Adsorbent For Removal Of Hexavalent Chromium Research Articles

Preparation of waste face masks modified with MnO2/poly(m-phenylenediamine) as a novel adsorbent for hexavalent chromium removal: Comprehensive batch and column study

Single-use surgical face masks (SFM) have become one of the most used personal protective equipment (PPE) for preventing the transmission of diseases, especially COVID-19. However, the environment is being threatened by the huge amount of plastic waste generated by this material. In this study, a novel environmentally-friendly in-situ-surface polymerization method was employed to modify the surface of SFM with m-phenylenediamine (mPDA) for removing hexavalent chromium. The synthesized adsorbent was characterized by Field Emission-Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared Spectroscopy (FTIR). The investigations showed that the polymer and oxidant solution can be reused for several cycles, which was not possible in the conventional chemical polymerization method with ammonium persulfate (APS). The influence of various variables on the adsorption process was assessed and the optimum results was reported (adsorbent dosage: 3 g L−1, contact time: 60 min, pH: 2). The modeling investigations demonstrated that the process is followed by pseudo-second-order kinetic and University of Tehran (UT) isotherm model's assumptions, respectively. The obtained thermodynamic parameters at the investigated temperatures revealed the spontaneity and endothermic nature of Cr(VI) adsorption on the modified adsorbent. The column study was conducted and the impact of the flow rate and the feed concentration of Cr(VI) were evaluated. The experimental findings were analyzed using the Thomas model to discover how the concentration changes over time in the column operation. It was revealed that when the flow rate rose, the service volume declined.

Biochar Nanocomposite as an Inexpensive and Highly Efficient Carbonaceous Adsorbent for Hexavalent Chromium Removal

Biochar is commonly used for soil amendment, due to its excellent water-holding capacity. The Cr(VI) contamination of water is a current environmental issue in industrial regions. Here, we evaluated the effects of two-step modifications on boosting biochar’s performance in terms of the removal of aqueous hexavalent chromium (Cr(VI)), along with investigating the alterations to its surface properties. The first modification step was heat treatment under air at 300 °C, producing hydrophilic biochar (HBC). The resulting HBC was then impregnated with zero-valent iron nanoparticles (nZVI), creating an HBC/nZVI composite, adding a chemical reduction capability to the physical sorption mechanism. Unmodified biochar (BC), HBC, and HBC/nZVI were characterized for their physicochemical properties, including surface morphology and elemental composition, by SEM/EDS, while functional groups were ascertained by FTIR and surface charge by zeta potential. Cr(VI) removal kinetic studies revealed the four-time greater sorption capacity of HBC than BC. Although unmodified BC showed faster initial Cr(VI) uptake, it rapidly worsened and started desorption. After nZVI impregnation, the Cr(VI) removal rate of HBC increased by a factor of 10. FTIR analysis of biochars after Cr(VI) adsorption showed the presence of Cr(III) oxide only on the used HBC/nZVI and demonstrated that the carbonyl and carboxyl groups were the main groups involved in Cr(VI) sorption. Modified biochars could be considered an economical substitute for conventional methods.

Fabrication of Hydrotalcite-like Copper Hydroxyl Salts as a Photocatalyst and Adsorbent for Hexavalent Chromium Removal

Cu-HyS-urea and Cu-HyS-NaOH, which are hydrotalcite-like copper hydroxyl salts, were prepared by two different methods, urea hydrolysis and precipitation, respectively. Both synthesis methods provided the successful formation of a copper hydroxyl salt, Cu2(OH)3NO3. From XRD and UV-DRS results, the product from the urea hydrolysis methods (Cu-HyS-urea) displayed higher crystallinity, small bandgap energy (Eg), and high light absorption ability because of some intercalated carbonate anions. For the Cr(VI) removal test, the Cu-HyS-NaOH showed superior adsorption of Cr(VI) than Cu-HyS-urea due to a higher specific surface area, confirmed by BET analysis. However, the Cu-HyS-urea presented higher photocatalytic Cr(VI) reduction under light irradiation than Cu-HyS-NaOH, owing to narrow Eg, less recombination, and a high transfer of the photogenerated charge carriers, proven by the results from photoluminescence, photocurrent density, and electrochemical impedance spectroscopy. Thus, this work provides a new function of the hydrotalcite-like copper hydroxyl salts (Cu-HyS-urea and Cu-HyS-NaOH) that can be utilized not only for adsorption of Cr(VI) but also as photocatalysts for Cr(VI) reduction under light irradiation.

