Valorization of heavy metal contaminated biomass: Recycling and expanding to functional materials

Due to the increasing global severe soil pollution, a large number of heavy metal elements are enriched in biomass grown in polluted areas and hyperaccumulators used for phytoremediation. Disposing of above contaminated biomass through traditional in-situ combustion, return to the field, and composting strategies can result in heavy metals re-entering the environment and causing secondary pollution, which poses a huge challenge to the safe disposal of waste biomass. Pursuing more efficient strategies is necessary to achieve green, clean utilization of contaminated biomass and enhance the value. Retaining heavy metals in biomass serves them as functional materials through effective measures can be a sustainable idea. This review described the characteristics of widely used traditional biomass disposal strategies and discussed commonly used thermochemical technologies for heavy metal immobilization. The progress and application status of value-added materials such as chemicals, soil additives, catalysts, absorbents, capacitors, and antibacterial materials prepared from contaminated biomass were systematic overviewed, and the future development direction was prospected. It can be emphasized from the study that the conversion of contaminated biomass into high-value materials is significant and provides a new idea for the green treatment of contaminated biomass and are beneficial to the improvement of phytoremediation technology. Contaminated biomass deserves further exploration and attention as a resource with infinite potential.