Enhancement Of Azo Dyes And Nitro Compounds Reduction By Quinonyl Ceramsites Under Anaerobic Condition

The main purpose of this dissertation is to explore a novel immobilized redox mediator to enhance azo dyes and nitro compounds anaerobic treatment. The novel immobilized redox mediator has the advantages of high mechanical strength, wide application, and low price. Anthraquinone-2-sulfonate (AQS) was immobilized on the surface of ceramsites to obtain the novel immobilized redox mediator using a series of physical and chemical methods. The ceramsites were referred as quinonyl ceramsites. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were used to characterize the surface texture of the quinonyl ceramsites. Catalytic activity of quinonyl ceramsites on biological reduction of azo dyes and nitro compounds under anaerobic condition was investigated. At the same time, accelerating effects of quinonyl ceramsites on chemical reduction of azo dyes were also investigated.The results showed that the optimal conditions for AQS immobilization were as follows: 3-aminopropyltriethoxysilane (APTES) dosage 4.73 g, silanization reaction time 3 h, anthraquinone-2-sulfonyl chloride (ASC) dosage 0.1 g and immobilization reaction time 8 h. The AQS concentration was 2.3μmol/g using an elementary analysis instrument.FTIR showed that quinonyl groups were successfully immobilized on ceramsites. It indicated that a novel immobilization method was developed. According to SEM micrographs, it showed that the surface of quinonyl ceramsites kept porous structure and they could keep the function as biological carriers.The salt-tolerant quinone-reducing consortium was enriched from anaerobic activated sludge of Dalian Chunliu River wastewater treatment plant. It was used in the following experiments and its AQS reduction ability was investigated. The results showed that the optimal conditions for the AQS biological reduction were:sodium formate acted as electron donor and its concentration was 3 g/L, pH 7, NaCl 50 g/L.It was observed that biological reduction rates of azo dyes and nitroaromatics were enhanced with the addition of quinonyl ceramsites in the biological reduction experiments. Biological reduction rates of Acid Yellow 36 (AY36), Reactive Red 2 (RR2), Acid Red 27 (AR27), and Acid Orange 7 (AO7) increased 1.9 to 5.6-fold, respectively, than those lacking ceramsites. For the reduction of nitrobenzene, parachloronitrobenzene and paranitrotoluene, biological reduction rates increased 0.3 to 0.9-fold. With the increase of immobilized AQS concentration, the biological reduction rate increased. The decolorization efficiencies of AY36 retained over 98% during three-time successive repeated experiments. The results indicated that the quinonyl ceramsites could keep high catalytic activity and stability during biological treatment process. Biolog results showed that the quinonyl ceramsites had good biocompatibility.The optimal conditions for chemical reduction of AY36 by Na2S were as follows:Na2S concentration 3.2 mmol/L, pH=6.0. On this optimal condition, the reduction rates of azo dyes could be greatly increased. The chemical decolorization processes of azo dyes were fitted by the first-order kinetics. The first-order dynamics constants of AY36, RR2, AR27 and AO7 increased 2.9 to 9.9-fold, respectively, compared with the controls lacking quinonyl ceramsites.