Assessment of thermal effects on the reverse osmosis of salt/water solutions by using a spiral wound polyamide membrane

The effect of varying the temperature of the feed water for reverse osmosis was studied for two aqueous solutions, one with a relatively high concentration of NaCl (5 g/1) and the second with a low salt concentration (0.8 g/1). The feed temperature was varied between 12–30° C and pressures of 20, 40 and 60 bars were employed. It was found that increasing the temperature resulted in an increase in both the salt passage and the permeate flow rate with increasing temperature. A sieve type mechanism can be used to qualitatively explain these results in terms of an increase of the pore size with temperature, thus allowing for more salt passage and permeate flow rate.