Construction Of Hydrophobic Photobioreactor Surface And Its Anti-Fouling Properties

Closed photobioreactor is the essential equipment for large-scale microalgae cultivation,in which the culture conditions(temperature,light intensity,pH and nutrient composition)can be controlled accurately.However,photobioreactor surface would be contaminated with microalgae and extracellular secretions in the microalgae culture process,which would decrease the light transmittance of photobioreactor,and lead to decrease of the yield of microalgae.In order to solve the problem of biofouling on photobioreactor surface,a series of photoreactive hydrophobic polymers were synthesized,and the hydrophobic polymers were grafted onto the surface of the photobioreactor by ultraviolet(UV),and the hydrophobically modified surface showed good antifouling performance.The modification method presented in this thesis is simple to implement and provides a new method for large-scale surface modification of photobioreactor materials.The contents of the thesis are as follows.In this thesis,the bifunctional 4-(2-bromo-2-methylpropionate ester)benzophenone(BP-Br)was synthesized by esterification reaction,and then the atomic transfer radical polymerization of trifluoroethyl methacrylate(TFEMA)was initiated by BP-Br.A series of photoreactive polytrifluoroethyl methacrylate(PTFEMA)were synthesized.The structure and properties of PTFEMA were characterized by IR,NMR,UV,GPC,DSC and TGA.The results showed that PTFEMA had the maximum UV absorption peak at 254 nm,which corresponds to the UV absorption of benzophenone.The polymerization degrees(DP)of the prepared PTFEMA were 25,35,55,75 and 95,respectively.The initial decomposition temperature of PTFEMA with different DP was about 250?.The glass transition temperature(Tg)ranged from 65? to 78?,and Tg increased with the increase of DP.A series of EVA-PTFEMA films were prepared using PTFEMA as modified material and EVA films as the substrate.Infrared spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy,atomic force microscopy and Zeta potential analyzer were used to characterize the chemical composition and morphology of EVA films before and after modification.The results showed that PTFEMA could be grafted onto EVA films by UV irradiation,and the grafting degree of PTFEMA-20,PTFEMA-35 and PTFEMA-100 on EVA surface was relatively high,and the surface F content of PTFEMA-100 was up to 42.76%.The roughness of EVA-PTFEMA films increased to about 20nm,but the PTFEMA did not change the surface electrical properties of the films.The dustproof performance of EVA films and EVA-PTFEMA films was tested in exposure to the air.It was found that the amount of airborne particles adsorbed on the EVA-PTFEMA films was still less than that of EVA films after exposure to the air for 24 h.At the same time,carbon black was used to simulate atmospheric particles to measure the dust retention on the EVA films before and after modification.It was found that the dust retention rate of EVA-PTFEMA films were greatly reduced.Besides,the dust retention rate of the modified films could be reduced by more than 50%compared with EVA films except EVA-PTEMA-60.The biological adhesion properties of EVA and EVA-PTFEMA films in Chlorella culture system were studied.The results showed that,the EVA-PTFEMA films had a certain anti-microalgal adhesion capability,and the number of adhered microalgal cells on EVA-PTFEMA films could be reduced by 6.8%-25.5%.The adhesion strength of microalgae on the films were studied by water gun cleaning experiment.The microalgae adhesion content on EVA-PTFEMA-3 5 and EVA-PTFEMA-100 membrane decreased by 81.8%and 85.9%compared with that before cleaning,while the microalgae adhesion on EVA membrane only decreased by about 26.2%,which showed that the adsorption capacity of the EVA-PTFEMA to microalgae was weakened.The light transmittance of EVA-PTFEMA-3 5 and EVA-PTFEMA-100 membranes was higher than that of other modified membranes before and after cleaning.The light transmittance of EVA-PTFEMA-100 membranes at 420 nm increased from 75.5%to 80.0%.The stability of EVA films before and after modification was tested in different environments.The results showed that after 15 days of soak in NaClO solution,the light transmittance of EVA-PTFEMA films at 420 nm and 680 nm was more than 78.5%and 84.7%,respectively,and the contact angle was stabilized at about 103.2°.The EVA-PTFEMA films also maintained stable in acidic and alkaline solutions for 15 days,and the results were almost the same as those in NaClO solutions.The long-term stability of EVA-PTFEMA films in methanol was tested.After 7 months of soak in methanol,the contact angle was still maintained at 98.9°,which was higher than that of EVA films(92.0°).