Sonochemical degradation of 3-methylpyridine (3MP) intensified using combination with various oxidants

Abstract

3-Methyl pyridine (3MP) is a toxic and hazardous organic compound having considerable negative impact on environment and living organisms. The objective of this work to report a novel treatment strategy based on sonochemical degradation of 3MP, in combination with oxidants such as hydrogen peroxide, Fenton’s reagent, peroxymonosulphate (PMS), and potassium persulphate (KPS) as well as solar irradiations. A bath sonicator operating at 25 kHz frequency and rated power dissipation of 100 W was applied in the work to study different approaches with an objective to enhance the removal of 3MP in lesser time. Effect of operating parameters such as pH (over the range of 2–10), treatment time, temperature (25–55 °C) and ultrasonic power (25 W to 150 W) on the degradation has been studied and the best conditions were used in subsequent combination approaches. It was demonstrated that ultrasound in combination with PMS, ferrous sulphate (FeSO4) and solar irradiations (approach of US/PMS/FeSO4/solar irradiation) is the best treatment strategy yielding maximum degradation as 97.4% with highest cavitational yield as 1.920 × 10−4 mg/J and highest synergetic Index as 2.70. Kinetic analysis revealed that first order mechanism fitted well to all the approaches involving different combinations of ultrasound, oxidising agents and solar irradiation. Degradation products were also analysed that established the degradation mechanism as C2 and C3 ring cleavages forming 1, 4-dihydro3-methylpyridine followed by Levulinic acid as non -toxic main by-product. Overall the work clearly demonstrated an effective treatment approach involving combined sonication with oxidants for remediation of 3MP also providing insights on kinetics and mechanism of degradation.