Improving the surface properties of adsorbents by surfactants and their role in the removal of toxic metals from wastewater: A review study

Heavy metals are pollutants that are naturally produced by human activities. Due to heavy metals' amount and toxicity in aqueous media, they are considered extremely harmful to human life. Therefore, it is necessary to find effective and efficient methods, as a severe challenge for reducing these pollutants to a permissible level. Among the various removal methods, the adsorption process has received much attention due to its benefits like low cost, ease of operation, high selectivity, and high removal efficiency. So far, various adsorbents such as activated carbon, agricultural waste, minerals, nanoparticles, and other inexpensive adsorbents have been used. Surface modification of these adsorbents by surfactants improves the adsorption properties, and as a result, enhances the adsorption capacity of adsorbents. This research has tried to discuss the use of surfactant-modified adsorbents to remove metal ions from aqueous media. In this study, heavy metals and various methods for removing them will also be studied. Also, isotherm, thermodynamic and kinetic behaviors of the sorption process are considered. The addition of anionic and cationic surfactants to the adsorbents can strongly alter the adsorbent's surface charge and directly affect the optimal pH value. Also, the maximum sorption efficiency using surfactant-modified adsorbents has been obtained at low temperatures (25 degrees C), which can be economically viable. According to previous studies, two surfactants such as SDS and CTAB, have shown a high ability to improve the adsorption efficiency and adsorption capacity of adsorbents. To this end, DNPH/SDS/Fe3O4 and CTAB/yeast adsorbents showed the highest removal efficiency (99.5%), which were able to remove Cr(VI) and CrO42- ions, respectively. Moreover, both adsorbents showed significant adsorption capacity. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

This study discusses the use of surfactant-modified adsorbents to remove metal ions from aqueous media. Through the study of heavy metals and various removal methods, and considering the isotherm, thermodynamic, and kinetic behaviors of the sorption process, it was found that adding surfactants such as SDS and CTAB at low temperatures significantly enhances adsorption efficiency and capacity.