Treatment of ultra-high concentration 2-diazo-4,6-dinitrophenol (DDNP) industry wastewater by the combined Fe/Cu/air and Fenton process

Abstract

Treatment of 2-diazo-4,6-dinitrophenol (DDNP) industry wastewater by 1^stFe/Cu/air–2^ndFenton–3^rdFe/Cu/air was studied to degrade the toxic refractory pollutants and improve the biodegradability. Three control experiments (i.e., 1^stFe⁰/air–2^ndFenton–3^rdFe⁰/air, Fe/Cu/air, and Fenton) were set up to confirm the superiority of 1^stFe/Cu/air–2^ndFenton–3^rdFe/Cu/air and the synergistic reaction between Fe/Cu/air and Fenton process. Furthermore, the key operating parameters including initial pH (1.5–7.0), Fe/Cu dosage (5–50 g L⁻¹), aeration rate (0–2.0 L min⁻¹), reaction time (0–180 min) and H₂O₂ dosage (0–40 mmol L⁻¹) were optimized, respectively. The results showed that high COD removal (87.1%), decolority (99.9%), DDNP removal (100%) and B/C ratio (0.58) was obtained by 1^stFe/Cu/air–2^ndFenton–3^rdFe/Cu/air process. It has a higher treatment efficiency than 1^stFe⁰/air–2^ndFenton–3^rdFe⁰/air due to the high reactivity Fe/Cu bimetallic particles. Therefore, the developed method in this study is a promising process for treatment of DDNP industry wastewater. Finally, the analysis results of UV-vis and FTIR reveal that the main groups (e.g., benzene ring, nitro and azo groups) of the pollutants could be decomposed effectively after 4.5 h treatment by 1^stFe/Cu/air–2^ndFenton–3^rdFe/Cu/air. The results also further confirm the superiority of 1^stFe/Cu/air–2^ndFenton–3^rdFe/Cu/air and the synergistic reaction between Fe/Cu/air and Fenton process. Thus, it is a promising technology for the treatment of ultra-high concentrated DDNP industry wastewater.