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    • 专利摘要:
    Procedure for the treatment of contaminated water. The invention relates to a process for water treatment consisting of the oxidation of the contaminants by combining h2 o2/light/ilmenite. The use of ilmenite as a catalyst has a double catalytic action, on the one hand the decomposition of oxygenated water according to a heterogeneous cwpo or fenton process taking advantage of the iron contained in its structure and on the other the photocatalysis. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2556561A1
    申请号:ES201431083
    申请日:2014-07-18
    公开日:2016-01-18
    发明作者:José Antonio CASAS DE PEDRO；Patricia GARCÍA MUÑOZ；Gema PLIEGO RODRÍGUEZ；Ana Mª BAHAMONDE SANTOS；Juan Antonio ZAZO MARTÍNEZ；Juan José RODRÍGUEZ JIMÉNEZ
    申请人:Universidad Autonoma de Madrid；
    IPC主号:
    专利说明:

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    iron and that the Fenton process under moderate conditions of use is unable to degrade. Therefore, the use of both CWPO-photoassisted combined processes would be a good option for the treatment of these effluents.
    5 Based on this background, a mineral has been used that contains both oxides, iron oxide and titanium oxide called ilmenite (FeTiO3), which can simultaneously give rise to both processes, obtaining a synergistic effect in the oxidation process of organic matter.
    10 No specific bibliography was found where the ilmenite mineral is used as a catalyst for the combined CWPO-photoassisted process. However, its use in photocatalysis does appear [Moctezuma et al., Photocatalytic degradation of Phenol with Fe / titania Catalysts; Top Catal (2011) 54: 496-503], [Truong et al., Photocatalytic reduction of CO2 on FeTiO3 / TiO2 photocatalyst; Catalysis Communications 19 (2012)
    15 85-89]. Its use in CWPO processes has not yet been published, although previous studies have been carried out on its ability to decompose H2O2. In this sense, Teel and collaborators performed the decomposition of hydrogen peroxide with ilmenite and other minerals in [Rates of Trace Minerals-Catalyzed
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    20 This mineral, FeTiO3, has been the main source of obtaining TiO2 by the industry. Various methods are widely studied in the literature on how to treat them and modify the ilmenite mineral to obtain rutile (TiO2) such as Akhgar et al. in [Preparation of nanosized synthetic rutile from ilmenite concentrate; Minerals
    25 Engineering 23 (2010) 587–589]. DESCRIPTION OF THE INVENTION
    The invention provides a process for water treatment consisting of the oxidation of organic pollutants by combining hydrogen peroxide (H2O2), light and ilmenite (iron ore and titanium).
    Ilmenite, which is used as a catalyst, is a mineral formed by the combination of layers of titanium oxide and iron oxide (FeTiO3). The iron and titanium present in ilmenite constitute the active phases used in both CWPO and photocatalysis processes. Therefore, the catalyst used in the
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    Therefore, in a preferred embodiment, the concentration of hydrogen peroxide is at least 80% by volume of the stoichiometric amount for mineralization.
    5 total contaminant. This is the amount of H2O2 needed to oxidize 100% organic pollutant to CO2 and H2O. Stoichiometric hydrogen peroxide is calculated as the amount of oxygen necessary for total oxidation of the contaminant, assuming that two molecules of H2O2 produce one molecule of O2.
    By means of the combined process of the present invention, the treatment of contaminated waters containing organic compounds is achieved, in a preferred embodiment the organic compounds are recalcitrant compounds, these effluents preferably being residual liquid effluents.
    "Recalcitrant compounds" means in the present invention the contaminating organic matter contained in liquid effluents, for example but not limited to hydrocarbons, phenolic compounds, halogenated solvents, dyes
    or aromatic compounds. Preferably said liquid effluents are waters from industrial processes, which contain contaminants such as for example
    20 organochlorines, such as chlorophenol, chlorobenzene, chloroguaicol, dibenzofuran and dibenzodioxins. Preferably the organic matter to be removed is phenol.
    As previously mentioned, the catalysts obtained according to the
    The process of the invention allows an effective oxidation of the organic compounds contained in liquid effluents, with high stability, without any signs of leaching of the metals that form ilmenite.
    In a preferred embodiment of the process of the invention the ilmenite can be
    30 recover after the CWPO-photoassisted reaction, due to its magnetic properties, and be reused in the same procedure facilitating its use in continuous processes of treatment of contaminated water.
    The term "catalytic wet oxidation with hydrogen peroxide" (catalytic wet
    35 peroxide oxidation, CWPO), includes several variants. Among them the Fenton reagent is one of the most frequent options. In this process the peroxide of


