School of Water Resources and Environment, and MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), 29 Xueyuan Road, Beijing, 100083, PR China.
Chemosphere. 2019 Dec;236:124256. doi: 10.1016/j.chemosphere.2019.06.226. Epub 2019 Jul 1.
Use of reclaimed water for irrigation is a main way for pharmaceutical compounds such as diclofenac getting into the soil environment. However, the role of minerals, especially iron oxides, in the diclofenac adsorption to soils with low soil organic matter (SOM) is still in the lack of evaluation. In this study, adsorption of diclofenac onto six minerals (five nature minerals-hematite, goethite, magnetite, kaolinite and aluminium oxide and one engineered mineral-activated aluminia) and five reference soils was investigated by column chromatography. Adsorption of diclofenac onto minerals and soils was totally reversible and interactions such as H-bonding were the primary mechanisms. Adsorption affinity of iron oxides was much higher than that of nature silicon and aluminum oxides. Diclofenac tended to be adsorbed by mineral surface -OH groups with high thermodynamic stability, which were dehydroxylated at high temperature. Compared with the SOM-dominated sorption of naphthalene, adsorption of diclofenac onto soils was controlled by bonding with surface -OH groups of iron oxides. Adsorption coefficients of diclofenac onto soils can be well predicted by contents of extracted Fe by diethylenetriamine pentaacetic acid (DTPA) instead of total iron oxides contents, suggesting that the bonding was adsorption site-dependent. These findings highlighted the importance of iron oxides in the adsorption of diclofenac (an anionic pharmaceutical compound) in soils with relatively low SOM (e.g., 1.03-3.45%). It also indicated that contents of effective surface -OH groups and DTPA-Fe were the promising parameters to develop the predictive models for diclofenac adsorption onto minerals and soils, respectively.
再生水用于灌溉是药物化合物（如双氯芬酸）进入土壤环境的主要途径。然而，矿物质（尤其是氧化铁）在低土壤有机质（SOM）土壤中对双氯芬酸的吸附作用仍缺乏评价。在这项研究中，通过柱色谱法研究了六种矿物质（五种天然矿物质-赤铁矿、针铁矿、磁铁矿、高岭土和氧化铝以及一种工程矿物质-活性氧化铝）和五种参考土壤对双氯芬酸的吸附作用。双氯芬酸在矿物质和土壤上的吸附是完全可逆的，氢键等相互作用是主要的机制。氧化铁的吸附亲和力远高于天然硅和铝氧化物。双氯芬酸倾向于被矿物表面的-OH 基团吸附，其热力学稳定性较高，这些-OH 基团在高温下脱羟。与萘以 SOM 为主的吸附相比，双氯芬酸在土壤中的吸附受与氧化铁表面-OH 基团的键合控制。双氯芬酸在土壤上的吸附系数可以很好地通过二乙三胺五乙酸（DTPA）提取的铁含量来预测，而不是总氧化铁含量，这表明这种键合是吸附位依赖性的。这些发现强调了氧化铁在低 SOM（例如 1.03-3.45%）土壤中对双氯芬酸（一种阴离子药物化合物）吸附的重要性。这也表明有效表面-OH 基团和 DTPA-Fe 的含量分别是开发预测模型的有前途的参数，用于预测双氯芬酸在矿物质和土壤上的吸附。
