Heavy metals removals from wastewater and reuse of the metal loaded adsorbents in various applications: A review

Water contamination has intensified over the past years as the world's population and industrial activities have grown. Heavy metals (HMs) are among the environmental contaminants commonly found in water and wastewater. These include Lead, Manganese, Chromium, Mercury, etc. Various techniques have been used to remediate this environmental challenge, among which adsorption which has proven to be an effective method because of its simplicity operation, excellent efficiency, low-cost, and possibility of operation under various conditions. The cost of preparing and using adsorbents is an essential element in determining their appropriateness for use in the handling of wastewater in comparison to alternatives. Adsorbent value can be calculated using the price of initial supplies, deducted cash flow, cost metrics, sorbent cost per gram of sorbate eliminated. Unfortunately, this method generates waste materials, providing an additional limitation toward scaling the technique. Moreover, after the HM has been extracted and laden onto the adsorbent, there is still a concern on of the fate of the metal-laden adsorbent. Most of the time these metals laden sorbents are released in the surroundings and contribute to secondary pollution. New applications for heavy metals loaded have been investigated. This review discusses the source and types of HMs in wastewater, the adsorption techniques for HMs removal, factors affecting adsorptions and characterization approaches of metal loaded adsorbents. This review article presents the various applications that have been investigated to reuse the loaded metal adsorbent and discusses possible applications where the metal-laden sorbent can be reused to circumvent secondary pollution. Furthermore, the paper covered a few bibliometric analyses that help find new research lines, identify significant authors, institutions, and nations, and map a research area's limits on the issue of heavy metal adsorption employing metal-loaded adsorbents.