Degradation of an azo dye by a fast and innovative pulsed light/H2O2 advanced oxidation process

Abstract

Pulsed light (PL) is a food processing technology initially intended for microbial inactivation that can potentially be applied in other UV-light based processes. PL lamps emit high intensity broad spectrum light from UV to infrared. This research tested the use of PL as part of an advanced oxidation process (AOP) for degrading polluting dyes. Experiments were performed in a batch reactor, and the efficiency of the AOP under different parametric values: dye concentration, pH and H2O2 doses on Direct yellow 106 decolourization was followed by spectrophotometry. Effects on chemical oxygen demand and electrical efficiency were also determined. Decolourization process follows a pseudo-first order kinetic. It was improved by increasing H2O2 concentrations and low pH; while there was little influence of dye concentration, perhaps due to the reactor configuration. The highest constant rate observed was 0.0410 cm2 / J. The decolourization by PL/H2O2 fits to a typical mechanism of a conventional UV/H2O2 process; since no direct photolysis or thermal effects were observed. Mineralization was incomplete likely due to the highly resonant structure of the dye. An electrical energy per order of 1009 kWh/m3 /order was calculated. Ninety % of colour removal was reached at 40 J/cm2 , which is achievable in less than 30 s by most of PL systems existing in the market. The PL/H2O2 process seems to be useful for decolourization of wastewater and could offer the advantage of a very fast degradation.