Removal Of Organic Pollutants In Water By A Coupling System Of Ceramic Membrane Filtration/persulfate Activation/adsorption

The development of industrial,agricultural and household industries has led to the introduction of more types of pollutants into the environment.Except for traditional organic pollutants,emerging contaminants are also frequently detected in the environment,and it is urgent to develop novel and efficient water pollution treatment technologies.Membrane separation technology has the benefits of high separation efficiency,small footprint and simple operation and management.However,conventional microfiltration/ultrafiltration membranes are difficult to effectively remove organic pollutants from water through retention due to their large molecular weight.The combined process of peroxymonosulfate（PMS）activation and ceramic membrane separation enables efficient degradation of organic pollutants in water while membrane filtration.In addition,activated carbon adsorption is used to remove small molecules of organic matter that cannot be completely oxidized and decomposed.Based on the above ideas,two integrated coupled systems,M₀-Co@GAC/PMS with activated carbon catalyst activated PMS and M_Co-GAC/PMS with ceramic catalytic membrane activated PMS,were constructed in this study to achieve efficient degradation of organic pollutants while membrane filtration.In this study,the activated carbon catalyst Co@GAC and ceramic catalytic membrane M_Cowere obtained by loading cobalt oxides on granular activated carbon（GAC）and ceramic membrane through impregnation calcination method.Then M₀-Co@GAC membrane modules were prepared by filling the channels of ceramic membrane M₀with Co@GAC,and M_Co-GAC membrane modules were prepared by filling the channels of ceramic catalytic membrane M_Cowith GAC.Finally,the two membrane modules were applied to the submerged membrane filtration system,and two ceramic membrane filtration/persulfate activation/activated carbon adsorption integrated coupled systems M₀-Co@GAC/PMS and M_Co-GAC/PMS were successfully constructed.The catalytic degradation performance of M₀-Co@GAC/PMS and M_Co-GAC/PMS systems for bisphenol A（BPA）,ulfadiazine（SDZ）,4-chlorophenol（4-CP）,Phenol,methylene blue（MB）and rhodamine B（Rh B）were investigated.The catalytic mechanism of M₀-Co@GAC/PMS and M_Co-GAC/PMS systems for BPA were investigated.The stability and reusability of the above two systems were evaluated,and the anti-pollution performance of ceramic membranes in both systems was comparatively studied.The specific research results are as follows:（1）In M₀-Co@GAC/PMS and M_Co-GAC/PMS systems,the removal rates of BPA were 93.1%and 96.5%,and the removal rates of TOC were 44.9%and 54.1%with 60 min.These results indicate that both coupled systems exhibit excellent catalytic degradation performance and mineralization ability for organic pollutants.The removal of BPA by the two systems under different experimental conditions showed that M₀-Co@GAC/PMS and M_Co-GAC/PMS systems are suitable for treating BPA wastewater with low concentration.In addition,lowering the operating membrane flux and appropriately increasing the PMS dosage are beneficial to the catalytic degradation reaction of the coupled system.（2）BPA removal and free radical burst experiments in different membrane filtration systems showed that the removal of BPA in M₀-Co@GAC/PMS system was achieved by adsorption（～59.1%）and catalytic degradation（～33.7%）of Co@GAC filled in M₀.In M₀-Co@GAC/PMS system,activation of PMS by Co₃O₄on the surface of Co@GAC generates SO₄^·-and·OH.In the M_Co-GAC/PMS system,the removal of BPA was achieved by adsorption of GAC（～50%）and catalytic degradation of M_Co（～50%）.And Co₃O₄on the surface of M_Cois responsible for PMS activation to generate SO₄^·-and·OH.In addition,both SO₄^·-and·OH were the dominant active species in both coupled systems.（3）The removal effects of M₀-Co@GAC/PMS and M_Co-GAC/PMS systems for SDZ,4-CP,Phenol,MB and Rh B indicated the excellent versatility of these two coupled systems for organic pollutants.The BPA removal results of M₀-Co@GAC/PMS and M_Co-GAC/PMS systems with natural river water as background water showed that both coupled systems could maintain good catalytic degradation performance in real water sample,and the catalytic degradation performance of M_Co-GAC/PMS system was superior.（4）The BPA removal rate of M₀-Co@GAC/PMS system was stable at about 90%in the six experimental cycles of experiment,and the dissolved Co²⁺concentration decreased with the increase of the cycles.The XRD and SEM characterization of the used Co@GAC showed that there was no significant difference in crystal structure of Co@GAC and the surface of Co@GAC retained sufficient amount of Co₃O₄.The BPA removal rate of M_Co-GAC/PMS system was stable above 91%in five experimental cycles.And the SEM characterization of the used M_Coshowed that a remarkable quantity of Co₃O₄was still retained on the surface of M_Co.Therefore,both M₀-Co@GAC/PMS and M_Co-GAC/PMS systems exhibit good stability and reusability.（5）The anti-pollution performance of ceramic membranes in both systems was investigated using natural river water as background water,and the results suggest that the addition of PMS can effectively mitigate membrane contamination.And the transmembrane pressure of the M_Co-GAC decreased significantly with the increase of PMS concentration in the system,indicating that the PMS solution was more effective in mitigating membrane contamination of the M_Co-GAC.In addition,the results of membrane cleaning experiments showed that flushing the contaminated M₀and M_Cowith PMS solution can effectively reduce membrane contamination,especially the membrane contamination of M_Cois significantly decreased.