Effect And Prediction Of Hydrophobic Properties Of Polymer Membranes On Scaling Mechanism

Membrane process has been widely used in desalination and wastewater treatment with the development of society.But membrane fouling is one of the main obstacles to the stability of membrane operation.Therefore,it is very important to understand deeply the fouling mechanism of membrane and find the membrane with better anti-fouling performance.In this paper,in view of the scaling problem of inorganic and organic substances on the surface of membrane in the membrane processes,several typical commercial microfiltration membranes were used as test surfaces,and gypsum and lysozyme were used as inorganic and organic scalant models to explore the effect of hydrophobic properties of different polymer membranes on the scaling mechanism of scalant and evaluate their anti-fouling performance.On this basis,the scaling tendency of some polymer membranes that was potentially used for membrane process was predicted.Gypsum was used as inorganic scalant model.The adhesion mass of gypsum crystals to different membranes was studied by adhesion experiment,and interaction energies between the polymer and gypsum crystals were calculated using the molecular dynamics simulation method.Scaling mechanism on the polymer membranes from the aspect of the membrane chemistry and surface morphology was discussed.The results showed that membrane chemistry has the most significant impact on its adhesion energy to gypsum crystals: gypsum crystals are more likely to scale on the hydrophilic membrane surface,and the hydrophobic membrane has better anti-fouling performance than hydrophilic membranes.The number of polar groups in the membrane molecules has higher effect on the adhesion energy than the variety of polar groups.The anti-adhering properties of the membranes increase with decreasing absolute adhesion energy.Surface morphology of membranes was also crucial to its scaling behavior under the condition that the adhesion energy of membranes was close to each other.The larger pore that exceeds a proper range leads to less adhesion mass.Subsequently,the membranes potentially used for membrane process were successfully predicted from the aspect of membrane chemistry in terms of their anti-scaling propensity using same molecular dynamics simulations.Lysozyme was used as organic protein scalant model,the scaling tendency of lysozyme crystals on the different polymer membranes was compared,and the scaling mechanism was explained and discussed.The effects of hydrophilic and hydrophobic properties,surface electric charge,roughness and characteristic functional groups in molecular chains on the scaling behavior of membrane surfaces were studied.The results showed that resistance to protein fouling of the hydrophilic polymer membrane was better than that of the hydrophobic membrane,which was contrary to the antifouling property of gypsum.The higher the number of hydrophilic groups in the polymer molecular chain that can react with solvent water,the better the resistance to protein fouling.Membrane surface properties,such as surface electric charge performance and roughness of the membrane surface have a certain effect on the fouling tendency of lysozyme crystals on membrane surface: polymer membranes with opposite charges and lysozyme molecules with positive charges showed an electrostatic interaction under a certain p H of solution.And when the Zeta potential showed a small difference,the influence on fouling tendency of lysozyme crystals to different membrane surface is small;The smaller the surface roughness,the better the resistance to protein fouling.The paper provides an insight that the chemical and physical structures of membrane should be rationally selected for a better antifouling property,and giving a guidance on method to the researchers and manufacturers for the screening,modification and fabrication of membranes in the development of anti-scaling membrane in membrane technology.