Characteristics and mechanisms of cadmium adsorption from aqueous solution using lotus seedpod-derived biochar at two pyrolytic temperatures.

Herein, biochar derived from lotus seedpods, as an effective adsorbent, was prepared by pyrolysis method at 300 and 600 °C. The physicochemical characteristics and cadmium adsorption properties were studied systematically by batch adsorption experiments, FTIR, SEM-EDX, XRD, and XPS. Cd adsorption onto lotus seedpod-derived biochar was better fitted using Freundlich isotherm and pseudo-second-order model. Adsorption capacity of biochar produced at 300 and 600 °C was 31.69 and 51.18 mg g, respectively. The Cd adsorption capacity of biochar was related to its characteristics determined by pyrolysis temperature, including carbonization, surface area, surface morphology, and surface functional groups. Cd adsorption on lotus seedpod-derived biochar revealed that adsorption was controlled by multiple mechanisms including surface complexation, ion exchange, surface precipitation, and Cd-π interaction. This study showed that lotus seedpod-derived biochar is an effective and environmentally friendly adsorbent for water treatment.