Dissertation > Environmental science, safety science > Environmental pollution and its prevention > Water pollution and its control

Electro Kinetic Behavior on the Surface of PVDF Hollow Fiber Membrane Modified by Low-Temperature Plasma Method

Author ZhangYanCheng
Tutor ChangQing;YangQing
School Lanzhou Jiaotong University
Course Environmental Engineering
Keywords Zeta potential Hollow fiber membranes Low - temperature plasma graft Streaming potential Membrane fouling
Type Master's thesis
Year 2011
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Polyvinylidene fluoride (PVDF) material has excellent chemical stability, resistance to radiation, heat resistance, and good mechanical strength, and is widely used in water treatment, chemical, biological, pharmaceutical and other fields. As a major membrane microfiltration and ultrafiltration are used one of the materials, the surface energy is low, hydrophobicity, colloidal particles, oil and microorganisms easily adsorbed on the surface cause membrane fouling during use. This is the main factor of the membrane during use, the separation efficiency decreases to limit the application of PVDF membrane separation system. PVDF hollow fiber membranes, the low temperature plasma is the use of the plasma irradiation, the surface of the membrane activated initiator free radicals, then the introduction of a carboxyl group or an amide group-containing monomer to graft reaction, and eventually introduced to the surface carboxyl group and an amide group easily hydrolyzable The polar group to increase the hydrophilicity of the film surface to enhance surface energy. Because the hydrolysis of the grafted product with a negative electrode, it is possible to effectively inhibit the adsorption of colloidal particles, oil and micro-organisms on the membrane surface, thereby improving the separation efficiency of PVDF hollow fiber membranes. This thesis through the analysis of the mechanical properties of the PVDF modified membrane, the SEM photo, the infrared spectra, the grafting rate study PVDF hollow fiber membrane of the low temperature plasma, including plasma modified only treatment, plasma initiator radical grafting polymerization coated grafted polypropylene, coated graft acrylamide and plasma polymerization graft - while the modification effect of the irradiation method, and gives reasonable modified parameters. Do optimize the process parameters of the coated graft AA, optimal factor level combinations. Design flow potential measuring device simultaneously, the fast boost Determination PVDF hollow fiber membrane 0.001mol · L-1 KCl solution flow potential, and that the membrane pore PVDF modified membrane and the membrane surface charge significantly stronger than unmodified membrane. Using siphon method to test the water flux of the modified film, and a flux variation with pH, ??show that the of PVDF modified film at lower pH flux larger. Attapulgite colloidal solution in order to study the modified membrane the pollution performance differences in the separation process, for filtration dope film in the contamination process of flux and flow potential over time variation. This paper results are as follows: (1) R \u0026 D Co., Ltd. Changzhou rather large plasma production of HD2 type of low-temperature plasma processing instrument plasma modified polyvinylidene fluoride hollow fiber membrane. Ar is a plasma gas, the modified film has good mechanical properties, a higher grafting rate, etching is not serious in the case of the film surface of the graft monomer, using the following process parameters, ① coating pick graft-polymerized acrylic acid: first the film was immersed in a 50% acrylic acid solution for 3min, the glow discharge power is 60W, time 2min; the ② coated graft acrylamide: The membrane was immersed in a 10% solution of acrylamide 10mmin, glow discharge Power 70W, 3mmin; ③ only plasma surface treatment: glow discharge power 130W discharge time 10min; ④ plasma-initiated radical graft polymerization: the technology used in the glow discharge 210W, processing time is 3min introduction of acrylic the monomer grafted 30mmin; ⑤ plasma polymerization graft - simultaneous irradiation method: the processing process is the first plasma treatment of the film surface 30s, Power 50W, introducing an acrylic monomer, adjusting the power to 25W, the processing time is 90s. (2) homemade streaming potential measurement device, 0.001 mol · L-1 KCl solution as background electrolyte solution, the experimental determination of the flow potential of the hollow fiber membrane surface flow potential and membrane holes AP membrane pressure at both ends, the greater the the greater the absolute value of streaming potential, and the potential and the differential pressure △ P linear relationship between the calculated under neutral conditions coated grafted acrylic coating grafted acrylamide, plasma polymerization of the graft - simultaneous irradiation method, plasma caused by free radical graft polymerization and only plasma membrane pore Zeta potential of the modified membrane surface treatment-4.15mV,-3.3mV-3.19mV,-2.66mV,-1.87mV. The charge density is 0.9464 × 10-5C · m2, 0.7549 × 105C-m2, 0.7275 × 105C · m2, 0.6066 × 105C · m2, 0.4265 × 10-5C · m2. (3) modified membrane flux test showed that the coated graft acrylic coated graft acrylamide, plasma polymerization grafting - simultaneous irradiation method, plasma-initiated radical graft polymerization and plasma surface treatment changed flux recovery rate of the film followed by 9.9%, 38.3%, 72.3%, 28.2%, 68.5%; flux recovery rate of the modified membrane flux with changes in pH range (maximum flux recovery rate minus min) followed by 15.9%, 22.7%, 9%, 6.7%, 7.6%, and the flux increased as the pH decreases. The initial bubble point pressure of the analysis of the test results illustrate coated graft acrylic acid and acrylamide modified membrane pore size of the membrane did not change significantly; plasma polymerization grafting - simultaneous irradiation method, plasma-induced free radical graft polymerization and plasma surface treatment modified membrane pore size larger. (4) to attapulgite colloidal solution for filtering dope, test-modified polyvinylidene fluoride hollow fiber membrane separation performance and anti-pollution properties, The results showed that while the the irradiation method grafted acrylic acid and acrylamide modified membrane flux attenuation The slow, steady flow of potential value, Plasma Surface Modification of membrane flux decline fastest, stable flow potential value of the minimum.

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