Photocatalytic ozonation of pyridine‐based herbicides by N‐doped titania

Abstract

BACKGROUND A mixture of three pyridine herbicides in water (clopyralid, triclopyr and picloram) has been treated with photocatalytic processes, involving oxygen or ozone. Nitrogen doped and undoped titania were used in the process. Toxicity evolution during photocatalytic ozonation was monitored considering BOD, Daphnia parvula and fitotoxicity trials. RESULTS N doped titania with an optimized photoactivity was tested in photocatalytic ozonation, leading to nearly 95% mineralization in 180 min. This catalyst was characterized by SEM, TEM, XRD and XPS techniques (13.5 nm crystal size, anatase phase, 1% N, and formation of O‐Ti‐N linkage). No loss of photocatalytic activity was observed after five consecutive runs. Although no toxicity from the parent compounds was observed, this parameter increased during the early stages of the oxidation process. When parent compounds were totally degraded and dechlorination was completed, toxicity decayed again to negligible values. CONCLUSION N doping improves bare titania photoactivity through an optimum amount of N. Photocatalysis/ozone showed better behavior than photocatalysis/oxygen in herbicide removal and mineralization, and no significant loss of activity was observed after five runs. Toxicity initially increased due to toxic byproducts formation; however, it decreased after their abatement. © 2015 Society of Chemical Industry

N–TiO2 Photocatalysts: A Review of Their Characteristics and Capacity for Emerging Contaminants Removal

“…At those conditions, 95% of picloram, 45% of clopyralid, and 90% of triclopyr were removed after 180 min of irradiation. Higher and lower ratios decreased the degradation rate [131].…”

Ozonation, photocatalysis and photocatalytic ozonation of diuron. Intermediates identification

“…N doped titania photocatalyst was prepared applying a sol-gel method followed by thermal treatment and calcination according to literature and previous works [16,14].…”

“…Undoped titania achieved 40% TOC reduction after 180 min while N doped TiO2 led to 80% under the same operating conditions. Physical properties of solids and its photoactivity behaviour have previously been discussed [14].…”

“…In this work, a lab manufactured N-doped titania has been used. N doping improvements on photoactivity and characterization of the solid have previously been studied in-depth in a mixture of three pyridine based herbicides, under photocatalysis and photocatalytic ozonation processes [14]. Moreover, N-doping may be considered as a starting point in catalyst recovering due to the increase in particle size.…”

Absorption and photocatalytic degradation of VOCs by perfluorinated ionomeric coating with TiO2 nanopowders for air purification

“…Decomposition of pyridine has been widely studied because this aromatic nitrogenated heterocycle, despite representing a serious hazard for human organs, is broadly used as industrial solvent and is present as building block in a large number of common fine chemicals, agrochemicals, and pharmaceuticals [108][109][110][111][112]. Several researches reported its decomposition by pyrolysis as well as by biodegradation [107,[111][112][113][114][115][116][117].…”