Recent developments in heavy metal remediation from polluted water: sources, environmental impacts, and sustainable hybrid treatment strategies

Abstract

The adverse effects of contaminants such as heavy metals on the environment and human health make their presence in water a major global concern. Heavy metals like lead, cadmium, mercury, arsenic, and chromium are highly toxic and originate from sources including mining, agricultural runoff, industrial waste, and improper waste disposal. Their persistence in aquatic environments leads to bioaccumulation in the food chain, posing risks of mutagenicity, neurotoxicity, and carcinogenicity. Conventional water treatment methods, such as ion exchange, chemical precipitation, and membrane filtration, have limitations related to secondary waste production, cost, and efficiency. Significant advancements in remediation technologies, like adsorption using carbon-based materials, nanomaterials, microbial biodegradation, electrochemical methods, and combined techniques, offer promising solutions for addressing heavy metal pollution. Metal-organic frameworks, functionalised polymers, and carbon-based nanomaterials possess high adsorption capacities, while bio-sorbents derived from bacteria, fungi, and algae present sustainable alternatives. Techniques such as photocatalysis and electrocoagulation are increasingly recognised as efficient and eco-friendly water treatment options. While each method has its own drawbacks, like sludge formation in chemical precipitation, high membrane demands, or limited adsorption selectivity, combining two or more approaches can mitigate these issues and enhance overall efficiency. This review critically explores the sources of heavy metals, their environmental impacts, and recent innovations in remediation, with a focus on cost-effective and sustainable solutions. Advanced treatment technologies such as electrospun membranes, photocatalysts and electrochemical systems have demonstrated 80–99% removal efficiency for specific heavy metals and organic contaminants under ideal conditions, with improved flux and degradation rates compared to traditional methods. Future research should aim to refine novel materials, scale up technologies, and evaluate long-term field viability. Combating heavy metal pollution necessitates ongoing research and policy initiatives to protect ecosystems and secure safe water supplies.