Adsorption Of Cr Ions Research Articles

The study of removal chromium (VI) ions from aqueous solution by bimetallic ZnO/FeO nanocomposite with Siltstone: Isotherm, kinetics and reusability

In this study, nanocomposites of Baghanwala Siltstone (BSS) with ZnO (BSS/ZnO), FeO (BSS/FeO), and BSS/ZnO/FeO were successfully prepared for the removal of hexavalent chromium [(Cr (VI)] from aqueous solutions via a batch adsorption process. The characterization studies by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) found successful synthesis of the composites and demonstrated the occurrence of different active functional groups that played an active role in Cr ion adsorption. The effect of Cr initial concentrations (25–100 mg/L), adsorbent dose (0.5–2 g/L), pH (2–8), and contact time (0–160 min) on Cr remediation from contaminated water was examined. The order of Cr ion removal was BSS/ZnO/FeO (77-87%) > BSS/ZnO (74-83%) > BSS/FeO (71-77%) > BSS (68-74%). The as-synthesized BSS/ZnO/FeO led to successful Cr removal (87%) at a 25 mg/L Cr concentration at pH 4.0. The Cr ion adsorption by the BSS/ZnO/FeO nanocomposite was well explained by the Langmuir adsorption isotherm model (R2 > 0.99), while the kinetic experimental data was well fitted with the pseudo-second-order model (R2 > 0.99). Among the as-synthesized adsorbents, the BSS/ZnO/FeO nanocomposite showed excellent stability and reusability in seven sorption cycles. The results showed that the as-synthesized BSS/ZnO/FeO nanocomposite had the greatest adsorption potential for removing Cr ions from contaminated water.

Combined Role of Fe Nanoparticles (Fe NPs) and Staphylococcus aureus L. in the Alleviation of Chromium Stress in Rice Plants.

Chromium (Cr) is a toxic heavy metal whose high concentration in soil badly affects plant growth, photosynthesis, and overall yield. Metal-derived nano-particles and metal-resistant bacteria can strengthen the plant defense system against different abiotic stresses; however, little is known about the use of nanoparticles in conjunction with bacteria. This study examined the combined effect of Fe nanoparticles (Fe NPs) and a chromium-resistant bacterium Staphylococcus aureus, on rice plants grown on chromium saturated medium. Chromium stress reduced rice growth, biomass, and chlorophyll contents by causing oxidative damage leading to overproduction of electrolyte leakage, hydrogen peroxide, and malondialdehyde. Fe NPs significantly improved plant growth, biomass, yield, and photosynthetic activity by enhancing the chlorophyll contents and alleviating oxidative damage. Application of Fe NPs also reduced the uptake and accumulation of Cr in the plants by increasing the bioavailability of micronutrients to the plant. The Fe NPs decreased oxidative damage and enhanced the enzymatic and non-enzymatic activity in the plant to withstand Cr stress compared to the plants without Fe NPs treatments. The inoculation of rice plants with the chromium-resistant bacteria S. aureus further enhanced the positive impact of Fe NPs by transforming the toxic form of chromium (Cr6+) into a less toxic form of chromium (Cr3+). The bacterial inoculation reduced Cr uptake by plants through adsorption of Cr ions, resulting in decreased chromium ion bioavailability. At chromium level 100 mg/kg, the foliar application of Fe NPs from 0 to 20 mg/L increased the total chlorophyll contents from 2.8 to 3.9. The application of S. aureus further enhanced the chlorophyll contents from 4.4 to 5.4, respectively. The current study suggested that combining Fe NPs and S. aureus could be a viable strategy for reducing Cr toxicity and accumulation in rice plants and most likely other plants.

