The performance and mechanism of Cr(VI) adsorption by biochar derived from Potamogeton crispus at different pyrolysis temperatures

Abstract

To evaluate the impact of preparation temperature on the structure characteristics and Cr(VI) adsorption capability of Potamogeton crispus biochar (PCB), PCB was prepared at 300, 500, and 700 °C, respectively. Characterization results based on BET, XRD, SEM-EDS, Raman, and FTIR measurements showed that the physicochemical features of PCB were dictated by the pyrolysis temperature, which had a substantial impact on the surface morphology and functional group composition of biochar. The specific surface area and pore volume of PCB increased with the increase of pyrolysis temperature, while more oxygen-containing groups were existent on the surface of biochar produced by low temperature pyrolysis. The pseudo-second-order model and the Freundlich model were used to explain the Cr(VI) adsorption process by PCB, inferring that multilayer chemisorption occurred on the heterogeneous surface of biochar. PCB had superior adsorption properties, being 34.37, 5.99, and 2.51 mg/g, respectively, under the addition of PCB300, PCB500 and PCB700. In addition, pH value had a strong impact on the disposal of Cr(VI) with the best removal effect at pH 2.0. The process of Cr(VI) adsorption through SEM-EDS, XRD, FTIR, and XPS included physical adsorption, electrostatic interaction, complexation and reductive adsorption and so on. Therefore, PCB may have been a promising application prospect for removing Cr(VI) from aqueous solutions due to its high performance and economical characteristics.