) concentration of 20 mg/L were 93% and 23.25 mg/g, respectively. A pseudo-first-order kinetic model was determined for the Cr(VI) removal process and the Cr(VI) removal rate constants were highly dependent on the mass ratios of Fe3S4 loaded on biochar, initial MGB and Cr(VI) concentrations and solution pH. X-ray photoelectron spectroscopy (XPS) and flame atomic absorption spectrometric (FAAS) analysis demonstrated that Cr(VI) was preferentially adsorbed on MGBs and subsequently reduced to Cr(III) by MGBs. Electron paramagnetic resonance (EPR) spectroscopy and iron redox transformations revealed that the Cr(VI) removal enhancement was attributed to efficient surface Fe(III)/Fe(II) cycling via electron transfer with the persistent free radicals (PFRs) of biochar. These novel findings provide new insights into the Fe(III)/Fe(II) cycle induced by biochar and the prospects of using magnetic greigite/biochar composites for remediation of Cr(VI)-rich wastewaters.

Application of Polypyrrole flexible electrode for electrokinetic remediation of Cr(VI)-contaminated soil in a main-auxiliary electrode system

A new electrokinetic remediation (EKR) system for remediation of hexavalent chromium (Cr(VI))-contaminated soil was explored in this study, which consists of main electrodes and unenergized auxiliary electrodes. Specifically, the graphite and Polypyrrole (PPy) were applied as main and auxiliary electrodes respectively, and the PPy used was chemically incorporated into linen fabric (LF). Five EKR experiments lasting 72 h were carried out in order to explore the Cr(VI) removal mechanism of the new EKR system. In the presence of PPy, the distribution of electric field along the ion migration direction and electric current were all improved and the Cr(VI) concentration around the auxiliary electrode was dropped. The changes of these parameters promoted the removal of Cr(VI) and the maximum removal efficiency of Cr(VI) in soil was 91.7%. It can be concluded that PPy auxiliary electrode coupled with EKR (PPy-EKR) had a positive effect on the removal of Cr(VI), which could not only accelerate the migration of Cr ions by affecting the distribution of electric field, but also contribute to adsorption and reduction of Cr(VI). Consequently, this research paved a road for the future application of main-auxiliary electrodes system for Cr(VI) removal in soil remediation.

Preparation of Zn-Doped Biochar from Sewage Sludge for Chromium Ion Removal.

Recycling and reuse waste can result in significant savings in materials and energy. In this study, the adsorption of Cr(VI) was analyzed using activated carbon (AC) and biochar (BSC) made from sewage sludge. BSC materials were synthesized using zinc chloride as an activator coupled with carbonized sewage sludge. Specific surface area, pore size distribution, and pore volume were determined by measuring nitrogen adsorption-desorption (BET). BSC morphology was measured using field-emission scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Results showed that the surface area and average pore volume of the BSC were 490 m2 g-1 and 0.8 cm3 g-1, respectively. SEM results revealed that BSC had uniform pore size. Effects of varying the initial Cr(VI) concentrations, pH values, and dosages of BSC on adsorption performance were also determined. Results showed that the maximum removal efficiency of Cr(VI) was above 99%, and adsorption capacity of 50% ZnCl2-BSC was 677 mg g-1.

A Novel Nitrogen Enriched Hydrochar Adsorbents Derived from Salix Biomass for Cr (VI) Adsorption

Hydrochars were prepared from Salix by hydrothermal carbonization, and characterized by FT-IR, 13C NMR, XPS, UV-vis, TG, SEM and BET techniques. The results showed that the hydrochars with molecular sieve-type open pore structure contained numbers of oxygen and nitrogen functional groups, which benefited the adsorption and diffusion of adsorbent Cr (VI). The hydrochar obtained from 26 h reaction (HC-26) was indicated an excellent adsorbent compared to the commercial activated carbon, and its maximum removal efficiency for Cr (VI) reaches up to 99.84% at pH 1. Langmuir´s model is well fitted the experimental equilibrium adsorption data of total Cr. The bath experiment results showed that Cr (VI) could be removed rapidly in the first 300 min. Furthermore, the adsorption kinetics process of HC-26 could be described by pseudo-second-order model. Based on the above results, HC-26 could be acted as a potential efficient adsorbent for removal of Cr (VI) from aqueous solution.

Adsorption of Cr(VI) from aqueous phase by high surface area activated carbon prepared by chemical activation with ZnCl2

Abstract Prepared activated carbon from fox nutshell by chemical activation with ZnCl2 in the N2 atmosphere was used for Cr(VI) removal from aqueous solution. Activated carbon was produced at 600 °C activation temperature with a 2.0 impregnation ratio for 1 h of activation time has been found as 2869 m2/g, 1.96 and 1.68 cm3/g of highest BET surface area, total pore volume and micropore volume, respectively. Batch mode adsorption studies were carried out by varying agitation speed, pH, temperature, agitation time and initial Cr(VI) concentration. The adsorption of Cr(VI) was pH dependent and showed maximum removal efficiency of Cr(VI) at pH 2.0. Adsorption studies of 10–25 mg/L initial Cr(VI) concentration were conducted at pH of 2.0 and temperature of 30 °C. The equilibrium, kinetics, and thermodynamics of Cr(VI) adsorption were studied. The adsorption capacity of Cr(VI) from the synthetic wastewater was 43.45 mg/g. The experimental adsorption equilibrium data was fitted to Langmuir adsorption model with an adequate adsorption capacity of 46.21 mg/g.

