Research On The Preparation Of Fe Based MOFs Nanocomposite Membrane And The Characteristics Of Arsenic Removal

Due to industrial production,the world is facing a relatively serious arsenic pollution.Many residents drink arsenic water for a long time,resulting in a variety of diseases.Metal Organic Frameworks(MOFs)are a new type of porous solid compounds,which are usually assembled by metal center ions(or ion clusters)and organic ligands through coordination bonds.MOFs materials have the characteristics of both organic and inorganic materials,with high porosity,high specific surface area,and unsaturated active metal sites.Therefore,MOFs materials have been widely concerned in many fields,such as catalysis,adsorption,removal of heavy metal ions,removal of pollutants in water and preparation of composite membranes.At present,there have been reports of using MOFs materials to remove arsenic from water,but there are few reports of using MOFs composite membrane to remove arsenic.According to the characteristics of Fe BTC(BTC = 1,3,5-Benzenetricarboxylic acid)which can be synthesized rapidly in water phase at room temperature,two methods of preparing PAN-Fe BTC(PAN = polyacrylonitrile,BTC = 1,3,5-Benzenetricarboxylic acid)composite membrane were proposed,which were layer by layer assembly method and interfacial polymerization method.The results show that a thin layer of Fe BTC with uniform distribution and flat surface can be prepared on the surface of the basement membrane by interfacial polymerization method,and the flux drop is less.However,if layer by layer assembly method is adopted,a thick layer of Fe BTC can be loaded on the surface of the basement membrane only after several times of assembly,but the flux of the membrane will be greatly reduced and it can not be used under the condition of gravity(0.07bar).During the preparation of composite membrane,with the increase of precursor concentration and reaction time,the Fe BTC layer on the surface of the composite membrane becomes thicker,but the surface roughness of composite membrane increases.In order to prepare the composite membrane,the PAN membrane should be carboxylated firstly.The results show that the optimum concentration of Na OH for PAN membrane hydrolysis is 1.0 mol/L.In addition,the removal efficiency of pentavalent arsenic and trivalent arsenic by the composite membrane prepared by interfacial polymerization method was studied,and the effects of p H,coexisting ions and coexisting humic acid components on arsenic removal were also explored.The removal rate of pentavalent arsenic by the composite membrane prepared by interfacial polymerization method is much higher than that of trivalent arsenic.With the increase of the concentration of precursor and the reaction time,the removal efficiency of pentavalent and trivalent arsenic increased.When the concentration of precursor is 10 mmol/L and the interfacial polymerization time is 20 min,the removal rates of pentavalent and trivalent arsenic do not change much in the range of p H 2?10.The removal rates of pentavalent and trivalent arsenic remain above 90% and 50% respectively.The presence of Ca2+and Mg2+can improve the removal efficiency of pentavalent and trivalent arsenic,while the presence of CO32-and PO43-can greatly reduce the removal efficiency.Cl-,NO3-have almost no effect on the removal of pentavalent and trivalent arsenic by the composite membrane.Humic acid can slightly reduce the removal efficiency of pentavalent and trivalent arsenic.