Efficient hydroxyl radical production with Sodium salts of surfactants ozonation for treatment of organic acid pollutants in wastewater

Abstract

A comparative study was constructed to correlate sodium salts of surfactants that are Disodium Ethylene Diamine Tetra Acetic acid (EDTA-Na2), Sodium Dodecyl Sulfate (SDS), and Sodium Dodecyl-Benzene Sulfonate (SDBS) for synergic effect in ozone decay at low pH. An enhancing tendency (EDTA-Na2>SDBS>SDS>No surfactants) in the degradation of a model pollutant “Oxalic acid (OA)” via ozonation was observed. EDTA-Na2 significantly contributed to the degradation and TOC removal, HO• production with ozonation at pH 4.5 in 50 min showing higher efficiency twice than SDBS and 3 times greater than SDS. The rate of OA degradation and TOC removal was related to EDTA-Na2 concentration, as significant increase was observed by increasing the concentration of EDTA-Na2 (1 to 10 mg/L) at pH 4.5. The production of radicals like HO•, O2− and O2 was further confirmed through radicals scavenging experiments using tert-Butyl Alcohol (t-BA), para-Benzoquinone (p-BQ), and NaN 3 (Sodium azide) as scavengers, using Electromagnetic Spin Resonance (ESR) Spectroscopic technique. Furthermore, OA’s degradation pattern was analyzed through the Gas Chromatography-Mass Spectrometry (GC–MS) technique, in which the degradation pattern of EDTA-Na2 was analyzed by High Performance Liquid Chromatography (HPLC) and UV/Vis spectroscopy. This study sheds new light on the replacement of catalyst nanoparticles to activate ozone at acidic pHs and is believed to extend the scope of ozonation for complete oxidation of organic acid with surfactants.