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-Fentonþbiochar Fentonþ
biochar>photo-Fenton Fenton. The Fenton process was also efficient for the regeneration of
the dye-saturated biochar. The photo-Fentonþbiochar 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.