Bioremediation of Toxic Metals Using Aquatic Macrophytes: Challenges and Opportunities

Environmental pollution caused by urbanization, agricultural intensification, and industrialization has led to an increase in the disposal of toxic effluents in aquatic environments. Most ecosystems in the world receive a variety of toxic metals (TMs) that exceed the capacity of water bodies to absorb or recycle them, thereby threatening aquatic and human life. Physicochemical remediation methods encounter problems because of the high cost, labor input, and use of chemicals with long residence times that later add toxic by-products. However, bioremediation techniques are a safe option for mitigating environmental pollution because of their high efficiency, cost-effectiveness, non-intrusiveness, eco-friendliness, ease of application, and social acceptance. Submerged and free-floating macrophytes were found to be more effective in the bioaccumulation of TMs than emergent macrophytes. Furthermore, most studies have suggested the use of macrophytes for the removal of TMs from water bodies; however, studies on the management of phytoremediated biomass are scarce. This review demonstrates the role of various macrophytes for the removal of TMs from water bodies and suggests techniques for the disposal and recycling of phytoremediated biomass with accumulated TMs. Further, the applications of genetically modified plants, nanotechnology, and native hyperaccumulators have been suggested as suitable candidates for greater efficiency of phytoremediation and appropriate management of TMs in the environment in the future.