Preparation and application of porous and nonporous hydrophobic gas transfer hollow fiber membranes

In this doctoral thesis, production and characterization studies of porous and nonporous hydrophobic hollow fiber membranes were carried out by dry/jet wet phase inversion method. In addition, the hollow fiber which exhibits the best gas transfer performance according to characterization results has been tested for its utility in laboratory scaled O2 and H2 based membrane biofilm reactors. Production and characterization studies of hollow fiber membranes were carried out in Prof. Dr. Dinçer TOPACIK National Research Center on Membrane Technologies laboratories. Hollow fiber membranes were produced by dry/jet wet phase inversion method using a pilot-scale hollow fiber production device. In the production studies, parameters such as dope and bore liquid contents and air gap distance which affect the membrane morphology and performance were tested by varying. In the spinning solution, 20-30% wt. PVDF (Polyvinylide fluoride), 2.5-5% wt. PA (Propionic acid) or PVP K10 (Polyvinylpyrrolidone) and NMP (N methyl pyrrolidone) mixtures, fully water or mixtures of water with NMP at either 70% or 90% as a bore liquid were used. The productions were carried out at 0 and 10 cm air gap distances. Viscosity values of samples taken from spinning solutions before each production process were tested. Characterization studies of all produced membranes have been carried out. Characterization studies of hollow fiber membranes have been completed by taking Stereo and SEM images, detecting surface contact angles, progressing FTIR-ATR analyzes, surface roughness measurements, mechanical strength tests and determining gas transfer performances. In the light of SEM images, it has been concluded that porous and nonporous hollow fiber membranes could be produced in the scope of the thesis. The gas transfer performance tests have been found to have the highest oxygen transfer coefficient the hollow fiber membrane with a spinning solution composition 20% wt. PVDF / 70% wt. NMP / 5% PVP K10, the bore liquid being completely water and produced at 10 cm air gap distance. FTIR-ATR analyzes showed that PA was not retained in the membrane matrix. For this reason, the PA which is supposed to increase the gas transfer performance has no effect in this sense. In the continuation of the production and characterization studies, the hollow fiber membrane which has the best gas transfer performance was used to provide gas transfer and support layer in O2 and H2 based membrane biofilm reactors. In this part of the study, the reduction of nitrate and ammonium oxidation in hydrogen and oxygen based membrane biofilm reactors (MBfRS) were investigated. Different hydraulic retention times (HRT) and gas pressure conditions have been tried. In both systems, when the initial operating conditions were not taken into consideration, the highest nitrate nitrogen removal in the H2-based membrane biofilm reactor was 74% at 12 h of HRT, 4 psi of hydrogen gas pressure and 10 mg/L of influent nitrate nitrogen. The highest ammonium oxidation in the O2-based membrane biofilm reactor was 83% at 7.5 h HRT, 4 psi O2 pressure and 15 mg/L of influent ammonium nitrogen. The hollow fiber membrane performed the gas transfer function without bubble during the operation of reactor.