Heavy-metal spent adsorbents reuse in catalytic, energy and forensic applications- a new approach in reducing secondary pollution associated with adsorption

Heavy metal ions are toxic causing a variety of health complications. Heavy metal ions mainly include Cr(VI), Hg(II), Pb(II), Cd(II), Cu(II), Fe(III) and Co(II). The adsorption technique is the most practical in removing metal ions from water since it is cost effective, simple to operate and has high removal efficiency. After heavy metals adsorption the spent adsorbent need to be disposed. The approach to focus on heavy metal laden adsorbents is because these present a greater challenge towards potential secondary pollution since the heavy metal contaminants cannot be degraded. If improperly disposed, heavy metals spent adsorbent can led to secondary environmental pollution. Many options are being used to reduce secondary pollution such as spent adsorbent regeneration and recycling with the aim of reusing the adsorbent for adsorption. In this review various methods of adsorbent regeneration are discussed highlighting their limitations. The aim of this review is to discuss other novel alternative approaches of dealing with heavy metals spent adsorbents. The new strategies include heavy metals spent adsorbents reuse in catalytic, energy and forensic applications. These approaches are new and very few reports are available. However, from the results of the reports, the aforementioned methods promise to be a viable option and more research needs to be directed towards them.