Natural, low-cost adsorbents for toxic Pb(II) ion sequestration from (waste) water: A state-of-the-art review

Pb(II) ions is an inorganic pollutant that is present in the environment. Its presence affects both human health and ecosystem. Economically, amongst many wastewater treatment approaches, adsorption is both cheap and environmentally friendly for removing Pb(II) ion from contaminated water. In this state of the art review, about 227 research and review based publications on adsorption-based studies between 1989 and 2021, which have used various materials as adsorbents of Pb (II) ions, were selected and reviewed for more evaluation. A number of adsorbents which have been reported in these literatures for the adsorption of Pb(II) ion are agrobased, modified agrobased, clay minerals, modified/nanocomposite clay minerals, silica-based, zeolite-based and chitosan-based adsorbents, respectively. The adsorption potential of the adsorbents is exhibited under optimum experimental conditions. The unmodified and modified agro based adsorbents were shown to exhibit the greatest Pb(II) adsorption capacity, with great potential for further exploration, compared to the others afore-listed. The effects of operating parameters such as pH, initial metal ion concentration, adsorbent dose and reaction time are discussed. Furthermore, in order to comprehend the nature of adsorption process between the adsorbent and contaminant (Pb(II)), thermodynamic analyses of adsorption systems are intensively described. All these discussions revealed the applicability of adsorption process for toxic Pb(II) ions removal with respect to wastewater treatment techniques. The review concludes by commenting on the various adsorbents' adsorption capacity and proposes some studies that should also be considered in future works.

Automated summary

Amongst various wastewater treatment approaches, adsorption is a cost-effective and environmentally friendly method for removing Pb(II) ions from contaminated water. This review selected and evaluated about 227 research and review based publications on adsorption-based studies using different materials as adsorbents of Pb (II) ions. The results showed that unmodified and modified agro-based adsorbents exhibited the highest Pb(II) adsorption capacity compared to other types of adsorbents, indicating their potential for further exploration.