Valorization of sawdust by mineral acid assisted hydrothermal carbonization for the adsorptive removal of bisphenol A: A greener approach.

sawdust was valorized using acid-assisted hydrothermal carbonization and used in the removal of endocrine disruptor bisphenol A (BPA). The effect of acid addition on the hydrothermal carbonization of sawdust and removal of BPA was studied. Two different hydrochars were prepared using deionized water (HC) and hydrochloric acid solution (HC) as feed water. The prepared hydrochars were characterized using FESEM, EDS, XRD, Raman spectroscopy, FTIR, TGA, and surface area analysis to study the structural and functional changes. Then they were compared in the removal of bisphenol A. Out of the two hydrochars prepared, acid-assisted hydrothermal carbonized hydrochar (HC) showed better removal efficiency. Hence, HC was used to study the influence of different parameters like pH, adsorbent dosage, and initial bisphenol A concentration by one variable at a time approach. Further, the study of interactive effects and optimization of adsorption of bisphenol A onto HC was carried out using RSM-CCD. The isotherm, kinetics, and thermodynamic studies revealed that the adsorption of bisphenol A could be explained by the Freundlich isotherm, pseudo-second-order kinetics fitted well in all the initial BPA concentrations, and the adsorption of bisphenol A onto HC was exothermic and spontaneous.