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The ZrSn composites materials were prepared in one pot by chemical co-precipitation method. SnO2 was incorporated to ZrxOy modifying the molar percentage from 1 to 5 mol%. The ZrSn composites were characterized by different techniques: XRD, FTIR, DRS, SEM, N2 physisorption and HR-TEM. The ZrSn composites were dried at 80 °C and thereafter were evaluated in the photodegradation of phenol under UV irradiation. The percentages of degradation and mineralization were determined after a reaction time of 150 min by UV–Vis spectroscopy and Total Organic Carbon analysis (TOC), respectively. The composite containing SnO2 in a 3 mol% showed the highest photoactivity with a 72% of photodegradation, a higher value compared with the obtained with TiO2-P25 (62%). Finally, a possible reaction mechanism was proposed based on certain studies, which allows to follow the formation of the active species •OH, •O2− and h+. The formation of the •OH specie was measured by fluorescence spectroscopy whereas the inhibition of the species •O2− and h+ was determined by UV–Vis spectroscopy. The results showed that the ZrSn composites not promotes the hydroxyl radical formation. In addition, the holes capture showed a full-loss of the photoactivity while the minimization of (•O2−) radicals in the reaction media results in a decrement of the photoactivity. The formation of heterojunctions and the presence of localized states in the synthesized composites offer an excellent alternative for a fast photodegradation of phenol.

El óxido de zinc (ZnO), es un material semiconductor del tipo II-VI, el cual posee una energía de banda prohibida (Ebp) de 3.37 eV a 298.15 K y la estructura cristalina termodinámicamente más estable es la del tipo de la wurtzita (hexagonal). Con estas características, el ZnO es un candidato excelente para múltiples aplicaciones industriales tales como; la electrónica, magnética, fotocatalítica, optoelectrónica, metalúrgica, alimentaria, cosmética, farmacológica, cerámica, polimérica y muchas otras más. En el presente trabajo, se identificaron y cuantificaron las fases cristalinas presentes en muestras sólidas obtenidas por precipitación química, considerando la relación estequiométrica en medio alcalino. Para el análisis de las fases cristalinas presentes en los sólidos obtenidos se empleó la técnica de Difracción de rayos-X (DRX), los difractogramas se obtuvieron en un intervalo de 4 a 90 de 2θ, a una velocidad de paso de 0.02y de la aplicación del método de Refinamiento Rietveld se llevó a cabo con el empleo del software Materials Using Diffraction Analysis (MAUD). Los resultados cualitativos permitieron considerar la presencia predominante de fase wurtzita (ZnO), la smithsonita (ZnCO3), hidróxido de zinc (Zn(OH)2) y acetato de zinc (ZnC4H6O4). Los resultados del refinamiento permitieron identificar la presencia de fases secundarias de ZnO en estos sólidos, tales como la estructura de roca de sal (halita) y la blenda de zinc.

Advanced oxidation processes such as photocatalysis have assumed enormous importance in the scientific field as viable sustainable alternatives to be applied to the elimination of persistent organic pollutants present in water reservoirs for human consumption. Persistent organic compounds like pesticides that belong to the chlorophenol family are a global public health priority since they are associated with serious diseases like cancer and can even cause death at low concentrations of prolonged exposure. This work proposes the use of activated Ni/Al layered double hydroxides as photocatalysts for the degradation of 2,4-dichlorophenol. The study variables associated with the properties of the catalysts were the Ni/Al metal ratio as well as the synthesis conditions. To determine the structural properties of catalytic precursors and catalysts, the techniques of XRD, FTIR, UV-DR, DGTA, TPD, SEM-EDS and TEM were used. The photodegradation tests were carried out in a Bach type reactor with a high energy uv lamp. The results of the photocatalytic degradation of 2,4-dichlorophenol in aqueous solution showed good photocatalytic activity with a degradation efficiency of up to 94% attributed to the presence of Ni in the crystalline and amorphous structures of NiO–NiAl2O4 oxides by means of a combined oxidation-reduction mechanism due to the effect of holes and superoxide and hydroxyl radicals not associated with the memory effect of reconstruction of layered double hydroxides.

