The role of ion charge density and solubility in the biosorption of heavy metals by natural biofilm matrix of polluted freshwater: the cases of Mg(II), Cr(VI), and Cu(II)

One major cause of aquatic pollution is the accumulation of heavy metal ions. This review is aimed to examine the application of natural biofilm as biosorbent for Mg(II), Cr(VI), and Cu(II), as an eco-friendly, economical, and efficient remediation strategy. Biofilm matrices were collected from different freshwater ecosystems to observe their biosorption properties. The compared EPM values of the different biofilms showed a universal trend. Additionally, the adsorption kinetics of all three ions occurred within 1 minute. The amount of adsorbed Mg(II) was higher than Cu(II), owing to the larger charge density of Mg(II). Interestingly, the b values revealed that Mg(II) was desorbed the quickest among the three ions, which is likely to be influenced by its highest solubility. Thus, both charge density and solubility determined the ions’ biosorption characteristics. Therefore, physicochemical properties of heavy metal pollutants should be understood to achieve an effective bioremediation by natural biofilm.