Adsorbent For Removal Of Cr Research Articles

Insights into Starch Coated Nanozero Valent Iron-Graphene Composite for Cr(VI) Removal from Aqueous Medium

Embedding nanoparticles into an inert material like graphene is a viable option since hybrid materials are more capable than those based on pure nanoparticulates for the removal of toxic pollutants. This study reports for the first time on Cr(VI) removal capacity of novel starch stabilized nanozero valent iron-graphene composite (NZVI-Gn) under different pHs, contact time, and initial concentrations. Starch coated NZVI-Gn composite was developed through borohydrate reduction method. The structure and surface of the composite were characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and point of zero charge (pHpzc). The surface area and pHpzc of NZVI-Gn composite were reported as 525 m2 g−1 and 8.5, respectively. Highest Cr(VI) removal was achieved at pH 3, whereas 67.3% was removed within first few minutes and reached its equilibrium within 20 min obeying pseudo-second-order kinetic model, suggesting chemisorption as the rate limiting process. The partitioning of Cr(VI) at equilibrium is perfectly matched with Langmuir isotherm and maximum adsorption capacity of the NZVI-Gn composite is 143.28 mg g−1. Overall, these findings indicated that NZVI-Gn composite could be utilized as an efficient and magnetically separable adsorbent for removal of Cr(VI).

Adsorptive removal of Cr(VI) from aqueous solution using blackberry leaves - column study

The present study represents the blackberry leaves as the bio-sorbent for the removal of Cr(VI) ion from aqueous solution in continuous process. The effect of process parameters like, pH (1-8), influent metal ion concentration (10, 20 and 30 mg.L−1), flow rate (10, 30 and 40 ml.min−1), bed depth (4, 6 and 10 cm) were investigated to determine the breakthrough time. The result demonstrates that breakthrough time increases with the increase of bed depth and influent metal ion concentration but decreases with the increase of flow rate as at the lower flow rate the adsorbent gets less time to saturate. The empirical or semi-empirical models like Thomas, Bohart-Admas, Yoon-Nelson, Wolborska models were used to analyse the experimental data. FTIR studies were carried out to find out the functional groups, like Surface O-H, Aliphatic C-H, Aldehyde C-H, Carboxylate anion C=O, -SO3, Sulphonic acid S=O are responsible for the adsorption of the Cr(VI) ions onto the blackberry leaves. Desorption studies indicate that elution by dilute HNO3 through the fixed bed of the adsorbent columns could be regenerated and reuse for several times.

Adsorptive removal of Cr(VI) from aqueous solution using blackberry leaves - column study

Adsorptive removal of Cr(VI) from aqueous solution using blackberry leaves - column study

Adsorption of chromium(VI) from saline wastewater using spent tea-supported magnetite nanoparticle

Spent tea-supported magnetite (ST/Mag) nanoparticles were synthesized as an adsorbent for the removal of hexavalent chromium [Cr(VI)] from saline wastewater. Prepared ST/Mag adsorbent was characterized using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Various factors affecting the uptake behavior such as pH, contact time, initial concentration of metal ions, adsorbent dose, coexisting ions, and desorption behavior were studied using batch tests. The results revealed that adsorption of Cr(VI) was highly pH dependent and the kinetics of the adsorption followed by the Avrami fractional-order and pseudo-second-order kinetic models. The results showed that the adsorption isotherms were more accurately represented by Langmuir and Liu isotherm models with a sorption capacity of 30.0 mg g−1. Adsorption experiments with co-ions indicated that the adsorptive removal of Cr(VI) ions was slightly decreased. Desorption studies using alkaline eluents showed maximum recovery of ST/Mag and only 10% decrease occurring in maximum adsorption capacity after five cycles. The ST/Mag nanoparticles proved to be a very prospective adsorbent for Cr(VI) uptake from industrial high-TDS effluents.

Characterization and application of biomass gasifier waste material for adsorptive removal of Cr (VI) from aqueous solution

This study was performed to investigate the latent potential of biomass gasifier waste material (BGWM) as an adsorbent for removal of Cr (VI) from aqueous solution. The present work also proposes an alternate use of gasifier refuge BGWM with great economic feasibility. The effects of initial pH, BGWM concentration, Cr(VI) concentration, temperature and contact time were investigated on the removal of Cr (VI) from aqueous solution. The maximum removal of Cr (VI) was found to be 99.67% at optimum condition of initial pH 2, contact time 80 min, initial Cr (VI) concentration 10 mg L−1, adsorbent dose 5 g L−1, agitation speed 120 rpm, and temperature 35°C. The adsorbent was characterised by SEM, EDX, XRD, BET and FTIR analysis to get important information about its effective application for Cr (VI) removal. The BET surface area of 165.287 m2 g−1 for BGWM was found comparable to that of commercial silica. Batch adsorption experiments showed that pseudo‐second‐order kinetics model and Langmuir isotherm model fitted the adsorption data very well. Thermodynamic parameters revealed the feasibility, spontaneity and endothermic nature of Cr (VI) adsorption onto BGWM. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 95–102, 2016

