Fabrication Of Quasi-symmetric Thin-layer Inorganic Membrane And Its Applications For Forward Osmosis Process

Due to its low power consumption and high water recovery, forward osmosis(FO) membrane separation technology has unique advantages in solving theshortage of water resource and reducing energy consumption. It has been playingan increasingly important role in the field of water treatment and green energysupply.Semi-permeable membrane is a key factor affecting FO performance.Generally, a membrane is considered ideal for FO process only when both of thefollowing two criteria are met:(1) its active layer is dense enough to reject salinematter, and (2) its support layer is thin enough to reduce internal concentrationpolarization (ICP) and ensure stable water flux.The silica inorganic ceramic membrane fabricated from the sol-gel processhas been widely applied in gas separation owing to its high mechanical strength,high-temperature duration and acid-and-alkali corrosion resistance. While itsapplication in the water treatment is still at an elementary stage.In this dissertation, an inorganic FO membrane with stainless steel meshbackbone was fabricated from sol-gel process by layer-by-layer deposition. Thefabrication process was optimized in order to obtain an ideal FO membrane. Theobtained inorganic FO membrane was morphologically characterized and its FOperformance was also evaluated in detailed. The scanning electron microscopy(SEM) observation indicated that after4-layer deposition, the45μm thickinorganic FO membrane exhibits semi-symmetric structure, silica sols attach onthe stainless steel mesh without obvious interphase boundary, and the active layeris dense. The atomic force microscopy (AFM) observation confirmed that theinorganic FO membrane is relatively smooth with the roughness of3.263nm. Allthese aforementioned structural properties meet the criteria of ideal FO membrane.Furthermore, the performance of inorganic FO membrane was al evaluated intself-designed FO reactor. The experimental results suggested that the inorganicFO membrane can provide a stable water flux and low salt flux, its water flux ishigher than the organic FO polymer membranes reported by other literature.Finally, the inorganic membrane is compared with commercial accessible HTI FOmembrane and RO membrane in seawater desalination test. HTI membrane andinorganic membrane performance is much better than the RO membrane. Waterflux of inorganic FO membrane is32.47L·m-2·h-1, which is2.55times higher than that of HTI membrane. But the salt flux of inorganic FO membrane is2.52timeshigher than HTI membrane. Preliminary results showed that, performance ofinorganic FO membrane in salty water treatment is close to that of HTI membrane.After further fabrication optimization and surface modification, the performanceof inorganic FO membrane in salt/water separation can be improved or evensuperior to HTI membrane.