Adsorption of Chromium (VI) from Synthetic and Real Tannery Wastewater: Using Natural and Commercial Adsorbents

Chromium is one of the most prevalent toxic heavy metals in the environment and is known to cause cancer, and cellular damage. Various treatments can effectively remove Chromium ion from wastewater. However, majority of those methods are not environmentally friendly. Here, we investigated the efficacy of stem cactus activated carbon (SCAC) and commercial activated carbons (CAC) to remove hexavalent chromium from synthetic and real wastewater. In this study, the stem cactus adsorbent was thoroughly characterized. The effect of initial concentration of Cr (VI), contact time, adsorbent dose, shaking speed, and pH on the adsorption process were examined using Micro Plasma Atomic Emission Spectroscopy and UV-Vis Spectroscopy. The data were analyzed using R-software (version 4.4.3 (2025-02-28)) and Origin (2022). The trends in removal efficiency were examined descriptively using line graph. The adsorption equilibrium isotherms and kinetics models were fitted to the data to evaluate the biosorption mechanisms and compare the sorption capabilities of the two biosorbents (SAC and CAC). Under optimal conditions (0.15g SCAC, pH 2, contact time 60 min, shaking speed 200rpm, and an initial Cr (VI) concentration of 6mg/L), Cr (VI) removal efficiencies reached 98.4% and 99.2% from real and synthetic wastewaters, respectively. The adsorption data fitted both the Langmuir and Freundlich isotherm models, suggesting mixed homogenous and heterogenous surface characteristics on the adsorbent. The adsorption process is an endothermic process and respects the pseudo second order kinetics model. The present study suggests that plant-based adsorbents represent an effective alternative for Cr (VI) ion removal.