Adsorptive decontamination of organophosphate pesticide chlorpyrifos from aqueous systems using bagasse-derived biochar alginate beads: Thermodynamic, equilibrium, and kinetic studies

Removal of emerging contaminants such as pesticides from aqueous systems is of growing concern. The usage of sustainable materials as adsorbents is an eco-friendly approach to water purification. Sugarcane bagasse is an abundant waste material that can serve as a sustainable source for preparing adsorbents. This work investigated the removal of chlorpyrifos from aqueous systems using a composite adsorbent prepared from sugarcane bagasse-derived biochar and encapsulated in alginate. The batch studies were conducted to examine the effect of contact time, initial pH, initial concentration of adsorbate, sorbent dosage and temperature on the extent of chlorpyrifos removal by biochar alginate beads. Adsorption thermodynamics, equilibrium isotherms, and kinetics were studied to elucidate the chlorpyrifos uptake phenomenon. The error functions were used to determine model parameters using non-linear regression approach. Biochar alginate beads showed 86 % chlorpyrifos removal under optimized conditions. The adsorption capacity was found to be 6.25 mg g−1 for pH 10 at 10 ppm chlorpyrifos concentration. The analysis of experimental isotherm data revealed Freundlich isotherm model to be the best fitting with regression coefficient value of 0.9332 Kinetic studies showed that adsorption followed intraparticle diffusion model with R2 value of 0.9750, where Boyd model was further studied to confirm rate constant. Adsorption of chlorpyrifos onto biochar beads is showed to be exothermic with type of adsorption to be physisorption.