Abstract
MnO2 is identified as a highly efficient sonocatalyst and sonophotocatalyst for the complete removal of even very small concentration of Indigo carmine (IC) dye pollutant from water. The effect of various reaction parameters, viz. dosage of the catalyst, concentration of pollutant, volume of reaction system, pH, dissolved gases, presence of anions/salts and oxidants etc. on the rate of degradation is evaluated and optimum parameters are identified. The degradation follows variable kinetics depending on the concentration of the substrate. The rate of degradation is facilitated by acidic pH. Classic oxidants H2O2 and S2O82− behave differently, with the former inhibiting and the latter enhancing the degradation. The effect of anions/salts on the degradation is complex and ranges from ‘inhibition’ (PO43−, CO32−, HCO3−) and ‘no effect’ (SO42−, Cl−) to ‘enhancement’ (NO3−, CH3COO−). The high affinity of MnO2 for O2 and its extremely efficient adsorption of H2O2 and the substrate play key roles in the efficiency of the process. Participation of lattice oxygen from MnO2 in the reaction, whenever the dissolved or adsorbed oxygen is deficient, is an important highlight of the process. Major transient intermediates formed during the process are identified by LC–MS. Combination of sonocatalysis with UV photolysis (sonophotocatalysis) enhances the efficiency of degradation and mineralization of IC.
Highlights
Ultrasound (US) irradiation and US e initiated heterogeneous catalysis have been investigated extensively in recent years as potential tertiary treatment processes for the removal of even very small concentration of chemical and bacterial pollutants from water [1, 2, 3, 4, 5, 6, 7, 8, 9]
The catalyst MnO2 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared (FTIR) spectroscopy and diffuse reflectance spectroscopy (DRS)
Concentration of the substrate, catalyst loading, pH, reaction volume, frequency of the ultrasound used, availability of O2, presence of salts and other contaminants etc. are important parameters that determine the efficiency of the process
Summary
Ultrasound (US) irradiation (sonication) and US e initiated heterogeneous catalysis (sonocatalysis) have been investigated extensively in recent years as potential tertiary treatment processes for the removal of even very small concentration of chemical and bacterial pollutants from water [1, 2, 3, 4, 5, 6, 7, 8, 9]. These advanced oxidation processes (AOP) have been proven effective for the degradation and eventual mineralization of many types of recalcitrant organic pollutants such as pesticides, phenols, pharmaceuticals and dyes. Another approach is to modify the characteristics of the catalyst by doping, supporting and coating [10, 11, 12, 13, 14]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
