Municipal solid waste derived biochars for wastewater treatment: Production, properties and applications

A huge amount of municipal solid waste (MSW) is produced with urbanization process, posing serious threats to the surroundings and human health. The preparation of MSW-derived biochar is an effective strategy for the waste reclamation. MSW-derived biochar possesses great potential in wastewater purification by adsorption and catalysis. In this review, biochar prepared from classified MSW (e.g. food waste and waste paper) was found with larger specific surface area and porosity than the mixed MSW-derived biochar. Meanwhile, pre-treatment and post-treatment means are summarized to improve the structure and composition of biochar, which could further strengthen its adsorption capacity and catalytic activity. The -COOH, -C = O, -C = C, -OH group sites and aromatic structure of MSW-derived biochar could adsorb pollutants through electrostatic interaction, surface complexation, ion exchange, hydrogen bonding and π-π interaction. Moreover, thanks to the -COOH, -C = O, -OH groups, N-doped structures, defective sites and iron ion species, the food waste-derived biochar exhibits excellent persulfate activation properties. Finally, the future challenges and research directions are suggested, which is conductive to promoting the resource utilization of MSW. Some consideration and recommendation about MSW-derived biochar for water treatment are provided, which facilitates the popularization of the innovative mode “waste control by waste” in aquatic environment remediation.