Superwettable Polyether Sulfone Membrane For Oil-water Separation Using Reverse Thermal Separation Method (RTIPS)

As the treatment of oily wastewater has become a major challenge to environmental treatment,there is a growing call for the application of membrane separation technology in the field of oily wastewater treatment.Unfortunately,while membrane separation technology stands out for its high throughput,high oil removal,light weight,mechanical flexibility,compact design,small space requirement,low energy consumption and low cost,membrane contamination emerged as the primary problem limiting the use of this technology.Facing this situation,obtaining separation membranes with superwettability has become one of the preferred research fields.This study was conducted repeatedly with the aim of preparing synthetic materials with excellent properties based on co-mixing modification and the RTIPS method.The main studies are as follows:Dopamine-induced titanium precursors were bionitrized and the separation membranes were produced using the RTIPS method.Firstly,the precursors were induced to complete the generation and mixing of HNP aggregates within the casting solution to obtain the results of uniform distribution of modified particles.Secondly,the spongy internal structure,which was obtained by the RTIPS method,provided the conditions for the polymers to adhere more easily.Finally,the successful introduction of particles was proved by FTIR,EDS and XPS.On the other hand,it was proved that the selectivity of the modified membrane was more than 99%by the flux and separation test,and the high flux of 3301.71 L/m²h was obtained The water contact angle test showed that the hydrophilicity was successfully enhanced with the introduction of particles.On this basis,the modified membranes under optimal conditions were tested for recycling,and it was confirmed that the separation membranes obtained at this time have the conditions to form hydrophilic layers more easily and facilitate recycling（the recovery rate could be guaranteed to be more than80%）.The hydrophilicity of the membranes was effectively enhanced by the presence of hydroxylapatite containing more hydrophilic groups.In this work,hydroxyapatite was modified by the strong adsorption of dopamine,and the modified nanoparticles with good dispersion were obtained.XRD,SEM,TEM,FTIR and other characterization methods were used to analyze the particles,which not only proved that dopamine could be successfully adsorbed on the surface of hydroxyapatite,but also that the coating only changed the particle size and dispersion,and had no obvious effect on the morphology and structure.Then,the modified hydroxyapatite was introduced into the casting solution,and the phase separation process was completed by the RTIPS method.The prepared membrane materials were subjected to spectral analysis,and it was found that the characteristic peaks belonging to hydroxyapatite appeared in the FTIR spectrum,and the results of uniform particle distribution were obtained by elemental distribution in EDS,which proved the initial success of this modification.After water flux and oil-water separation tests and circulation experiments,it was confirmed that the separation membrane had high permeability（1515.46 L/m²h,14 times higher than the original membrane）and high selectivity（99.80%and 99.92%）under the optimal preparation conditions（HA:DA=1:2,1wt%）.The variation of tensile test results demonstrates the success of the modification of the mechanical properties of the separation membranes.In addition,the modified membranes with higher hydrophilicity were verified in cycling experiments to demonstrate a significant improvement in the anti-pollution properties of the modified membranes.The self-cleaning mixed matrix membranes were prepared by RTIPS method using PDA@Cu Fe₂O₄particles coated with dopamine as filler.First,XRD,SEM,TEM,FTIR,TGA and other characterization methods confirmed that Cu Fe₂O₄has been successfully coated by polydopamine layer,and completed its dispersion in the casting liquid and size changes,the morphology and related properties have little influence.Then the results of contact angle characterization,tensile test,water flux test,oil-water separation test and cycle test were analyzed,and the following results were obtained:1)a separation membrane with high efficiency for separating oil and water was obtained（1707.78 L/m²h,16 times higher than pure membrane,and more than 99.9%removal rate）;2)the maximum hydrophilic modification condition was1.0 wt%,which can guarantee the higher mechanical properties and excellent hydrophobic property;3)The morphology and underwater oleophobicity of the modified membrane after the corrosion test did not change,proving that this modification improved the corrosion resistance provided by the separation membrane,providing some data reference and theoretical basis for the practical application of this membrane;4)the modified membranes obtained with a 50%recovery ratio even after four cycles thanks to the anti-fouling properties obtained.Finally,the study on the degradation of pollutants by visible light demonstrated that the altered film had photocatalytic performance,and by comparing the various cleaning methods of the polluted film,it was confirmed that the modified film got a better self-cleaning property.