Effect of new photocatalytic coagulant on NF membrane fouling

In this research, the results of the photocatalytic coagulation of humic acids (HAs) in aqueous solution were investigated, and the effect of the photocatalytic coagulation on the fouling of nanofiltration (NF) membrane was investigated. Nanoparticles of copper-doped titania were synthesized by a sol-gel method using titanium isopropoxide and cuperous chloride. The behavior of a thin-film composite NF membrane was investigated as a function of solution chemistry (ionic composition and strength and calcium and organic concentration). In the membrane fouling test, calcium bridges between the natural organic matter (NOM) and the membrane led to severe flux decline because of the development of densely compacted fouling layer on the membrane surface. The photocatalytic coagulation was applied to remove humic acids prior to membrane filtration. In the photocatalytic coagulation, the UV absorbance, chemical oxygen demand (COD), and cations decreased by 99%, 90%, and 10%, respectively, while anions and conductivity increased to 39% and 79%. The results emphasized that the photocatalytic coagulation could be an effective alternative solution for the elimination of the humic acids and for the prevention of the membrane fouling.