Removal of chromium and nickel from aqueous solution in constructed wetland: Mass balance, adsorption–desorption and FTIR study

The present study was conducted to investigate the chromium and nickel removal from aqueous solutions in constructed wetland microcosms using Canna indica Lin. species. Effects of different hydraulic retention times (HRTs), initial metal concentrations and depth of gravel beds on removal of chromium and nickel were studied. Maximum removal of chromium and nickel was found to be 98.3(±0.32) and 96.2(±1.52) %, respectively, at initial concentrations of 10 mg l−1 and at an HRT of 48 h in 0.95 m gravel bed depth constructed wetland microcosms. The attempt was made to know the possible mechanism of metals removal and their mobility within the plant. In order to reuse the exhausted gravel, desorption possibilities were tested. Desorption of 35, 25 and 33% of chromium and 60, 98 and 100% of nickel from gravel were achieved with 0.50 mM EDTA, 0.1 M HNO3 and 0.1 M CaCl2 solutions, respectively.