| Toxic,harmful and difficult-to-degrade organic wastewater has received great attention from the industry due to its poor biodegradability and difficulty in treatment.This kind of wastewater is usually treated with ultraviolet rays,high ferocity,ozone,etc.However,due to the single technical method,the treatment effect of multi-component organic wastewater is not good.The discharge plasma in the liquid phase can produce ultraviolet rays,active substances(ozone,hydrogen peroxide),free radicals(·OH,·O,·H.)and shock waves,which are very effective for the treatment of toxic,.harmful and difficult-to-degrade organic wastewater.In this paper,a gas-liquid mixed-phase pulse discharge reactor is designed to solve the problem of efficiency decline in high conductivity wastewater with liquid phase discharge plasma.Use a microporous ceramic plate to isolate the electric field and concentrate the electric field locally.The main feature of the new reactor is to isolate the ion current by passing gas during the discharge process.The new reactor has simple structure,long service life and high working efficiency.When the liquid-phase discharge reactor degrades high-conductivity wastewater,the ions in the liquid will form a strong ion flow.The ion current consumes electrical energy to generate heat and reduces the field strength between the two electrodes,resulting in a decrease in the concentration of active materials generated by the discharge plasma and a decrease in the degradation rate of organic matter.The structural features in the new reactor reduce the effect of ion flow in high-conductivity wastewater and increase the degradation rate of organic wastewater.The.experiment compared the influence of the relative dielectric constant and thickness of plexiglass medium and 'microporous ceramic medium on the decolorization of methylene blue.A thin medium with a relatively large dielectric constant is more likely to generate plasma.Under the same conditions,the decolorization rate of the new reactor using 2mm thick microporous ceramic medium is the highest.In the experiment of discharge plasma degradation of organic wastewater simulated by methylene blue,it was found that the decolorization rate increased with the increase of peak voltage and discharge frequency;with the increase of carrier gas flow rate,it showed a trend of first increasing and then decreasing;The larger the electrode spacing,the lower the decolorization rate of organic wastewater.The best parameters obtained from the experiment are the peak voltage of 20 kV,the discharge frequency of 100 Hz,the air flow rate of 150 mL/min,and the electrode spacing of 13 mm.Under this condition,a new gas-liquid mixed-phase discharge reactor was used to explore the characteristics of high conductivity organic wastewater.The experimental results prove that the decolorization rate of organic wastewater decreases with the increase of its volume.Although the conductivity of organic wastewater increases,the treatment effect will become worse.However,the new reactor is suitable for treating high-conductivity wastewater.After 35-minute discharge plasma treatment of organic wastewater with a conductivity of 15,000?S/cm,the decolorization rate still reaches more than 80%,and the effect is far better than the direct needle-plate discharge reaction.In this paper,the mechanism of generating active substances by discharge plasma is also analyzed,and it is believed that hydroxyl,hydrogen peroxide and ozone play a major role in the decolorization of organic wastewater.The acidic substances generated during the decolorization of methylene blue and the formation of nitric acid and nitrous acid in the organic wastewater after ionization in air both lower the pH of the organic wastewater.In this paper,a simple analysis of the decolorization path of methylene blue is made.By detecting the type of intermediate products,it is proposed that the decolorization of methylene blue is the result of the oxidative decomposition of hydroxyl radicals and ozone after demethylation. |
PDF Full Text Request