As(V) removal using biochar produced from an agricultural waste and prediction of removal efficiency using multiple regression analysis

Arsenic contamination in drinking water is a matter of concern for many countries. An efficient and low-cost solution for this hazard is essentially needed on urgent basis. Therefore, in this study, banana pith (an agricultural waste) was used for biochar production and later it was modified with iron and applied for arsenic adsorption from aqueous solution. Produced biochar was characterized for proximate, ultimate, and surface analyses. Interestingly, after iron impregnation, the surface area of biochar increased (31.59 m²/g) by nearly 8 times. Morphological analysis showed that iron particles firmly held within the pores after impregnation. Arsenate (As(V)) adsorption behavior of iron-impregnated banana pith biochar was evaluated through a batch study by considering various parameters like dose, concentration, pH, temperature, and competing anions. Compared to impregnated biochar, raw biomass and its biochar showed a lesser affinity for arsenate in aqueous solution. The adsorption isotherm of As(V) on banana pith biochar was covered in the temperature range of 298 to 318 K, and kinetic data of adsorption was experimentally generated at 298 K. Langmuir model for the sorption isotherms and pseudo-second-order kinetic model for the sorption kinetics represented the experimental data. The thermodynamic study showed negative Gibb’s free energy (− 46.88 kJ/mol at 298 K, − 48.58 kJ/mol at 308 K, − 50.73 kJ/mol at 318 K) that suggested spontaneity of the adsorption process. Negative enthalpy (ΔH° = − 10.55 kJ/mol) showed exothermic nature of adsorption of arsenic, while negative entropy (ΔS° = 0.123 kJ/mol.K) suggested enthalpy-driven adsorption process. Mechanism of arsenic adsorption onto iron-impregnated banana pith biochar has also been discussed in detail. Based on the experimental observation, a predictive model for arsenate removal has been developed in this study. The findings of the present study elucidated that iron-impregnated banana pith biochar can be used as a low-cost adsorbing material for As(V) from aqueous solutions.