Pb(II) adsorption by KOH-modified rice straw biochar from battery wastewater

This data includes the XRF and FTIR characterisation of biochar derived from rice straws; RSM modelling; the influence of factors on adsorption; isotherm, kinetic, and thermodynamic modelling; and all tables and figures. XRF spectra revealed the elemental composition of KOH-modified biochar (KRSB) before and after Pb(II) adsorption. The key elements involved were K, P and Ca, attributed to their significant reduction in percentage after adsorption. FTIR spectra derived from FTIR-RSB (pristine biochar), KRSB (KOH-modified biochar) and KRSB-Pb (modified biochar after Pb adsorption). The FTIR spectra revealed oxygen-containing functional groups (-OH, -COO⁻, C–O–C) that facilitated complexation and precipitation. Five factors—dose, initial PbII concentration, contact time, temperature, and pH—were used in RSM modelling and optimisation. The resulting model was adequate with high R² and low p-value. The adsorption followed dual Langmuir-Temkin isotherm models and a pseudo-second-order kinetic model. The Pb(II) adsorption was endothermic with negative Gibbs free energy.