紫外辐射对高岭土混凝过程的影响机制

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

高岭土普遍存在于水源水体中,对水处理过程以及污染物的迁移转化有着重要的影响.本文以聚合氯化铝作为混凝剂,通过烧杯实验系统考察了紫外辐射对高岭土混凝过程的影响规律.结果表明,在中性和偏酸性环境下,紫外辐射对高岭土悬浊液的混凝过程具有一定的促进作用.当溶液pH、混凝剂投量以及辐射时间分别为7.0、30 mg·L^(-1)和2.0 h时,紫外辐射后高岭土在混凝出水中的去除率可由原来的81.05%增至93.90%.这可能与光辐射后高岭土结构中的—OH伸缩振动吸收强度降低,Si—O伸缩振动吸收峰和Si—O弯曲振动吸收峰有所增强有关,使得高岭土表面的活性位点(—OH)数量下降;宏观上表现为微粒表面所带负电性下降,有利于在混凝过程中脱稳沉降.然而,在碱性条件下,其沉降性能却略低于未经紫外辐射处理的水样.

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^-1and 2. 0h,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.