In the context of circular economy, waste generated by fruit processing can be used to produce new materials with a wide range of uses. This study presents a method to synthesize biochar from peach kernel or grape pit waste. The adsorbents were tested in the removal of hexavalent chromium from synthetic wastewater with Cr6+ concentrations specific to plating processes. Characterization by BET, SEM, FTIR, and TG-DTG confirmed the formation of porous structures, and a well-functionalized surface. The effects of contact time, initial Cr6+ concentration, and adsorbent dose were investigated in static conditions. Both materials are efficient in hexavalent chromium removal, with sorption equilibrium achieved within 180 min. Kinetic studies indicated that the removal process follows a pseudo-second-order model. Equilibrium studies showed that optimal sorption occurred at pH = 6, with sorption capacities of 78.54 mg/g for biochar from peach kernels and 67.57 mg/g for biochar from grape pits. Hexavalent chromium followed a Sips adsorption isotherm for both biochars. Following the reusability study, it can be concluded that biochar from peach kernels maintains removal efficiency higher than 75% after four cycles.
Cârjilă et al. (Thu,) studied this question.