Preparation Of MOFs Membranes And Evaluation Of Separation Performance

In the traditional industries of China and the world,a large amount of capital,manpower and material resources have been invested in the separation process of by-products and excess raw materials in industrial reactions.It is extremely important to develop a low-energy,sustainable industrial separation method.Based on the current environmental pollution and industrial production needs,for the dyed pigment wastewater,layered oil-water mixture,H2/CO2 and C3H6/C3H8 mixed gas,the four different properties of the mixed system,using membrane separation technology,combined with the excellent properties of MOFs materials,Film materials were prepared on different supports by selecting UiO-66 and ZIF-8.According to the application range,three different functional membrane materials were designed and prepared for membrane dye separation of dye pigment,layered oil-water mixture and H2/CO2 and C3H6/C3H8.Due to the special group on the surface of UiO-66,it is applied to pigment separation.UiO-66 grains with uniform particle size and size of about 200nm,300nm,700nm and 900nm were prepared by selecting different proportions of synthetic liquid.UiO-66 grains with uniform particle size and small size were prepared to prepare pigments.Separation membrane.The UiO-66 film was prepared by vacuum filtration on a cellulose acetate film carrier by using 200 nm UiO-66 crystal grains.The UiO-66 crystal grains were deposited to form a certain crystal gap and layer gap structure.The pigment solution is subjected to a certain retardation when it passes,so that the contact time of the crystal with the pigment is prolonged;on the other hand,the pore structure effectively intercepts the macromolecular pigment,which is favorable for pigment separation.At the same time,the surface of the acid-promoted UiO-66 synthesized by the experiment was exposed to H+,so that the anionic pigment in the pigment solution easily reacted with it to achieve the effect of pigment separation.Membrane separation has a greater advantage than general powder adsorption.Firstly,there is no problem of difficult recovery of adsorbent,membrane module replacement is simple;and membrane separation can achieve high-throughput high-efficiency separation.This experiment provides a new model for pigment separation and provides a new idea for the application of membranes to pigment separation.UiO-66 crystal regular octahedral structure and its surface specific hydrophilicity were used to prepare a film on stainless steel mesh carrier for oil-water separation.The polyvinyl alcohol(PVA)modification was used to protect the carrier,and the UiO-66/stainless steel mesh composite membrane was prepared by secondary growth and in situ growth.The experimental results and characterization results confirmed that the membrane network has a regulatable hydrophobic/oleophobic property,nature.The contact angle results show that it has the properties of lipophilic in air,super oleophobic in water and hydrophobic under oil.According to the principle of wettability,water or oil is preferentially introduced on the surface to wet it,and the surface will show oleophobicity./hydrophobic nature.Its separation of cyclohexane/water is as high as 99.0%,and the separation flux is close to 76.9L·m-2·s-1,which provides an excellent application background for the development of MOFs membranes for the treatment of laboratory and industrial wastewater.Due to the special pore size of 3.4 A of ZIF-8 crystal,it is applied to gas separation.ZIF-8 seed crystal layer was prepared by spin-coating ZIF-8 grains on the surface of porous alumina(?-Al2O3)support by a homomixer.By changing the number of spin coatings,a seed layer with different grain density per unit area was prepared,and the ZIF-8 film layer was prepared under the same secondary growth conditions.The density of the film layer increased with the number of spin coatings.improve.Among them,the film which was spin-coated four times and then grownn for two hours can effectively separate gas molecules with similar molecular dynamic diameters,and the actual separation coefficient is larger than the Knudsen diffusion coefficient,which proves that the film layer is dense.The H2/CO2 separation factor is at most 2.64,but the separation permeation rate is low.The actual separation coefficient of C3H6/C3H8 mixed component gas is 3.9,which is much higher than the Knudsen diffusion coefficient of 1.05.It is proved that ZIF-8 membrane has obvious separation effect on C3H6/C3H8 mixed component gas.The study is for ZIF-8 membrane.Strict research data is provided for industrial separation of H2/CO2 and industrial separation of C3H6/C3H8.