Influence of presence of tannic acid on removal of sodium dodecylbenzenesulphonate by O 3 and advanced oxidation processes

BACKGROUND: The objective of the present investigation was to determine the role of the tannic acid (TAN) component of organic matter dissolved in water, in the removal of sodium dodecylbenzenesulphonate (SDBS) by ozone and by O 3 /H 2 O 2 , O 3 /granular activated carbon (GAC) and O 3 /powdered activated carbon (PAC) advanced oxidation processes. RESULTS: Low doses of TAN (1 mg L −1 ) during SDBS ozonation cause (i) an increased ozone decomposition rate and (ii) an increased SDBS removal rate. The SDBS removal rate with ozone in the presence of TAN was reduced when HCO 3 − ions were added. A rise in TAN concentration increased the SDBS removal rate, with a linear relationship between added TAN and the removal rate. SDBS was removed more effectively by O 3 /GAC, O 3 /PAC and O 3 /H 2 O 2 systems in the presence of TAN. CONCLUSIONS: Results obtained indicated two mechanisms involved in the generation of HO · radicals by the O 3 /TAN interaction: (i) direct generation of HO · radicals from the reaction between ozone and TAN, and (ii) increased generation of O 2 −· radicals in the medium, enhancing the transformation of ozone into HO · radicals by different radical reactions. In O 3 /GAC and O 3 /PAC systems, HO · radicals are mainly generated in the O 3 /TAN interaction, which is a homogeneous reaction with fast kinetics, whereas the O 3 /GAC and O 3 /PAC interactions are in a heterogeneous phase with much slower kinetics, and are therefore not competitive in the generation of HO · radicals. Copyright © 2008 Society of Chemical Industry