Integrated microbial and nanotechnology-based approaches for sustainable heavy metal remediation in water systems

The presence of heavy metals in various water systems is regarded as a serious global threat to the environment and public health. Conventional remediation strategies are often limited in terms of efficiency, cost, and the generation of secondary waste. This review discusses the emerging combination of microbial bioremediation technologies and nanotechnology, an environmentally friendly and economically viable alternative. Microorganisms, including bacteria, fungi, and algae, can employ a range of natural and metabolic mechanisms to sequester and detoxify metal pollutants, including biosorption, bioaccumulation, and biotransformation. Meanwhile, engineered nanomaterials, specifically magnetic nanoparticles (MNPs), carbon-based materials, and nanobiocomposites, offer associated benefits due to their extremely high surface area, reactivity, and selectivity. Bio-nano hybrids exhibit an exceptionally strong synergism: nanomaterials increase microbial viability and metal uptake, while microbial matrices stabilize nanoparticles and enable green in-situ synthesis. We will focus on innovative uses, such as magnetically recoverable biosorbents, microbial nanofactories for producing catalytic metal particles, and genetically engineered microbes with functionalized nanomaterials for targeted metal removal. This effective system often remediates Pb²⁺, Cd²⁺, and Cr⁶⁺ contaminants to nearly the same extent as conventional systems, without significant loss of reusability. The combination of microorganisms and nanoscience in this way thus presents an effective catalytic advance for environmentally responsible water remediation and for catalyzing the potential future, intentionally scaled remediation available using principles of greenness and circular economies.