Biomass-derived biochar: From production to application in removing heavy metal-contaminated water

Wastewater treatment may help to reduce water shortages, whilst concurrently recover energy and nutrients, leading to some of the exploitation of important sources being offset. Compared to other approaches, wastewater purification via adsorption is highly-desirable. The reason is that with this simple and better-to-regenerate technique, heavy metals could be removed even under lower concentration of metal ions. Due to numerous advantages and tunable physicochemical properties, biochar has received most attention for the control of water contamination. This contributes to the solving ecology issues. Significantly, the link between biochar and the rehabilitation of resources should be studied, so that the role of biochar during the wastewater and environmental treatment is well-comprehended and scale-up. In this review, the biochar production from biomass through different routes and their critical properties are critically reviewed and presented. In addition, the activation methods of biochar are also presented and thoroughly compared. More importantly, the application of biochar in heavy metal removal is scrutinized. The factors that affect the heavy metal adsorption capacity and performance are critically evaluated. Finally, limitations and future perspectives for biochar production and application in the removal of heavy metal from wastewater are highlighted in this review.