Preparation And Water Treatment Performance Of Active Nanoparticle Hybrid Membranes

As a new and efficient wastewater treatment technology,membrane separation technology can effectively remove pollutants from wastewater,but its application is limited by membrane fouling.Therefore,in order to improve the separation efficiency and inhibit membrane fouling,the combined technology of membrane separation and advanced oxidation processes（AOPs）will be used in this study to construct a hybrid membrane with catalytic activity by in-situ loading nanoparticles on the non-woven fabric（NWF）microfiltration membrane and applying it to water treatment.By separating,trapping and catalytic coupling to remove pollutants in wastewater,the results of selective separation,high catalytic efficiency,green energy saving,recycling,and inhibition of membrane fouling are achieved.The main research contents about the prepared membranes are as follows:（1）The Cu O@PDA/PEI-NWF hybrid membrane was prepared and its properties were studied.Peroxymonosulfate（PMS）catalyst（copper oxide nanoparticles,Cu O NPs）was firmly loaded on polydopamine（PDA）modified NWF membrane by a typical in situ deposition method.The large-scale loading of～5 wt%Cu O NPs on PDA-modified NWF membrane was verified by Scanning electron microscopy（SEM）,Energy dispersive spectrometer（EDX）,X-ray photoelectron spectroscopy（XPS）and X-ray Diffraction（XRD）characterization techniques.In cyclic catalytic 60 minutes,the quality of 0.2 g Cu O@PDA/PEI-NWF（content of Cu O NPs～0.01 g）under the concentration of 1 m M PMS activation to produce reactive oxygen species(ROS,including ¹O₂、SO₄^·-and^·OH).In the p-nitrophenol（4-NP）（10 ppm,1L）feed solution with p H 6,the 4-NP removal rate is about 65%,and the dynamic removal constant（k）reaches 0.019 min^-1,that is,the k can reach 1.9 min^-1 when the load is 1.0 g Cu O NPs.After standardized nanocrystalline catalyst weight,the k is the highest compared with the removal of 4-NP by activated PMS induced AOPs in some reported references.Then,the effects of the dosage of PMS and p H on the catalytic removal of different concentrations of 4-NP were also discussed.The results showed that the removal effect of 4-NP was further improved with the increase of the dosage of PMS,and the removal effect of 4-NP was the best when the p H was neutral.Cu O@PDA/PEI-NWF/PMS cycle system has shown good robustness and sustainability in treating simulated wastewater with 4-NP in the background of Pearl River water.Under the effect of circulating membrane catalysis system for 360 minutes,Cu O@PDA/PEI-NWF can make the removal rate of 4-NP（20 ppm,2 L）in simulated 4-NP（20ppm,2 L）polluted water with the background of Pearl River water reach more than 90%,and the chemical oxygen demand（COD）decrease about 80%under the condition of 2 m M PMS.The work has shown that Cu O@PDA/PEI-NWF has high efficiency and long-lasting catalytic degradation performance and mineralization ability,and does not require complicated catalyst separation/regeneration process.In addition,Cu O@PDA/PEI-NWF/PMS cycle system was used to treat acidic orange 7（AO-7）wastewater（20 ppm,1 L）.The results showed that the removal rate of AO-7 could reach～100%after 180 minutes of cyclic catalytic oxidation under2 m M PMS.COD was reduced by～65%and k was 0.18 min^-1,indicating that Cu O@PDA/PEI-NWF/PMS had good mineralization ability against other troublesome persistent organic pollutants（POPs）in water.（2）The Ti O₂-PDA@PVDF hybrid membrane was prepared and its properties were studied.Through the typical in-situ deposition method,dopamine hydrochloride was used to co-deposit the NWF membrane for surface modification.Then through the blending of 3-amino-propyl-triethoxysilane（APTES）and Ti O₂ NPs,and APTES was grafted onto Ti O₂ NPs.Through the Michael addition reaction,the ammoniated Ti O₂ NPs particles were captured by PDA deposited on PVDF NWF membrane and used as seed points,and then immersed in the mixed solution of tetrabutyl titanate and urea for hydrothermal reaction.After full hydrolysis,the dense Ti O₂NPs（～8.4 wt%）coated Ti O₂-PDA@PVDF membrane was finally obtained.Using SEM,EDX,XPS and XRD characterization techniques,the photocatalyst（anatase type Ti O₂ NPs）was successfully modified on the PDA-modified NWF membrane.In this work,the microfiltration properties of Ti O₂-PDA@PVDF,the pollution resistance to fulvic acid（FA）,and the self-cleaning properties of photocatalysis were investigated.The removal rate of FA（20 ppm）can reach 86%by Ti O₂-PDA@PVDF within 10 min filtration.When Ti O₂-PDA@PVDF is seriously polluted by FA（100 ppm）filtration,the pure water flux recovered by FA polluted membrane after UV/H₂O₂ cleaned（336 L/m²h）is 116 L/m²h higher than that after backwashing（220 L/m²h）,indicating that Ti O₂-PDA@PVDF has excellent anti-pollution performance.In particular,when the concentration of H₂O₂ is 4 m M,UV/H₂O₂（4 m M）self-cleaning membrane both in surface morphology（similar to the fresh Ti O₂-PDA@PVDF）,chemical structure(1022cm^-1 FA structure infrared absorption peak close to disappear),water affinity（the difference of water relaxation time before and after the membrane surface contact△T=525 ms,minimax）,pore size distribution（pore size at 20 nm,pore size of fresh Ti O₂-PDA@PVDF at 25 nm）,filtration performance（FA flux loss at 52%within 10 min,minimum）,and anti-contamination performance（FA flux at 383 L/m2h,at 10 min,maximum）,recovering to the level of unpolluted,showing more effective self-cleaning performance of photocatalysis.Its photocatalytic self-cleaning mechanism is under the excitation of UV,the anatase Ti O2 NPs of FA fouled membrane generated photoproduction electronic（e^-）and optical cavity（h⁺）,e^-absorb light energy transition to bring and migrated to the membrane surface,through the reduction of H2O2produce ROS（including^·O₂^-、^·OH and ¹O₂）.ROS can trigger the breaking of the C-C bond that connects the carboxyl group to the benzene ring in the FA structure,which further leads to the disconnection of surface hydrogen bond formed by Ti O2 NPs and FA,so as to peel and fall off from the membrane surface,realizing the photocatalytic self-cleaning process of Ti O2-PDA@PVDF.Furthermore,this work also shows that Ti O₂-PDA@PVDF also has a good adsorption capacity for heavy metal ions,the adsorption capacity（q_e）of Cr⁶⁺、Sb³⁺、Tl⁺are207 mg/m²,182 mg/m²and 158 mg/m²,respectively.