Removal of Phosphorus by Ferric Ion-Rich Solutions Prepared Using Various Fe(III)-Containing Minerals

Abstract

Various biological, chemical, and physical technologies have been studied to effectively remove total phosphorus (T-P) from wastewater. Among them, some mineral suspensions and cations in the aqueous phase have shown great potential for promoting phosphorus removal via chemical precipitation. Herein, we investigated the efficiency of T-P removal using various chemical-based cations (Fe2+, Fe3+, Mg2+, and Al3+); ferric ions (Fe3+) showed the highest T-P-removal efficiency (33.1%), regardless of the type of anion (Cl−, NO3−, and SO42−). To prepare natural Fe3+-rich solutions, three different Fe(III)-rich minerals (hematite, lepidocrocite, and magnetite) were treated with various HCl concentrations to maximize the dissolved Fe3+ amounts. Lepidocrocite in 2 N HCl showed the most effective Fe3+-leaching ability (L-Fe dissolved solution). Almost no significant difference in Fe3+ leaching was observed between HCl and H2SO4, whereas lepidocrocite-2 N H2SO4 showed the highest T-P-removal ability (91.5%), with the formation of amorphous Fe(III)-P precipitates. The L-Fe dissolved solution exhibited a higher T-P-removal efficiency than polyammonium chloride under real wastewater conditions. Our results can provide fundamental knowledge about the effect of cations on T-P removal in wastewater treatment and the feasibility of using the Fe3+ leaching solution prepared from Fe(III)-containing minerals for efficient T-P removal via chemical precipitation.