Metal‐Ion and UVC Light‐Catalyzed Oxidation and Biodetoxification of Ponceau Xylidine in Aqueous Solution: A Comparative Study.

Metal ion (Mn+ ${{{\rm M}}^{{\rm n}+}}$ /oxidant) and UV light catalyzed (UV/oxidant) mineralization and biodetoxification of Ponceau Xylidine (PX) was undertaken in this study. Hydrogen peroxide (HP) and ammonium persulphate (APS) were employed as oxidants and Fe2+ ${{{\rm F}{\rm e}}^{2+}}$ and Ag+ ${{{\rm A}{\rm g}}^{+}}$ as metal ion catalysts. Although highest mineralization in Fe2+ ${{{\rm F}{\rm e}}^{2+}}$ /APS and UV/HP systems was exhibited at pH 1 (63.09 %) and 3 (64.83 %), respectively, lowest was shown by Ag+ ${{{\rm A}{\rm g}}^{+}}$ /oxidant systems at any pH. The Fenton process achieved mineralization of ≈48.50 % within the pH range of 3 to 6.15. The study established Fe2+ ${{{\rm F}{\rm e}}^{2+}}$ as a better catalyst than Ag+ ${{{\rm A}{\rm g}}^{+}}$ , and HP, a better oxidant (2.5 times more effective) than APS. Mineralization with UV/HP at 120 min is highest at pH 3 (92.0 %) and 6.15 (86.17 %). Various inorganic anions were found to inhibit mineralization. The maximum and minimum inhibition was shown by Cl- ${{{\rm \ }{\rm C}{\rm l}}^{-}}$ in UV/HP and UV/APS systems respectively. The inhibition effect of NO3- ${{{\rm N}{\rm O}}_{3}^{-}}$ decreases with concentration till 0.01 mM, beyond which an increasing trend was observed. This study also demonstrates that the biodetoxification efficiency of various systems is in the order: UV/HP>UV/APS>Fe2+ ${{{\rm F}{\rm e}}^{2+}}$ /HP. Thus, UV/HP is the most suitable system for the treatment of PX, displaying a biodetoxification efficiency of 83.0 % and mineralization of 92.0 %. [ABSTRACT FROM AUTHOR]