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.