Catalytic decomposition of potassium monopersulfate: influence of variables

Potassium monopersulfate has been decomposed in aqueous solution in the presence of Co(II). The effect of the main operating variables has been assessed. Minimum variations in pH exert a considerable influence on the process kinetics. Thus, when no pH adjustment is considered, the actual effect of variables like initial monopersulfate and/or catalyst concentration may be hindered. As expected, temperature enhances the monopersulfate decomposition rate by following the Arrhenius law. The activation energy in the proximity of 85 kJ/mol has been obtained. Amongst the different solids tested in the monopersulfate decomposition, only the perovskite LaTi0.15Cu0.85O3 has shown a significant catalytic activity

Catalytic decomposition of potassium monopersulfate: the kinetics

Potassium monopersulfate has been decomposed in aqueous solution in the presence of Co(II). The process has been simulated by means of a mechanism based on elementary reactions. Rate constants have been taken from literature reports or, alternatively, assimilated to analogous reactions occurring in Fenton´s chemistry. Several operating conditions have been successfully applied

Els colors de la vida

Els colors de la vid

La bella dorment: Un conte de llavors

La bella dorment: Un conte de llavor

Tots els colors de l'Arc de Sant Martí

Tots els colors de l'Arc de Sant Mart&iacute

Ungüents, pomades, cremes, cosmètics i altres potingues...

Ungüents, pomades, cremes, cosmètics i altres potingues..

Simulated solar driven photolytic ozonation for the oxidation of aqueous recalcitrant-to-ozone tritosulfuron. Transformation products and toxicity

The authors are grateful to Junta de Extremadura (Project IB16022), co-financed by the European Funds for Regional Development, for economically supporting this work. Moreover, it is also acknowledged the ‘Servicio de Análisis Elemental y Molecular (SAEM)’ of ‘Servicios de Apoyo a la Investigación de la Universidad de Extremadura (SAIUex)’ for the helping with the intermediate products analyses.This work reports the combination of ozone and solar radiation as an advanced oxidation process to remove the herbicide tritosufuron (TSF) in water. Firstly, the recalcitrance of TSF has been assessed, obtaining an ozonation second order rate constant of 5–154 M−1 min−1 in the range of pH from 5 to 8; while the rate constant with HOradical dot was found to be (1.8–3.1)·109 M−1 s−1. Secondly, the simultaneous application of simulated solar radiation in between 300 and 800 nm and ozone resulted positive in the oxidation rate of TSF. Mineralization extent was also higher. Less effective oxidation was achieved after limiting the radiation to the range 360–800 nm or 390–800 nm; also completely inappropriate for mineralization. Thirdly, the detected transformation products (TPs) demonstrated the vulnerability of TSF molecule to be attacked by HOradical dot in the sulfonylurea bridge. The combination of ozone and radiation of 300–800 nm led to the most effective removal of the TPs. Finally, after the photolytic ozonation treatment toxicity was also evaluated in terms of phytotoxicity towards the germination and root elongation of Lactuca Sativa seeds, and toxicity by immobilization tests of Daphnia Magna.Junta de Extremadura (Project IB16022)European Funds for Regional Developmen

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

The authors thank the economic support received from Gobierno de Extremadura and CICYT of Spain through Projects GRU10012 and CTQ2012-35789-C02-01, respectively. Mr. Rafael Rodríguez Solís thanks Gobierno de Extremadura, Consejería de Empleo, Empresa e Innovación, and FSE Funds for his Ph.D. grant (PD12058).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.Gobierno de Extremadura GRU10012CICYT of Spain CTQ2012-35789-C02-01Gobierno de ExtremaduraFSE Funds (PD12058

Photocatalytic ozonation of 4-chloro-2-methylphenoxyacetic acid and its reaction intermediate 4-chloro-2-methyl phenol

