Background and purpose: Molasses is colored, toxic and non-biodegradable compound which is found in the wastewater of fermentation industries. This study investigated the kinetic and efficiency of molass dye removal and mineralization in the yeast wastewater using nanocomposite catalysts in ozonation process.

Materials and methods: The catalytic ozonation process (COP) of colored effluent of biological treatment of yeast production factory was carried out using semi-continuous flow cylindrical reactor and the effects of operational parameters such as initial pH value (4-10) and reaction time (5-60 min) on removal efficiency of dye and mineralization were investigated. After determining the kinetic parameters of reaction, the effects of some other parameters such as adsorption and reuse of the catalyst were calculated and the efficiency was compared with single ozonation process (SOP) and granular carbon as catalyst.

Results: The removal efficiency of dye of molass factories effluent and its kinetic, at the condition of initial dye concentration 4521 ADMI, catalyst concentration 2 g/L and 60 min reaction time were 95% and 0.045 min^-1, respectively; while these parameters in SOP and granular activated carbon as catalyst were 71% with 0.018 min^-1 and 86% with 0.028 min^-1, respectively. But, the mineralization and its kinetic in COP were 74% and 0.023 min^-1, respectively, in which initial TOC was decreased from 510 mg/L to 132 mg/L.

Conclusion: The nanocomposite was found to have the best efficiency in dye degradation and TOC removal and it is easy to recover and reuse over and over by magnet. The main mechanism of dye degradation in COP was chemical oxidation and less occurred by adsorption.