Metal oxide nanobiochar materials to remediate heavy metal and dye pollution: a review

The access to drinkable water is a critical challenge in the context of the rising urbanization and industrialization, calling for advanced technologies to clean contaminated waters and wastewater. Here we review the use of metal oxides biochar composites to treat pollution by hevay metals and dyes. We focus on the synthesis of metal oxide nanobiochar; the treatment of pollution by mercury, lead, methylene blue and methyl orange; life cycle analysis; and techno-economical assessment. Metal oxide nanoparticles can act as photocatalysts to allow for the complete mineralization of organic pollutants. For instance, the doping of tin oxide nanoparticles into biochar surface degraded 99.5% of methylene blue dye after 105 min. Ball-milled magnetic nanobiochar achieves 99% mercury removal in 720 min. The presence of biochar enhanced the uptake of contaminants on nanoparticles and facilitated the photocatalytic reaction