Characterization and Comparative Performance of TiO2 Photocatalysts on 6-Mercaptopurine Degradation by Solar Heterogeneous Photocatalysis

Luis A González-Burciaga,Adela Lemus-Santana,José B Proal-Nájera,Cynthia M Núñez-Núñez,Miriam M Morones-Esquivel,Manuel Avila-Santos

doi:10.3390/catal10010118

Abstract

The crystallographic properties of two titanium dioxide (TiO2) photocatalysts, P25, and commercial C1-TiO2 reactive grade, were analyzed by X-ray diffraction (XRD) and the band-gap was calculated with UV–Vis spectrometry with integration sphere. Then, their performance was tested in the degradation of 6-mercaptopurine (6-MP) by heterogeneous photocatalysis with solar radiation under different pH conditions and the addition of hydrogen peroxide (H2O2); the degradation efficiency was monitored by UV–Vis spectrophotometry. The XRD analysis showed that both photocatalysts studied have anatase phase, while only P25 contains rutile; the band gap values were lower, in both catalysts, than those reported for catalysts obtained by the sol-gel method. With both photocatalysts, degradation experiments showed efficiency greater than 98% in experiments in the presence of H2O2 regardless of pH. The properties of the photocatalysts, along with the data obtained from the experimentation, helped determine the best semiconductor for the degradation of 6-MP with these operating conditions in this work.

Highlights

Advanced oxidation processes (AOP), heterogeneous photocatalysis among them, are emerging alternative technologies developed to remove or degrade recalcitrant organic compounds present in wastewater [1,2]; such compounds have high chemical stability and/or low biodegradability.AOPs are based on the generation of strongly reactive radical species, like hydroxyl radicals (OH, standard electrode potential varied between +1.8 and +2.8 VNHE ), which degrade a wide range of organic pollutants quickly and non-selectively into non-toxic products like CO2, H2 O and inorganic compounds [1,2,3]
The 6-MP is mainly used for the treatment of acute lymphoblastic leukemia [4], to extend the duration of remission achieved with other medications [5], which can last from 2 to 3 years after diagnosis [6]
These results indicate a faster activation of the photocatalysts TiO2 P25 and C1-TiO2 to the exposure to high radiation emission, in this case, solar energy

Summary

Introduction

Advanced oxidation processes (AOP), heterogeneous photocatalysis among them, are emerging alternative technologies developed to remove or degrade recalcitrant organic compounds present in wastewater [1,2]; such compounds have high chemical stability and/or low biodegradability. AOPs are based on the generation of strongly reactive radical species, like hydroxyl radicals (OH, standard electrode potential varied between +1.8 and +2.8 VNHE ), which degrade a wide range of organic pollutants quickly and non-selectively into non-toxic products like CO2 , H2 O and inorganic compounds [1,2,3]. 2.5 mg/kg/day [7,8] Due to their characteristics and high doses, removing chemicals as 6-MP has become a challenge

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Methods

Conclusion