Development of eco‐friendly adsorbent from peanut shell biochar for the textile wastewater remediation

Abstract Malachite Green (MG) is a cationic triphenylmethane dye which is widely used in the textile and aquaculture industries. It is recognized as a persistent and hazardous organic pollutant due to its carcinogenic, genotoxic, and ecotoxic characteristics. Present investigation targets the development of sustainable adsorbent from the waste peanut ( Arachis hypogaea ) shells by using microwave‐assisted pyrolysis method and alkali‐induced activation to enhance surface properties. This synthesized alkali‐activated peanut shell biochar was systematically characterized using XRD, SEM EDX, FTIR, and batch adsorption experiments were performed to investigate the removal of MG from aqueous solution, examining the influence of pH, contact time, temperature, and adsorbent dosage. Adsorption capacity for peanut shell biochar is 28.34 mg of dye per gram of biochar and for alkali activated peanut shell biochar is 63.24 mg of dye per gram of biochar. Adsorption mechanism involves best fit for Freundlich isotherm indicating heterogeneous surface with varying adsorption sites, with second order kinetics. It is a spontaneous endothermic process involving weak Vander Waal's and pi‐pi interactions as prevalent processes of adsorption. The findings confirm that alkali activation significantly improves porosity, surface functionality, and adsorption capacity. PSB and NaOH PSB treatment significantly reduced turbidity (51%), TSS (36%), Oil and Grease (59%), BOD and COD. Nearly 35% reduction in the Water Quality Index (WQI) was observed after the biochar treatment rendering water quality suitable for washing and other purposes.