Facile preparation of polyethyleneimine modified activated sludge-based adsorbent for hexavalent chromium removal from aqueous solution

ABSTRACT Polyethyleneimine modified activated sludge (AS-PEI) was prepared and used for the removal of Cr(VI) in wastewater. Characterized results exhibited that PEI was successfully anchored on the surface of activated sludge. At 25 ºC and pH = 5.0, the maximum adsorption amount of Cr(VI) on AS-PEI was 86.96 mg/g. The adsorption amount of AS-PEI for Cr(VI) decreased as the pH values increased. The existence of Cl-, SO4 2- and PO4 3- decreased the Cr(VI) adsorption, and HA enhances the Cr(VI) adsorption. The electrostatic interaction combined reduction was the main mechanism of Cr(VI) adsorption. Cr(VI) loaded adsorbent can be regenerated in alkaline solution and AS-PEI can be reused.

Facile synthesis of heterojunction of MXenes/TiO2 nanoparticles towards enhanced hexavalent chromium removal

Increasing the surface area and active sites of adsorbent for hexavalent chromium removal in water is considered an effective and efficient way to enhance reduction and adsorption performance. Here 2D/0D heterojunction of Ti3C2 MXenes/TiO2 nanoparticles with different amounts of TiO2 were synthesized using a one-step hydrothermal method and the reduction and adsorption of Cr (VI) at different pH values of composite material were analyzed. The results show that the Ti3C2/TiO2 composite material allows significantly enhanced removal ability of toxic Cr (VI) in water, compared to pure Ti3C2 nanosheets. The effective removal of Cr (VI) in water was 99.35%. The Ti3C2/TiO2 composite can not only rapidly and efficiently remove Cr (VI) from potassium dichromate solution by reducing Cr (VI) to Cr (III), but simultaneously adsorbs the reduced Cr (III). Therefore, the 2D/0D heterojunction of Ti3C2 MXenes/TiO2 nanoparticles has potential application prospects in the reduction adsorption of Cr (VI).

Eucalyptus sawdust derived biochar generated by combining the hydrothermal carbonization and low concentration KOH modification for hexavalent chromium removal

In this study, Eucalyptus sawdust was hydrothermally carbonized, and the resulting biochar was modified by a low concentration potassium hydroxide. The morphology and surface property was characterized by SEM-EDS, BET, FTIR and XPS techniques. A series of batch adsorption experiments were conducted to screen out the optimum conditions, and to investigate the isotherm, kinetics and thermodynamic behaviors. The results indicated that a high adsorption capacity of hexavalent chromium (qe 45.88 mg/g) was achieved by the combining of hydrothermal carbonization at 220 °C and 0.05 N potassium hydroxide modification, and a high biochar yield (47.61%) was obtained. The isotherm, kinetics and thermodynamic studies suggested that the spontaneously and endothermically chemical adsorption was the main mechanism, which was partially supported by BET, FTIR and XPS results. This finding suggested that the combination of hydrothermal carbonization and a subsequent low alkali modification was an effective method to prepare a high-performance adsorbent for hexavalent chromium removal.

Kinetics, Isothermal and Thermodynamic Modelling Studies of Hexavalent Chromium Ions Adsorption from Simulated Wastewater onto Parkia biglobosa-Sawdust Derived Acid-Steam Activated Carbon

The adsorption potential of activated Parkia biglobosa -sawdust carbon for hexavalent chromium ions removal from its wastewater at various operating variables of contact time, initial hexavalent chromium ions concentration, adsorbent particle size and temperature was investigated and evaluated under batch operation mode. Results indicated the impact of operating variables on the adsorption of hexavalent chromium ions. The adsorption process followed Lagergren pseudo first-order kinetics. The adsorption mechanism was film diffusion-controlled. Freundlich and Harkins-Jura isotherm models provided the best correlation ( R 2 = 0.96) of the equilibrium adsorption data. The maximum monolayer adsorption capacity () was found to be 17.54 mg/g. Calculated thermodynamic quantities were evaluated. It was found that the adsorption process was spontaneous, feasible, and endothermic and predominantly of physisorption process with little chemisorption. Therefore, acid-steam activated carbon produced from Parkia biglobosa wood sawdust has potential for application as an effective adsorbent for hexavalent chromium removal from wastewaters

The residue of alginate extraction from Sargassum muticum (Brown seaweed) as a low-cost adsorbent for hexavalent chromium removal from aqueous solutions

The residue of alginate extraction from Sargassum muticum (Brown seaweed) as a low-cost adsorbent for hexavalent chromium removal from aqueous solutions

