复杂非静电作用影响下城市污水PPCPs长期吸附去除机制研究与工艺优化

In recent years, there is an increasing concern about pharmaceuticals and personal care products (PPCPs), newly identified as micro-pollutants, due to their potential ecological risks. Sewage treatment plant (STP) is well demonstrated as the most significant way for PPCPs to enter the environement. Therefore, PPCPs’ discharge control from STP’s effluents is the key to reduce their ecological risks. In our previous pilot-scale experiment (1.5 year, 2.2 m3/d, 40000 BV), commercially-available standard anion resins (ARs) achieved stable and effective removals of PPCPs-like aromatic substances in the STPs’secondary effluent, approximately 72% UV254 removals. However, the heterogeneity of PPCPs in STP effluent makes it very difficult to clarify the long-term PPCP removal patterns from STP effluent during cyclical adsorption-regeneration operation (i.e., the long-term PPCP removal mechanism) by the stoichiometry method, like those conducted in natural organic matter (NOM) removal mechanism in drinking water treatment (mainly humic substances). Furthermore, very limited data regarding the potential effect of the important resin properties (including charged functional groups, porosity, and chemical matrix) on the long-term PPCP removal mechanism exists, which will limit the optimization of resin properties to achieve higher PPCP removal from STP effluent. .Based on the occurrence and distribution of PPCPs in STPs’ effluent worldwide, approximately 30-40 frequently-detectable, high-concentration PPCPs will be selected as the representative targeted analytes with varied chemical forms in different therapeutic classes. The automated solid phase extraction-high performance liquid chromatography method coupled with electrospray ionization tandem mass spectrometry (ASPE-HPLC-MS/MS) will be developed to determine these PPCPs in different tested waters. Subsequently, the PPCPs’ adsorption/desorption mechanisms on standard ARs will be investigated in detail to find out which PPCPs will be adsobed, desorped or oxidized in the novel process. Furthermore, the effect of resin structure, i.e., polymer type, pore size, and ion exchange group, on the PPCP’s adsorption/desorption mechanisms will be investigated to optmize the resin composition. Finally, another pilot-scale experiment will be conducted to demonstrate the effect of optimized resin composition. This research will be helpful for the control of PPCPs and other toxic aromatic substances from STPs.

城市污水处理厂(STPs)是控制药物和个人护理品（PPCPs）生态风险的关键节点。长期现场中试研究证明，阴离子树脂固定床工艺能够稳定吸附去除STPs出水中PPCPs等芳香物质（UV254去除率高达72%），是PPCPs排放控制的潜在解决方案之一。受非静电作用复杂性的影响，目前尚无法阐明分子结构差异对不同PPCPs在阴离子树脂固定床上长期“吸附－洗脱”行为的影响（即PPCPs长期吸附去除机制），无法针对性开展工艺升级、提高PPCPs去除效果。本课题拟筛选STPs出水中7大类高检出频率、高浓度PPCPs作为代表性目标分析物，通过构建不同介质水样中PPCPs的LC-MS/MS定量分析方法，重点阐明阴离子树脂固定床工艺PPCPs长期吸附去除机制，并深入探讨聚合物、孔径、离子交换基团等树脂结构差异对PPCPs长期吸附去除机制的影响，为优化固定床工艺树脂构成、提高PPCPs去除效果提供理论依据。

城市污水处理厂(STPs)是控制药物和个人护理品（PPCPs）生态风险的关键节点，本课题组前期研究通过长期现场中试证明阴离子树脂固定床工艺是城市污水PPCPs排放控制的有效解决方案之一（UV254去除率高达72%），阐明PPCPs分子结构差异对其在树脂固定床上长期吸附去除机制的影响是提高城市污水PPCPs去除效果的理论前提。. 本课题筛选了STPs出水中检出频率高、浓度高的5大类12种PPCPs作为代表性目标分析物，构建了它们在树脂固定床工艺不同介质水样中的自动固相萃取-液相色谱-电喷雾三重四级杆串联质谱(ASPE-HPLC-ESI-MS/MS) 定量分析方法，方法回收率61~110%，相对标准偏差2~14%；检出限0.02 ~1.5 ng•L-1，定量限0.06 ~5 ng•L-1。. 本课题重点阐明了阴离子树脂固定床工艺PPCPs长期吸附去除机制。在树脂固定床长期“吸附－洗脱”循环运行过程中，尽管还存在氢键、疏水作用和π-π作用，强碱（酸）性阴（阳）离子树脂主要通过静电作用去除水中主要以阴（阳）离子形式存在的PPCPs，即离子交换基团差异很大程度上决定了PPCPs长期吸附去除机制；聚合物类型（苯乙烯系 vs. 丙烯酸系）对PPCPs长期吸附去除效果存在一定影响；树脂孔径（凝胶 vs. 大孔）差异对PPCPs长期去除机制无明显影响；在不同再生液中（超纯水、盐溶液、含碱再生液和盐酸），盐溶液洗脱效果相对较好，其离子强度对洗脱效果无显著影响。. 本课题研究发现：城市污水中优势DOM（如腐殖酸、蛋白质/氨基酸、长链脂肪酸）的长期吸附去除机制与PPCPs相同，均存在两个吸附洗脱平衡的阈值（即进水中有机物和树脂上有机物之间的平衡以及树脂上有机物与再生液中有机物之间的平衡）。只有树脂上有机物的积累量处于这两个阈值之间时，有机物才能实现稳定的去除和富集。