Enhanced Adsorption of Hexavalent Chromium Ions on Polyamine Polyurea Polymer: Isotherm, Kinetic, Thermodynamic Studies and Batch Processing Design

In the present study, polyamine polyurea polymer was employed for adsorption of Cr(VI) ions from aqueous solution. Adsorption studies were carried out to examine the effects of parameters such as pH, contact time, initial concentration of Cr(VI), and temperature. Optimum pH value and the contact time of the system were found to be 2.5 and 240 minutes, respectively. Thermodynamic parameters that calculated with the results of temperature studies showed the adsorption processes have exothermic, reversible, and spontaneous nature. The compared isotherm data clarified that Cr(VI) adsorption onto polyamine polyurea polymer (PPP) was proper with Langmuir isotherm with maximum adsorption capacity of 135.1 mg g−1. Pseudo-second-order kinetic model was found to be descriptive for the kinetic mechanism of Cr(VI) adsorption onto PPP. Single-stage batch adsorber was designed using equilibrium data for removal of Cr(VI) at various solutions. Consequently, the PPP has been found to be effective adsorbent for removal of Cr(VI) from water media.

Adsorptive removal of Cr(VI) from aqueous solutions with an effective adsorbent: cross-linked chitosan/montmorillonite nanocomposites in the presence of hydroxy-aluminum oligomeric cations

On the basis of laboratory research, the adsorbent of cross-linked chitosan/Al13-pillared montmorillonite (CCPM) was examined on the removal of Cr(VI) from aqueous solutions. In order to determine the effects of process parameters namely cross-linked chitosan-to-clay ratio, temperature, initial solution pH, initial Cr(VI) concentration, adsorbent dose, and contact time on Cr(VI) uptake, batch studies were systematically conducted. Equilibrium data were applied to the Langmuir and Freundlich isotherm models and best described by the Langmuir isotherm model. It was shown that monolayer adsorption capacity was 15.67 mg/g of Cr(VI) obtained by the Langmuir isotherm model. The kinetics of adsorption correlated well with the pseudo-second-order equation. Moreover, the intra-particle diffusion model was applied to investigate the mechanism of adsorption. Furthermore, thermodynamic parameters including free energy change, enthalpy change, and entropy change revealed that the adsorption of Cr(VI) onto CCPM was endothermic and spontaneous. The results suggest that CCPM is an effective adsorbent for removing Cr(VI) ions from aqueous solutions.

Effect of Fulvic Acid on Adsorptive Removal of Cr(VI) and As(V) from Groundwater by Iron Oxide-Based Adsorbents

Natural contamination has become a challenging problem in drinking water production due to metal contamination of groundwater throughout the world, and arsenic and chromium are well-known toxic elements. In this study, iron oxide-coated sand (IOCS) and granular ferric hydroxide (GFH) were used to study the effects of fulvic acid (FA) on the adsorptive removal of Cr(VI) and As(V) from synthetic groundwater. IOCS and GFH were characterized by SEM/EDS, and experiments were performed at different pH levels (6, 7, and 8). The surface of IOCS and GFH showed a high content of Fe and O (75 and 60 % of the atomic composition, respectively), suggesting that they can highly effectively adsorb Cr(VI) and As(V). Adsorption tests with the simultaneous presence of As(V) and FA, on the one hand, and Cr(VI) with FA, on the other hand, revealed that the role of FA on chromate and arsenate adsorption was insignificant at almost all pH values investigated with both adsorbents. A small influence as a result of FA was only observed for the removal of As(V) by IOCS at pH 6 with a decrease of 13 and 23 % when 2 and 5 mg/l were added to the synthetic water, respectively. It was also found that organic matter (OM) was leached from the IOCS during batch adsorption experiments. The use of FEEM revealed that humic-like, fulvic-like, and protein-like organic matter fractions are present on the IOCS surface.