Cr(VI) adsorption by montmorillonite nanocomposites

Various montmorillonite (Mt) nanocomposite adsorbents were prepared with Al13 cations, dodecyl trimethyl ammonium chloride (DTAC) or dodecyl amine (DA) and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and BET surface area and pore size analyses. The adsorption of hexavalent chromium, Cr(VI) onto various Mt nanocomposites as a function of adsorbent dosage, initial Cr(VI) concentration, contact time and solution pH was investigated. The results showed that the obtained nanocomposites had large basal spacing and good porous structure, and the specific surface areas followed the order: OH-Al-Mt>DA-Al-Mt>DTAC-Al-Mt>Na+-Mt>DTAC-Mt>DA-Mt. The removal efficiency of Cr(VI) ions increased with increasing the adsorbent dosage and contact time, but decreased with increasing initial Cr(VI) concentration, as expected. The adsorption of Cr(VI) was highly pH-dependent and the maximum removal efficiency of Cr(VI) was found in the acid environment. The adsorption equilibrium time was 2h and the adsorption kinetic data of Cr(VI) on various adsorbents were well described by the pseudo-second-order kinetics model, which indicated that the adsorption reaction of Cr(VI) ions with the adsorbents was mainly due to chemical adsorption. Both the Langmuir model and Freundlich model fitted the equilibrium data well, which suggested that the Cr(VI) adsorption onto various adsorbents was both as monolayer and on heterogeneous surface conditions. The adsorption results indicated that among all the adsorbents used in this experiment, the dodecyl amine and Al13 cations composited with Mt (DA-Al-Mt) was the most effective for removing Cr(VI) from wastewater.

Synthesis and Application of Modified Zero-Valent Iron Nanoparticles for Removal of Hexavalent Chromium from Wastewater

Zero-valent iron nanoparticles (nZVI) modified with sodium dodecyl sulfate (SDS) as an anionic surfactant were successfully synthesized and applied to Cr (VI) removal. The prepared nanoparticles were characterized by field emission scanning electron microscope (FSEM), energy-dispersive spectrometry (EDS), and Fourier transform infrared spectrophotometer (FT-IR). Meanwhile, the surface charges of the stabilized nanoparticles were also determined. In this study, the kinetics of particle aggregation and sedimentation were investigated. It was found that the modified nanoparticles had great stabilization. Effects of pH, contact time, dosage of nanoparticles, and initial Cr(VI) concentrations on removal efficiency of the heavy metal ions were investigated and optimized. The maximum removal efficiency of Cr(VI) was obtained at pH 3.0 and 25 °C, at the value of 98.919 %. Cr(VI) removal occurred fast, and achieved equilibrium after 120 min. The maximum removal capacity reached up to 253.68 mg g−1 dry nanoparticles at a 300-mg L−1 Cr(VI)-containing sample. Kinetics study showed a rapid removal dynamics fitting pseudo-second-order kinetic model. The equilibrium data was nicely fit to the Freundlich model and indicates the adsorption of Cr(VI) was highly favorable. The obtained results indicated that nZVI modified by SDS could be used as an efficient alternative for removal of heavy metals with enhanced removal capacity and application stability.

Effective removal of hexavalent chromium from aqueous solutions by adsorption on mesoporous carbon microspheres

High-surface-area mesoporous carbon microspheres were successfully synthesized by a spraying method with the purpose of removing Cr(VI) from waste water. Various factors influencing the adsorption of Cr(VI), including pH, adsorption temperature, and contact time were studied. As the adsorption process was pH dependent, it showed maximum removal efficiency of Cr(VI) at pH 3.0. Pseudo-second-order model was found to best represent the kinetics of Cr(VI) adsorption. The adsorption parameters were determined using both Langmuir and Freundlich isotherm models, and Qm value was as high as 165.3mg/g. The thermodynamic parameters including standard Gibb’s free energy (ΔG0), standard enthalpy (ΔH0) and standard entropy (ΔS0) were investigated for predicting the nature of adsorption, which suggested the adsorption was an endothermic and a spontaneous thermodynamically process. Furthermore, Fe3O4-loaded MCMs were prepared to rapidly separate the adsorbent from the solution by a simple magnetic process. Fe3O4-loaded MCMs had a high adsorption capacity of 156.3mg/g, and a good regeneration ability with a capacity of 123.9mg/g for the fifth adsorption–desorption cycle.

