Preparation Of Antibacterial Loose Nanofiltration Membrane And Study On The Regularity Of Membrane Fouling In Constant Pressure Cross-flow

Loose nanofiltration（NF）membrane technology has many advantages,such as low energy consumption,friendly environmental,simple operation and easy to scale production,so it is of great significance to realize the effective separation of high concentration inorganic salt from dye wastewater.Therefore,the preparation of NF membrane with high flux,high rejection,strong anti-fouling and excellent antibacterial activity is urgently needed.In addition,membrane technology makes it possible to treat wastewater efficiently,but membrane fouling has restricted the wide application of membrane technology in industry.Therefore,it is of great significance to explore the influence of operating conditions on the membrane fouling in the process of constant pressure cross-flow filtration and establish the flux prediction model under the corresponding fouling mechanism,which is of great significance to deeply understand the membrane fouling process for membrane industry automation and membrane cleaning process.This paper mainly makes the following two parts:（1）The chelate reaction between PEI and metal ion(Ag⁺/Cu²⁺/Fe³⁺)had been used to prepare the composite NF membrane with anti-bacterial activity by electrostatic self-assembly.Ag⁺-PEI/Cu²⁺-PEI/Fe³⁺-PEI NF membrane prepared at optimized condition achieved good permeate flux(121L·m^-2·h^-1·MPa^-1/71L·m^-2·h^-1·MPa^-1/73 L·m^-2·h^-1·MPa^-1),high rejection for acid fuchsin（96.5%/94.5%/91.6%）and low rejection for Mg SO₄（31.5%/27.5%/23.7%）.In addition,three composite NF membranes also showed good anti-fouling performances((FRR_Fe3+=91.5%)>(FRR_Cu2+=83.2%)>(FRR_Ag+=76.4%))in the long-term experiment.More importantly,the excellent anti-bacterial activity of the Ag⁺-PEI/Cu²⁺-PEI/Fe³⁺-PEI membranes were respectively reached to 99.61%（99.95%）,97.63%（92.01%）,95.26%（90.02%）against E.coli（S.aureus）.Hence,the prepare composite NF membranes were of great significance for dye recycle,salt removal and alleviating membrane biological fouling.（2）Based on the role of shear stress in the particle mass balance,the relationship between Reynolds number（Re）and the geometry of filtration module（the channel length and height）was employed to establish a model predicting the variety of permeate flux in the constant pressure cross-flow mode.The proposed model showed higher accuracy for laminar/turbulent flow regime（relative errorσ=4.43%/1.91%）than Makardij’s model（σ=9.44%/12.92%）and Glen Bolton’s model（σ=11.88%/6.42%）.Meanwhile,the validity of the proposed model showed a good agreement by using different suspensions and membranes.Additionally,the value of model parameter k andαincreased with the increasing of suspension concentration and TMP for both laminar and turbulent flow regimes;k increased whileαdecreased with the increasing of temperature for both flow regimes.k in laminar flow was smaller than that in turbulence flow whileαin laminar flow was larger than that in turbulent flow.Finally,the new criterion relations between Sherwood number（Sh）,Reynolds number（Re）and Schmidt number（Sc）in both flow regime was studied.the exponent of the new criterion relations dependence on Re in the laminar flow regime（a=1.69,b=0.336）and turbulent flow regime（a=0.0023,b=0.898）for constant pressure cross-flow membrane filtration process was obtained.