Preparation Of Modified Forward Osmosis Membrane Based On ZIF-67 And Research On Its Desalination Performance

Forward osmosis membrane（FO）technology has been widely used in water treatment because of its unique advantages such as strong separation ability,low energy consumption and low membrane fouling tendency.However,due to the properties of FO membrane materials,problems such as membrane pollution,membrane water flux reduction,internal concentration polarization and so on will also occur in the process of FO,so the modification of the structure,physical and chemical properties of FO membrane has become the focus of current research.In this study,ZIF-67 and ZIF-67@CNT-COOH,which have strong hydrothermal stability and high specific surface area,are synthesized.ZIF-67,CNT-COOH and ZIF-67@CNT-COOH are used as modification additives to improve the structure and performance of FO membrane.The ZIF-67 nanomaterial was synthesized by an eco-friendly method and characterized by XRD,FTIR,SEM and N₂ adsorption-desorption.The CA/ZIF-67 FO membrane was prepared by using ZIF-67 as the modified additive.The effects of ZIF-67 content,the content of pore-forming lithium chloride agent,the mixing temperature and the coagulation bath temperature on the properties of the FO membrane were discussed,and the optimum preparation parameters of the FO membrane were determined.Under the optimum preparation conditions,CA/ZIF-67composite matrix FO membrane was prepared,and its structure was characterized by FTIR,SEM,contact angle and AFM.In addition,the separation performance of CA/ZIF-67 mixed matrix FO membrane was compared with HTI commercial membrane and CA membrane.The results showed that the selectivity and permeability of CA/ZIF-67 mixed matrix FO were improved.CNT-COOH was characterized by XRD,FTIR,SEM and N₂adsorption-desorption.Using CNT-COOH as a blend additive,CA/CNT-COOH mixed matrix FO membrane was prepared,and the effects of additive CNT-COOH content,pore-forming agent lithium chloride content,the mixing temperature and the coagulation bath temperature on the properties of the mixed matrix FO membrane were discussed.The optimum preparation parameters of CA/CNT-COOH composite matrix FO membrane were determined.Under the optimum preparation conditions,CA/CNT-COOH mixed matrix FO membrane was prepared,and its structure was characterized by FTIR,SEM,contact angle and AFM.The separation performance of CA/CNT-COOH mixed matrix FO membrane was compared with HTI commercial membrane and CA membrane.The results showed that the separation performance of CA/CNT-COOH mixed matrix FO membrane was improved.ZIF-67@CNT-COOH nanomaterials were synthesized by in-situ generation method and characterized by XRD,FTIR,SEM and N₂ adsorption-desorption.Using ZIF-67@CNT-COOH as the blending additive,CA/ZIF-67@CNT-COOH mixed matrix FO membrane was prepared.The effects of the additive ZIF-67@CNT-COOH content,pore-forming agent lithium chloride content,the mixing temperature and the coagulation bath temperature on the properties of the mixed matrix FO membrane were investigated.The optimum preparation parameters of CA/ZIF-67@CNT-COOH FO membrane were determined.Under the optimum preparation conditions,CA/ZIF-67@CNT-COOH mixed matrix FO membrane was prepared and characterized by FTIR,SEM,contact angle and AFM.The separation performance of CA/ZIF-67@CNT-COOH mixed matrix FO membrane was compared with HTI commercial membrane and CA membrane.The results showed that the selectivity and permeability of CA/ZIF-67@CNT-COOH mixed matrix FO membrane were better than those of CA FO membrane and commercial HTI membrane.HTI commercial membrane and self-made CA membrane,CA/ZIF-67 mixed matrix FO membrane,CA/CNT-COOH mixed matrix FO membrane,CA/ZIF-67@CNT-COOH mixed matrix FO membrane application experiments were carried out to study the changes of their water flux and salt intercepting rate.The water flux of the four kinds of FO membranes prepared is significantly higher than that of HTI commercial membranes,but the water flux stability of HTI commercial membranes is significantly better than that of the four kinds of self-made FO membranes,and the stability of the salt intercepting rate of HTI commercial membranes is significantly better than that of the four kinds of self-made FO membranes.Among the four kinds of self-made FO membranes,the salt interception rate of the mixed matrix FO membrane and water flux was significantly higher than that of the CA FO membrane,among which,the water flux and salt interception rate of the CA/ZIF-67@CNT-COOH mixed matrix FO membrane was the best,and the stability was relatively good.