Structural analysis and the effect of the chromium on LTA (Na) zeolite synthesized from kaolin

The release of heavy metals ions into water resources is an environmental issue due to their high toxicity, long-lasting stability, and bioaccumulation in the food chain. Currently, the discharge of Mayan leather manufacturing plants’ wastewater into the Aji Chai River in East Azerbaijan (Iran) has increased the concentration of heavy elements such as chromium, copper, and zinc, so that the upper free aquifer of the Mayan Plain has become salty due to the feeding from this River. To overcome such a problem, we synthesized a highly functional Linde Type A (LTA) Na-zeolite from Kaolin as the raw material. In this regard, the impact of parameters such as synthetic temperature, adsorption temperature, and pH on the Cr adsorption capacity of zeolite on wastewater solutions obtained from this area was investigated. The structural analysis through XRD, SEM, BET, and FTIR, coupled with the Rietveld refinement method demonstrated that upon adsorption of Cr ions into the LTA zeolite structure, the lattice parameter decreases. Additionally, the results of this study suggest that the synthesized LTA zeolite has a very high adsorption rate in both acidic and alkaline environments in a way that a 100% removal rate was recorded at pH = 3. The as-synthesized zeolite has efficiently removed chromium from industrial waste waters flowing into this area.

Hexavalent Cr ion adsorption and desorption behaviour of expanded poly(tetrafluoro)ethylene films grafted with 2-(dimethylamino)ethyl methacrylate

ABSTRACT A new polymeric adsorbent for Cr(VI) ions based on an expanded poly(tetrafluoroethylene) (ePTFE) film was prepared by the combined use of the pretreatment with oxygen plasma and photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA). The grafting of DMAEMA was characterized by XPS and FT-IR spectroscopic measurements. The adsorption behaviour of DMAEMA-grafted ePTFE (ePTFE-g-PDMAEMA) films was investigated as a function of the experimental parameters, such as the initial pH value, temperature, and grafted amount. The adsorption capacity and initial adsorption rate had the maximum values at the initial pH value of 3.0. On the other hand, the adsorption capacity became almost constant at temperatures higher than 30°C, although the adsorption rate increased over the temperature. The adsorption behaviour obeyed the pseudo-second-order kinetic model and well expressed by the Langmuir isotherm equation with higher correlation coefficients. These results indicate that the adsorption of Cr(VI) ions occurs through the electrostatic interaction between protonated dimethylamino groups on a grafted PDMAEMA chain and ions. Cr(VI) ions were successfully desorbed from Cr(VI)-loaded ePTFE-g-PDMAEMA films in the eluents, such as NaCl at 0.50 M, NH4Cl at 0.50M, and NaOH at 1.0 mM, and ePTFE-g-PDMAEMA films were repeatedly used for adsorption of Cr(VI) ions without appreciable loss in the adsorption capacity. It should be noted that Cr(VI) ion adsorptivity with a high initial rate was conferred to the ePTFE films. The results obtained in this study emphasize that ePTFE-g-PDMAEMA films can be applied as an adsorbent for Cr(VI) ions.

Chromium adsorption using waste tire and conditions optimization by response surface methodology

Chromium adsorption was investigated using waste tire adsorbent (WTA) and the process variables (pH, adsorbent dosage, Cr ions initial concentration, contact time) were optimized through response surface methodology. Initial metal ions concentration (20–820mg/L), pH (1.0–9.0 for Cr(VI) and 1.0–5.0 for Cr(III)), contact time (288–1440min) and adsorbent dose (0.1–2.1g/100mL) were selected and optimized as experimental variables, which affected the Cr adsorption significantly. The optimum conditions for maximum Cr(VI) adsorption were found as; 336.63mg/L initial concentration, pH 4.8, contact time 882.5min, whereas for Cr(III), the optimum levels of process variables were 1.2g/100mL and 337mg/L, 3.0, 910.18min and 1.3g/100mL solution, respectively. The sorption capacities were 105.84 and 174.55mg/g for Cr(VI) and Cr(III), respectively. At optimized conditions, 79.6% (214.72mg/g) Cr was sequestered from tannery effluents. The Langmuir isotherm and pseudo-first order kinetic model fitted well to the Cr adsorption data. The FTIR study revealed the involvement of hydroxyl, amino and carboxylic acid functional groups in the adsorption of Cr ions.

Adsorption of Cr Ion by Activated Carbon Prepared from Corncob Xylitol Residue

Corncob xylitol residue was soaked with H3PO4 for 16h and carbonized in microwave for 9min to obtain activated carbon. Methylene blue and iodine adsorption values were determined and were 119.92mg/g and 839.47mg/g, respectively. The adsorption property on Cr6+ was determined and the proper adsorption condition was pH2, 30min, 80°C. The maximum Cr adsorption capacity was 50mg/g.