Removal of Chromium (VI) from Aqueous Solution Using Electro-Fenton Process

Chromium (Cr) is considered to be mutagenic and carcinogenic, and is one of the most important pollutants that have been widely used in various industrial applications. Due to its adverse health impacts, Cr must be removed from effluents before being released into the water environments. The objective of the present study was to investigate the effect of electro- Fenton process (EFP) using iron electrodes in presence of sodium sulfate salt on the elimina- tion of Cr(VI) from aqueous solution. The effect of various parameters such as pH, voltage, initial Cr(VI) concentration, hydrogen peroxide dosage and cyanide concentration (as inter- ference ion), on the process efficiency of Cr(VI) removal have also been tested. The results indicate that the optimum pH, voltage and hydrogen peroxide dosage in EFP were determined to be 3, 30 V and 50 mL/L, respectively. The results of this research also demonstrated that EFP efficiency decreased with increasing initial Cr(VI) concentration. Moreover, EFP effi- ciency Cr(VI) removal decreased with increasing cyanide concentration; accordingly, the cyanide acts as interference ion in EFP and can reduce the removal efficiency of Cr(VI). According to the obtained results, the maximum removal efficiency of Cr(VI) at optimum condition was 97 % after 25 min. These findings suggest that EFP is suitable option for removing Cr(VI) from aqueous solution.

Biosorption of Cr(VI) ions from aqueous solutions by a newly isolated Bosea sp. strain Zer-1 from soil samples of a refuse processing plant.

The adsorption behavior of Cr(VI) ions from aqueous solution by a chromium-tolerant strain was studied through batch experiments. An isolate designated Zer-1 was identified as a species of Bosea on the basis of 16S rRNA results. It showed a maximum resistance to 550 mg·L(-1) Cr(VI). The effects of 3 important operating parameters, initial solution pH, initial Cr(VI) concentration, and biomass dose, were investigated by central composite design. On the basis of response surface methodology results, maximal removal efficiency of Cr(VI) was achieved under the following conditions: pH, 2.0; initial concentration of metal ions, 55 mg·L(-1); and biomass dose, 2.0 g·L(-1). Under the optimal conditions, the maximum removal efficiency of Cr(VI) ions was found to be nearly 98%. The experimental data exhibited a better fit with the Langmuir model than the Freundlich model. The biosorption mechanisms were investigated with pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. These results revealed that biosorption of Cr(VI) onto bacterial biomass could be an alternative method for the removal of metal ions from aqueous solution.

Sorption study of chromium sorption from wastewater using cereal by-products

The present work is aimed at exploring carbon which was prepared by calcination of Cereal By-Product (CBP) and used as adsorbent for the removal of Chromium (VI) from a surface treating industry. The effects of various parameters such as adsorbent dosage, pH, contact time were studied. As the adsorption process is pH dependent, it showed maximum removal efficiency of Cr(VI) in the pH range of 6–8 for an initial chromium concentration of 132 mg/L. Effect of temperature on the equilibrium constant was studied and the thermodynamic parameters like standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°) were also investigated. The positive values of ΔH0 and ΔG0 indicated an endothermic and a non spontaneous thermodynamically adsorption, respectively. Pseudo second-order model was found to best represent the kinetics of Cr(VI) adsorption. Intraparticle diffusion studies show that the mechanism of adsorption was mainly dependent on diffusion. The Langmuir, Freundlich and Temkin isotherm were used to describe the adsorption equilibrium studies of calcinated cereal by-product at 20 °C. Temkin isotherm showed better fit than Freundlich and Langmuir isotherms. It was demonstrated that the removal effectiveness reached nearly 90.37% when using optimal conditions as used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported.

Kinetics, thermodynamic, and adsorption studies on removal of chromium(VI) using Tulsion A-27(MP) resin

ABSTRACT The kinetics, thermodynamic, and adsorption studies on removal of chromium(VI) from aqueous and in presence of industrial solvents 2-methoxyethanol and 2-ethoxyethanol with macroporous resin Tulsion A-27 was studied at varying concentration of Cr(VI), adsorbent dosage, pH, contact time, and temperature. Batch shaking sorption experiments were carried out to evaluate the performance of Tulsion A-27(MP) anion exchange resin in the removal of Cr(VI) from aqueous and mixed aqueous solvents, 2-methoxyethanol and 2-ethoxyethanol. The concentrations of Cr(VI) in aqueous and mixed aqueous solvents were determined by UV-Visible spectrophotometer. As the adsorption process is pH dependent, it showed maximum removal efficiency of Cr(VI) in the pH range of 5–6 for an initial chromium concentration of 0.0011 M. Effect of temperature on the equilibrium constant was studied and the thermodynamic parameters were evaluated. Kinetic experiments revealed the dominance of adsorption. The sorption models, Langmuir and Freundlich adsorption isotherms, were discussed on amount of Cr(VI) uptake. The resin was analyzed by infrared spectroscopy and scanning electron microscopy before and after the adsorption process. The sorption of Cr(VI) by the anion exchange resin was reversible and so it has good potential for the removal/recovery of Cr(VI) from aqueous and mixed aqueous solvents. The anion exchange resin can be used for the efficient removal of Cr(VI) from water and wastewater.