紫外辐射对小分子有机酸化学凝聚性作用途径探讨

通过烧杯实验系统考察了紫外辐射对脂肪羧酸类和酚酸类小分子有机酸的化学凝聚性的作用途径.结果表明,溶液pH对柠檬酸、草酸、酒石酸和丁二酸等脂肪羧酸类有机物的混凝性能影响较小.紫外辐射处理后,脂肪羧酸类小分子有机物的混凝去除率均高于未经紫外辐射处理的水样.进一步研究表明,紫外辐射过程中发生了光化学反应,使得脂肪羧酸的表面负电性降低,进而提高了其化学凝聚性.与脂肪类小分子有机酸不同,苯酚、水杨酸和苯甲酸的化学凝聚性较差,且受紫外辐射过程的影响小.单宁酸的混凝性能较好,pH=6时的去除率最高可达90%以上,这可能与其分子中脂肪酸碳链结构的存在以及单宁酸分子较大,易与PACl的水解产物发生吸附电中和反应有关.

Effects of UV Radiation on the Aggregation Performance of Small Molecular Organic Acids

This study systematically investigated the effects of UV radiation on the aggregation of small molecular aliphatic carboxylic acids and phenolic acids by jar test. Experimental results show that solution pH has little effect on the coagulation of small molecular aliphatic carboxylic acids including citric acid, oxalic acid, tartaric acid, and succinic acid. For the solutions pretreated with UV light, the removal rates of the selected aliphatic carboxylic acids in coagulation are higher than that without UV radiation. Further study shows that photochemical reactions occur during UV radiation which decreases the negative charge in aliphatic carboxylic acids, and thereby increases their aggregation properties. Different from aliphatic carboxylic acids, phenol, salicylic acid, and benzoic acid have poor coagulation properties, and UV radiation does not have notable effects on their aggregation in the coagulation process. The coagulation performance of tannic acid is better than the other phenolic acids. At pH=6, its removal rate is above 90%, which may be contributed to the aliphatic carboxylic acid structure in its molecular. Meanwhile, the large molecular of tannic acid is also easier to be adsorbed by the hydrolysis products of PACl.