Metal-organic Framework (UiO-66) Coated ?-Al₂O₃ Self-assembled Ultrafiltration Membrane For Water Purification

Due to the characteristics of controllable functional materials and membrane-forming conditions,high water yield,low operating pressure,high efficiency and energy saving and recycling characteristics,self-assembled membrane is applied in the field of water purification.In this paper,UiO-66 coated?-Al₂O₃composites were firstly synthesized using?-Al₂O₃as template to induce the growth of high hydrophilic UiO-66 on its surface to form uniform UA self-assembled ultrafiltration membrane for the purification of oily seawater.This study has important theoretical significance and good application prospects.In this paper,spherical?-Al₂O₃ was prepared by homogeneous precipitation method,and then?-Al₂O₃used as template to induce the growth of UiO-66 on its surface to synthesize?-Al₂O₃/UiO-66(Zr)functional material(UA)by in-situ growth method.To further improve the hydrophilicity of functional materials,bimetallic UiO-66(Zr/Y)was loaded on the surface of?-Al₂O₃to synthesize?-Al₂O₃/UiO-66(Zr/Y)functional material(MC-UA).The optimal preparation conditions of the two functional materials were studied,and the two functional materials were investigated by SEM,EDX,FTIR,XRD and water contact angle.Besides,under the control of liquid redistributor,the diatomite support layer and UA functional layer were successively formed on the porous support by layer-by-layer technology to obtain UA self-assembled membrane.To form uniform self-assembled membrane,the optimal membrane forming condition was studied,and the self-assembled membranes formed under optimum condition were used to clean oily seawater.The dosage of UA,membrane running time,recycling and long-term running performance were studied.Finally,MC-UA self-assembled membrane was used to treat oily seawater and compared with UA self-assembled membrane.The results show that UA and MC-UA synthesized under optimal conditions with the particle size of around 3?m have rough surface,good sphericity and uniform size distributions.UiO-66 has been successfully synthesized and coated on the surface of?-Al₂O₃particles and yttrium has successfully doped into the lattice of UiO-66without changing the crystal structure.The water contact angel of functional materials reduced from 26.2°(UA)to 23.5°(MC-UA).The most uniform self-assembled membrane can be formed by control flow field distribution through variable hole diameter liquid redistributor(hole diameter of 2&3.5 mm,opening ratio of 28.83%)and stainless steel wire mesh(80 mesh)under 0.01 MPa.UA self-assembled membrane shows high efficiency and separation performance when the membrane running time is 30 min.The UA self-assembled membrane can be recycle,and the treatment classes can be adjusted according to the permeate water quality.After 5treatment classes,the oil retention ratio and suspended solid removal ratio are 97.14%and 98.23%,respectively.Compared with UA self-assembled membrane,MC-UA self-assembled membrane shows higher underwater oleophobicity(the underwater contact angle of UA and MC-UA self-assembled membrane are 141.3°and 144.9°,respectively),lower membrane resistance(the membrane resistance of UA and MC-UA self-assembled membrane are 3.05×10¹¹?2.83×10¹¹m^-1,respectively),high separation performance(after 5 treatment classes,the oil retention ratio and suspended solid removal ratio are 97.73%and 98.75%,respectively)and higher anti-fouling performance(after 8 cycles,oil retention ratio of UA and MC-UA self-assembled membrane are 69.33%and 75.80%,respectively).Therefore,the self-assembled membrane with high flux,low membrane resistance and attractive membrane performance is expected to achieve broad application.