Modified self-cleaning PVDF membrane coated with silver carbonate/titanium dioxide composite photocatalyst

• Main Authors: Nung-Tsai Wei, 魏農財
• Other Authors: Sheng-Jie You
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/24572487495418771986

碩士 === 中原大學 === 生物環境工程研究所 === 103 === Membrane technology has widely used in various industries because of its high removal efficiency and compact treatment unit. However, as the operation time increases, accumulation of dissolved organic and inorganic constituents on membrane surface has promoted to aggravate the problem of membrane fouling. Membrane fouling deteriorates the permeability of the membrane and consequently increases operation pressure and increase energy consumption of the process. Membrane surface modification with catalyst semiconductors is proven as an effective method for fouling reduction. Hydroxyl radicals generated during photo excitation of catalyst surface by light is powerful to degrade organic compounds. Recently, numerous elements both metals and non-metal have been used to enhance energy adsorption of convention catalyst such as TiO2 and ZnO under visible light to prepare green catalyst. In this study, Ag2CO3/TiO2 composite catalyst was prepared by a simple co-precipitation of pristine TiO2 (Degussa, P25) with AgNO3 and Na2CO3 under room temperature of 25 ± 2 ºC. Effect of TiO2 loading on the photocatalytic degradation of reactive black 5 dye under visible light (40 W halogen lamp) were evaluated. The results showed that 60 w/w% of TiO2 have the best performance in photocatalytic test with the color removal efficiency of xx in 5 h. With this result, the catalyst of 60 w/w.% TiO2 at different mass volume of 1 g, 2 g and 4 g was loaded on commercial Polyvinyliden fluoride (PVDF) membrane sheets, which its surface were preliminary treated by plasma graft polymerization with poly(acrylic acid). Membrane surface morphology and polarity of membrane were characterized using a scanning electron microscope and a contact angle measurement, respectively. Antifouling performance of membranes was carried out using several test solutions including (i) Bovine Serum Albumin (BSA), (ii) alginate acid and (iii) secondary effluent wastewater from municipal wastewater treatment plant. Obviously, Ag2CO3/ TiO2 enhanced hydrophilicity of membrane with a significant reduction of contact angle from 121º to 0º. In the antifouling test, water flux rapidly decreased for all membranes after it was fitered with test solutions. The membrane with 2 g catalyst loading showed the best antifouling property for BSA and alginate acid with water flux recovery rate of 94% and 95%, respectively at the irradiation time of 60 min. Interestingly, the highest water recovery rate with 59% was found for secondary effluent wastewater at the lowest catalyst loading of 1g. It is unclear yet what factors have played important role in this result. It might be related to a complexicity of feed wastewater or the increase of membrane surface roughness with increasing catalyts load. To confirm these results, a long-term test is required with a better instument analysis.