Cadmium removal from wastewater by foamed magnetic solid waste-based sulfoaluminate composite biochar: Preparation, performance, and mechanism

Abstract

Conventional magnetic biochar presents disadvantages such as fragility and high cost of imparting magnetic properties, and its fragility leads to the risk of free dispersion and low recovery rate in field applications. To solve these problems, sulfoaluminate cement was used as cementitious material, mixed with natural magnetite and biochar, and combined with foaming technology to prepare a new granular adsorbent in this work. The adsorbent exhibited excellent properties with compressive strength (1000 mN), specific surface area (49.32 m2 g−1), and magnetic properties (13.95 emu g−1). The adsorption capacity for Cd2+ was 45.94 mg g−1 at 25 °C, and it increased with the increase of ambient temperature. The adsorption mechanism was mainly dominated by the chemical interactions of monolayer adsorption, including coordination and complexation between Cd2+ and surface functional groups (e.g. –COO–Cd, –O–Cd), Cd–π interactions on aromatic structures, and the precipitation mechanism (Cd(OH)2, CdCO3).