Oak (Quercus robur) Acorn Peel as a Low-Cost Adsorbent for Hexavalent Chromium Removal from Aquatic Ecosystems and Industrial Effluents

The efficiency of low-cost, abundantly available local forestry waste, oak (Quercus robur) acorn peel (OP), to remove toxic Cr(VI) from aqueous solutions was studied in a batch system as a function of contact time, adsorbate concentration, adsorbent dosage, and pH. In an equilibrium time of 420 min, the maximum Cr removal by OP at pH 2 and 10 was 100 and 97 %, respectively. The sorption data fitted well with Langmuir adsorption model. Evaluation using Langmuir expression presented a monolayer sorption capacity of 47.39 mg g−1 with an equilibrium sorbent dose of 5 g L−1 and pH 7. Uptake of Cr by OP was described by pseudo-second-order chemisorption model. ICP-OES, LC-ICPMS analysis of the aqueous and solid phases revealed that the mechanism of Cr(VI) removal is by ‘integrated adsorption and reduction’ mechanism. ESEM-EDX and XRD analysis of OP before and after adsorption also confirmed that both adsorption and reduction of Cr(VI) to less toxic Cr3+ forms followed by complexation onto the adsorbent surface contributed to the removal of Cr(VI). Consistent with batch studies, OP effectively removed (>95 %) Cr from the real water samples collected from lake and sea. The results of this study illustrate that OP could be an economical, green, and effective biomaterial for Cr(VI) removal from natural aquatic ecosystems and industrial effluents.

Potential of Melaleuca diosmifolia leaf as a low-cost adsorbent for hexavalent chromium removal from contaminated water bodies

The present study describes for the first time the utilization of dried twigs of Melaleuca diosmifolia, fallen off from the plant, to detoxify and remove hexavalent chromium or Cr(VI) from aqueous systems. Initial characterization by gas chromatography revealed that the selected biomaterial is one of the natural sources of eucalyptol. It constituted high concentrations of reducing compounds (iron, phenols and flavonoids). Batch studies revealed that the biosorbent (5gL−1) was able to remove 97–99.9% of 250mgL−1 Cr(VI) at wide-ranging pH (2–10) and temperature (24–48°C). Adsorption kinetics was well described using the pseudo-second-order kinetic model, while the equilibrium adsorption data were interpreted in terms of the Langmuir isotherm model. The monolayer adsorption capacity was 62.5mgg−1. Both inductively coupled plasma optical emission spectrometry and liquid chromatography analyses of the aqueous and solid phases revealed that the mechanism of Cr(VI) removal was ‘adsorption-coupled reduction’. Scanning electron microscope, infrared spectroscopy and X-ray diffraction analyses of the biosorbent before and after adsorption also confirmed that both adsorption and reduction of Cr(VI) to Cr(III) followed by complexation onto functional groups of the active surface contributed to the removal of Cr(VI) from aqueous solution. The selected biomaterial effectively (99.9%) removed Cr(VI) in lake and sea water samples, highlighting its potential for remediating Cr(VI) in real environmental conditions.

Teff straw characterization and utilization for chromium removal from wastewater: Kinetics, isotherm and thermodynamic modelling

Significant numbers of studies have been reported on use of various types of agricultural wastes as adsorbent. Teff straw originates from Ethiopia where chromium pollution is one of the major pollution problem. Therefore, in the present study, teff straw was tested as an adsorbent for hexavalent chromium removal from aqueous solution. Characterization of teff straw was done using various instruments such as X-ray diffraction, scanning electron micrograph (SEM) and Fourier transform infra-red (FTIR) spectroscopy. Batch experiments were carried out to study the effects like pH, initial chromium concentration, contact time and dose of teff straw on the efficiency of the adsorption process. Adsorption of Cr(VI) on teff straw adsorbent was by a complex process. Better realistic description of adsorption kinetics was seen from pseudo-second order rate equation. The equilibrium sorption characteristics of Cr(VI) from aqueous solutions with concentrations in the range of 100–900mg/L were studied at different temperatures in the range of 288–318K, and temperature increment was found to have a positive effect on the sorption process. Langmuir isotherm gave better representation over wide range of temperature. At adsorbent dose=10g/L, pH 2 and contact time=6h, maximum Cr(VI) uptake per unit mass of teff straw (qmax) was found as 58, 70, 79, and 86mg/g at 288, 298, 308, and 318K, respectively. The negative value of change in Gibbs free energy (ΔGo) indicated spontaneous adsorption of Cr(VI) onto teff straw adsorbent. Isosteric heats of adsorption (ΔHst,a) were low at low levels of surface coverage and increased progressively.

