Electrochemically Enhanced Removal Of Nitrobenzene From Aqueous Solution On Activated Carbon Fibers(ACF)-Ozone Technique

As a kind of advanced oxidation technology, coupling of activated carbon fibers(ACF)-ozone(O3) is widely used in the removal of organic matter in water. In the ACF-O3 system, a small amount of hydrogen peroxide was formed by the reaction of ACF and O3, which led to the conversion of O3 to hydroxyl radical. Thus the organic pollutants in water was degraded by hydroxyl radical. When a negative electric field is applied to the ACF in the ACF-O3 system, a large amount of hydrogen peroxide was produced on the surface of ACF, which makes the organic pollutant degraded more quickly. As a refractory organics, nitrobenzene was chosen as the target pollutant in order to compare the oxidation efficiency of organic pollutants in the two systems. Therefore, the cathode electric field can enhance the removal of nitrobenzene in the ACF-O3 system. On the other hand, O3 can change the surface structure and chemical properties of ACF, which led to the gradual decrease of the catalytic activity of ACF, and limited the application of this advanced oxidation technology. When negative electric field was applied on ACF, it was found that the negative electric field can protect the ACF from destroying of O3 and maintain the high catalytic activity of ACF.In this study, the different experimental factors were studied, such as current intensity, O3 flow rate, and initial pH value of the reaction solution, the type and concentration of the electrolyte, the properties of ACF, following conclusions are obtained. Compared with the ACF-O3 system, the removal efficiency of NB in electrochemically enhanced ACF-O3 system was significantly improved. This is because ACF has large adsorption capacity on NB. On the other hand, ACF as an electrocatalytic makes the transformation of O3 for hydroxyl radicals resulting in the removal of nitrobenzene in water. The effect of current intensity on NB removal efficiency in the electrochemically enhanced ACF-O3 system is not significant. However, when the O3 concentration in the gas phase is increased, the removal efficiency of nitrobenzene in water is increased. The pH value of the initial reaction solution has a great influence on the catalytic activity of ACF in ACF-O3 system. In a certain range, the higher the pH value, the stronger the catalytic ability of ACF. However, NB removal efficiency was not affected by the pH value of the initial solution in the electric enhanced ACF-O3 system. The presence of inorganic salts such as sodium sulfate, sodium nitrate and sodium chloride will results in inhibiting of catalytic ability of ACF in O3 system. In the electrically enhanced ACF-O3 system, when the sodium nitrate electrolyte was used as the standard, the sodium sulfate electrolyte had a promoting effect while sodium chloride electrolyte had a negative effect on the degradation efficiency of the system.) Whether the negative electric field was applied in ACF-O3 system or not, nitric acid modification of ACF can inhibit the degradation of nitrobenzene and ammonia modification has a promoting effect on the removal of nitrobenzene.