Synergistic Removal Of Aqueous Rhodamine B By Low Temperature Plasma And Activated Carbon Fiber

In recent years, with the rapid development of printing and dyeing industry,the produced nonbiodegradable, toxic and hazardous wastewater became one of themajor sources of environmental pollution. The wastewater of printing and dyeingindustry contained dyes, pastes, additives, oils, acids, alkalis, fiber impurities, sandsubstances, inorganic salts and other substances, and dye wastewater was one of theimportant components; because of the variety and complex structure, it wasdifficult to treat the dye wastewater. Activated carbon fiber was an efficientabsorbent material used in dye wastewater treatment and good removal effect wasobserved, but the cost was higher for industrial application. Advanced oxidationtechnology was a new wastewater treatment technology, which was generallyapplicable and completely degradable for refractory pollutants. Dielectric barrierdischarge plasma technology was a kind of advanced oxidation technology; thetechnology had a good effect, fast oxidation rate and broad application prospects.In this paper, Rhodamine B was selected as the research object, dielectric barrierdischarge plasma and activated carbon fiber were used for the removal of aqueousRhodamine B, and meanwhile the synergistic removal mechanism was studied.Firstly, the effect of the initial solution pH, salinity, temperature andadsorption time on the removal of rhodamine B by activated carbon fiber wasconducted. It was found that the adsorption amount of Rhodamine B was decreasedwith the increasing of pH value. The NaCl concentration had little effect on theadsorption amount, the Langmuir isotherm and the second-order kinetic model weresuitable to describe the adsorption of rhodamine B onto activated carbon fiber, andthe adsorption was an endothermic process, internal diffusion model could be usedto describe the adsorption. The power of dielectric barrier discharge plasma had thegreatest impact on the modification of activated carbon fiber, and enhanced maxadsorption capacity of the modified activated carbon fiber reached20%. Langmuirisotherm and the second-order kinetic model were also applicable to the modifiedactivated carbon fiber for the adsorption of rhodamine B. The adsorption amount ofthe modified activated carbon fiber decreased with increasing pH value andsalinity. Secondly, the effect of input power, gas ventilation, initial concentration ofrhodamine B and initial solution pH on the rhodamine B remove by dielectricbarrier reactor were examined. The experimental results showed that the increase ofgas ventilation and the decrease of initial solution pH or the concentration of theinitial solution were conducive to the improvement of rhodamine B degradationrate. The increasing input power could increase the degradation rate of rhodamineB, but the higher the input power could reduce the degradation rate. The produced OH, O3and H2O2during discharge played an important role in the removal ofRhodamine B. The removal rate of Rhodamine B was reduced by the adding of freeradical scavenger tert-butanol and isopropanol, and the removal rate of RhodamineB was improved with the increasing of the generated O3and H2O2. Liquidchromatography-mass spectrometry (LC-MS) was used to analyze the deradationintermediate of rhodamine B after dielectric barrier discharge plasma treatment,and the results showed that the gradual removal of ethyl and the destroy ofconjugated structure might be the main degradation way.Finally, the effect of different initial pH values, additive quantity of activatedcarbon fiber and activated carbon fiber reuse frequency on rhodamine B removal bydielectric barrier discharge plasma and activated carbon fiber were studied.Through the contrast of the separate dielectric barrier discharge plasma removingeffect and adsorption removal effect, it was found that good synergistic effect wasobservd under different initial pH values, there was little effect on the synergisticeffect by increasing the dose of activated carbon fiber, and activated carbon fibershowed better reuse effect in synergistic treatment. It was found that the acidicfunctional groups on the surface of the activated carbon fiber increased after thesynergistic treatment by Fourier transform infrared spectroscopy analysis. Thedegradation intermediates of rhodamine B after dielectric barrier discharge plasmaand activated carbon fibers treatment were analyzed by LC-MS, and the resultsshowed that the gradual removal of ethyl from rhodamine B molecule and thedestroy of conjugated structure of rhodamine B molecule might be the maindegradation way.