Study On The Preparation And Application Of CTA Forward Osmosis Membrane

Forward osmosis whose driving force is the osmotic pressure is a new membrane separation technology in recent years. The forward osmosis ?FO? can be widely used in brine treatment, waste water purification, food concentration, drug release and aerospace because of its excellent performances of low fouling, low energy consumption, high salt rejection rate,high water flux and using in low temperature.This paper studied the effect of the preparation conditions on cellulose triacetate ?CTA?FO membrane performance. These conditions such as the polymer concentration, type and amount of additive, evaporation time, membrane thickness, heat treatment time and solute type and concentration of the draw solution have been studied.The optimum condition has been gotten ?mass ratio?: the concentration of CTA is 16.2%;the solvent made up by acetone and NMP is 82.3% ?the acetone is 10%.?; the lactic acid as the additive is 1.5%; the dissolution temperature is 60 ?; the coagulation bath is deionized water?DI? whose temperature is 20 ? though regulating the influence factors. The water flux of the prepared membrane is 20.2 L/?m²·h? and the salt flux is 14.6 g/?m²,h? using the 1 mol/L NaCl as draw solution and the DI as the feed solution.The osmotic pressure acts as the driving force in the FO process so the types and concentrations of the draw solution play an important role in the performance of the FO. The solution of NaCl,Na2SO₄,MgCl2 and MgSO₄ were respectively set as the draw solution ?1 mol/L? and the DI as the feed solution. When the lmol/L MgSO₄ was as the draw solution and the DI as the feed solution, the minimum water flux was 10.6 L/?m²·h?. When the 1 mol/L MgCl2 was as the draw solution, the membrane had the optimal water flux. When the NaCl solutions with different concentrations were as the draw solution, the CTA4 membrane showed the excellent performance and when the concentration of the NaCl was 5 mol/L, the flux of the CTA4 was above 50 L/?m²·h?.The effect of membrane thickness on the performance and morphology has been studied.The study showed that when the thickness of the CTA4 membrane was 50 ?m,the performance and morphology were optimal.The anti-fouling and high-concentration waste-water treatment performance of the optimal CTA4 membrane have been researched and the results were: ?1? when the 1 mol/L NaCl was as the draw solution and the waste-water from the oil field was the feed solution,the water flux of the membrane was 17.2 L/?m²·h?. After the membrane was washed by DI for 5 min, the flux recovery rate could reach 98% of the primary membrane flux and the flux recovery could reach 19.8 L/?m²·h?; ?2? the flux was up 9 L/?m²·h? when the 5 mol/L NaCl was as the draw solution and the spent electroplating bath ?300 g/L NiSO₄·6H₂O and 40 g/L NiCl2·6H₂O? was the feed solution. The recovery of NiSO₄·6H₂O was 44.5%, and the recovery of water was 53.5%.