Recent studies in adsorption of Pb(II), Zn(II) and Co(II) using conventional and modified materials:a review

Heavy metal contamination and its detrimental effects on human health and environment have been a worldwide concern. Over the years, various technologies have been adapted to tackle this problem. Adsorption is still considered to be one of the most feasible and cost-effective methods for treating wastewater contaminated with heavy metals. Adsorbents such as activated carbon, clay, zeolites and silica have been studied extensively in the past. Modification of these conventional adsorbents and the synthesis of nonconventional adsorbents such as nanocomposites and metal organic frameworks (MOF's) have been the main focus of study in recent times. This review article attempts to present a detailed account of various adsorbents and their removal efficiencies for the treatment of wastewater contaminated with lead(II), zinc(II) and cobalt(II) in the current decade. Influence of various parameters, adsorption isotherms and kinetics best described for their removal have also been reviewed in detail. It is observed that most of the adsorbents followed pseudo second order kinetics suggestive of a chemisorption process. After conducting a thorough review of more than 120 recently published papers, it can be inferred that nanomaterials and nanocomposites have shown excellent adsorption capacity for removal of these heavy metals.