Adsorption Mechanism Of Chromium Research Articles

Removal of chromium (VI) using spirulina assisted synthesized mesoporous iron oxide nanoparticles

Worldwide demand for clean and safe drinking water is a serious concern due to sharply rising industrialization and the growing population. In this work, Spirulina (microalgae) based green synthesis of mesoporous iron oxide nanoparticles (MIONPs) was performed for the adsorption of chromium (VI) in an aqueous solution. Synthesized MIONPs were characterized by XRD, FT-IR, Raman Spectroscopy, Zeta Potential, Particle Size Analyzer, and FESEM with EDX. The mesoporous nature of synthesized material was confirmed using Brunauer–Emmett–Teller (BET) with a pore diameter of 3.837 nm. The adsorption mechanism of Chromium (VI) by synthesized MIONPs was explained using XPS analysis. The various other parameters including pH, Temperature, ion concentration, adsorbent dose, and contact time were also studied in batch experiments for chromium removal. The synthesized material shows the best adsorption efficiency on pH 2, 100 min of contact time, and a temperature of 70 ℃. The Langmuir isotherm model with an adsorption efficiency of 92.8505 mg/g shows better adsorption than the Freundlich isotherm model for synthesized material. The pseudo-second-order model with chemisorption kinetics explains better chromium adsorption with an R2 value of 0.99863 than the pseudo-first-order model. Regeneration studies analyse the recyclable use of green synthesized MIONPs during the adsorption of chromium. This study could be useful for the removal of multiple heavy metals at a time from drinking water safely without harming the ecosystem and hence it is employable to meet the sustainability goals.

Adsorption of Chromium (VI) from aqueous phase using Aegle marmelos leaves: Kinetics, isotherm and thermodynamic studies

Batch studies were used to investigate the adsorption effectiveness of Aegle-marmelos leaves in removing Chromium(VI) metal ions from the aqueous phase. Adsorption was studied using factors such as adsorbent dosage, pH, contact time, metal ion concentration and temperature. At optimum conditions, removal of 86.6% of Cr(VI) at a pH of 2 was attained by the adsorbent. The Langmuir adsorption model fitted best to the experimental isotherm data The kinetics and mechanism of chromium adsorption were accurately explained by the kinetics model of pseudo second order. According to the thermodynamic characteristics such as entropy(ΔS⁰), Gibbs free energy(ΔG⁰) and enthalpy(ΔH⁰) measured at 298, 303 and 308 K, the adsorption process is endothermic and spontaneous. The analysis of the adsorbent's surface morphology and adsorption capability is supported by FTIR, SEM, and EDS technique. All these findings confirm that Aegle-marmelos leaves could be employed as a probable adsorbent for extracting chromium(VI) in an aqueous solution.

Adsorption mechanism of chromium(III) using biosorbents of Jatropha curcas L.

The removal of Cr3+ from water solutions by biosorbents from the rind, endosperm, and endosperm + episperm of the Jatropha curcas was evaluated. Adsorption tests were performed in batch systems for evaluating the influence of the solution's pH, adsorbent mass, contact time, initial Cr3+ concentrations, and solution temperature during the adsorption process. Kinetic, adsorption isotherm, and thermodynamic studies were performed to investigate the mechanisms that control adsorption. Ideal conditions for the adsorption process included pH of the solution of 5.5 and 8gL-1 adsorbent mass, within 60min time contact between adsorbent and adsorbate. Maximum adsorption capacities by Langmuir model for rind, endosperm, and endosperm + episperm of the J. curcas were, respectively, 22.11, 18.20, and 22.88mgg-1, with the occurrence of chemosorption in mono and multilayers. Results show that the biosorbents obtained from J. curcas have a high potential to recuperate Cr3+ from contaminated water sources.

Adsorption mechanism of Chromium(III) from water solution on bone char: effect of operating conditions

The adsorption capacity of bone char (BC) towards Cr(III) from an aqueous solution was studied in this work. The characterization of the BC showed that the BC is mainly composed of hydroxyapatite, Ca10(PO4)6(OH)2, and its point of zero charge was 7.7. The infrared spectroscopic analysis of the BC loaded with Cr(III) revealed that the Cr(III) adsorbed on BC interacted with the phosphate of the hydroxyapatite. The adsorption capacity increased 2.6 times by raising the solution pH from 3 to 5. This tendency was due to the interactions between the surface charge and the cationic species of Cr(III) in aqueous solution. The adsorption capacity was enhanced 2.5 and reduced 1.3 times when the temperature was increased from 15 to 25 °C and from 25 to 35 °C, respectively. The effect of temperature on the adsorption capacity of BC showed an anomalous behavior since the adsorption capacity exhibited a maximum at T = 25 °C. It was demonstrated that the main adsorption mechanism of the Cr(III) species was coordination to the phosphate ions and the Ca(II) in the BC was substituted or replaced by the Cr(III) species from the solution. This latter result was further corroborated by XPS analysis.

