Rate of dibutylsulfide decomposition by ozonation and the O3/H2O2 advanced oxidation process.

A process of dibutylsulfide (DBS) oxidation using advanced methods of oxidation with ozone and hydrogen peroxide was studied. It was demonstrated that depending on pH value there are two mechanisms of DBS oxidation present: ionic and radical. The ionic mechanism predominates in acidic environment and the radical mechanism predominates in alkaline environment. At high pH ozone stability decreases and hydrogen peroxide has a deciding effect on DBS oxidation rate. At pH 9, and at high concentration of hydrogen peroxide (ranging from 0.1 to 1 mol/L), a clear increase in DBS decomposition rate was observed. That was caused by production of hydroperoxide radicals in reaction of hydrogen peroxide and ozone. In solutions pH value of which is close to 2, the rate of DBS oxidation by ozone alone is slower than in a O(3)/H(2)O(2) system, regardless the H(2)O(2) concentration. For higher H(2)O(2) concentrations (ranging from 0.1 to 1 mol/L), regardless the pH value of the solution, oxidation in a O(3)/H(2)O(2) system is faster, compared to a situation in which ozone is a sole oxidizer. For H(2)O(2) concentrations below 0.1 mol/L and when pH>2DBS oxidation in O(3)/H(2)O(2) system is slower compared to the situation in which ozone was the only oxidizer.

Effect of temperature and initial dibutyl sulfide concentration in chloroform on its oxidation rate by ozone.

A scheme of dibutyl sulfide (DBS) oxidation with ozone and generation of transitional products was determined in this study. The main identified intermediate product was dibutyl sulfoxide (DBSO), and the main end product of DBS oxidation was dibutyl sulfone (DBSO2). It was determined that for three temperatures: 0, 10 and 20 degrees C there was certain initial DBS concentration for which half-times observed in experimental conditions were equal and independent from temperature. Generation of phosgene and water as by-products was confirmed for the reaction of DBS with ozone in chloroform. Results of the described study allowed to present generalized mechanism of sulfide oxidation with ozone.