Simultaneous adsorption of trace sulfamethoxazole and hexavalent chromium by biochar/MgAl layered double hydroxide composites

Environmental contextWater contamination by antibiotics and heavy metals entails potential risks to both the environment and human health. Composite materials based on MgAl-layered double hydroxides and biochar simultaneously adsorbed the toxic sulfamethoxazole and CrVI metal species. These findings indicate that biochar/metal hydroxide composites could be valuable adsorbents for the simultaneous removal of trace antibiotics and metals from water. AbstractWater contamination by antibiotics and heavy metals has drawn wide attention because of the potential risks it poses to both the environment and human health. In this study, a series of adsorbents was successfully synthesised based on MgAl-layered double hydroxides (LDHs) and biochar (BC) derived from Pennisetum sinese Roxb. The batch adsorption experiment results showed that the obtained composites could effectively adsorb trace sulfamethoxazole (SMX) and CrVIsimultaneously. The simultaneous adsorption of trace SMX and CrVI are well described by the pseudo-second-order kinetics and Freundlich isotherm models. Characterisation of the composites after adsorption showed that the composites adsorbed SMX mainly by π-π bonds, hydrophobic interactions and hydrogen bonds. Electrostatic interaction, anion exchange, intraparticle diffusion and hydrogen bonding are the main mechanisms for CrVI adsorption onto the composites. This study indicates that the biochar/MgAl layered double hydroxide composites are promising adsorbents for the simultaneous removal of trace antibiotics and CrVI.