Purification of Waste Water Containing Surfactant by Photo-catalytic Oxidation and Ultrasonic Treatment

为了开发废水处理的新工艺，采用光催化和声溶氧化法对表面活性剂进行了分解。对于连续工艺，即在光催化工艺使总有机碳（TOC）浓度大幅降低后，采用超声波工艺。超声照射后TOC浓度略有下降。但TOC去除率达不到100%。这一定是由于TOC浓度过低导致TOC的分解难以进行。在光催化与声溶联合工艺中，表面活性剂的分解速率随搅拌速度的增加而降低。在较低的搅拌速度下，作为光催化剂的TiO_2颗粒可能会定位在驻波节点上。因此，催化剂的表观反应性降低。添加适量玻璃微珠的催化剂悬浮液经26kHz超声波照射后，发现催化剂颗粒与玻璃微珠聚集沉淀。玻璃微珠的加入量与粒子聚集的关系可以用布兰特-希德曼理论来解释。在200kHz的超声波照射下，催化剂颗粒的沉淀物被重新分散。再分散后的催化剂仍具有与原催化剂相同的光活性。根据上述结果，我们提出了一种新的混合废水处理工艺。该过程由两个罐组成。一个是分解罐，里面有低压汞灯和高频超声波发生器。另一种是带有低频超声波发生器的回收罐。废水在分解池中处理后流入回收池，在回收池中通过低频超声波照射分离光催化剂颗粒。分离的颗粒返回分解槽。

In order to develop the new process for the waste water treatment, the decomposition of surfactant was carried out by using the photo-catalytic and sonolytic oxidations.For the consecutive process, that is, after the concentration of total organic carbon (TOC) was considerably decreased with the photo-catalytic process, ultrasonic process was applied. The TOC concentration was slightly decreased by ultrasound irradiation. However, the TOC removal efficiency of 100% was not reached. It must be that the decomposition of TOC hardly progresses since the TOC concentration was too low.For the combined process of the photo-catalysis and the sonolysis, the decomposition rate of surfactant decreased with the stirring speed. In the case of the lower stirring speed, the particles of the TiO_2 as photo-catalyst may be localized at the nodes of standing wave. Therefore, the apparent reactivity of catalyst decreases.The aggregation and precipitation of the catalyst particles with glass beads were found when the ultrasonic at 26kHz was irradiated to the suspension of catalyst added the appropriate amount of glass beads. The dependency of the amount of added glass beads on the aggregation of the particles can be explained by the theory of Brant-Hiedemann.The precipitates of the catalyst particles were re-dispersed by the irradiation of ultrasonic at 200kHz. The re-dispersed catalysts still held the same photo-activity as the raw catalysts.From the above results, we propose a new hybrid process for waste water treatment. The process consists of two tanks. One is a decomposition tank with a low-pressure mercury lamp and an ultrasonic generator of high frequency. Another is a recovery tank with a ultrasonic generator of low frequency. Waste water is treated in the decomposition tank and flows into the recovery tank where the photo-catalyst particles are separated by the irradiation of ultrasonic at low frequency. Separated particles are returned to the decomposition tank.