    Hydrogen decomposes catalytically in the presence of iron, producing hydroxyl radicals, which have a high oxidation capacity.
    The term "photocatalysis" includes several variants. Among them, the most frequent
    5 consists in the excitation of a broadband semiconductor such as TiO2 when it absorbs light preferably from the ultraviolet range, giving rise to pairs of charges (electron-holes) that migrate to the catalyst surface and generate hydroxyl radicals that are responsible for the degradation of organic matter.
    Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The following examples are provided by way of illustration, and are not
    15 is intended to be limiting of the present invention. EXAMPLES
    The invention will now be illustrated by tests carried out by the 20 inventors, which demonstrates the effectiveness of the product of the invention.
    Examples Example 1. CWPO and photocatalysis of phenol with the mineral as a catalyst with 25 different doses of H2O2 oxidant
    The dose of H2O2 plays a fundamental role in the photocatalytic CWPO process. Reactions were carried out with different percentages, from 20% to 100%, corresponding to the theoretical stoichiometric amount needed to oxidize the phenol to CO2 and H2O.
    30 CWPO phenol photoactive experiments were performed, with a starting concentration of 100 mg · L-1, an initial H2O2 concentration of between 100 and 500 mg · L-1 and a mineral concentration of 200 mg · L-1, At atmospheric pressure These reactions were performed in a Suntest XLS solar simulator with an irradiance of 550 W · m-2
    35 with a spectrum similar to sunlight between wavelengths of 300-800 nm and
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    a process efficiency of 100%, however, with the use of the CWPO photo-assisted process using ilmenite, as demonstrated in this example with 80% higher mineralizations than the theoretical ones are achieved with the combination of these two processes, causing a reduction in oxidant consumption
    5 On the other hand, the degradation percentages obtained for 80% and 100% oxidant are very similar.
    From this study it was obtained as a main result that the optimum concentration of
    Oxidant corresponds to 80% of the stoichiometric amount, whereby the second embodiment of this invention proceeded with said amount of oxidant.
    The concentration of H2O2 corresponding to 80% is assumed to be optimal since higher amounts do not imply significant improvements in the final degradation of
    15 organic load and with that amount the theoretical amount of degradation was improved. Example 2. Effect of catalyst size on the CWPO-photoassisted process.
    20 In this example, different particle sizes of the ilmenite mineral were used.
    The following steps were carried out: a) Grinding of the catalytic material (ilmenite) in a ball mill; b) Screening of the material obtained at different grinding times;
    25 c) Characterization of the material as a function of size; and d) Performing phenol oxidation reactions in the CWPO photoassisted process
    The grinding was carried out in a ball mill with 30 ceramic balls of 1 cm in diameter (trade mark Orto Alresa 17 cm high and 13 cm in diameter)
    30 tracking the material at 24, 48, 72 and 96 hours of grinding. The different samples of the ore taken from the mill at different times have been called day-1, day-2, day-3 and day-4 for the times of 24, 48, 72 and 96 hours of grinding respectively. The ground amount was 50 grams of the mineral. The material sizes were decreasing depending on the milling time.
    35
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    Table 2. Particle size as a function of ore grinding time.
    Grinding time (hours) Mean particle diameter (dp) (μm)
    24 5
    48 2
    72 one
    96 <1
    As expected, grinding time significantly affects the size of the
    5 ore Table 2 shows changes in the average particle size from 5 μm after 24 h of grinding to less than 1 μm after 96 h. In the latter, most particles have a size of the order of nanometers. These differences in size affect the reaction times necessary for the oxidation of phenol by the CWPO-photoassisted process.
    10 Photoassisted phenol CWPO experiments were performed, with a starting concentration of 100 mg · L-1, an initial H2O2 concentration of 400 mg · L-1 (considered as optimal at the first point of this invention) and a concentration of 200 mg mineral · L-1, at atmospheric pressure. These reactions were performed in them.
    15 conditions indicated in Example 1. The catalysts used were presented in Table 2. The reaction was carried out in flat 12 cm diameter borosilicate glass reactors stirred with a stir plate and with a reaction volume of 500 mL. The initial amount of H2O2 corresponds to the stoichiometric amount needed to oxidize the phenol to CO2 and H2O by 80%.
    The concentrations of phenol and other intermediate aromatic oxidation compounds were quantified by HPLC. Short chain acids were analyzed by ion chromatography. Total organic carbon (COT) was quantified with a COT analyzer equipped with an infrared detector.
    25 Experiments were carried out on total decomposition of H2O2, achieving the same degree of phenol mineralization to CO2 and H2O but different times depending on the grinding time of the mineral and therefore with its size.


    Table 3 compares the time required to reach the same reaction point for the different samples of the minerals.
    Table 3. CWPO-photoassisted reaction time as a function of ore grinding time. Conversion percentages of phenol, total organic load and hydrogen peroxide achieved with each mineral sample.
    Grinding time (h) X PHENOL (%)X TOC (%)X H2O2 (%)mean dp (μm)Reaction time (min)
    0 10097100> 100720
    24 100971005600
    48 100971002540
    72 10097100one500
    96 10097100<1390
    Table 3 shows that a smaller particle size requires less time to carry out the same percentage of photodegradation, indicating an increase in the
    10 reactivity with the decrease in particle size.
    The difference in reaction time between the mineral Day-1 (24 hours) and Day-4 (96 hours) is remarkable. While with a size of around 5 μm, the reaction ends after 600 minutes of treatment with the CWPO-assisted process, when the
    15 size decreases to nanometric sizes (<1 μm) the reaction time becomes 390 minutes, achieving a reduction in time of 35% to achieve the same degradation value of organic matter.
    The main point of this invention is the correlation of particle size 20 with the reactivity of the mineral, which is evidenced by these results. Example 3. Stability of minerals with different concentrations of H2O2
    The stability of the catalysts constitutes an essential characteristic for the
    25 process The leaching of iron in oxidation processes of organic pollutants with H2O2 is closely related to the presence of oxalic acid in the liquid phase, a byproduct of phenol oxidation as demonstrated in the literature [Zazo et al., "Catalytic wet peroxide oxidation of phenol with Fe / active carbon catalyst; App. Cat. B: Env 65 (2006) 261-268].
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    权利要求:
    Claims (1)
    [1]
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    ES2556561B1|2016-11-03|
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    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2016203082A1|2015-06-16|2016-12-22|Universidad Autónoma de Madrid|Method for eliminating nitrates from water using photocatalytic reduction|
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