Crossflow 방식 응집-정밀여과 공정의 케이크층 저감 메커니즘

Abstract

Cake layer in crossflow microfiltration (CFMF) can be reduced by coagulation, enhancing membrane flux. This is because enlarging particle size by coagulation Increases shear-Induced diffusivity and the back-transport of rejected particles. However it is known that the enlarged particles are disaggregated by the shear force of the pump while passing through it. This study is to look at the disaggregation in relation with cake layer reduction. Kaolin and potysulfon hollow fiber microfilter are used for experiment. The reduction of cake resistance by coagulation is observed in a range of 17% to 53% at the various coagulation conditions. The particle size analysis results of the experiments show that aggregated particles In feed are completely disaggregated by pump but re-aggregation of particles occurs In membrane. This suggests that the re-aggregation of particles is critical to cake reduction and flux enhancement, since the aggregated particles are completely broken. The mechanisms for re-aggregation In membrane are the same with those for coagulation in feed tank. Charge neutralization is better for CCFMF than sweep flocculation although it has two drawbacks in operation.