Integrated hydrochar-bacteria strategy for heavy metal removal

Heavy metal accumulation in soil and water is highly detrimental to environmental sustainability and living organisms because of its long-term retention, toxic nature, and potential to develop various health issues. Bacterial remediation strategy is considered relatively efficient, environmentally friendly and a sustainable approach with minimal adverse impacts when compared to other remediation methods. Bacteria exhibit strong heavy metal adsorption capability through various mechanisms including biosorption, bioaccumulation, bio-reduction and enzymatic conversion. However, bacterial agents are sensitive to various environmental stresses, which diminish their capability to accomplish a stable remediation outcome. Hydrochar, a carbonaceous material with higher porosity, surface area and abundant functional groups, can be integrated with bacteria as a supporting agent to overcome this challenge. The synergistic interaction of the hydrochar-bacterial system effectively eliminates heavy metals from environmental matrices by mechanisms such as complexation, ion-exchange, adsorption and redox reactions. Moreover, hydrochar can serve as a suitable habitat for bacterial colonization. Furthermore, hydrochar can be regarded as a cost-effective material, as it can be synthesized from various biowaste resources. This manuscript aims to elucidate the hazardous effects of heavy metals on living organisms, the mechanism of toxic metal removal by bacteria and hydrochar, and how the hydrochar-bacteria synergistic system helps to elevate the removal efficiency and bacterial viability through the supportive role of hydrochar. By discussing these interactions, this paper highlights the potential of hydrochar as a supporting matrix for bacteria, thereby enhancing the removal efficiency of hazardous metals. It further explores barriers and research frontiers potentially vital for making such systems scalable and environmentally benign in the long haul.