The Research On The Treatment Of 1,4-Dioxane In Water By Photocatalytic Membrane

In recent years,water environmental pollution has increasingly become a sensitive concerned issue to governments and the public.The scope of concern includes not only the pollution caused by traditional organic pollutants,but also by some new pollutants.With the continuous development of environmental analysis technology,more and more emerging micro-pollutants are detected in water bodies,soil and sewage in different countries and regions.1,4-dioxane,as one of the new pollutants,has toxic effects on human health.It has been listed as a possible carcinogen（B2）by the United States Environmental Protection Agency（EPA）.1,4-dioxane is ubiquitous in wastewater and landfill leachate,and widely exists in natural water bodies.However,the conventional water treatment process is limited by its technology to degrade the 1,4-dioxane thoroughly.Therefore,it is very necessary and meaningful to study a simple and economical water treatment technology for1,4-dioxane removal.Heterogeneous photo-Fenton technology has many characteristics,such as fast reaction rate,strong oxidation and wide range of applicated pH.It can remove undegradable organic matter in water effectively and improve the utilization rate of catalyst.In this paper,goethite was used as photocatalyst and coated on the ceramic membrane,and then the coated ceramic membrane as photocatalytic ceramic membrane was applied to heterogeneous photo-Fenton technology to remove1,4-dioxane in water.The preparation of photocatalytic ceramic membranes,the fouling mechanism of ceramic membranes and the removal efficiency of 1,4-dioxane are studied in this paper.The main contents are as follows:1.Goethite photocatalysts were prepared by precipitation.Dipping coating and silane coupling method was used to load the catalysts on ultrafiltration ceramic membranes to make photocatalytic ceramic membrane.The experimental results show that the silane coupling agent solution prepared by the mixture of 99.5 mL deionized water and 0.5 mL silane coupling agent G-407 is more suitable for catalyst loading.By means of SEM,XRD and EDS to investigate the surface morphology,crystal structure and element composition of photocatalytic ceramic membrane.It was confirmed that this method could not cause denaturation of catalyst and blockage of membrane pore.Goethite catalysis was successfully loaded on the surface of the ceramic membrane.2.The anti-fouling performance and fouling mechanism of the photocatalytic ceramic membrane for bovine serum albumin solution filtration were investigated.In the bovine serum albumin filtration experiment,when the operating pressure is 0.07Mpa,the membrane flux can be restored to 94%by adding H₂O₂ and ultraviolet light to the photocatalytic ceramic membrane system at 50 min.The transmembrane pressure decreased from 0.055 Mpa to 0.052 Mpa and tended to be stable by adding H₂O₂ and ultraviolet radiation to the reaction system at 90 minutes when the operating flux is 100 LMH.The results show that the photocatalytic ceramic membrane provides a photocatalytic reaction site for BSA degradation,which can effectively control the fouling rate of the membrane and has a certain anti-fouling ability.The fouling mechanism of the membrane was deduced by calculating the value of flow state factor n,and n=1.75 was obtained,which indicated that the filtration process was controlled by"complete blocking"and"Internal pore blocking".3.Treatment of 1,4-dioxane with photocatalytic ceramic membrane.Firstly,the experiment results show that catalysts,H₂O₂ and UV have synergy,the treatment performance of 1,4-dioxane by heterogeneous photo-Fenton system combination of the three components is optimal.The production of hydroxyl radicals in different combination was also investigated to find the reason for the 1,4-dioxane removal.Then,the effects of initial concentration of 1,4-dioxane,dosage of hydrogen peroxide and ultraviolet wavelength on the photocatalytic treatment of 1,4-dioxane were investigated.The results show that when the concentration of 1,4-dioxane solution was 10 mg/L,the concentration of hydrogen peroxide was 2 mM and the ultraviolet wavelength was 254 nm,the treatment performance was optimal,and the removal rate of 1,4-dioxane reached 77.32%in 2 h.Finally,the removal performance of1,4-dioxane by photocatalytic ceramic membrane was investigated in continuous flow filtration system.The experimental results show that the lower the membrane flux is,the higher the removal rate of 1,4-dioxane is.However,because the membrane surface may not be fully loaded by catalyst,low efficiency of electron transfer and the smaller molecular weight of 1,4-dioxane can directly pass through the membrane pore,the removal rate of 1,4-dioxane is only 21%when the membrane flux is 4.15 L/（m²·h）.Hence,the removal rate can be improved by modified catalyst or replace ceramic membrane with smaller pore size.It was also found that the degradation of TOC in the solution was relatively low,indicating that 1,4-dioxane was not completely degraded.The formation of degradation products such as ethylene glycol dimethyl ester,ethylene glycol,formic acid,oxalic acid and methoxyacetic acid was found in the reaction process by gas chromatography-mass spectrometry.Two degradation pathways of 1,4-dioxane were analyzed.