A comprehensive review of heavy metals (Pb²⁺, Cd²⁺, Ni²⁺) removal from wastewater using low-cost adsorbents and possible revalorisation of spent adsorbents in blood fingerprint application

An increasing amount of water pollution is being caused by an increase in industrial activity. Recently, a wide range of methods, including extraction, chemical coagulation, membrane separation, chemical precipitation, adsorption, and ion exchange, have been used to remove heavy metals from aqueous solutions. The adsorption technique is believed to be the most highly effective method for eliminating heavy metals from wastewater among all of them. However, it generates secondary waste that can pose a risk to the environment. Agricultural waste has potential to be collected and converted into carbon nanomaterials, then coated with metal oxides for the removal of Pb²⁺, Cd²⁺, and Ni²⁺ ions and then the reuse of heavy metal spent adsorbents in blood fingerprint detection (BFP) can be studied. This review highlights the eco-friendly nature and abundant availability of these materials while advocating for their integration into mainstream wastewater treatment practices. It explores the prospect of revalorizing spent adsorbents in blood fingerprint applications, demonstrating a dual-purpose utilisation that bridges environmental remediation with advancements forensic sciences. Different method of removal of Pb²⁺, Cd²⁺ and Ni²⁺, removal technique as well as other reuse applications of spent adsorbents are also discussed.