Green engineering of chitosan-bioactive glass for efficient removal of Cr(VI) and Cu(II) ions from aqueous systems

In India, water pollution has become a severe environmental issue that affects millions of individuals as well as ecosystems across the country. The current research article deals with removing the heavy metal hexavalent chromium and bivalent copper ions from aqueous wastewater using an environmentally friendly and low-cost binary mixture of chitosan (CS), bioactive glass (BAG). The new bioactive glass is prepared by using biosilica extracted from cow dung ash, calcium oxide extracted from eggshell ash, and phosphorus pentoxide. The CS/BAG blend is made using the sol-gel process and characterized with XRD, FT-IR, BET, TGA, and SEM, which demonstrate a porous structural image during blending. Batch adsorption studies investigate various parameters, including pH, contact time, initial metal ion concentration, and adsorbent dosage. The data are then assessed using adsorption kinetics and isotherms (Langmuir, Freundlich, D-R, and Temkin isotherm models). The analysis reveals that the best parameters for Cr(VI) removal pH 4 and Cu(II) removal pH 5 are 300 min of contact time, 0.5 g of adsorbent, and an initial metal ion concentration of 50 ppm. The adsorption isotherm model has a good fit with the Freundlich isotherm for hexavalent chromium (R² = 0.9529), bivalent copper (R² = 0.9615), and pseudo-second-order kinetics for hexavalent chromium (R² = 0.9836) and bivalent copper (R² = 0.9893). In conclusion, the CS/BAG binary blend has an extraordinary ability to efficiently remove heavy metals, particularly hexavalent chromium compared with bivalent copper ions, from industrial wastewater.