Efficient Removal of Azo Dye from Wastewater Using the Non-Toxic Potassium Ferrate Oxidation–Coagulation Process

Munkhtsooj Jargalsaikhan,Sanghyun Jeong,Am Jang,Jieun Lee

doi:10.3390/app11156825

Munkhtsooj Jargalsaikhan, Sanghyun Jeong + Show 2 more

Open Access

https://doi.org/10.3390/app11156825

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Abstract

The wastewater effluents from textile industries contain highly toxic metal complex dyes. For instance, azo dye has received significant attention owing to its toxicity and environmental stability. This study investigated the oxidation and coagulation processes to effectively remove azo dye from wastewater effluents. Potassium ferrate (K2FeO4) was selected as an oxidant because it has a high oxidation potential, is environmentally stable, and does not generate toxic byproducts. Moreover, it has a combination effect of coagulation and oxidation. Its performance was compared with a single oxidation process (using NaOCl) and a single coagulation process (using FeCl3·6H2O). Based on the jar test experiment, the optimized pH was estimated to be 3 and the optimal dosage was 56.4 mg/L for K2FeO4, and it removed nearly 100% of orange II azo dye (OD) and lissamine green B dye (LGB). However, its removal efficiency decreased when the pH increased to 12. In all processes, dye removal was completed in 5 min of the reaction. Overall, OD and LGB were effectively removed by K2FeO4, compared to the NaOCl and FeCl3·6H2O. This indicates that the combination of oxidation and coagulation of K2FeO4 outperformed the single treatment process without toxic byproduct production.

Highlights

The textile industry produces a significant amount of dye effluent, which contains highly toxic metal complex dyes [1]
This study aimed to investigate the treatment efficiency of K2 FeO4 for dye wastewater treatment with an emphasis on removing orange II azo dye (OD) and lissamine green B
Given its high redox potential and simultaneous generation of ferric coagulating species, K2 FeO4 was successfully applied to the treatment of dye wastewater

Summary

Introduction

The textile industry produces a significant amount of dye effluent, which contains highly toxic metal complex dyes [1]. Azo dyes, containing one or more azo groups (-N=N-) in their chemical structure, account for 50–70% of the synthetic dyes that are used in textiles, papers, food, cosmetics, and pharmaceuticals [6,7]. Given their abundant structural diversity, high molar extinction coefficient, sensitivity to light, and wetness, azo dyes are toxic and mutagenic; they lead to the discoloration of natural water. Azo dyes cannot be effectively treated by conventional biological processes because they are chemically stable [13]

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