Temperature Impact on Reverse Osmosis Permeate Flux in the Remediation of Hexavalent Chromium

Abstract

Reverse osmosis technique was applied in removing hexavalent chromium ions from artificial wastewater. Different operating conditions were studied to monitor the separation process using commercial Reverse Osmosis BW30XFR membrane. Different concentrations of hexavalent chromium; 5, 30, and 100 ppm were tested. Samples were subjected to incrementally increasing operating pressure; 10, 30, and 45 bar and flow rates; 2.2, 3.4, and 4.5 L/min under various temperatures; 25, 35, 45, and 55 °C. Collected permeate and concentrations were measured after each experiment using a UV spectrophotometer. Results obtained presented a higher rejection percentage at lower feed concentrations with a value up to 99.8% for 5 ppm in comparison to 94.3% for 30 ppm and 77.2% for 100 ppm concentration due to concentration polarization; however, it showed no effect of increasing operating flow rates. Moreover, the increase in feed temperature from 25 to 55 °C had positively increased permeate flux to more than 300 times. The permeate flux at 25 °C is recorded for all tested samples in the range of 30 to 158 kg/h·m2, this range has risen at 55 °C under the same conditions to the range of 70 to 226 kg/h·m2, indicating alteration within the membrane pore size due to temperature increase and high applied pressure concluding high sensitivity of polymeric membranes towards changing permeate flow rate with increasing temperatures.

A Study of Copper (II) Ions Removal by Reverse Osmosis under Various Operating Conditions

“…This is due to increased concentration polarization on the membrane surface. These findings are consistent with those presented in the literature [23,31,33], concluding that the removal % of metal ions decreases as the feed concentration increases. This is due to the increasing resistance of solution across the membrane due to increased concentration polarization on the membrane surface.…”

“…This is due to increased concentration polarization on the membrane surface. These findings are consistent with those presented in the literature [23,31,33], concluding that the removal % of metal ions decreases as the feed concentration increases.…”

“…The justification for this is the increase in the amount of solute across the membrane, which acts as a driving force. These results are in close agreement with those presented in the literature [23,[31][32][33], concluding that the permeate flux increases with pressure increases.…”

“…viscosity and changes in the physical properties of the polymeric membrane, such as pore size or diffusivity [34]. These results are consistent with those reported in the literature [23,31,35], concluding that the permeate flux increases with the increase in temperature.…”

“…The results show that when the temperature increased from 25 to 45 • C with other constant parameters (P = 10 bar, Q F = 3.2 L/min, C F = 50 ppm), the permeate flux increased 45% from 46.12 to 67.0 (kg/m 2 •h) (permeate flux is increasing 2% every 1 • C); this is due to the reduction in the solution viscosity and changes in the physical properties of the polymeric membrane, such as pore size or diffusivity [34]. These results are consistent with those reported in the literature [23,31,35], concluding that the permeate flux increases with the increase in temperature.…”