Electrocatalytic degradation of humic acid using particle electrodes of activated carbon loaded with metallic cobalt.

A column granular electrode loaded with metallic cobalt was prepared using powder activated carbon (namely Co/AC) and used in a continuous electrochemical reactor to degrade humic acid (HA). The results of XRD indicated that the form of catalyst prepared at 600 °C for 4 h mainly consisted of Co0, whereas it consisted of CoO when prepared at 450-500 °C for 4 h. The Co0 possessed better catalytic effects in the degradation of HA than CoO. When C0 of HA was 200 mg L-1, the C/C0 approached 0.06-0.12 under 0.1 A, pH of 7.0, 0.01 M Na2SO4, and 20 min of hydraulic retention time (HRT). The current, HRT, initial pH, electrolyte type and concentration influenced the degradation of HA. The ESR signals indicated that both H∗ and OH were catalytically generated by Co/AC electrode. Compared to AC electrodes, the Co/AC electrodes showed a faster reaction Tafel slope (68 mV dec-1) and larger electrochemical double-layer capacitance (Cdl = 1.93 mF cm-2). The degradation and removal of HA was achieved by both the electro-oxidation and electro-reduction in the Co/AC electrode system.