Adsorptive removal of Cr(VI) from aqueous solutions by cross-linked chitosan/bentonite composite

Cross-linked chitosan/bentonite composite (CCB) was prepared, and characterized by Fourier transform infrared (FTIR) spectroscopy, BET surface area and pore diameter analyses, X-ray diffraction (XRD) patterns and thermal gravimetric analyses (TGA). The adsorption of hexavalent chromium Cr(VI) onto CCB as a function of adsorbent dosage, initial Cr(VI) concentration, solution pH, and contact time was investigated through batch experiments. The removal towards Cr(VI) decreased with increasing solution pH from 2 to 11 and initial Cr(VI) concentration, while it increased with increasing adsorbent dosage. The adsorption kinetic data of Cr(VI) on CCB were well described by the pseudo-second-order model. The equilibrium data were correlated by the Langmuir isotherm model. The maximum monolayer Cr(VI) adsorption capacity for CCB at pH 2 and 293 K was 89.13mg/g. The mechanisms for the adsorption of Cr(VI) on CCB at pH 2 may include electrostatic interaction and chemical interaction between CCB and Cr(VI) ions.

Removal of Hexavalent Chromium from Aqueous Solutions using Some Plants Bark Powder as Adsorbents

Heavy metals that have been associated only with chemists have now become a concern of environmentalist also. They impact the ecosystems when released into water bodies or soil by various human activities resulting in the environmental pollution. High concentration of Cr (VI) is harmful to animal and human health. The hexavalent chromium exists in aquatic media as water soluble complex anions and persist. These are concentrated in industrial waste water especially from the tannery industries and release of effluents from industries adversely affects the environment. The removal of heavy metals from aqueous solutions is carried out by different physical, chemical and biological methods. Now a days, use of plants waste products such as: barks, manures or lignocellulosic materials, for the removal of heavy metals from polluted water are becoming of more concern. In the present study, low-cost and easily available material such as plant barks for the removal of chromium VI from its aqueous solution was investigated. Bark powders of plants namely, Pongamia glabra, Tamarindus indicus, Tesphesia populnea, and Mangifera indica obtained from nearby saw mills, were used as adsorbent for the removal of Cr (VI) from aqueous solutions in excess of maximum permissible limits. Adsorption for chromium (VI) was found to be highly dose dependent compared to the other parameters observed with almost 100 % efficiency at pH 2, contact time of 2h at room temperature with 3 g l-1 bark dosage. The adsorption capacities of all the plant barks for chromium (VI) was found to be comparable to other commercial adsorbents currently employed for the removal of heavy metals from aqueous wastes. The results have demonstrated the immense potential of plants bark powder as an alternative adsorbent for removal of Cr(VI) ions from polluted water.

Combined Effect of Sunflower Stem Carbon–Calcium Alginate Beads for the Removal and Recovery of Chromium from Contaminated Water in Column Mode

Adsorptive removal of Cr(VI) was investigated in a downflow fixed bed column using sunflower stem carbon–calcium alginate beads (SSC-CAB) at various bed heights (28.0, 38.0, and 52.0 cm), initial Cr(VI) concentrations (10–20 mg/L), and flow rates (1.0–3.0 mL) at preoptimized pH = 2.0 for achieving the breakthrough curves. The adsorption capacity was calculated using the Bohart-Adams (BA) model which is widely used for column adsorption. The highest adsorption capacity of 4.09 mg/L was recorded at a bed height of 52.0 cm, flow rate of 1.0 mL/min, and an initial Cr(VI) concentration of 10.0 mg/L. The breakthrough time increased with a decrease in flow rate and Cr(VI) concentration and an increase in bed height. The adsorption capacity (N0) at 50% breakthrough time was 20 mg/L. Cr(VI) loaded SSC-CAB adsorbent was washed with 0.5 M HCl solution at a flow rate of 2.0 mL/min, and the efficiency of the adsorbent regenerated by the desorbing agent was examined in three sorption/desorption cycles. Regeneration eff...

Green synthesis of graphene sand composite (GSC) as novel adsorbent for efficient removal of Cr (VI) ions from aqueous solution

Cr (VI) is one of the most toxic contaminants recognized as a carcinogenic and mutagenic agent and needs complete removal from wastewater before disposal. In the present study, a novel graphene based adsorbent was synthesized from sugar and sand using green chemistry approach and adsorption of Cr (VI) ions from aqueous solution was studied by batch adsorption technique under varying experimental conditions like contact time, pH, adsorbent dose, initial Cr (VI) concentration and temperature. The characterization of the prepared graphene sand composite (GSC) was accomplished by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction(XRD) analysis, Raman spectroscopy, electron diffraction measurements, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy (EDX) and surface area measurements. The specific surface area of the GSC before and after activation was determined to be 100m2/g and 157m2/g, respectively. The optimum adsorption of Cr (VI) by the new adsorbent, coined as GSC, was observed at pH 1.5 The maximum adsorption capacity of GSC for Cr (VI) was found to be 2859.38mg/g at room temperature which is claimed to be one of the exceptionally high values reported so far in the literature. The equilibrium sorption data were fitted satisfactorily to the Langmuir adsorption model with R2 value of 0.99108. The progress of the adsorption process was found to follow the second order kinetics. The results obtained in this study illustrated that the prepared graphenic material could be an effective and economically viable adsorbent for removal of Cr (VI) ions.

