Studies On Regeneration Of Activated Carbon By Dielectric Barrier Discharge And Scaling Up Of The Reactor

Activated carbon (AC) adsorption is an effective method in the treatment of the low concentration, high toxic and refractory wastewater, and wastewater from emergency environmental accident. The conventional use of AC adsorption alone is limited in that the contaminants are not degraded but instead transferred to the solid phase from liquid phase. To reuse the spent AC, an appropriate regeneration step is necessary to meet the environmental and economical requirements, which has motivated researchers to develop new methods for regeneration of spent activated carbon. The dielectric barrier discharge (DBD) plasma can generate varies of active species, such as hydroxyl radicals, ozone and active oxygen etc., which is a hotspot in environmental pollution control.Aiming at clarifying regeneration mechanism of AC by DBD plasma, design of the reactor, power supply for the reactor and operation of the reactor, we combined the granular activated carbon (GAC) adsorption and DBD, to decompose the phenolic pollutants adsorbed on GAC and regenerate GAC simultaneously. The main work was conducted in terms of the feasibility of pollutants degradation and GAC regeneration by DBD, active species generation and transference during DBD process, and DBD regeneration of GAC by the addition of a titanium dioxide catalyst. A methodology of scaling up the DBD plasma reactor was proposed, and the up-scaled reactors of1kg and10kg GAC were used to regenerate GAC. The detailed work and the summarized results are as follows:1. A DBD plasma reactor driven by bipolar pulsed power was used to regenerate the GAC adsorbed Bisphenol A (BPA), The effects of pulse voltage, pulse repetitive rate, treatment time and air flow rate were investigated. Experimental results indicated that increasing pulse voltage, pulse repetitive rate, and air flow rate could enhance the degradation of BPA. The energy efficiency of BPA degradation using bipolar pulse power was10times higher than that using high frequency power. After three cycles of adsorption/DBD regeneration, the regeneration efficiency (RE) remains close to80%, and the result of RE using bipolar pulse power was higher than that using high frequency power with5%,6%and11%, respectively.2. The generation of active species during bipolar pulse DBD process.·OH and H2O2were quantitative determined by chemical method at different operational parameters by bipolar pulse power and high frequency power. The results showed that the production of·OH and H2O2on GAC powered by bipolar pulse power was10-20%higher than those powered by high frequency power, and the energy efficiency of active species using bipolar pulse power was6times higher than that using high frequency power. The phenol degradation and mineralization and its main products generation on GAC characteristics were investigated, which was powered by bipolar pulse power. The experimental results indicated that increasing pulse voltage, air flow rate and water content of GAC could enhance the removal and TOC of phenol, and the generation time of three main byproducts was earlier, and their final production decreased, the phenol and TOC removal achieved93%and50%at optimized conditions, respectively.3. We have investigated a catalytic method to promote the regeneration of the saturated GAC by the addition of TiO2catalyst under the DBD. The TiO2-GAC hybrid was fabricated by an impregnation-desiccation method and characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherms and Boehm titration to investigate its adsorption and catalytic characteristics before and after the adsorption and DBD processes. In addition, the phenol degradation and GAC regeneration characteristics were investigated, TiO2-GAC exhibited remarkable catalytic activity, increasing the phenol degradation by19%, TOC removal by9%, energy efficiency by27%, and RE by14%relative to GAC in DBD treatment.4. A methodology of scaling up the DBD reactor for GAC regeneration was proposed, and the up-scaled reactors of1kg and10kg were developed. The1kg DBD reactor driven by bipolar pulse power was built to treat exhausted GAC. The feasibility of GAC regeneration using the up-scaled reactor was systematical assessed by monitoring the GAC regeneration RE and phenol degradation on GAC at different electrical, supply gas and GAC parameters. Under the optimized conditions RE and the phenol degradation reached94%and70%, respectively. After four adsorption-regeneration cycles, RE decreased from94%to55%. The10kg DBD reactor was used to regenerate GAC exhausted by real wastewater, and the results showed that after two cycles, RE decreased from74%to66%. The results have laid the groundwork for further industrial progress.