Removal of High-Concentration Fe(III) by Oxidized Multiwall Carbon Nanotubes in a Fixed Bed Column

The use of modified multiwall carbon nanotubes (MWCNTs) for high concentration of ferric iron removal from acid mine drainage was studied. Fourier transform infrared spectrum demonstrated that hydroxyl and carbonyl functional groups were introduced to the surface of MWCNTs after oxidation with nitric acid. The adsorption behavior of modified MWCNTs was then investigated in removing 50-200 mg/L Fe(III) through batch and continuous flow fixed bed experiments. Batch experiment results demonstrated that the Fe(III) adsorption capability of MWCNTs after oxidation had increased by 32%. Adsorption equilibrium was achieved during the first 90 min. Langmuir model can be successfully employed for the equilibrium of isotherms with R2=0.9878 and qmax=89.05 mg/g. In addition, the effect of column bed depths and the influent Fe(III) concentrations were studied through the continuous fixed-bed adsorption studies. Results indicated that Fe(III) uptake favoured particularly higher bed depth and lower influent concentration. The bed uptake capacity of Fe(III) was found to be in a range of 30.30-41.51 mg/g, which was much lower than in batch experiment.