Removal of heavy metals by tight γ-Al2O3 ultrafiltration membrane at low pressure

The removal of chromate (Cr(VI)) and copper (Cu(II)) from water was investigated by using ultrafiltration (UF) as a possible alternative to the conventional methods of metal ions removal. The influence of experimental parameters such as pH, pressure and concentration was investigated on different solutions (K2Cr2O7, CuSO4 and Cu(NO3)(2)). The influence of salts' presence (NaNO3 and Na2SO4), with different concentrations, on metal removal was studied. The rejection of Cr(VI) was found to be improved with the increase of pH (with high rejection of 97% at pH above 9), whereas for Cu(II) the best rejections were obtained at 2.60 (with high rejections of 80% and 50%, for Cu(NO3)(2) and CuSO4). The increase of the applied pressure causes an increase of metals' rejections and fluxes. Furthermore, an insignificant polarization concentration phenomenon was observed. The Cr(VI) rejection was observed to be independent from the increase in concentration (>90% for all concentrations, ranging from 10 to 150 mg (Cr(VI))/L) and a decrease in rejection with increasing concentration was observed for copper salts. The permeate flux was found to be lower at higher feed concentration, but varied only marginally with change in pH value. The metals' retentions depend strongly on the solute type (including charge valency and hydration energy). The gamma-Al2O3 UF was found to be an efficient process to remove/recover heavy metals from industrial discharges.