Treatment of Fly-Ash-Contaminated Wastewater Loaded with Heavy Metals by Using Fly-Ash-Synthesized Iron Oxide Nanoparticles

Every year, a huge amount of water is polluted by various sources, out of which coal fly ash (CFA) is one of the major pollutants. CFA has a large number of toxic metals, which reaches water bodies by coming in contact with water or rain. Due to heavy-metal contamination, water becomes unfit for drinking for human beings, which in long term may cause several disorders. Thus, iron oxide nanoparticles (IONPs) recovered from waste, such as CFA, could be the most promising material for treating wastewater, due to their low-cost, recyclable nature and magnetic property. The synthesis of IONPs from CFA involves three sequential steps. The first step involves extraction of ferrous materials from CFA, followed by acidic treatment of ferrous materials to obtain acidic leachate, and lastly the precipitation of iron oxides by an alkali. The particle size of the synthesized IONPs varied from 30–70 nm and purity was about 90–93%, as confirmed by transmission electron microscope (TEM) and electron diffraction spectroscopy (EDS). Further, the synthesized IONPs were used for the remediation of various heavy metals, especially Pb and Cr ions from 20% CFA aqueous solutions. The heavy-metal removal efficiency of IONPs varied from 40–70%. The developed method suggests heavy-metal removal from wastewater by using an economical and greener route.