Department of Civil and Environmental Engineering, Louisiana State University, 3255 Patrick Taylor Hall, Baton Rouge, Louisiana 70803, United States.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600, Dübendorf, Switzerland.
Langmuir. 2023 Mar 14;39(10):3752-3761. doi: 10.1021/acs.langmuir.2c03487. Epub 2023 Feb 6.
In the face of significant challenges to practical applications of photocatalysis for water treatment, recent reports revealed a potential route to overcome a problem posed by dissolved organic matter (DOM). These studies showed that inhibition of photocatalytic processes by DOM is driven largely by competition for active surface sites on TiO or other catalysts, and controlling the type of DOM present in solution could significantly mitigate DOM fouling. Whether or not control of solution parameters could achieve the same preventative action is not known. Here, a series of DOM isolates, including humic acid (HA) and transphilic (TPI), hydrophobic (HPO), or colloidal fractions of organic matter from a membrane bioreactor mixed liquor supernatant, were tested for inhibitory activity under a range of pH values (3, 5, 7, and 9) and ionic compositions (NaCl, CaCl, and Al(SO) with ionic strengths (IS) ranging from 0 to 3 M). The resulting TiO-DOM agglomerates were monitored for size and ζ-potential. Inhibitory profiles were generated using -chlorobenzoic acid (CBA) as probe with varying concentrations of inhibitory DOM for each solution condition to discern the extent of surface-phase quenching of radicals. Manipulation of pH clearly impacted inhibition, and the effect varied by DOM type; for example, interference occurred at all pHs for HA, at neutral or basic pHs for TPI, and only at pH 7 for HPO. Particle sizes did not correlate with inhibitory action of DOM. Increases in ionic strength induced growth of TiO and TiO-DOM agglomerates, but again, particle sizes did not correlate to inhibition by DOM. The changes to IS, regardless of ion type, were not affected by the presence of TPI or HPO. Since particle stability did not correlate directly with photocatalytic activity, we suggest that surface-based quenching reactions arise from site-specific adsorption rather than generalized particle destabilization and aggregation.
面对光催化在水处理实际应用中面临的重大挑战，最近的报告揭示了一种克服溶解有机物（DOM）问题的潜在途径。这些研究表明，DOM 对光催化过程的抑制主要是由于其与 TiO2 或其他催化剂的活性表面位点的竞争引起的，而控制溶液中 DOM 的类型可以显著减轻 DOM 结垢。目前尚不清楚是否可以通过控制溶液参数来达到同样的预防效果。在这里，一系列 DOM 分离物，包括腐殖酸（HA）和迁移性（TPI）、疏水性（HPO）或膜生物反应器混合液上清液中的胶体有机物，在一系列 pH 值（3、5、7 和 9）和离子组成（NaCl、CaCl2 和 Al（SO4）2，离子强度（IS）范围从 0 到 3 M）下进行了抑制活性测试。监测了 TiO2-DOM 聚集体的大小和 ζ-电位。使用 -氯苯甲酸（CBA）作为探针，根据每种溶液条件下抑制性 DOM 的浓度生成了抑制谱，以辨别自由基表面相猝灭的程度。pH 值的调节明显影响了抑制作用，而且这种影响因 DOM 类型而异；例如，HA 在所有 pH 值下都有干扰，TPI 在中性或碱性 pH 值下有干扰，而 HPO 仅在 pH 7 时有干扰。颗粒大小与 DOM 的抑制作用无关。离子强度的增加诱导 TiO2 和 TiO2-DOM 聚集体的生长，但同样，颗粒大小与 DOM 的抑制作用无关。无论离子类型如何，离子强度的变化都不受 TPI 或 HPO 的影响。由于颗粒稳定性与光催化活性没有直接相关，因此我们认为基于表面的猝灭反应是由特定于位点的吸附引起的，而不是普遍的颗粒失稳和聚集。
