Rapid sand filters (RSFs) have shown potential for removing organic micropollutants (OMPs) from groundwater. However, the abiotic removal mechanisms are not well understood. In this study, we collect sand from two field RSFs that are operated in series. The sand from the primary filter abiotically removes 87.5% of salicylic acid, 81.4% of paracetamol, and 80.2% of benzotriazole, while the sand from the secondary filter only removes paracetamol (84.6%). The field collected sand is coated by a blend of iron oxides (FeOx) and manganese oxides (MnOx) combined with organic matter, phosphate, and calcium. FeOx adsorbs salicylic acid via bonding of carboxyl group with FeOx. The desorption of salicylic acid from field sand indicates that salicylic acid is not oxidized by FeOx. MnOx adsorbs paracetamol through electrostatic interactions, and further transforms it into p-benzoquinone imine through hydrolysis-oxidation. FeOx significantly adsorbs organic matter, calcium, and phosphate, which in turn influences OMP removal. Organic matter on field sand surfaces limits OMP removal by blocking sorption sites on the oxides. However, calcium and phosphate on field sand support benzotriazole removal via surface complexation and hydrogen bonding. This paper provides further insight into the abiotic removal mechanisms of OMPs in field RSFs.

快速砂滤器 (RSF) 已显示出去除地下水中有机微污染物 (OMP) 的潜力。然而，非生物去除机制尚不清楚。在本研究中，我们从两个串联运行的现场 RSF 收集沙子。初级过滤器的沙子非生物性地去除了 87.5% 的水杨酸、81.4% 的扑热息痛和 80.2% 的苯并三唑，而二级过滤器的沙子仅去除了扑热息痛 (84.6%)。现场收集的沙子表面涂有氧化铁 (FeOx) 和氧化锰 (MnOx) 的混合物，以及有机物、磷酸盐和钙。FeOx 通过羧基与 FeOx 的键合来吸附水杨酸。水杨酸从田砂中的解吸表明水杨酸没有被 FeOx 氧化。MnOx 通过静电相互作用吸附扑热息痛，通过水解-氧化生成对苯醌亚胺。FeOx 显着吸附有机物、钙和磷酸盐，进而影响 OMP 的去除。田间沙表面的有机物通过阻挡氧化物上的吸附位点限制了 OMP 的去除。然而，田间沙子上的钙和磷酸盐通过表面络合和氢键支持苯并三唑的去除。本文进一步深入了解 OMP 在野外 RSF 中的非生物去除机制。