Adsorption of Bisphenol S (BPS) By Clay Minerals

Bisphenol S (BPS), 4,4’- sulphonyl diphenol, is an analog of bisphenol A, and a serious endocrine disrupting chemical that impacts the hypothalamic development in humans and animal lymphocyte proliferation. BPS is being used as an alternative to BPA in daily applications, and BPS production is expected to rise to 8.4 million tons by 2018. BPS is extensively used as a monomer in the production of epoxy resins, cyclic carbonates, as an electroplating solvent, and in everyday products like thermal paper, canned foods, and baby bottles. BPS was detected in human urine samples from seven countries, with the U.S. samples having the highest level of 0.299 ng BPS/mL urine. Wastewater biosolids from wastewater treatment plants are bisphenol sources. The biosolids can be applied to land. Thus, this research investigates BPS adsorption onto important soil components- clay minerals. Conducted in organic-free water, batch sorption studies investigated the sorption of 10 ppm BPS onto sterilized kaolinite and montmorillonite clay minerals. The studies were conducted in acid-washed, amber glass vials, with no headspace with 24 hours mixing in a rotary mixer. The following clay mineral:BPS ratios (mass in g/volume in mL) were investigated: 1:4, 1:5, 1:10 and 1:12. Using high-performance liquid chromatography to quantify BPS concentrations, the maximum BPS removals for kaolinite and montmorillonite were 8.5% and 48%, respectively. These percent removals corresponded to a 1:5 kaolinite:BPS ratio and a 1:10 montmorillonite:BPS ratio, indicating that BPS sorbs to montmorillonite more readily. Kaolinite had minimal BPS sorption. Ongoing studies will investigate the impact of relevant environmental conditions on BPS sorption