Effectiveness of Different Adsorbents in Removing Heavy Metals from Municipal Wastewater: A Review Study

Today, the removal of heavy metals from industrial and urban wastewater is considered as one of the serious issues and challenges facing humanity. The present study was carried out with the aim of investigating the efficiency of different adsorbents in removing heavy metals from municipal wastewater. In this study, various adsorbents such as natural adsorbents such as forest adsorbents, and wood waste, agricultural waste, fruit and vegetable peels, coal, and biochar were discussed. In addition, the role and application of nanoabsorbents, nanocomposites and carbon nanotubes in urban wastewater treatment were studied. The literature review showed that bioabsorbents are more beneficial for removing heavy metals from urban wastewater due to being economical and environmentally friendly. Natural materials that are usually used as adsorbents have different capacities to remove heavy metals from wastewater. Among the natural adsorbents, the use of agricultural residues, biochars and coal-based adsorbents has received more attention. However, most of the research has been done on a laboratory scale. According to the obtained information, nanoabsorbents can also remove toxic metals from municipal wastewater. Studies showed that the most widely used nanomaterials as adsorbents for removing heavy metals include graphene, iron oxide, magnesium oxide, activated carbon, manganese oxide, zinc oxide, titanium oxide, and carbon nanotubes. Despite the key role of nanomaterials in the removal of heavy metals, considering that these materials are still not cheap compared to traditional materials (such as activated carbon), the use of bioadsorbents can be effective in urban wastewater treatment.