Eco-friendly and facile integrated biological-cum-photo assisted electrooxidation process for degradation of textile wastewater

• Cellulose in the textile effluent was degraded by 93% employing hydro gels of Bacillus cereus.
• Indirect electro oxidation resulted in 95% decolourization mediated by OCl− ions.
• Photo assisted indirect electro oxidation resulted in 95% decolourization as well as 68% COD reduction via OCl radicals.
• The coupled treatment allows decolorization and an overall reduction of COD by 80%.

The present article reports an integrated treatment method viz biodegradation followed by photo-assisted electrooxidation, as a new approach, for the abatement of textile wastewater. In the first stage of the integrated treatment scheme, the chemical oxygen demand (COD) of the real textile effluent was reduced by a biodegradation process using hydrogels of cellulose-degrading Bacillus cereus. The bio-treated effluent was then subjected to the second stage of the integrated scheme viz indirect electrooxidation (InDEO) as well as photo-assisted indirect electro oxidation (P-InDEO) process using Ti/IrO2–RuO2–TiO2 and Ti as electrodes and applying a current density of 20 mA cm−2. The influence of cellulose in InDEO has been reported here, for the first time. UV–Visible light of 280–800 nm has been irradiated toward the anode/electrolyte interface in P-InDEO. The effectiveness of this combined treatment process in textile effluent degradation has been probed by chemical oxygen demand (COD) measurements and 1H – nuclear magnetic resonance spectroscopy (NMR). The obtained results indicate that the biological treatment allows obtaining a 93% of cellulose degradation and 47% of COD removal, increasing the efficiency of the subsequent InDEO by a 33%. In silico molecular docking analysis ascertained that cellulose fibers affect the InDEO process by interacting with the dyes that are responsible of the COD. On the other hand, P-InDEO resulted in both 95% of decolorization and 68% of COD removal, as a result of radical mediators. Free radicals generated during P-InDEO were characterized as oxychloride (OCl) by electron paramagnetic resonance spectroscopy (EPR). This form of coupled approach is especially suggested for the treatment of textile wastewater containing cellulose.

Figure optionsDownload high-quality image (289 K)Download as PowerPoint slide