Highly stable and covalently functionalized magnetic nanoparticles by polyethyleneimine for Cr(vi) adsorption in aqueous solution

Covalently functionalized magnetic nanocomposite by polyethyleneimine (PEI) acted as superior adsorbent for removal of Cr(vi) form water.

Adsorption isotherm and kinetic studies of hexavalent chromium removal from aqueous solution onto bone char

The adsorption of hexavalent chromium [Cr(VI)] onto bone char was optimized as a function of pH, initial Cr(VI) concentration, and bone char dosage using aqueous solution in batch tests. The initial Cr(VI) concentrations were varied between 5 and 800mg/L to investigate equilibrium, kinetics, and the adsorption isotherms. About 100% of Cr(VI) was removed at initial pH of 1.0 with initial Cr(VI) concentration of 10mg/L, using 2g of bone char after 2h. The maximum adsorption capacity of the bone char was 4.8mg/g for an initial Cr(VI) concentration of 800mg/L. The adsorption kinetics of Cr(VI) onto bone char followed a second order kinetic model. The adsorption isotherm followed the Langmuir model for Cr(VI) adsorption. In general, bone char demonstrated promising results as an effective adsorbent for removal of Cr(VI) from the aqueous solution. The results from this study could be useful in designing a filtration unit with bone char as the adsorbent in a full-scale water and wastewater treatment plant for the removal of Cr(VI) from contaminated water.

Evaluation of Kinetics of Leaching of Lignins and Tannins in Batch Adsorption of Cr (VI) by Emblica officinalis Leaf Powder (EOLP)

The present paper is aimed to assess the contents of lignin and tannin leached in the batch adsorption test filtrate and to evaluate the kinetics of leaching of lignin and tannins. For the purpose, raw Emblica officinalis leaf powder (EOLP) has been used as adsorbent for removal of Cr (VI) from aqueous solution in batch mode of operation. Test results indicate that EOLP imparts lignin and tannin in batch test filtrate. Both lignin and tannin contents are related to pH, chemical oxygen demand (COD), initial Cr(VI) concentration (C0) residual Cr(VI) concentration in batch test filtrate (C),amount of adsorbent (Wad) and the time of contact (t). Dimensionless parameters are developed and the lignin and tannin contents are well correlated with dimensionless parameters. From the studies conducted on rate of leaching of both soluble lignin and tannins, the kinetics of leaching of soluble lignin and tannin follow a pseudo second order type rate kinetics. Linear regression models are developed based on pseudo second order kinetics for determination of lignin and tannin contents in batch test filtrate. However, these findings need further verification in future investigations.

Hydrothermal carbonization synthesis of a novel montmorillonite supported carbon nanosphere adsorbent for removal of Cr (VI) from waste water

In this work, a novel montmorillonite supported carbon nanosphere adsorbent (Mt-spC) was fabricated successfully by a green and facile technique called hydrothermal carbonization, which was used to remove Cr (VI) from an aqueous solution. The batch adsor'ption results showed that, when the adsorption equilibrium time was 60min and the optimum adsorption pH was 2, this novel Mt-spC adsorbent exhibited excellent performance (156.25mg/g) for the removal of Cr (VI), which was much higher than that of raw Mt and the previously reported values of other materials. Kinetic and isotherm studies showed that Cr (VI) adsorption was more favorable at a higher concentration and monolayer adsorption occurred on the adsorbents. Therefore, it can be suggested that this novel Mt-spC nanocomposite could be a good candidate for removing Cr (VI) from waste water, and this research provides a new route for the development of new environmental remediation nanomaterials.

