Removal of hexavalent chromium, an analogue of pertechnetate, from aqueous solution using bamboo (Acidosasa edulis) shoot shell

Bamboo-derived adsorbents for environmental remediation: A review of recent progress

The bamboo family of plants is one of the fastest-growing species in the world. As such, there is an abundance of bamboo residues available for exploitation, especially in southeast Asian, central African and south American regions. The preparation of efficient adsorbents from bamboo residues is an emerging exploitation pathway. Biochars, activated carbons or raw bamboo fibers embedded with nanoparticles, each class of materials has been shown to be highly efficient in adsorption processes. This review aims to summarize recent findings in the application of bamboo-based adsorbents in the removal of organic, inorganic, or gaseous pollutants. Therefore, this review first discusses the preparation methods and surface modification methodologies and their effects on the adsorbent elemental content and other basic properties. The following sections assess the recent progress in the adsorption of heavy metals, organics, and gaseous substances by bamboo-based adsorbents, focusing on the optimum adsorption capacities, adsorption mechanisms and the optimum-fitting kinetic models and isotherms. Finally, research gaps were identified and directions for future research are proposed.

Eco-benign preparation of biosorbent using Momordica Charantia for the efficient removal of Cr(VI) ions from wastewater

Environmental pollution is the major issue of 21st century. The toxic industrial effluents are crucially damaging aquatic environment, in the form of heavy metals, dyes and acids. The heavy metals are toxic, carcinogenic, non-degradable and therefore must be removed to save natural environment and human health. Batch sorption efficiency of Momordica Charantia L. stem and root (MCS and MCR) was studied for Cr(VI) metal ions removal under controlled adsorption parameters. The adsorbed and residual concentration of Cr(VI) was determined by atomic absorption spectrophotometer (AAS). The adsorbent surface morphology was determined by FTIR, BET, SEM and elemental analysis by EDX. The Freundlich and Langmuir equilibrium isotherm and pseudo 1st and 2nd order kinetic models were studied to understand bio-sorption mechanism. The Freundlich isotherm and pseudo 2nd order kinetic was best fitted model for MCS and MCR bio-sorption process. The maximum Langmuir adsorption capacity (q max) was 312.50 and 400 (mg/g) for MCS and MCR respectively. The trend of removal efficiency (%) and metal uptake (q e) was in order as MCS > MCR. All data was statistically analyzed using mean values ± standard deviation (SD). In conclusion, MCS and MCR are suggested as excellent sorbents for the elimination of numerous contaminants from the wastewater.

Selective Removal of Hexavalent Chromium from Wastewater by Rice Husk: Kinetic, Isotherm and Spectroscopic Investigation

Chromium (Cr) in water bodies is considered as a major environmental issue around the world. In the present study, aqueous Cr(VI) adsorption onto rice husk was studied as a function of various environmental parameters. Equilibrium time was achieved in 2 h and maximum Cr(VI) adsorption was 78.6% at pH 5.2 and 120 mg L−1 initial Cr(VI) concentration. In isotherm experiments, the maximum sorption was observed as 379.63 mg g−1. Among four isotherm models, Dubinin–Radushkevich and Langmuir models showed the best fitting to the adsorption data, suggesting physical and monolayer adsorption to be the dominant mechanism. The kinetic modeling showed that a pseudo-second order model was suitable to describe kinetic equilibrium data, suggesting a fast adsorption rate of Cr(VI). The results of FTIR spectroscopy indicated that mainly –OH and C–H contributed to Cr(VI) adsorption onto rice husk. This paper provided evidence that rice husk could be a cost-effective, environment-friendly and efficient adsorptive material for Cr(VI) removal from wastewater due to its high adsorption capacity.

Facile synthesis of Zr4+ incorporated chitosan/gelatin composite for the sequestration of Chromium(VI) and fluoride from water

The development of industrialization and agricultural activities have carried various negative impacts to living organisms in recent decades and also, the frequent problem of inorganic pollution have been environmental anxiety to the community. Among these, Cr⁶⁺ and F^- are priority poisonous pollutants from many industries. In this work, we present a low-cost synthesis procedure to obtain biocompatible zirconium incorporated chitosan-gelatin composite (CS-Zr-GEL) were fabricated and explored for the adsorptive removal of toxic Cr⁶⁺ and F^- from water. The adsorption mechanism of toxic Cr⁶⁺ and F^- was done by batch mode as a function of contact time, solution pH and co-existing ions. The obtained materials were extensively studied by several physico-chemical techniques to access their properties by X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) analysis. Additionally, the fabricated adsorbent is highly dependent on solution pH. The kinetic and isotherm data were fitted using pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity for CS-Zr-GEL is 138.89 and 12.13 mg/g at 323K for Cr⁶⁺ and F^- respectively. These findings demonstrate that the CS-Zr-GEL adsorbent represents a promising candidate that would have a practical influence on water/wastewater treatments.

The preparation of a novel iron/manganese binary oxide for the efficient removal of hexavalent chromium [Cr(vi)] from aqueous solutions

To remove hexavalent chromium Cr(vi) efficiently, a novel Fe–Mn binary oxide adsorbent was prepared via a “two-step method” combined with a co-precipitation method and hydrothermal method. The as-prepared Fe–Mn binary oxide absorbent was characterized via transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), thermogravimetric analysis (TGA), zeta potential, BET and X-ray photoelectron spectroscopy (XPS). The results indicated that the morphology of the adsorbent was rod-like with length of about 100 nm and width of about 50–60 nm, specific surface area was 63.297 m² g⁻¹, has the composition of α-Fe₂O₃, β-MnO₂ and MnFe₂O₄ and isoelectric point was observed at pH value of 4.81. The removal of Cr(vi) was chosen as a model reaction to evaluate the adsorption capacity of the Fe–Mn binary oxide adsorbent, indicating that the Fe–Mn binary oxide adsorbent showed high adsorption performance (removal rate = 99%) and excellent adsorption stability (removal rate > 90% after six rounds of adsorption). The adsorption behavior of the Fe–Mn binary oxide was better represented by the Freundlich model (adsorption isotherm) and the pseudo-second-order model (adsorption kinetic), suggesting that the adsorption process was multi-molecular layer chemical adsorption. The possible adsorption mechanism of the Fe–Mn binary oxide for the removal of Cr(vi) included the protonation process and the electrostatic attraction interactions.

A novel Fe–Mn binary oxide adsorbent prepared via “co-precipitation and hydrothermal” method, for the efficient and fast removal of Cr(vi).