Investigation On Bionic Preparation And Performance Of The Nanofiltration Membrane With Polyelectrolyte And Inorganic Mineral

With the development of economic, the pollution from heavy metals water notonly cause significant economic losses, but also threaten seriously to people’s healthand survival.Therefore, the green and cost-effective methods for treatment of heavymetals water are imminent. NF membrane is an efficient technology for treatment ofwastewater. Polyelectrolytes (PEs) layer-by-layer (LbL) technique is a convenientand versatile way for forming multilayer nanofiltration membrane,.In this dissertation, positively charged nanofiltration (NF) membranes werefabricated by layer-by-layer (LbL) assembly of poly(ethyleneimine)(PEI) andpoly(sodium4-styrenesulfonate)(PSS) on the modified polyarcylonitrileultra-filtration substrate. The charge variation with each layer was characterized byzeta potential. ATR-FTIR, SEM and the weight changes of bi-layers was used toconfirm the LbL deposition of the polyelectroletes. The membrane of4.5bi-layerswith positively charge, smooth and compact which showed high rejection of95.66and95.00%for Ni2+and Cd2+, The permeation flux was about22.19and25.02L/(m2·MPa·h), respectively. The rejections sequence was CuSO4＞ZnSO4＞NiCl2＞CdCl2. The results suggested that the positively charged membranes through LbLdeposition of PEs exhibited high rejections of heavy metal ions.Secondly, the cross-linking PEI/PSS polyelectrolyte composite membraneswere prepared by various cross-linking agent in order to improve the stability of thePEs membrane. The results showed the rejection stability of the cross-linkedcomposite membrane was significantly improved, compared to the uncross-linked.The crosslinking PEI/PSS composite nanofiltration membrane showed rejection of98.88%for Ni2+and the flux of22.93L/(m2·MPa·h), with5%of glutaraldehyde and0.5%of sulfuric acid as crosslinking agent..Thirdly, the CaCO3/polyelectrolte composite membranes were prepared bycombining LbL technique and the biomimetic synthesis. The mineralization way andthe mineralization time were investigated. The results showed that the rejections ofthe CaCO3/polyelectrolte composite membranes were prepared by gaseous diffusionfor500mg/L concentration of Ni2+、Cd2+、Cu2+、Zn2+、Mg2+、Ca2+solutions were99.31%,100%,99.60%,100%,98.93%and98.70%, along with permeation fluxesof42.38,38.53,50.39,45.34,32.75and46.79L/(m2·MPa·h), respectively.Compared to PEI/PSS polyelectrolyte composite membrane and cross-linking composite membrane, the separation stability of the nanofiltration membrane withPEI/PSS and CaCO3inorganic mineral was significantly improved.