Synthesis Of Bis-A/HQ/DCS Copolymer And Application Performance Of Its Ultrafiltration Membranes

Polysulfones resin is a thermoplastic polymer materials, the main chain of polysulfones macromolecule consists of aromatic ring, sulfone, and ether. The rigidity of the material is provided by aromatic ring, the excellent resistance to heat and oxidation is supported by sulfone group, and the processing behavior of materials is strengthened by ether group. Because of this unique molecular structure, the polysulfones material has excellent mechanical strength and good resistance to hydrolysis, heat, acid and alkali. Polysulfones materials are widely used in ultrafiltration, nanofiltration, gas separation, and occupy an important place in the membranes market.As the most widely used polysulfone resin, bisphenol-A(Bis-A) polysulfone has poor resistance to solvent, and the toughness of material is also poor, these results in the application limitations of materials. Poly ether ether sulfone(PEES) resin has good toughness and solvent resistance. In order to improve the solvent resistance of polysulfone and the toughness of the material, the PEES segments was introduced to polysulfone main chain by copolymerization in this paper, and the synthetic copolymers were made into ultrafiltration membrane, and the membrane was used to treat the dyeing-fatliquoring effluents. The possibility of recovering and concentrating dyes and fatliquoring materials through membrane process was investigated on the laboratory scale.In this study, the Bis-A/HQ/DCS copolymers were synthesized by nucleophilic polycondensation of bisphenol-A (Bis-A), hydroquinone (HQ) with4,4'-dichloro-diphenyl sulfone (DCS). The structure of copolymer was characterized by Infrared Spectroscopy (FT-IR) and Proton Nuclear Magnetic Resonance Spectroscopy ('H-NMR); the thermal properties of the copolymer was analyzed by Differential Scanning Calorimetry (DSC) and Thermal Gravimetric (TG). The solvent resistance of the product was investigated by dissolving the polymers with different solvents. The results showed that the resistance to solvent and heat of polysulfone resin was improved by introducing polyether ether sulfone segments into polysulfone.The effect of the reaction conditions on the performance of the product had been discussed. The results showed that the synthetic product with higher molecular weight and the higher yield could be achieved by increasing initial monomer concentration. The catalysis of K2CO3was better than others, and the catalytic activity of K2CO3could be enhanced by dissolving it with amount of water, which can promote the formation of phenoxy salt, and the rate of the polymerization were faster.The ultrafiltration membranes were prepared by phase inversion process with PSF homopolymer or Bis-A/HQ/DCS copolymer, respectively. The flux and the rejection of ultrafiltration membrane was analyzed. The hydrophilic character of untrafiltration membranes was characterized by surface contact angle. The surface morphology and cross-sectional structure of ultrafiltration membranes were observed by Scanning Electron Microscope(SEM). And the mechanical strength of ultrafiltration membranes was also tested. The measurement showed that the hydrophilic Bis-A/HQ/DCS ultrafiltration membrane was more hydrophilic than PSF ultrafiltration membrane, and the separation performance of Bis-A/HQ/DCS ultrafiltration membrane was good. The SEM indicated that lots of micropores on the surface of ultrafiltration membrane, and the cross-sectional structure consists of a thin dense cortex layer and a loose spongy support layer.The Bis-A/HQ/DCS ultrafiltration membrane was applied to the recovery of dyes and fatliquoring materials from effluents of dyeing-fatliquoring process, and the effect of operating conditions on ultrafiltration was also discussed. The result of UF processes showed that the TSS, Chroma, TN, TDS and COD reduced100%,96.2%,86.6%,96.4%and91.8%, respectively. The flux recovery ratio of membranes reached96%after washing with cleaning solution (pH=10) The retentate stream can be reused in the dyeing-fatliquoring process and save about30%dyes and fatliquoring agent. The permeate stream that can be reused in the picking step before the tannage. The physical mechanical properties of leather treated with recoverd solutions was close to the leather which was made by the traditional technology. The UF process reduced the pollution of the leather industry to the environment, simplified the wastewater process, and saved chemicals and water.