| Nowadays, with the increasing demand for seafood and the yields of them continue to decline, the field of marine aquaculture has been aspired to develop more sustainably and efficiently. Marine aquaculture wastewater treatment is imminent. As a matter of fact, seawater salinity effect has negative influence on the performance of the CAS for high salt expresses an adverse stress to microbial cells leading to weakened efficiency of COD or ammonia nitrogen removal. Polysulfone (PS) is a kind of polymeric membrane material which has an excellent mechanical strength, excellent heat resistance and chemical properties. However, its hydrophobic property leads to a low flux in ultrafiltration membrane, limiting its application in practical water treatment.For this, this paper studied how to improve PS hydrophilic properties, a kind of ultrafilration (UF) membranes with good hydrophilicity and good retention properties were prepared and then discussed their separation performance in marine aquaculture wastewater.Firstly, sulfonated polysulfone (SPS) was designed, and then, the SPS powders were blended with PS to fabricate hydrophilic ultrafiltration membranes by phase inversion. The hydrophilicity, morphology of PS/SPS blended membranes were studied. Also, humic acid (HA) removal, permeation flux were studied by the prepared UF membranes. Besides, we studied the effects of heat treatment on the structure and properties of the membranes. Finally, we discussed the experimental study of the optimal blend membranes performance in marine aquaculture wastewater treatment with the unmodified PS membrane, the purchased PS membrane compared. The conclusions were as follows:1. The SPS powders were synthesized from direct sulfonation method using PS as raw material, chloroform as solvent, CSA diluted with chloroform as the sulfonating agent. Analysis of the product by infrared spectroscopy and TGA curves illustrated the successful introduction of sulfonic acid group to the PS molecule chain. The DS and IEC values of the synthesized SPS powders were calculated to be 30 wt% and 0.64 meq/g, respectively using titration methods.2. We used immersion precipitation phase inversion method to prepare PS/SPS blend ultrafiltration membrane successfully. With the increase of SPS content, the finger-like pore structure of the membrane gradually became lager. The results showed that when PS/SPS ratio was 85%/15%, the blended UF membrane had the better properties and separation performance. The contact angle was 67.21°, reduced by 10.07% compared with the unmodified PS UF membrane, the water uptake increased from 14.41% to 49.5% with respect to the unmodified PS UF membrane and the PS/SPS blended UF membrane. For the porosity, the PS/SPS blended UF membrane was 73.14%, increased by 37.74% compared with the unmodified PS UF membrane. After the device was stable, the flux of PS/SPS blend UF membrane was 116.55 L/m2h, increased by 76.94%with the unmodified PS UF membrane, the retention rate of the PS/SPS blended UF membrane was 87.8% and the retention rate basically unchanged. After the PS/SPS with 85%/15% blend ultrafiltration membranes were soaked in 85℃ water 20 min for heat treatment, the sulfonic acid groups showed cross-linking reaction at high temperatures by analyzing the infrared spectra and XPS spectra, the heat treatment had effect on the membrane structure, the membrane finger-like pore structure tapered became thinner. The HA flux reduced by 15.67% and tne the retention rate basically unchanged.3. We studied the marine aquaculture wastewater treatment of the unmodified PS membrane, the optimal performance of PS/SPS with the ratio of 85%/15% blend ultrafiltration membrane and the purchased PS membranes. The results showed that when PS/SPS ratio was 85%/15%, the blended UF membrane had the better separation performance. After the device was stable, the flux was 163.18 L/m2h, increased by 136% and 18.9% compared with the unmodified PS UF membrane and the purchased PS UF membrane, respectively. The raw water COD contents were 4.03... |
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