Studies On Preparation And Fruit Juice Concentration Of Cellulose Triacetate Forward Osmosis Membrane

Forward osmosis (FO) is the induction of a net flow of water from alow-concentration feed solution to a high-concentration draw solution through asemi-permeable membrane. The process is driven by the osmotic pressure gradientacross the membrane. The main advantages of using FO are that it operates at no orlow hydraulic pressures, it has high rejection of a wide range of contaminants, it has alower membrane fouling propensity, less energy input and higher water recovery thanpressure-driven membrane processes. Hydraulic pressure is not necessarily required,giving FO an economic benefit over other membrane technologies which have beenapplied to seawater desalination, water purification, wastewater treatment, powergeneration, concentration of digested sludge liquids, food process and pharmaceuticalproduction.FO has attracted significant attention and has been extensively studied in recentyears. Membrane and draw solution selection are two of the most critical aspects toconsider in FO process design. Cellulose triacetate based membranes for forwardosmosis were prepared by immersion precipitation. Water flux and reverse saltdiffusion increased, membrane selectivity decreased as increasing the1,4-dioxane/acetone ratio; Membrane selectivity decreased as increasing the lacticacid content, when the lactic acid content was7.6%, the water flux was highest; Waterflux and reverse salt diffusion decreased, as increasing the evaporation time; Waterflux and reverse salt diffusion decreased, membrane selectivity increased asincreasing the casting thickness; Increasing annealing temperature, water flux andreverse salt diffusion decreased.The optimized CTA membrane had a smooth and hydrophilic surface, the surfaceroughness was41nm. Results indicated that the optimized membrane showed14L·m-2·h-1water flux and0.032mol·m-2·h-1reverse solute flux using a feed solutionof pure water and draw solution of0.56mol/L CaCl2. Furthermore, reverse solute diffusion phenomenon and fruit juice concentrationusing the optimized CTA membrane was studied. The results indicated that sameosmotic pressure, but different draw solutes make membrane performance different.Draw solution of CaCl2showed the highest water flux and lowest reverse solutediffusion. In the concentration process of fruit juice, high water flux, and high totalsoluble solids were achieved by increasing draw solution osmotic pressure anddecreasing feed solution concentration. Using CaCl2as draw solution concentratingorange juice, the FO membrane was cleaned by pure water once every4h. After16hconcentrating, total soluble solids increased from11°Brix to44°Brix.