Alkali modified hydrochar of grape pomace as a perspective adsorbent of Pb2+ from aqueous solution

Abstract

Hydrochar produced via hydrothermal carbonization of grape pomace was considered as novel sorbent of Pb2+ from aqueous solution. In order to enhance the adsorption capacity, hydrochar was chemically modified using 2 M KOH solution. Both materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction technique. Batch experiments were performed to examine the effect of sorbent dosage, pH and contact time. Obtained results showed that the KOH treatment increased the sorption capacity of hydrochar from 27.8 mg g(-1) up to 137 mg g(-1) at pH 5. Adsorption of lead 'on either of the materials was achieved through ion-exchange mechanism, chemisorption and Pb2+-Tr interaction. The Sips isotherm model gave the best fit with the experimental data obtained for Pb2+ sorption using activated hydrochar. The adsorption kinetic followed a pseudo second-order model. Thermodynamic parameters implied that the Pb2+ binding for hydrochar surface was spontaneous and exothermic process. Findings from this work suggest that the hydrothermal carbonization is a promising route for production of efficient Pb2+ sorbents for wastewater treatment.