Yuemin Zhao

Electrochemical capacitance behavior of a packed bed electrochemical reactor toward phenol electro-oxidation

The electrochemical capacitance behavior of a packed bed electrochemical reactor (PBER) toward phenol electro-oxidation in aqueous solution was studied. In the absence of phenol, a decrease in the response current (i) coupled with an increase of the specific capacitance (Cs) was obtained for PBER compared with a flat-bed electrochemical reactor. However, following intercalation of phenol, simultaneous improvement of i, and reduction of Cs were observed. The reasons for the former were ascribed to an increased resistance, an abundant pore structure for charge, and electrolyte transportation owing to the packing of the fixed granular active carbon (GAC) filler, whereas anode extension and formation of the polyoxyphenylene film on the anode and the GAC surface were responsible for the latter. Although significant attenuation (42.06xa0% after 300 cycles at current density 1.90xa0mAxa0cm−2) of Cs was observed for PBER in the long cycle test, the non-negligible Cs value (30.86xa0mFxa0cm−2) holds great promise for pulsating power supplies. An equivalent circuit associated with electrochemical capacitance and resistance distribution was proposed, which gives an exhaustive explanation of the electrical characteristics during the phenol electro-oxidation process.

Coupling of anodic oxidation and adsorption by granular activated carbon for chemical oxygen demand removal from 4,4'-diaminostilbene-2,2'-disulfonic acid wastewater.

Experiments were performed to reduce chemical oxygen demand (COD) from 4,4-diaminostilbene-2,2-disulfonic (DSD) acid manufacturing wastewater using electrochemical oxidation coupled with adsorption by granular activated carbon. The COD removal is affected by the residence time and applied voltage. When the residence time is increased, lower value of COD effluent could be obtained, however, the average current efficiency (ACE) decreased rapidly, and so does the applied voltage. In addition, aeration could effectively enhance COD removal efficiency and protect anodes from corrosion. Furthermore, the acidic condition is beneficial to the rapid decrease of COD and the values of pH effluent are independent of the initial solution pH. The optimization conditions obtained from these experiments are applied voltage of 4.8 V, residence time of 180 min and air-liquid ratio of 4.2 with the COD effluent of about 690 mg L⁻¹. In these cases, the ACE and energy consumption are 388% and 4.144 kW h kg⁻¹ COD, respectively. These perfect results from the experiments illustrate that the combined process is a considerable alternative for the treatment of industrial wastewater containing high concentration of organic pollutants and salinity.