Effect of Cr(III) on process performances of MBR systems

The paper investigates the effect of Cr(III) on the heterotrophic biomass of membrane bioreactors (MBRs) to understand the consequences on process performances. Respirometric tests are conducted to evaluate the consequences of chromium injection on oxygen consumption and oxygen uptake rate for the sludge sampled from a MBR pilot plant and, comparatively, for the sludge sampled from a conventional activated sludge treatment plant. MBR sludge is found to be more resistant to chromium injection than conventional activated sludge. Measurements of residual metal concentration are carried out to understand the mechanism of chromium adsorption and assimilation. The release of soluble microbial products, which play an important role on membrane fouling, is also investigated. Obtained information is completed by microscopic observations, aimed at identifying the variation of biomass structure and composition due to the presence of Cr(III).

Effective parameters for the adsorption of chromium(III) onto iron oxide magnetic nanoparticle

Most of the industrial wastewaters comprise toxic, biologically non-biodegradable, and heavy metals which tend to accumulate in the biological organisms causing different diseases. There are some novel technologies and strategies to remove these pollutants. Using the magnetic nanoparticles which are cheap, recyclable, and reusable can be considered as an effective method for removing the pollutants as they do not require conservation or complicated equipments. Using this method, dangerous and rare heavy metals can be restored to the industry. In this study, magnetic nanoparticles with the size of 30 nm were prepared and used for the removal of chromium from synthetic wastewater polluted by chromium sulfate. For this purpose, removal of various concentrations of chromium(III) from wastewater was investigated. The best concentration was achieved in the removal efficiency of 99.1 %. The optimal values of pH, rotation speed of magnetic stirrer, time, temperature, and the amount of nanoparticles were determined according to the primary concentration (500 mg/L). The mechanism of chromium adsorption onto iron oxide (Fe3O4) magnetic nanoadsorbent was also investigated. The results showed both Freundlich and Longmuir isotherms to be the best fit for the chromium adsorption, with Freundlich isotherm being more suitable.

Chromium removal from electroplating wastewater by coir pith

Coir pith is a by-product from padding used in mattress factories. It contains a high amount of lignin. Therefore, this study investigated the use of coir pith in the removal of hexavalent chromium from electroplating wastewater by varying the parameters, such as the system pH, contact time, adsorbent dosage, and temperature. The maximum removal (99.99%) was obtained at 2% (w/v) dosage, particle size <75 μm, at initial Cr(VI) 1647 mg l −1, system pH 2, and an equilibrium time of 18 h. The adsorption isotherm of coir pith fitted reasonably well with the Langmuir model. The maximum Cr(VI) adsorption capacity of coir pith at 15, 30, 45 and 60 °C was 138.04, 197.23, 262.89 and 317.65 mg Cr(VI) g −1 coir pith, respectively. Thermodynamic parameters indicated an endothermic process and the adsorption process was favored at high temperature. Desorption studies of Cr(VI) on coir pith and X-ray absorption near edge structure (XANES) suggested that most of the chromium bound on the coir pith was in Cr(III) form due to the fact that the toxic Cr(VI) adsorbed on the coir pith by electrostatic attraction was easily reduced to less toxic Cr(III). Fourier transform infrared (FT-IR) spectrometry analysis indicated that the carbonyl (C O) groups and methoxy (O–CH 3) groups from the lignin structure in coir pith may be involved in the mechanism of chromium adsorption. The reduced Cr(III) on the coir pith surface may be bound with C O groups and O–CH 3 groups through coordinate covalent bonding in which a lone pair of electrons in the oxygen atoms of the methoxy and carbonyl groups can be donated to form a shared bond with Cr(III).

Mechanism of hexavalent chromium adsorption by persimmon tannin gel

Mechanism of chromium adsorption by the persimmon tannin (PT) gel was examined. The PT gel can adsorb Cr highly effectively from aqueous solutions containing Cr(VI), while it adsorbed far smaller amounts of Cr from the solution containing Cr(III). The maximum Cr adsorption from the Cr(VI) solution occurred at pH 3. The Cr adsorption from the Cr(VI) solution by the PT gel was rapid, was faster than VO 2+ and Fe 3+ adsorptions, and was obeyed the Langmuir adsorption isotherm ( Q e=5.27 mmol g −1 and K=16.2 mM). The gel adsorbed Cr from the Cr(VI) solution (pH 1 and 3) showed no ESR signal of Cr(III), while the ESR signal of Cr(III) was observed in the residual solution at pH 1. Hexavalent chromium was, therefore, adsorbed on the PT gel through the esterification of chromate with catechol group. In other words, Cr(VI) should combine with catechol as a hard acid, CrO 2 2+ cation. Through the treatment of a Cr(VI) solution with the PT gel, chromium should be recovered as a Cr(IV)−tannin complex at pH 3 or a Cr(III) solution at pH 1 or lower pH region.

Recovery of chromium(VI) from wastewaters with iron(III) hydroxide—I: Adsorption mechanism of chromium(VI) on iron(III) hydroxide

Chromium(VI) [Cr(VI)] is adsorbed as HCrO − 4 on iron(III) hydroxide at pH below 8.5. The Cr(VI) adsorption is suppressed by the presence of other anions such as SO 2− 4 and SCN −, and enhanced by the presence of metal ions such as Cd(II) and Pb(II). The suppression is due to the competitive adsorption of other anions, depending upon the stability of their iron complexes. The enhancement is probably due to the increase in adsorption sites as a result of coprecipitation of metal ion with iron(III) hydroxide.