Preparation Of Casting Membrane And Its Performance Study Based On Cellulose Acetate

In recent years,due to industrial wastewater discharge,marine oil spills,hazardous waste emissions of organic chemicals,and other factors,there has been a significant threat to the ecological environment and human health.How to solve the problem of wastewater pollution has become an urgent issue that has attracted widespread attention from researchers.Traditional treatment technologies mainly include gravity separation,adsorption,flotation,and incineration.However,these technologies have disadvantages such as low separation efficiency,inability to sustain the separation process,high cost,and complex operation conditions.Therefore,there is an urgent need to develop an environmentally friendly,efficient,high-throughput,and easy-to-operate separation method.In this paper,a deacetylated cellulose acetate（d-CA）casting membrane was prepared by non-solvent phase separation（NIPS）with high separation throughput,high efficiency,easy operation and environmental protection.The casting membrane is then modified by deacetylation treatment,adding a pore-forming agent sodium chloride（Na Cl）,and copper sulfide（CuS）nanoparticles with good photocatalytic performance.The surface wettability,surface morphology and structure,chemical composition,mechanical properties,oil-water separation performance,and photocatalytic performance of the casting membrane are systematically studied.The main work of this paper includes:1、This paper uses a combination of theoretical analysis and experiments to systematically study the influence of different deacetylation times on the surface wettability of d-CA casting membrane.Combined with the theoretical and experimental values when the oil absorption and water absorption of d-CA casting membrane reached the equilibrium,the oil-water adsorption competition law of d-CA casting membrane was explored.Materials Studio（MS）software was used to simulate and calculate the chemical binding energy of d-CA-water and d-CA-oil molecular systems with different degrees of deacetylation,further revealing the surface wettability mechanism of d-CA casting membrane.The research results show that the d-CA casting membrane exhibits both hydrophilic and oleophilic properties in the air after deacetylation treatment.With the increase of deacetylation degree,its hydrophilic properties are significantly enhanced.Meanwhile,through the analysis of oil-water competition experiment,the hydrophilic properties of the d-CA casting membrane are greater than the oil-philic properties with the increase of deacetylation time in the case of coexistence of oil and water.Thus,it shows the hydrophilic and hydrophobic properties under the oil.The unique surface wettability of the d-CA casting membrane makes it have a wide range of applications in the field of oil-water separation.2、This paper employs a combination of solution casting,NIPS,and deacetylation treatment methods to successfully prepare a highly efficient d-CA porous casting membrane with high oil-water separation flux by introducing a pore-forming agent Na Cl.The effects of Na Cl content on surface wettability,pore morphology,surface structure,mechanical properties,oil-water separation and other properties of porous casting membranes were systematically studied.The results show that the membrane has excellent comprehensive performance.The separation flux of d-CA4 porous casting membrane can reach 22,000 L·m^-2·h^-1under gravity alone.The separation efficiency of d-CA4 porous casting membrane is maintained at 99.1%with the introduction of Na Cl particles.In addition,due to its special surface wettability,it is super hydrophilic and super oil philic in air,oil hydrophobic in water,and super hydrophobic under oil,and therefore has significant self-cleaning ability.Even after25 oil-water separation cycles,the water separation flux and separation efficiency of porous d-CA casting membrane remain at 18,000 L·m^-2·h^-1and 99.1%,showing good pollution resistance and reuse performance.3、In this paper,CuS/d-CA casting membranes without dense epidermal layer were successfully prepared by a combination of solution casting,NIPS,deacetylation and other methods,and CuS/d-CA casting membranes with multistage pore structure were prepared by the introduction of pore-forming agent Na Cl.The effects of Na OH solution,CuS and visible light on the removal of dense epidermal layer were systematically studied,and the photocatalytic properties of CuS/d-CA casting membranes and multi-pore CuS/d-CA casting membranes were tested.The result show that in the presence of Na OH solution and CuS,the epidermal dense layer of CuS/d-CA casting membrane can be effectively removed,thus forming a casting membrane without epidermis structure.The degradation rate of methylene blue（MB）dye can reach 99.0%within 160 min under visible light irradiation.After the addition of H₂O₂,the degradation efficiency of MB dye reached 99.0%in 16 min.The multi-pore CuS/d-CA casting membrane prepared by adding Na Cl particles has a degradation efficiency of up to 99.0%of the MB dye in only 100 min,which is 60min shorter than that of CuS/d-CA casting membrane.The degradation efficiency of the MB dye in the CuS/d-CA casting membrane only takes 12 min to reach 99.0%when the H₂O₂-assisted photocatalysis is added,and it has better photocatalytic performance.