Discarded biodiesel waste–derived lignocellulosic biomass as effective biosorbent for removal of sulfamethoxazole drug

This work aims to evaluate the removal of pharmaceutical drug using discarded biodiesel waste–derived lignocellulosic-based activated carbon biomaterial. Lignocellulosic-based activated carbon (LAC) biomaterial was prepared from Jatropha shell (biodiesel processing waste) by a zinc chloride activation method. The LAC biomaterial was characterized using various techniques including powder XRD, FT-IR, SEM-EDAX, and BET analysis. LAC biomaterial was applied to examine the adsorption of sulfamethoxazole (SMZ) drug in aqueous solution under ambient temperature. Various experimental parameters such as the effect of pH, treatment time, adsorbate concentration, and LAC dose of adsorption experiments were thoroughly examined and optimized. Under the optimal conditions, LAC biomaterial showed the maximum adsorption removal efficiency of SMZ drug. The kinetic models of Lagergren first-order, pseudo-second-order, intraparticle diffusion, and Bhangam's equation for SMZ removal onto LAC were used to recognize the probable mechanism of adsorption manner. From the experimental results, the Freundlich isotherm model (K_f = 83.56 mg g⁻¹ (L mg⁻¹)^1/n) shows similar fit than the Langmuir (Q₀ = 206.2 mg g⁻¹) and Dubinin-Radushkevich (Q_m = 150.69 mg g⁻¹) condition models of adsorption isotherms. The rate constants of adsorption were found to confirm the pseudo-first-order kinetic and Bhangam's models with a significant correlation. The separation factor (R_L) showed the favorable condition of the adsorption isotherm for the experimental system. The desorption results indicate that the ionic molecular exchange of SMZ from the hydroxyl group of LAC surface plays an important role in the recycling processes. Therefore, these results proved that the prepared low-cost LAC biomaterial could be used as an efficient adsorption material for the effective removal of pharmaceutical drugs in aqueous samples.