Modeling and optimization of removal of Pb(II) in aqueous solutions by biochar derived from neem leaves using central composite design of response surface methodology

The optimization of Pb(II) adsorption from synthetic wastewater using engineered biochar obtained from the waste biomass (fallen neem leaves) was explored in detail. Employing a central composite design (CCD), the efficacy of neem biochar (NBC) was investigated by following the adsorption parameters such as pH, Pb(II) concentration, and contact time. Through response surface methodology, a maximum adsorption efficiency of 98.54% was optimized for the adsorption parameters maintained at 325 mg L-1 as a concentration of Pb(II) in the experimental solution, the pH was kept at 5, and the contact time held was 120 min. Experimental data were compared with optimized results, and the results are in line with each other. Langmuir adsorption isotherm and pseudo-second-order kinetics were involved in the adsorption of Pb(II) on NBC. The pristine NBC and Pb@NBC were characterized by XRD, XPS, and FESEM with EDX mapping; besides, water contact angle and zeta potential measurements confirm the presence of oxygen-containing functional groups on the surface of biochar effectively involved in the removal of Pb(II).