Oxidation of Congo red by Fenton coupled with micro and nanobubbles

ABSTRACT

Dye wastewater is a kind of refractory organic wastewater. Fenton coupled with micro-nano bubbles (MNBs+FT) was used for the degradation of Congo red (CR), aiming at simplifying the organic pollutants degradation process and reducing the cost of the process. The optimum condition of Fenton alone, the outlet pressure of the cavitation process and different combinations on the degradation of CR dye wastewater were discussed in this study. The results showed that the degradation of CR (100 mg/L) could reach 94.4% by using the MNBs+FT at the pH of 7, which was 72% higher than that using Fenton oxidation alone and 79% higher than that using MNBs alone. Based on the same degradation efficiency, the traditional Fenton process alone required 8 times the dose of oxidants of these combination systems, and the synergy coefficient of MNBs+FT was up to 2.44. ESR analysis indicated that ·OH was the predominant active species during the degradation of CR and MNBs+FT improved the utilization efficiency of H₂O₂ and produced more ·OH. Besides, the MNBs+FT could extend the pH range of the high-efficiency oxidation reaction, and it could also keep a high degradation rate under neutral conditions, which eliminated the process of adjusting the pH and reduced the anti-corrosion requirements of the equipment. According to the economic analysis results, the total cost of treatment for the MNBs/FT was about 13% of the cost of only the Fenton process. This study provides a reference for the application of MNBs+FT systems in full-scale dye wastewater treatment.

GRAPHICAL ABSTRACT

KEYWORDS:

• Fenton
• micro-nano bubbles
• azo dye
• hydroxyl radical
• synergy coefficient

Acknowledgments

This work was supported by the National Natural Science Foundation of China [grant number 51774285, 52074287, 51704291], Natural Science Foundation of Jiangsu Province of China [grant number BK20180656], and Qing Lan Project.

Declaration of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability statement

All data generated or analysed during this study are included in this article.

Additional information

Funding

This work was supported by National Natural Science Foundation of China: [Grant Number 51704291, 51774285, 52074287]; Natural Science Foundation of Jiangsu Province: [Grant Number BK20180656]; Qinglan Project of Jiangsu Province of China: [Grant Number None].