Preparation Of Prussian Blue Analogue/Polyvinylidene Fluoride Catalytic Membrane And Removal Performance Of Refractory Organic Pollutants

Water pollution is a global problem to be solved urgently.The high toxicity,degradation difficulty,and bio-accumulation of refractory organic pollutants in water make it imperative to explore effective technologies for their removal.The presence of these pollutions constitutes a grave threat not only to human health but also to the ecological environment.Therefore,it is particularly urgent to carry out research on the efficient removal of refractory organic pollutants in water.Ultrafiltration,a pressure-driven membrane separation technique,is widely used in the field of water treatment with the advantages of low energy consumption,straightforward operation,and no secondary contamination.However,the removal rate of conventional ultrafiltration membranes for organic pollutants is generally low,necessitating measures to enhance their removal capacity.Recently,nano-catalytic materials-based catalytic membranes have emerged as an efficient means of removing refractory organic pollutants from water.Therefore,this study focuses on synthesizing catalytically active Prussian blue analogues（PBAs）particle using the co-precipitation method and incorporating them into polyvinylidene fluoride（PVDF）membranes to develop PBAs/PVDF catalytic membranes.The separation performance,catalytic performance and catalytic mechanism of the prepared catalytic membranes were investigated by activating hydrogen peroxide（H₂O₂）and peroxymonosulfate（PMS）.The followings are the details of the research contents and main conclusions.（1）A catalytically active iron-cobalt Prussian blue analog（Fe-Co PBA）synthesized by the co-precipitation method was incorporated into PVDF to prepare PVDF/Fe-Co PBA Fenton catalytic membranes through the immersion precipitation method.The impacts of Fe-Co PBA loading on the performance of the catalytic membranes in removing methylene blue（MB）as the target organic pollutant were investigated.The results indicated that with increasing Fe-Co PBA loading amount,the flux of the PVDF/Fe-Co PBA catalytic membranes first increased and then decreased,while the removal efficiency and mineralization efficiency of MB first increased and then slightly decreased.When the Fe-Co PBA loading amount was 10 wt%,the flux of the catalytic membrane was 418.47 L/（m²·h）,which was 3.24 times higher than that of pure PVDF membrane.When the H₂O₂ concentration was 400 mmol/L,the removal efficiency and mineralization efficiency of MB by the catalytic membrane were 99.9%and 48.9%,respectively.The removal efficiency of other organic pollutants（dyes,macromolecular organics,antibiotics）by catalytic membrane reached 90%.The Fenton catalytic membrane has universality in the removal of organic pollutants.Radical quenching experiments and electron paramagnetic resonance（EPR）analysis showed that hydroxyl radical（·OH）,superoxide radical（·OOH）,and singlet oxygen（¹O₂）were the intermediate active species in Fenton catalytic membrane reaction,and ¹O₂ was the main active species.After ten cycles of catalytic use,the catalytic membrane can still achieve a removal efficiency of more than 97.4%for MB,and the presence of interference anions has little influence on the removal of MB.Furthermore,the Fenton catalytic membrane exhibits excellent repeatability and anti-interference abilities.When the Fe-Co PBA loading amount was 10 wt%,the flux recovery rate of the catalytic membrane in the bovine serum albumin（BSA）contamination system increased from 34.9%for the pure PVDF membrane to 92.7%after Fenton cleaning.This indicates that the Fenton catalytic membrane exhibits excellent Fenton self-cleaning performance.（2）Four different types of PBAs（Co-Co PBA,Fe-Co PBA,Ni-Co PBA,Cu-Co PBA）were synthesized by using different metal salt types.Additionally,four PVDF catalytic membranes were prepared using the immersion precipitation method.The four catalytic membranes were studied for their effect on the degradation of the target antibiotic pollutant tetracycline（TC）using activated PMS.The results indicated that the four PBAs in the preparation of PVDF membrane,the flux of Co-Co PBA/PVDF catalytic membrane（Co-Co PCM）was 454.96 L/（m² h）,which was 3.52 times higher than that of pure PVDF membrane.Among the four kinds of PVDF membrane activated PMS for TC removal,Co-Co PCM had the highest TC removal efficiency and reaction efficiency constant,which were 98.0%and0.088 min^-1,respectively.Furthermore,the activation energy of the Co-Co PCM/PMS system was the lowest（19.929 k J/mol）,as evidenced by fitting results obtained using the Arrhenius equation.The optimal PMS concentration for the Co-Co PCM/PMS system was 5 mmol/L,the optimal loading amount of Co-Co PBA was 10 wt%,the applicable p H range was 3～12,with a concentration range of 0～80 mg/L.The removal rates of different kinds of antibiotic pollutants by Co-Co PCM catalytic membrane were 98%,indicating that the catalytic membrane had good universality in removing antibiotic pollutants.Free radical quenching experiments and EPR analysis proved that the intermediate active species of the Co-Co PCM/PMS system were sulfate radical(SO₄^·-),·OH,and ¹O₂,the main active site during the activation of PMS by Co-Co PCM catalytic membrane was the Co site.Even after undergoing ten catalytic cycles,the removal efficiency of TC by the four PVDF catalytic membranes only decreased by 6%,indicating excellent repeatability of the catalytic membrane.Moreover,different interfering anions had a small effect on the removal of TC by the PVDF catalytic membrane/PMS system,with only 5%reduction in the removal efficiency under different water samples,indicating good anti-interference properties of the catalytic membrane.