This work has been supported by the CICYT of Spain (Project CTQ2012-39789-C02-01). Mr. Rafael Rodríguez Solís thanks the Gobierno de Extremadura, Consejería de Empleo, Empresa e Innovación and FSE Funds for his Ph.D. grant (PD12058).Aqueous 4-chloro-2-methylphenoxyacetic acid (MCPA) has been treated by the systems UVA/TiO2/N2, O3, TiO2/O3, UVA/O3, UVA/TiO2/O2, and UVA/TiO2/O3. Under the conditions investigated (T = 20 °C, pH = 4.5, Qgas = 30 L/h, V = 1 L, CO3= 5 ppm, CMCPA = 5 ppm, CTiO2= 0.5 g/L), MCPA is removed in less than 30 min. Photocatalytic ozonation is the most efficient process both in terms of MCPA removal rate (100% conversion in less than 15 min) and mineralization extent (60% after 3 h and 25 °C). 4-Chloro-2-methyl phenol (CMP) is detected in those systems combining TiO2 and UVA radiation. The presence of ozone involves the complete depletion of CMP following its generation. The direct rate constant between CMP and ozone corroborates the high reactivity observed (7.2 ± 0.3 × 104 (M s)−1, 4.4 ± 0.2 × 105 (M s)−1, and 2.9 ± 0.7 × 106 (M s)−1 at pHs 4, 7 and 10, respectively). Identified intermediates detected in the UVA/TiO2/O3 applied to MCPA correspond to oxygenated species derived from the parent compound after loss of some substitution groups. No significant toxicity of intermediates is observed in BOD5, Daphnia parvula, and Culex pipiens larvae tests.CICYT of Spain (Project CTQ2012-39789-C02-01)Gobierno de ExtremaduraFSE Funds (PD12058

Synergism between peroxymonosulfate and LaCoO3-TiO2 photocatalysis for oxidation of herbicides. Operational variables and catalyst characterization assessment

Authors thank economic support received from Junta de Extremadura, CICYT of Spain and FEDER funds through Projects GR15033 and CTQ2015/64944-R, respectively. Mr Rafael Rodríguez Solís also acknowledges Gobierno de Extremadura, Consejería de Empleo Empresa e Innovación, and FSE Funds for his PhD grant (PD12058). Catalyst characterization was provided by Facility of Analysis and Characterization of Solids and Surfaces of SAIUEx (financed by University of Extremadura, Junta de Extremadura, MICINN, FEDER and FSE).BACKGROUND. This paper reports the use of novel coupled LaCoO3-TiO2 as photocatalyst with double route of peroxymonosulfate (PMS) activation. First, as a photocatalyst due to titania; and second, through PMS heterogeneous decomposition onto LaCoO3 particles. Thus, photocatalytical activity was tested for removing a mixture of four herbicides of different recalcitrance (metazachlor, tembotrione, tritosulfuron and ethofumesate). RESULTS. The presence of light and PMS highly enhanced herbicides removal rate: 3.5–5 times increases were obtained with UVA light. Oxidant concentration, catalyst load, pH and temperature were assessed. Herbicides were completely oxidized depending on their recalcitrant nature and the operational variables. 55% TOC conversion was reached using Oxone® 5 × 10−4 mol L−1. Phytotoxicity assays denoted no inhibition after 180 min of photocatalytic treatment (∼80% initial inhibition). Solid properties of Co/Ti = 0.1:1 ratio were studied by means of SEM (LaCoO3 aggregates linked to a variety of shapes and sizes of TiO2), XRF (6.1% of LaCoO3), XPS (superficial Co3+, La3+ and Ti4+), XRD (anatase, rutile and rhombohedral LaCoO3) and UV–vis diffuse reflectance (visible range absorption and bandgap of 2.88 eV for TiO2). CONCLUSION. Catalysts based on LaCoO3-TiO2 combined with peroxymonosulfate seem to be suitable for removing organic pollutants, with a moderate conversion of TOC and elimination of toxicity.Junta de Extremadura GR15033CICYT of Spain CTQ2015/64944-RFEDER foundsGobierno de ExtremaduraFSE Funds (PD12058)University of ExtremaduraJunta de ExtremaduraMICINNFS