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

Abstract

Increasing flow rate from 150 to 450 L/h did not change water flux but further increase to 600 L/h decreased it, which were between 2.74 and 4.1 L/m(2)h. Rising flow rate from 150 to 450 L/h enhanced final salt flux but rising flow rate to 600 L/h caused opposite effect on salt flux and maximized solute resistivity. As temperature of feed was elevated from 20 to 30 degrees C, water flux increased to 7.2 L/m(2)h but changing temperature to 35 and 40 degrees 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 degrees C. Ascending draw solution concentration from 1 to 2 M enhanced water flux to 12 L/m(2)h but its further increase to 4 M reduced it. Salt flux did not change linearly and rose to the highest level at 2 M draw salt concentration. The highest value of solute resistivity was obtained at 3 and 4 M 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 450 L/h, process temperature of 30 degrees C and 2 M salt concentration were optimum process conditions for water flux. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.