Study On Cleaning Of The Fouled PVDF Hollow Fiber Membrane

The effective cleaning on fouling is the very important segment in the application of membrane. In one-year experiment and study, the cleaning work is aimed at the organic fouling of PVDF hollow fiber membrane, which comes from the zymotic solution. Through the research of two kinds of cleaning system, which include the alkaline cleaning system and the oxidizing cleaning system, the high-efficiency cleaning agent and method is found. The concrete work is done as follows.SEM and FTIR are chosen as the qualitative analysis method. The weighing method is chosen as the quantitative analysis method. Through the three kinds of analysis on the fouling membrane, the worthy basis for the choice of cleaning method is established.In the process of research, the temperature-flux rectifying curve and the standard concentration—absorbency curve are fitted to unify the experiment data.Parallel research is done on the two kinds of cleaning system. In the alkaline cleaning system, the infiltrative agent confected by surfactant agents is added in the alkaline solution. In the oxidizing cleaning system, the hydrochloric acid is added in the KMnO₄ solution. These two kinds of compound cleaning are both increasing the cleaning effect largely.In the research of alkaline cleaning system, the infiltrative agent is confected by SDS and AEO. When the mol ratio of SDS: AEO is 1:3, the surfactant tension of the compound solution is the lowest. At the meantime, two orthogonal experiments are done to show the cleaning effects and the influential factors. The cleaning effects with infiltrative agent is good in the second four -factor- three -level orthogonal experiment. By the range analysis the most important factor is pH, and the least is time. And this chemical cleaning doesn't make any damages on the PVDF hollow fiber membrane in mechanics performance. At last, the membrane is analyzed by SEM, FTIR and the weighing method. The result showed that the absorption of surfactant agents is obvious.In the research of oxidizing cleaning system, the applicable conditions of using KMnO₄ solution is found from the investigations on the PVDF hollow fiber membrane which is treated in the KMnO₄ solution used as oxidant. Through examining the changes of four items which conclude flux, pressure of appearing bubble, pressure of burst, tensile strength and tensile ratio, the applicable conditions is found. The using concentration of KMnO₄ solution is under 1000ppm, using temperature is under 35℃, and using concentration of hydrochloric acid is under 500ppm in this thing. To gage the using quantum of KMnO₄, the concept of consumable quantum of unit membrane area is put forward, and the result is 0.1472mol/m². The cleaning dynamical equation is fitted. At last, good cleaning method is found through contrasting the different cleaning methods which include the fore-and-aft cleaning effect of adding the hydrochloric acid and the one of adding reducing agent NaHSO₃, tough this chemical cleaning makes some damages on membrane in mechanicsperformance. The membrane after cleaning is analyzed by SEM, FTIR and the weighing method. The result showed that the method is good.From the characteristic of the two kinds of cleaning system, the high-efficiency cleaning agent and method is found through the research on the cleaning effect of multi-procedure cleaning. The multi-procedure cleaning is: the first, the oxidizing cleaning with KMnO4 added the hydrochloric acid; the second, the reducing cleaning with NaHSO3; the end, the alkaline cleaning. To carry out the on-line cleaning in industry, a kind of cleaning equipment is devised according to the principle of the Two Way Flow (TWF) technology, and two cleaning schemes is constituted. The result showed that the two cleaning schemes are both practicable.