Comparative Study on the Decolorization of Orange II by Zero-valence Tin in Citric and Hydrochloric Acids

Shizuo Nishide,Makoto Shoda

doi:10.5539/eer.v2n1p1

Abstract

Zero-valence tin reductively degraded a persistent azo dye, Orange II to produce colorless aromatic amines. The effects of acid concentrations and initial Orange II concentrations on the decolorization of Orange II by tin in citric and hydrochloric acids were investigated. The decolorization reaction in citric acid was faster than that in hydrochloric acid at 2.5 and 5 mM acid concentrations. The faster reaction would be related to the characteristic dissolution reaction of tin in citric acid. The first-order kinetic was applicable in citric acid over the examined range of 0.1 - 0.4 mM initial Orange II. However, at more than 0.2 mM initial Orange II the first-order kinetic was not applicable in hydrochloric acid and thus the relaxation first-order reaction kinetic was applied. The result that zero-valence-tin/citric acid system demonstrated successful decolorization in repeated use supports the possibility of its application for azo dye wastewater.

Highlights

One million tons of synthetic dyes are produced worldwide every year and mainly used in textile mills
The first-order kinetic was applicable in citric acid over the examined range of 0.1 - 0.4 mM initial Orange II
We demonstrated the applicability of the two-stage-treatment of chemical reduction by zero-valence tin and biological oxidation of a persistent azo dye, Orange II (Nishide & Shoda, 2011)

Summary

Introduction

One million tons of synthetic dyes are produced worldwide every year and mainly used in textile mills. The physico-chemical methods, such as adsorption, chemical coagulation and electrochemical oxidation, are viable option for the elimination of azo dyes, these processes have major drawbacks. Electrochemical oxidation of dye wastewaters is slow process and process know-how is not fully understood (Mannu & Chauhari, 2002). Other emerging techniques, such as Fenton’s reagent (H2O2+Fe2+), ozonation, UV irradiation and the combined use of these processes may have potential for azo dyes. Such technologies usually involved complicated procedures or are economically unfeasible (Pearce et al, 2003)

Methods

Results

Conclusion