| The main purpose of this dissertation is to exploit a novel eurytopic immobilized redox mediator to promote the anaerobic biotransformation efficiency of refractory organic pollutants, such as azo dyes and nitroaromatic compounds (NACs) etc. For this purpose, the pyrrole (Py) electropolymerization-doping technology was proposed as a method for immobilizing redox mediator. According to the experimental results of selective enrichment and literature reports, functionalized polypyrrole (PPy) composites were prepared under galvanostatic mode by incorporation of a model redox mediator, anthraquinone-2,6-disulphonate sodium (AQDS), as doping anion during the electropolymerization of Py monomer on active carbon felt (ACF) electrode. Various analysis techniques including elemental analysis, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) were used to characterize this new composite, AQDS/PPy/ACF. Then, the resulting composites used as a novel immobilized redox mediator for catalyzing anaerobic biotransformation of two N-substituted aromatic compounds, azo dyes and NACs, were explored in batch biological experiments. The catalytic activity and stability of AQDS/PPy/ACF, and whether the selection pressure exerted by AQDS/PPy/ACF was high enough to maintain the predominance of the potent AQDS-reducing bacteria were mainly detected.Quinone-reducing community was successively enriched from freshwater aquatic sediments and anaerobic activated sludge with glucose as the electron donor and concentrated AQDS as the electron acceptor. This resulting community showed high reductive activity not only for AQDS, but also for some other quinoid compounds, including some anthraquinone dyes and their intermediate. In addition, the experiment results also revealed that hydrogen-oxidizing, rather than acetate-oxidizing bacteria, were the predominant AQDS-reducing microorganisms in the community. These facts indicated that this community had great potential for application in practice. The optimal conditions for both growth and reduction are as follows: pH=7.0; temperature 30℃; inoculation amount 8%; the concentrations of Na2S·9H2O, glucose and AQDS 0.037 g·L-1, 0.5 g·L-1 and 150 mg******L-1, respectively. PPy film, AQDS/PPy, was successively formed on two different electrode substrate materials, platinum (Pt) and ACF, under galvanostatic mode using 0.024 M AQDS as dopant and 0.1 M Py monomer as carrier by controlling the potential between 0.6 and 1.2 V. FTIR and elemental analysis measurements confirmed that PPy deposited on electrode surface and AQDS was inserted into PPy matrix with the mole ratio of about 6:1 for Py: AQDS. Meanwhile, the result of electrochemical activity characterization by adopting cyclic voltammetry technology indicated that the PPy film prepared using AQDS as dopant had excellent doping stability, and that dedoping phenomenon was difficult to take place. Electrode substrate material was a decisive factor for the catalytic activity and stability of the corresponding PPy composites, AQDS/PPy/ACF and AQDS/PPy/Pt, because of the great effect on the morphology of the PPy film and the adhesion between them. The results of SEM proved that when ACF was selected as substrate material, some globular PPy deposit homogenously distributed on the randomly dispersed netting fibers of ACF, which made the prepared PPy composite possessing three-dimensional structure and larger specific surface area. Moreover, current density and reaction time had some effect on the morphology, mechanical properties and specific surface area. Therefore, the AQDS/PPy/ACF composite of good catalytic activity and stability can be prepared by selecting suitable current density and reaction time.Functionalized PPy composites, AQDS/PPy/ACF, played a catalytic role in the anaerobic decolorization for most of the azo dyes, and effectively improved the decolorization efficiency of azo dyes. The anthraquinone-2,6-disulphonate ion doped in PPy matrix serves as the catalytic active site, and the high biological catalytic activity of AQDS is retained by taking advantage of the good biocompatibility and physico-chemical characteristics of PPy. For example, the presence of the AQDS/PPy/ACF prepared under the optimal electropolymerization conditions: current density j=1 .79 mA·cm-2, reaction time 3600 s, made the decolorization efficiency of model compound KE-3B increased from about 29% to about 80%, and the value of decolorization rate constant improve 3.2-fold. Meanwhile, it was found that AQDS/PPy/ACF exhibited a good catalytic stability, and that the decolorization efficiencies of six-time successive repeated experiments kept almost constant, the reason for which was that the adhesion between the PPy deposit and the substrate material was effectively enhanced by selecting ACF as electrode. In addition, pH, temperature, the glucose concentration, the amount of bacteria and PPy composite had some effect on the catalytic activity of AQDS/PPy/ACF. The optimal catalytic conditions for the decolorization of KE-3B are as follows: pH=7, temperature 35℃, the concentration of glucose 0.5 g·L-1.The incorporation of functionalized PPy composites, AQDS/PPy/ACF, greatly accelerated the anaerobic biotransformation rate of nitrobenzene, 2,4- and 2,6-dinitrotuluene (DNT), and the corresponding first-order reduction rate constants were increased from 0.137, 0.190 and 0.173 d-1 to 0.696, 1.078 and 0.828 d-1 respectively, which represent increments of about 5-fold. The presence of AQDS/PPy/ACF did not change the fate of NACs transferring to corresponding amino compounds, just enhanced the electron transfer from glucose to them. Therefore, it acted as an effective redox mediator in the anaerobic biotransformation of NACs. In addition, the results of molecular ecological techniques not only confirmed that the anthraquinone-2,6-disulphonate ion doped in PPy matrix served as the catalytic active site, but also showed that the selection pressure exerted by this kind of polymeric AQDS maintained the dominance of potent AQDS-reducing bacterial, which can ensure the good catalytic effect for continuous operation.Based on the above results, it can be concluded that the electropolymerization-doping technology is an excellent method of immobilizing redox mediator, which provides us a new idea for impelling the application of redox mediator in practical treatment of wastewater. The novel immobilized redox mediator AQDS/PPy/ACF prepared by this method not only possesses the intrinsic effective catalytic activity and eurytopicity of AQDS, but also has good catalytic stability. Therefore, AQDS/PPy/ACF has great potential application for accelerating the anaerobic biotransformation refractory organic pollutants.
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