Sorption of micropollutant estrone to a water treatment ion exchange resin

Micropollutants occur in natural waters from a range of sources. Estrogenic compounds are naturally excreted by humans and hence stem predominantly from wastewater effluents. Due to the small size and concentration of such micropollutants their removal is difficult. In this study a technology – magnetic ion exchange (MIEX®) - developed to remove natural organic matter from surface water, was investigated. Estrone interacts with polymeric materials such as ion exchange resins or membranes through a number of mechanisms including specific and non-specific interactions. To understand the mechanisms and subsequence implications of this interaction sorption and desorption of estrone was studied as a function of pH, temperature, natural organic matter concentration, sulfate concentration and ionic strength. The results demonstrated that the resin removed around 70% estrone at high pH conditions (>10.4) when estrone was predominantly negatively charged. However, below pH 10.4, when estrone was neutral, approximately 40% of estrone still sorbed due to hydrogen bonding. The optimum temperature for estrone sorption was observed to be from 15 to 35 °C, while the presence of other anions had implications for estrone removal due to competition for anion exchange sites. Desorption of estrone was most effective with 2 M NaCl regeneration brine concentration when estrone was negatively charged (98% desorption). However, when estrone was neutral there was no significant difference between 1 M and 2 M NaCl. The results presented in this study indicate that polar non-ionic micropollutants were removed by magnetic ion exchange due to sorption to the resin polymer. Consequently, this study has implications for improved understanding of micropollutant removal by such resins. Beyond the possibilities of exploiting ion exchange for the removal of micropollutants, the accumulation of micropollutants on polymeric materials in water treatment is a potential risk to be monitored