Synergistic approach: Microwave assisted carbonisation and high energy ball milling for bionanomaterial fabrication- Analyzing Thermodynamic and kinetic models for arsenite ion adsorption

Abstract

Arsenic contamination in water poses a significant global health threat, necessitating urgent and comprehensive measures to address this pervasive issue. This research investigates the efficacy of a novel microwave-assisted bionanomaterial derived from Calotropis procera stem, an abundant and eco-friendly adsorbent, for removing arsenite ions from aqueous solutions. Surface properties of Bionanomaterial was Characterised using Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis revealed a significant increase in surface area (578 m2/g) after high-energy ball milling, with SEM images showing an uneven surface with enlarged holes. Optimal arsenite removal was achieved at pH 5, a contact time of 90 min, an adsorbent dosage of 4 g, an initial arsenite concentration of 30 ppm, and a temperature of 60 °C. The zeta potential analysis indicated a shift in the isoelectric point from pH 6.2 to pH 5.0, reflecting effective adsorption and surface charge modification. Thermodynamic parameters suggested that adsorption is endothermic and spontaneous, with the Freundlich isotherm model providing the best fit for the adsorption data. Kinetic studies revealed that the process is governed by rapid external diffusion, intraparticle diffusion, and surface chemisorption, consistent with pseudo-second-order kinetics. These findings highlight the bionanomaterial’s potential as a viable adsorbent for arsenic removal from aqueous solutions.