Application of cellulose-immobilized riboflavin as a redox mediator for anaerobic degradation of a model azo dye Remazol Golden Yellow RNL

This study described the anaerobic degradation of the azo dye Remazol Golden Yellow RNL (RGY-RNL) using cellulose-immobilized riboflavin (MC 3) as the redox mediator. This new solid support containing immobilized riboflavin was synthesized from succinylated mercerized cellulose, and was characterized by elemental analysis, FTIR, and solid-state C-13 NMR. MC 3 was resistant to pH 2-9, and anaerobic degradation of RGY-RNL using MC 3 in the presence of anaerobic sludge yielded a zero order degradation rate constant (k(O,obs)) equal to 0.189 mg/Lh, which was 56% better than experiments carried out without a redox mediator. Color removal efficiency after 48 h of degradation averaged 89.4% in experiments with MC 3 and 72% without the addition of a redox mediator. These results showed that MC 3 can be used to immobilize redox mediators, allowing reduction of wastewater treatment costs. (C) 2014 Elsevier B.V. All rights reserved.