Effect of process parameters on flux for whey concentration with NH3/CO2 in forward osmosis

Abstract

Increasing flow rate from 150 to 450L/h did not change water flux but further increase to 600L/h decreased it, which were between 2.74 and 4.1L/m2h. Rising flow rate from 150 to 450L/h enhanced final salt flux but rising flow rate to 600L/h caused opposite effect on salt flux and maximized solute resistivity. As temperature of feed was elevated from 20 to 30°C, water flux increased to 7.2L/m2h but changing temperature to 35 and 40°C reduced it. Salt flux was affected from process temperature in similar way as water flux was affected. Higher solute resistivity was obtained at 35 and 40°C. Ascending draw solution concentration from 1 to 2M enhanced water flux to 12L/m2h but its further increase to 4M reduced it. Salt flux did not change linearly and rose to the highest level at 2M draw salt concentration. The highest value of solute resistivity was obtained at 3 and 4M salt concentration. Effect of flow rate, feed temperature and salt concentration on water flux being expressed above was found similar to their effect on effective osmotic pressure difference and solute resistivity. This results show relation of water flux with effective osmotic pressure difference and solute resistivity.Carbohydrates passage from whey to draw solution was not detected but there was passage of other solubles from whey to draw solution. Flow rate of 450L/h, process temperature of 30°C and 2M salt concentration were optimum process conditions for water flux.