Removal of fulvic acid from water electrochemically using active carbon fiber electrode

Humic acids (HA) are a group of widely existing natural organic compounds and potential contaminants to underground water reservoirs. Fulvic acid (FA) is a typical humic acid of relatively low molecular weight. Electrochemical removal of FA from water by active carbon fiber (ACF) electrodes was studied by using light scattering photometer (LSP), fluorescence spectroscopy and total organic carbon analyzer (TOC). The experiments showed that FA molecules aggregated and that the average particle diameter in FA solution increased from below 10 nm to hundreds of nanometers during the treatment process. When iron was added to the anode, the FA could be coagulated efficiently at the early stage of the treatment. The proposed mechanism of the removal process is: adsorption of FA on ACF surface --> aggregation of FA --> desorption of FA aggregates from ACF --> coagulation of FA aggregates by nFe(OH)(2).mFe(OH)(3) dissolved from anode. Experiments were also repeated using graphite and stainless-steel electrodes, and the results were compared with that of ACF electrodes. FA aggregation was not observed in these experiments and most FA was not removed from the solution. At the end of this paper, FA samples from Huai River sediment were successfully treated using the ACF electrode.