Fast adsorption of microcystin-LR by Fe(III)-modified powdered activated carbon

Abstract

Microcystins (MCs) are cyclic hepatotoxic peptides produced by the bloom-forming cyanobacterium Microcystis and present a public health hazard to humans and livestock. The removal of MCs from contaminated water with powdered activated carbon (PAC) has been employed as a simple and economic treatment strategy. In this study, PAC-Fe(III) was prepared and utilized for the fast and efficient removal of MCs from water. PAC-Fe(III) exhibited superior microcystin-LR (MC-LR) removal capacity and efficiency compared to the unmodified PAC. The MC-LR removal efficiency of PAC-Fe(III) increased with decreasing pH within the pH range of 4.3 to 9.6. PAC-Fe(III) could be reused for 3 times by methanol elution while the MC-LR removal efficiency was still over 70 percent. The removal efficiency was positively correlated to the ionic strength of water and negatively correlated to alkalinity. Natural organic matter (NOM) such as humic acid (HA) and salicylic acid (SA) generated low interference with MC-LR adsorption by PAC-Fe(III). The complexation reaction between Fe3+ in PAC-Fe(III) and the functional groups of MCLR was suggested as the key mechanism of MC-LR removal by PAC-Fe(III). The results suggest that Femodified PAC is a promising material for the treatment of MC-contaminated waters.