Centre of Chemistry, Science Institute, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Edif. IC7, Puebla, Pue, 72570, Mexico.
Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment (NEWT), United States; Department of Civil & Environmental Engineering, Houston, TX, 77005, United States.
Water Res. 2020 Sep 15;183:116095. doi: 10.1016/j.watres.2020.116095. Epub 2020 Jun 28.
Photocatalytic water treatment has significant potential to disinfect and degrade recalcitrant organic pollutants while minimizing the need to add chemicals, but current approaches have poor energy efficiency due, in part, to inefficient utilization of photo-generated reactive oxygen species (ROS). Organic coatings such as cyclodextrin (CD) can adsorb target contaminants and bring them close to the photocatalyst surface to enhance ROS utilization efficiency, but the coatings themselves are susceptible to ROS attack. Here, we report an ROS-resistant fluorinated CD polymer (CDP) that can both adsorb contaminants and resist degradation by ROS, yielding a more efficient material for "trap and zap" water treatment. We produced the CDP through condensation polymerization of β-cyclodextrin and tetrafluoroterephthalonitrile, resulting in a cross-linked, covalently bound CD film that is much more stable than prior approaches involving physi-sorption. We optimized the coating thickness on TiO microspheres to improve the efficiency of contaminant degradation, and found that increasing the CDP content enhanced BPA adsorption but also occluded photocatalytic sites and hindered photocatalytic degradation. The optimum content of CDP was 5% by weight, and this optimal CDP-TiO composition had a BPA adsorption capacity of 36.9 ± 1.0 mg g compared with 24.1 ± 1.1 mg g for CD-coated TiO (CD-TiO) and 21.9 ± 1.5 mg g for bare TiO. CDP-TiO exhibited minimal photoactivity loss after 1000 h of repeated use in DI water under UVA irradiation (365 nm, 3.83 × 10 E Ls), and no release of organic carbon from the coating was detected. Photocatalytic treatment using CDP-TiO only showed a small decrease in BPA removal efficiency in secondary effluent after four 3-h cycles, from 80.2% to 71.7%. In contrast, CD-TiO and P25 removed only 29.8% and 6.2% of BPA after 4 cycles, respectively. Altogether, the CDP-TiO microspheres represent promising materials for potential use in photocatalytic water treatment.
光催化水处理具有消毒和降解难处理有机污染物的巨大潜力，同时最大限度地减少了化学品的添加，但目前的方法由于光生反应性氧物种（ROS）的利用效率低，因此能源效率较差。有机涂层，如环糊精（CD），可以吸附目标污染物并将其带到光催化剂表面附近，以提高 ROS 的利用效率，但这些涂层本身容易受到 ROS 的攻击。在这里，我们报告了一种抗 ROS 的氟化 CD 聚合物（CDP），它既能吸附污染物，又能抵抗 ROS 的降解，从而为“捕获和杀灭”水处理提供了更高效的材料。我们通过β-环糊精和四氟对苯二甲腈的缩合聚合制备了 CDP，得到了交联的、共价键合的 CD 膜，其稳定性远远超过以前涉及物理吸附的方法。我们优化了 TiO 微球上的涂层厚度，以提高污染物降解效率，发现增加 CDP 含量可以提高 BPA 的吸附量，但也会堵塞光催化位点并阻碍光催化降解。CDP 的最佳含量为 5wt%，这种最佳的 CDP-TiO 组成对 BPA 的吸附容量为 36.9±1.0mg g，而 CD 涂层 TiO（CD-TiO）和裸 TiO 的吸附容量分别为 24.1±1.1mg g和 21.9±1.5mg g。在 DI 水中重复使用 1000 小时后，CDP-TiO 在 UVA 照射下（365nm，3.83×10 E Ls）的光活性损失最小，并且从涂层中没有检测到有机碳的释放。使用 CDP-TiO 的光催化处理在经过四个 3 小时的循环后，在二级出水的 BPA 去除效率仅略有下降，从 80.2%降至 71.7%。相比之下，CD-TiO 和 P25 在 4 个循环后分别仅去除了 29.8%和 6.2%的 BPA。总的来说，CDP-TiO 微球是用于光催化水处理的有前途的材料。
