Nitrilotriacetic acid enhanced UV/Fe0/H2O2 process for salty wastewater treatment at neutral pH

Abstract

In this study, nitrilotriacetic acid (NTA) was used to enhance UV/Fe0/H2O2 process for highly salty wastewater at neutral pH. The addition of Fe0 could not accelerate the UV/H2O2 process for salty wastewater treatment at neutral pH due to the precipitation of Fe ions. While NTA added into UV/Fe0/H2O2 process which could form complex with Fe ion, the tartrazine removal could increase from 45.7% to 84.7% within 60 ​min. The k-value of the UV/Fe0-NTA/H2O2 system to remove tartrazine is also 2.2 times higher than that in UV/Fe0/H2O2 system. Meanwhile, the UV/Fe0-NTA/H2O2 process could obtain good performance for salt wastewater treatment under a wide salt concentration level of 0–0.2 ​M. It can also expand the application range of pH to neutral pH. SEM and XPS characterization showed that the corrosion rate of Fe0 in salty system was faster, and the presence of NTA could accelerate the recirculation of Fe3+/Fe2+ on the Fe0 surface. EPR spectroscopic analysis and scavenge experiments showed that •OH was the main reactive radical for the removal of tartrazine in the UV/Fe0-NTA/H2O2 system. In addition, the k-value for removing tartrazine in various types of salt systems in the UV/Fe0-NTA/H2O2 system was 3.2–4.2 times that of the UV/Fe0/H2O2 system. It demonstrated UV/Fe0-NTA/H2O2 processes fits to different types of salt system. Therefore, this study will provide a new method for the treatment of saline wastewater at neutral pH.

Keywords

• Highly salty wastewater
• Nitrilotriacetic acid
• UV/Fe0-NTA/H2O2 process
• Corrosion rate