Effect of anion interaction on the removal efficiency of nanofilters for potable water treatment

The interaction between the ions and the charge of membranes can affect theefficiency of pollutant removal. The present study investigated the removalefficiency of hexavalent chromium and nitrate ions from both actual and syntheticcontaminated water via two different commercial spiral wound polyamidenanofilters. In addition, the interaction of ions under different experimentalconditions was investigated by using a Box-Behnken design (BBD). The Box–Behnkendesign optimized the contributing factors which included pH (5-9), the initialconcentration of Cr (VI) (0.05-5 mg/L) and the initial concentration of nitrate (40-160mg/L). The maximum removal efficiency of both Cr (VI) and nitrate was achieved ata pH of 9.0, as 99 % and 90 % for the Iranian nanofilter (NF-I) and 98 % and 82 % forthe Korean nanofilter (NF-K), respectively. The results also indicated that as the initialconcentration of Cr (VI) increased, the removal efficiency was enhanced while theremoval efficiency of nitrate decreased according to the pH. However, by increasingthe initial concentration of nitrate, the removal efficiency of both the Cr (VI) andnitrate increased. For actual water samples at an optimum pressure of 0.6 Mpa (NFK) and 0.8 Mpa (NF-I), the removal efficiency of Cr(VI) and nitrate obtained was 95%and 76 % for the NF-K and 97 % and 86 % for the NF-I, respectively.

Keywords:

Box–Behnken design , Hexavalent chromium , Ion interaction , Nanofiltration , Nitrate , Potable water treatment