Investigation of magnetite graphene oxide- impregnated activated carbon of Rumex abyssinicus stem for adsorption of Cr (VI) from tannery wastewater

The untreated discharge of tannery wastewater can have severe consequences on both public health and environmental sustainability. The purpose of this study was to synthesize magnetite graphene oxide-activated carbon derived from Rumex abyssinicus for the adsorption of chromium ions Cr (VI) in tannery wastewater. The produced adsorbent demonstrated a high adsorption capacity of 100 mg/g and facile separation for reusability through external magnet assistance. The central composite design is a type of experimental design that uses a combination of factorial design and response surface methodology to model the relationship between the independent variables and the response variable. The synthesized adsorbent exhibited distinct characteristics, as revealed by SEM, showcasing a surface morphology with significant cracks in the up and down directions, an XRD amorphous structure, and FTIR analysis highlighting multi-functional groups. BET analysis indicated a specific surface area of 602 m²/g, and a point of zero charge of 7.2, suggesting an ideal environment for effective adsorbent-adsorbate interaction. Maximum Cr (VI) adsorption efficiency reached 95.9% under experimental conditions of 45 mg/L initial chromium, 1 g/100 mL dose, pH 4, and 90-min contact time. However, the actual tannery wastewater had a slightly lower level of chromium removal (82.3%), in case of attributed to the presence of numerous other anions. The adsorption isotherm and kinetics studies revealed that the Langmuir model best represented the experimental data (R² = 0.99), demonstrating homogeneous and monolayer adsorption. The kinetic study further supported chemisorption, with the pseudo-second-order model providing the best fit (R² = 0.99). The study’s result concluded that the adsorbent demonstrated promising potential as an effective technology for chromium removal from wastewater, holding significant implications for environmental remediation, regeneration of the adsorbent, and sustainable wastewater treatment.