Degradation of recalcitrant textile azo-dyes by fenton-based process followed by biochar polishing

Abstract

The use of advanced oxidative processes (AOPs) is an efficient alternative for the treatment of textile wastewaters. The aim of this study was to assess the dye removal efficiency of a Fenton-based degradation process followed by a polishing step using biochar prepared from rice husk. Six recalcitrant textile dyes - Reactive Red 195 (D1), Synolon Brown S2 (D2), Orange Remazol RGB (D3), Yellow Synozol K3 (D4), Reactive Orange (D5), and Reactive Black 5 (D6) – were treated with Fenton and photo-Fenton processes (with and without biochar polishing) under optimized conditions. The results showed a general efficiency ranking: photo-Fenton + biochar ≈ Fenton + biochar > photo-Fenton ≈ Fenton. The Fenton process was also efficient for the regeneration of the dye-saturated biochar. The photo-Fenton + biochar process achieved the following color removal percentages: D1 (98.8%), D2 (99.7%), D3 (98.9%), D4 (96.3%), D5 (94.2%) and D6 (94.8%). This process was applied to a real conventionally-treated textile wastewater and analysis showed a reduction in BOD (87.5% degradation), COD (62.5% degradation) and color (93.5% mean removal). These results reveal the possibility for the reuse of the treated water for non-potable industrial uses, for example, floor washing or the cleaning of machines and toilet areas.

Keywords:

• Textile wastewater
• dyes
• fenton reaction
• biochar
• environmental management

Acknowledgements

C.M. Radetski gratefully acknowledges the financial support from Universidade do Vale do Itajaí (Itajaí, Brazil) and the grant from CNPq - Brazil (Process 302124/2019-5). A.J. Feuzer-Matos, E. Sanches-Simões, and W. Pimentel-Almeida acknowledges master fellowships, while R. Ariente-Neto acknowledges post-doctorate fellowships from CAPES – Brazil.

Declaration of competing interest

The authors have no conflicts of interest to declare in relation to the work described in this study.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.