ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

UV light-assisted mineralisation and biodetoxification of Ponceau S with hydroxyl and sulfate radicals

Mihir K. Sahoo, Morten Marbaniang, and Rajeshwar N. Sharan

Centre for Advanced Studies in Chemistry, Department of Chemistry, (email)

E-mail: mksahoo@nehu.ac.in

Abstract: The present study reports simultaneous mineralisation and biodetoxification of Ponceau S (3-hydroxy-4-(2-sulfo-4-[4-sulfophenylazo]phenylazo)-2,7-naphthalenedisulfonic acid sodium salt), an azo dye, by UV light assisted oxidation with hydroxyl and sulfate radicals. Metal ion catalysts used in the work were: Fe²⁺ and Ag⁺, and the oxidants used were: hydrogen peroxide and S₂O₈^2-. Strategies adopted to make the processes environmentally benign and economically viable by achieving maximum mineralisation in the shortest possible time are described. Mineralisation efficiency (Em) of various systems was found to follow the order: E_m(Fe²⁺/H₂O₂/UV) > E_m(Fe²⁺/S₂O₈²⁻/UV) > E_m(Ag⁺/H₂O₂/UV) ≈ E_m(Ag⁺/S₂O₈²⁻/UV). Thus, Fe²⁺ and HP are the most suitable metal ion catalyst and oxidant respectively, showing higher efficiency at pH 3 followed by that at pH 6.6. It is possible to enhance the Fe²⁺/H₂O₂/UV process electrical energy efficiency by maintaining the concentration of Fe²⁺ at either 0.05 mM or 0.03 mM and that of the oxidant at 2.5 mM. The bioassay study revealed that the Fe²⁺/S₂O₈²⁻ /UV process biodetoxification efficiency is higher at pH 3 (93.7 %) followed by that at pH 6.6 (80.1 %) at the concentration of Fe²⁺ and S₂O₈²⁻ of 0.03 mM and 2.5 mM, respectively. Thus, not only the concentration of Fe²⁺, but also the nature of the oxidant and pH play an important role in the biodetoxification process and S₂O₈²⁻ possesses higher biodetoxification efficiency than H₂O₂.

Keywords: hydroxyl radical – sulfate radical – mineralisation – biodetoxification – electrical energy efficiency

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2016-0050

Chemical Papers 70 (8) 1066–1077 (2016)