Comparative Study of Removal of Hexavalent Chromium from Water Using Metal Oxide Nanoparticles

Hexavalent chromium is one of the important heavy metals found in water and wastewater. The hexavalent form of chromium is considered to be a human carcinogen because of its mutagenic and carcinogenic properties. This work has focused on the comparison of copper oxide nanoparticles and aluminium oxide nanoparticles for the removal of chromium(VI) from water. The cooper oxide nanoparticles (CuNP) and aluminium oxide nanoparticles (AlNP) were synthesised by sol gel method. Both the adsorbents were evaluated for the adsorption capacity using Langmuir and Freundlich adsorption model. The CuNP and AlNP were characterized for X-ray diffraction and SEM. The study indicated that the AlNP showed better removal as compared to CuNP and can be further explored as potential adsorbent for hexavalent chromium removal.

Magnetically recoverable mesoporous melamine–formaldehyde nanoparticles as an efficient adsorbent for hexavalent chromium removal

Functional porous nanoparticles have been considered as potential adsorbents for chromium (Cr) removal due to their unique properties such as high surface area, nanosized structure and specific affinity for heavy metal ions.

Capsular polypyrrole hollow nanofibers: an efficient recyclable adsorbent for hexavalent chromium removal

Capsular PPy-HNFs fabricated via in situ polymerization on organic templates showed an exceptional Cr(vi) adsorption capacity, up to 839.3 mg g−1.

Polyethylenimine modified biochar adsorbent for hexavalent chromium removal from the aqueous solution

A chemical modified biochar with abundant amino groups for heavy metal removal was prepared using polyethylenimine (PEI) as a modification reagent, and used as an adsorbent for the removal of Cr(VI) from aqueous solution. The biochars before and after modification were characterized by Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy etc. The adsorption of Cr(VI) by the modified biochar was obeyed pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Its maximum adsorption capacity was 435.7mg/g, which was much higher than that of pristine biochar (23.09mg/g). Results also indicated that the removal of Cr(VI) by the PEI modified biochar depended on solution pH, and a low pH value was favorable for the Cr(VI) removal. The results herein revealed that the PEI modified biochar had a good potential as a suitable material for sorption and detoxification of Cr(VI) from aqueous solution.

Removal of Chromium from Aqueous Solution by Custard Apple (Annona Squamosa) Peel Powder as Adsorbent

Chromium has been widely used in various industries like textile, leather, chemical manufacture, metal finishing, paint industry and many other industries. Since hexavalent chromium is a priority toxic, mutagenic and carcinogenic chemical when present in excess, it is very much required to remove chromium from effluents before allowing it to enter any water system or on to land. In the present study, the removal of hexavalent chromium by adsorption on the Custard apple peel powder as adsorbent has been investigated in the batch experiments. The agitation time, the adsorbent size, adsorbent dosage, initial chromium concentration, temperature and the effect of solution pH are studied. The Freundlich model for Cr (VI) adsorption onto Custard apple peel powder is proved to be the best fit followed by Langmuir model and Tempkin model based on high regression coefficient R^2 value. The adsorption behavior is described by a pseudo second order kinetics. The maximum metal uptake is found to be 7.874 mg/g. The morphology on the surface of adsorbents and also the confirmation of chromium binding on adsorbent surface at different stages were obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. The results obtained in this study illustrate that Custard apple peel powder is expected to be an effective and economically viable adsorbent for hexavalent chromium removal from industrial waste water.

Synthesis and adsorption properties of polymeric and polymer-based hybrid adsorbent for hexavalent chromium removal

Iron oxide modified polyglycidyl methacrylate graft copolymer (PGMA) hybrid adsorbent (PGMAFe), have been synthesized and characterized; and their use in Cr(VI) removal was studied. The adsorption capacities were determined at different pH values. The results showed the adsorption efficiency was highly pH dependent. Cr(VI) adsorption data were well fitted with the Freundlich adsorption isotherm model. The maximum Cr(VI) adsorption capacities of PGMA and PGMAFe sorbents were obtained at pH 4 as 132.5 and 162.9mg/g, respectively. The results of the kinetic experiments showed that Cr(VI) adsorption onto both sorbents followed the pseudo-second-order kinetic model. A series of column experiments were carried out to determine the breakthrough curves. The column was regenerated by eluting Cr(VI) with NaOH (10%, w/v) solution.