La contaminación del agua porarsénico es un problema grave de salud pública a nivel mundial. El empleo de compuestos mesoporosos tipo hidrotalcitas (HT) es una opción eficiente y práctica para la adsorción de arsénico, debido a su alta tasa de remoción y bajo costo. Se sintetizó mediante el método de coprecipitación un hidróxido doble laminar Mg/Fe para la eliminación de arsénico en agua contaminada. Dicho sólido fue tratado a 100 °C y a 350 °C. El sólido se caracterizó por XRD y DSC-TGA. Se realizaron pruebas de eliminación de arsénico por contacto al equilibrio en sistema por lotes con soluciones sintéticas de arsénico y muestras de manantial. El sólido tratado térmicamente a 350 °C mostró la mejor capacidad de eliminación de arsénico, con capacidad de adsorción de 447.7 mg de arsénico por g de adsorbente en un tiempo de 180 min. Esta capacidad se atribuye a la modificación estructural por el tratamiento térmico.

Photoelectrocatalysis is a novel technique that combines heterogeneous photocatalysis with the application of an electric field to the system through electrodes for the degradation of organic contaminants in aqueous systems, mainly of toxic dyes. The efficiency of these combined processes depends on the semiconductor properties of the catalysts, as well as on the anodic capacity of the electrode. In this study, we propose the use of active hydrotalcites in the degradation of Congo red dye through processes assisted by ultraviolet (UV) irradiation and electric current. Our research focused on evaluating the degradation capacity of Congo red by means of photolysis, catalysis, photocatalysis, electrocatalysis, and photoelectrocatalysis, as well as identifying the effect of the properties of the active hydrotalcites in these processes. The results show that a maximum degradation was reached with the photoelectrocatalysis process with active hydrotalcites and a copper anode at 6 h with 95% in a half-life of 0.36 h. The degradation is favored by the attack of the OH• radicals under double bonds in the diazo groups where the electrode produces Cu2+ ions, and with the photogenerated electrons, the recombination speed of the electron–hole in the hydrotalcite catalyst is reduced until the complete degradation.

Novel composite ZrO2-Bi2O2(CO)3 (ZrBi) materials were prepared in one step by the chemical co-precipitation method under the same synthesis conditions. Bi2O2(CO)3 was incorporated to ZrO2 adding in 0.5, 1 and 2 mol%. The ZrBi composites were characterized by different techniques: XRD, FTIR, PL, DRS, N2 physisorption, XPS, SEM and HR-TEM. A 50-50% methanol-water solution was used and the results showed that the photocatalytic hydrogen production rate in the ZrBi composites was significantly enhanced when 1 mol% of Bi2O2(CO)3 (ZrBi-1) is added, obtaining a hydrogen production of 8753 µmolH2*g-1. The novelty of this material is that is part microcrystalline and part crystalline, and despite having a band gap energy of 3.9 eV is used without calcining, having considerable energy savings. In addition, oxygen vacancies are observed as well as the presence of heterojunctions between the microcrystalline phase of ZrO2 and the orthogonal structure of Bi2O2(CO3). The presence of heterojunctions and oxygen vacancies increases the transfer of charges, decreasing the probability of recombination of carrier charges (hole-electron pair) and increasing photocatalytic efficiency.

In recent years, the search for solutions for the treatment of water pollution by toxic compounds such as phenols and chlorophenols has been increasing. Phenols and their derivatives are widely used in the manufacture of pesticides, insecticides, paper, and wood preservers, among other things. Chlorophenols are partially biodegradable but not directly photodegradable by sunlight and are extremely toxic&mdash, especially 2,4,6-trichlorophenol, which is considered to be potentially carcinogenic. As a viable proposal to be applied in the treatment of water contaminated with 2,4,6-trichlorophenol, this paper presents an application study of the thermally activated Mg/Fe layered double hydroxides as photocatalysts for the mineralization of this contaminant. Activated Mg/Fe layered double hydroxides were characterized by X-ray diffraction, thermal analysis, N2 physisorption, and scanning electron microscopy with X-ray dispersive energy. The results of the photocatalytic degradation of 2,4,6-trichlorophenol in aqueous solution showed good photocatalytic activity, with an efficiency of degradation of up to 93% and mineralization of 82%, degradation values which are higher than that of TiO2-P25, which only reached 18% degradation. The degradation capacity is attributed to the structure of the MgO&ndash, MgFe2O4 oxides derived from double laminate hydroxide Mg/Fe. A path of degradation based on a mechanism of superoxide and hollow radicals is proposed.

