Methodologies of Removal of Heavy Metals from Contaminated Water Using Various Waste Materials: A Comprehensive Review

The contamination of water with heavy metals like arsenic, cadmium, nickel, zinc, lead, and cobalt presents a pressing and formidable challenge for numerous countries. The surge in industrial activities has exacerbated the pollution of freshwater sources, resulting in an alarming escalation of toxic metal concentrations in lakes, rivers, and underground water reservoirs. Consequently, millions of individuals in developing nations face significant health risks associated with heavy metal exposure. Compounding this issue is the limited accessibility to advanced water treatment methods, intensifying the gravity of the situation. Extensive research efforts have been dedicated to investigating low-cost adsorbents derived from waste materials. It has been observed that the complete removal of heavy metals can be obtained using waste materials like eggshells, neem leaves, red mud, and black tea waste. The objective is to enhance the efficacy of heavy metal removal from water by employing modified waste materials as effective adsorbents. In this comprehensive review, concise and in-depth information about the utilization of readily available waste materials is provided, including black tea waste, fruit peels, vegetable peels, sawdust, and other similar resources. This review emphasizes the kinetics and mechanisms involved in removing heavy metals. Additionally, the factors that impact the efficiency and extent of heavy metal removal in different waste materials have also been discussed.