Study On The Application Of Redox Mediators To Accelerate The Anaerobic Degradation Of Dyes

Removal of dyes is a major concern when treating textile-processing wastewater because of its biological refractory, high chromaticity and high toxicity; Azo dyes represent the largest class of dyes, and they generally resist biodegradation due to their xenobiotic nature. One effective strategy for the biological treatment of azo dyes is the anaerobic/aerobic sequential treatment, and the anaerobic decolorization of azo dyes is usually the rate-limiting step.Therefore, it is signicant to explore the study on accelerating the transformation of reactive azo dyes.Activated carbon (AC) is well known for its adsorbent of pollutants, here we describe the role of AC as redox mediator in accelerating the reductive transformation of pollutants as well as a terminal electron acceptor in the biological oxidation of an organic substrate. The biological decolorization of acid red B(RB) was conducted in a series of batch experiments, which under the optimum pH, temperature were 7 and 30℃; This study explores the use of AC as an immobilized redox mediator, using glucose as the electron donor. The application of AC in bioreactors improve the decolorizaiton rate to 10%-50%, and RB removal efficiency was 93% within 4.0h; The rate of removal of azo dye using of power activated carbon is 1.3 times than granular activated carbon. To verify the enhanced conversion of the dye, the RB sorption capacity of the AC and the changes of RB compound was monitored by UV/visible spectrophotometer.As a result of the study on accelerating the transformation of reactive azo dyes, we investigated the batch expemments with reaction of sulfide, azo dye reduction results from a combination of biotic and abiotic processes during the anaerobic treatment of dye. Batch experiments were conducted to indicate AC can act as the terminal electron acceptor for the biological oxidation of glucose; Furthermore, AC greatly accelerated the chemical reduction of an azo dye by sulfide. The results taken as a whole clearly suggest that AC accepts electrons from the microbial oxidation of glucose and transfers the electrons to azo dyes, accelerating their reduction. With the changes of UV/visible scanned spectrograms and decolorization rate, we found that the products reduced from RB could enhance the biodecolorization. Based on the study of the RB degradation, a possible pathway for the AC-catalytic degradation is proposed, a possible accelerate role of degradation are both AC and the products reduced from RB.Considerating the adsorption ability of anaerobic sludge and AC, a modified two-stage pseudo-first order kinetics that takes into account adsorption and decolorization were established to describe the RB removal process within AC.