[Effects of UV Radiation on the Coagulation Process of Kaolin and Involved Mechanisms]

Kaolin commonly exists in water,and it has an important impact on the water treatment processes and contaminants'migration and transformation.In this study,PAC was used as flocculating agent to systematically investigate the effects of UV radiation on the coagulation process of kaolin by jar test.The results showed that under neutral and acidic conditions,UV radiation could promote the coagulation process of kaolin suspension.When the solution pH,coagulant dosage and irradiation time were 7.0,30 mg·L^-1 and 2.0 h,respectively,the kaolin remove rate of effluent after coagulation increased from 81.05% to 93.90% by using UV radiation.This might be related to the decrease of-OH stretching vibration absorption peak and the enhancement of Si-O stretching vibration absorption peak and Si-O bending vibration absorption peak after UV radiation,so that the number of the active spot (-OH) on kaolin surface declined.These changes might lead to decrease of the negative charge on kaolin surface,which promoted kaolin suspension to precipitate in coagulation process.However,under alkaline conditions,its settlement performance was slightly lower than the water samples without ultraviolet radiation treatment.