Preparation Of RGO/ZIF-8 Modified Nanofiltration Membrane And Experimental Study On Desalination Of Brackish Water

Nanofiltration?NF?can effectively separate small molecule organics and high-valent ions in aqueous solutions,and has the advantages of low operating pressure and low energy consumption,and has a wide application prospect in the field of water treatment.Modification of nanofiltration membranes has always been the focus of research,and the introduction of additive modification is an effective method for the modification of nanofiltration membranes,but the introduction of traditional additives will bring the conflicting relationship between permeability and retention,resulting in a significant"trade off"effect.Therefore,this article improves the preparation process of nanofiltration membranes,seeks new additives,and slows down the"trade off"effect.The aim is to obtain high-performance nanofiltration membranes to promote the further popularization of nanofiltration technology in practical applications.In this study,the self-made composite nanomaterial rGO/ZIF-8 was introduced into the functional layer of the nanofiltration membrane by the interfacial polymerization method?IP?,and the rGO/ZIF-8 composite nanomaterial membrane was prepared.Best introduction.Based on this,its anti-pollution,stability performance and application in brackish water were studied.The research results are as follows:?1?The composite nanomaterials rGO/ZIF-8 were synthesized by hydrothermal synthesis.rGO/ZIF-8 was characterized by new infrared and XRD characteristic peaks,surface morphology,and thermal stability different from ZIF-8 and rGO.?2?The composite nanomaterial rGO/ZIF-8 was introduced into the functional layer of the nanofiltration membrane,and a series of modified nanofiltration membranes were successfully prepared.The surface morphology,structure,and salt-separation performance were studied,and the effect of the added amount of rGO/ZIF-8 on the nanofiltration membrane.The results show that the modified nanofiltration membranes are negatively charged and the surface roughness is significantly different.The water flux of the prepared RZ-NF membrane is the highest,reaching 39.2 L/m²h,which is nearly double that of the origin-NF membrane.The rejection rate decreased slightly,from 95.8%to 85.6%;the optimal introduction amount of rGO/ZIF-8 was 0.005 wt%.At this time,the modified membrane had the strongest hydrophilicity,the largest surface roughness,and water flux reaching 40.6L/m²h,the rejection rate for Na₂SO₄ is 89.3%,and the separation performance is the best.?3?The stability performance and anti-pollution performance of different modified nanofiltration membranes were studied,and it was found that at higher pressures?when the operating pressure is increased from 0.6 MPa to 1 MPa?and continuous operation for 48 h,0.005RZ-NF membrane has more stable separation performance;using BSA,SA and HA as simulated pollutants,it was found that different membranes showed the same pollution trend for the three pollutants:HA<SA<BSA,in addition,0.005RZ-NF membrane for three pollutants showed the best anti-pollution performance.?4?Taking the actual brackish water as the object,we studied the separation behavior of the main salt ions in brackish water by 0.005RZ-NF membrane and found that the removal rate of Na⁺,Ca²⁺and Mg²⁺by the membrane was positively correlated with its ion concentration.The highest concentration is Na⁺?210.1 mg/L?,0.005RZ-NF membrane also had the highest removal rate of 49.1%;Ca²⁺and Mg²⁺concentrations were 80 mg/L and 36.2 mg/L,respectively,and their removal rates were 40% and 40%.29.6%.