Adsorptive Removal of Cr(VI) from Aqueous Solution on Hydrous Cerium—Zirconium Oxide. Part I: Process Optimization by Response Surface Methodology

Hydrous cerium-zirconium oxide (Ce0.25Zr0.75O2) was used for Cr(VI) removal by adsorption. The response surface methodology (RSM) was applied as a tool for the optimization of adsorption operational conditions (temperature, pH and adsorbent dose) with the combined effects of the key processing variables on the Cr removal efficiency (%RCr). The following conditions were found to be optimal: pH = 2, temperature = 28 °C, adsorbent dose = 4 g l-1. The %RCr obtained experimentally (92%) was in agreement with the value predicted by RSM (88%). The adsorption process followed the pseudo-second-order kinetic model and obeyed the Langmuir isotherm model. Thermodynamic parameters (ΔH°, ΔS° and ΔG°) indicated the exothermic and spontaneous nature of adsorption governed by physisorption interactions. Hydrous Ce0.25Zr0.75O2 showed high adsorption capacity (25 mg g-1), high desorption efficiency (80%), reached adsorption equilibrium quickly (30 minutes) and high chemical stability. The Cr(VI) adsorption on hydrous Ce0.2...

Adsorptive Removal of Cr(VI) from Aqueous Solution over Material: Optimisation through Response Surface Methodology

In the present study, organic-inorganic hybrid mesoporous material (HMC) were used to optimize the removal rate for Cr (VI) by applying Response Surface Methodological approach. Batch mode experiments were also carried out to assess the adsorption equilibrium in aqueous solution. The effect of three parameters, that is pH of the solution (1.52.5), initial concentration (100500 mg/L) and adsorbent dose (0.050.15 g/ 50 mL) was studied for the removal of Cr (VI) by HMC. BoxBehnken model was used as an experimental design. The optimum pH, adsorbent dose and initial Cr (VI) concentration were found to be 2.0, 0.05 g/L and 500 mg/L, respectively. Under these conditions removal adsorption capacity of Cr (VI) was found to be 337..

Adsorptive removal of Cr(VI) from aqueous solution onto different kinds of modified bentonites

Chromium(VI) removal is important for wastewater treatment, and adsorption is an efficient treatment process. In this paper, natural bentonite was exchanged to sodium bentonite (Na‐Bent) by adding NaCl. Hydroxy‐alumina pillared bentonite (OH‐Al‐Bent), octadecyltrimethylammonium chloride modified bentonite (OTMAC‐Bent) and organic‐inorganic pillared bentonite (OTMAC‐OH‐Al‐Bent) were prepared via exchange reaction and then characterized through FTIR and BET measuring. Batch experiments were conducted on adsorption of Cr(VI) by the prepared modified bentonites. The results showed that the adsorption of Cr(VI) by Na‐Bent and natural bentonite was neglected due to their weak adsorption performance. The adsorption capacity of Cr(VI) on OH‐Al‐Bent was much lower than on OTMAC‐Bent and OTMAC‐OH‐Al‐Bent. The adsorption isotherms of Cr(VI) by OTMAC‐OH‐Al‐Bent and OTMAC‐Bent both fit well with Freundlich and Langmuir adsorption model and the adsorption kinetics data of Cr(VI) fit well with the pseudo‐second‐order model. The adsorption efficiency was over 90%, suggesting that OTMAC‐OH‐Al‐Bent and OTMAC‐Bent were excellent adsorbents for effective Cr(VI) removal from aqueous solution. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 39–46, 2015

Kinetics for adsorptive removal of chromium(VI) from aqueous solutions by ferri hydroxide/oxohydroxides

Adsorption behaviors of chromate(VI) on two different iron oxides were investigated through batch experiments under different operational conditions. The operational variables studied included sorbent doses, sorbent species, solution pH, contact time, and initial metal ion concentrations. Both ferri hydroxide and ferri oxohydroxides were capable of removing Cr(VI) from aqueous solution effectively. The extent of metal ion removed from aqueous solution by both sorbents increased with increasing contact time and initial metal ion concentrations, while decreased with elevating solution pH initially. Sorption equilibrium time was observed in 150 min. Equilibrium isotherm data were analyzed using the Langmuir and Freundlich isotherms. The Freundlich model yields a better fit than the Langmuir model. Although kinetic measurements with both sorbents had a similar pattern, ferri hydroxide always showed higher sorptive potential for Cr(VI) than ferri oxohydroxides. Results also indicated that sorptive removal of Cr(VI) by both sorbents was observed to be negative in response to solution pH, due to changes in speciation of Cr(VI) in aqueous solution. At pH lower than 3.0, both iron oxides exhibited much greater capacities of removing Cr(VI) from aqueous solution than other treatments. Therefore, it is to conclude that adsorptive removal of Cr(VI) by both iron oxides is effective. Adsorption capacity is mainly determined by speciation of Cr(VI) in solutions, which is controlled and driven by solution pH.