Decolorization of Reactive Red 239 Via Heat Activated Persulfate

Ozlem Esen Kartal

doi:10.11648/j.ajpc.20180703.11

Abstract

Effluents of cotton dyeing process of textile industry is considered as extremely polluted due to presence of unfixed azo dyes and auxiliary chemicals. The complex aromatic structure and non-biodegradability nature of azo dyes involved new and efficient treatment technologies to eliminate intense color from textile wastewater. In recent years, in-situ chemical oxidation technology (ISCO) using persulfate (S2O82-) as an oxidant has appeared to be a promising method for removal of azo dyes. S2O82- can be activated by UV, heat or transition metals to generate sulfate radical (SO4-). In this study, decolorization of Reactive Red 239 (RR239) azo dye via heat activated S2O82- was explored. Experiments were conducted in a cylindrical batch reactor equipped with a water jacket. Effect of parameters such as temperature, pH and S2O82- concentration on decolorization of RR239 was investigated. The results show that decolorization efficiency was enhanced with increasing temperature from 45 to 55°C but further increase in temperature did not enhance decolorization. The pseudo first order rate constant values fit well Arrhenius equation, yielding an activation energy of 108.75 kJ mol-1 for decolorization of RR239. The highest decolorization efficiency was obtained at pH=3 under the tested pH range. As S2O82- concentration increased decolorization efficiency increased. 89.67% and 39.05% decolorization and aromatic degradation efficiencies were observed within 120 minutes of reaction time, respectively. These results show that heat activated S2O82- method was a feasible method for decolorization of RR239.

Highlights

Remediation of a large volume of wastewater originating from textile industry is of basic importance for preventing water pollution
Decolorization efficiency increased with increasing temperature up to 55 °C
Activation energy was calculated as 108.75 kJ mol-1 using Arrhenius equation. 89.67% of decolorization was observed at pH=3, whereas 54.04% and 49.58%

Summary

Introduction

Remediation of a large volume of wastewater originating from textile industry is of basic importance for preventing water pollution. Effluents of cotton dyeing process of textile industry are characterized by having an intense color and a low BOD5/COD ratio due to presence of unfixed reactive dyes. BOD5/COD ratio ranges from 0.06 to 0.35, indicating a low biodegradability of textile effluents [1,2]. The chromophore group of reactive dyes is mostly azo type and azo dyes are known to be toxic and mostly nonbiodegradable. Several treatment technologies have been considered for textile wastewater so far, they are not efficient in the presence of nonbiodegradable azo dyes. Removal of azo dyes by conventional aerobic biological treatment is not amenable and aromatic amines which show more toxic effect than dye molecules are formed under anaerobic conditions. Physical methods transfer dyes from one phase to another and cause secondary pollution [6]

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Results

Conclusion