Preparation Of Zn/Co-Based MOF Particles And Hybrid Fibrous Membrane For Organic Dyes Removal From Water

In recent years,the pollution of industrial wastewater containing dyes has become more and more serious,which seriously affects and threatens people's drinking water safety and health.The demand for efficient removal of dye wastewater in the environment is becoming more and more urgent.Metal Organic Frameworks?MOFs?are porous crystalline materials that self-assembled between metal ions and organic ligands through coordination bonds,featuring the structural diversity,high porosity,large specific surface and adjustable pore size,making them outstanding candidates for great application prospects in adsorption and catalysis.In this paper,based on these unique characteristics and structures of MOFs,the removal of organic dyes from water was studied by MOFs and polyarylonitrile?PAN?/MOF fibrous membranes.The mechanisms of adsorption of dyes by MOF/PAN fibrous membranes and degradation of dyes by Co-MOFs were also studied.The purpose is to explore the application of MOFs and their composites for dye treatment.The main research contents and results are as follows:1.Metal-organic frameworks?MOFs?exhibit great potential for dye adsorption.However,MOF powder is difficult to remove from aqueous solution,which hinders the practical application of MOFs.Integration of MOFs on polymeric fibrous membrane provides a new strategy to reach the achievements that not only keep the adsorption ability of MOFs for dyes,but also easily remove the MOF/dye complex fromwater.Here,wesuccessfullysynthesizezeoliticimidazole framework-67/Polyacry-lonitrile?ZIF-67/PAN?fibrous membrane with ZIF-67loading ratio of 54%by electrospinning method.The average diameters of ZIF-67nanoparticles and ZIF-67/PAN fibers are about 200 nm and 0.72?m,respectively.The adsorption process of MG on ZIF-67 nanoparticles or ZIF-67/PAN fibers followed a pseudo-second-order kinetic model and fitted Langmuir isotherm.The maximum adsorption capacities of ZIF-67 nanoparticles and ZIF-67/PAN fibers are 2545 and1305 mg·g^-1,respectively.After four regeneration cycles,the ZIF-67/PAN fibers membrane still exhibit over 92%of the original capacity of ZIF-67/PAN fibers.In addition,ZIF-67/PAN fibers also show good adsorption abilities for Congo red(849mg·g^-1)and Basic fuschin(730 mg·g^-1).Therefore,ZIF-67/PAN fibers would be as a promising adsorbent for the removal of dye in industrial application because of its simple preparation method,excellent adsorption property,ease of separation and favorable reusability.2.ZIF-8 nanoparticles were successfully synthesized by direct precipitation method under mild condition.ZIF-8 nanoparticles were used as adsorbents for the adsorption of methyl blue?MB?,acid fuchsin?AF?and malachite green?MG?from aqueous solution.The adsorption capacities are about 17162,13205 and 4838 mg·g^-1for MB,AF and MG,respectively.The adsorption process follows pseudo-second order kinetics and Langmuir models.The possible adsorption mechanism can be attributed to ionic banding between Zn²⁺and SO₃^2-,electrostatic interaction and?-?interaction.In addition,considering the difficulty of removing ZIF-8 nanoparticles from aqueous solution,ZIF-8/PAN fibrous membranes were successfully prepared via electrospinning to adsorb triphenylmethane dyes?MB,AF and MG?.The results show that ZIF-8/PAN fibrous membranes can not only be effectively removed from aqueous solution,but also maintain high adsorption capacity.3.Co-MOFs?ZIF-67,Co-BTC and Co-BDC?/peroxymonosulfate?PMS?system was developed to degrade Rhodamine B?RhB?from wastewater.The effect of catalyst dosage,PMS dosage,pH and temperature on the catalytic degradation of dyes were investigated.The results showed that the optimal dosage ratio of 1:1:1 in Co?II?/PMS/RhB system.and the catalytic efficiency increased significantly at initial pH of 1-5.The possible reason was that Co-MOFs could maintain better activity and better stability of PMS under acidic conditions.When the pH increased?7-9?,the stability of PMS decreased,even decomposed,thus the degradation efficiency decreased significantly.In addition,the degradation experiments of orange G and carmine were also carried out.In regeneration experiments,it was found that the catalytic efficiency could be maintained above 90%after five cycles.