Catalyst-type mixed metal oxides with different compositions and Co/Fe ratios were obtained from layered double hydroxides to be used as heterogeneous catalysts in the production of biodiesel. The effect of the Co/Fe ratio on the precursors of the catalysts was analyzed, considering their thermal, textural and structural properties. The physicochemical properties of the catalysts were determined by thermogravimetric analysis (differential scanning calorimetry and thermogravimetric), X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy and N2-physisorption. The conversion to biodiesel using the different catalysts obtained was determined by diffuse reflectance infrared Fourier-transform spectroscopy and 1H-Nuclear magnetic resonance spectroscopy, allowing us to correlate the effect of the catalyst composition with the catalytic capacity. The conditions for obtaining biodiesel were optimized by selecting the catalyst and varying the percentage of catalyst, the methanol/oil ratio and the reaction time. The catalysts reached yields of conversion to biodiesel of up to 96% in 20 min of reaction using only 2% catalyst. The catalyst that showed the best catalytic activity contains a mixture of predominant crystalline and amorphous phases of CoFe2O4 and NaxCoO2. The results suggest that cobalt is a determinant in the activity of the catalyst when forming active sites in the crystalline network of mixed oxides for the transesterification of triglycerides, with high conversion capacity and selectivity to biodiesel.

TiO 2 and Sn-doped TiO 2 materials were prepared by sol–gel method using titanium and tin alkoxides at different Sn concentration (0.1 mol%, 0.5 mol%, 1 mol%, 3 mol% and 5 mol%). Samples were characterized by thermo gravimetric analyzer with differential scanning calorimeter (TGA–DSC), X-ray Rietveld refinement, N 2 adsorption (BET), transmission electron microscopy (TEM), UV–vis spectroscopies technology and Raman spectroscopy. Only anatase phase was observed in pure TiO 2 , whereas anatase and brookite were obtained in Sn-doped TiO 2 samples. Sn dopant acts as a promoter in phase transformation of TiO 2 . The Rietveld refinements method was used to determine the relative weight of anatase and brookite, and crystallite size as a function of Sn concentration after calcination of samples at 673 K. It was also demonstrated the incorporation of Sn 4+ into the anatase TiO 2 structure. Sn 4+ inhibits the growth of TiO 2 crystallite size, which leads to an increase of the specific surface area of TiO 2 . From XRD analysis, the solid solution limit of Sn 4+ into TiO 2 is 5 mol% Sn. The photocatalytic activity on Sn 4+ doped TiO 2 was determined for the 2,4-dichlorophenoxyacetic acid reaction. The maximum in activity was attributed to the coexistence of anatase and brookite phases in the appropriate ratio and crystallite size.

A gallery of hydrotalcite-type mesoporous materials with different Mg/Al molar ratios were synthesized by the coprecipitation method. The materials were activated by heat treatment to test their activity in the photodegradation of 2,4,6-trichlorophenol under UV light irradiation. The physicochemical properties of the different synthesized and activated materials were determined using XRD, physical adsorption/desorption of N2, FTIR, SEM, DTA, and TGA. Their banned band energy was determined by UV-Vis to identify their potential to be used as a semiconductor in catalytic photodegradation processes. The results of photodegradation tests of 2,4,6-trichlorophenol showed that hydrotalcites have a high degradation capacity, up to 100% for the catalyst of Mg/Al ratio = 2, with a high mineralization capacity of 80%. The degradation capacity of most of the catalysts tested is mainly due to the presence of holes and the formation of superoxide free radicals, which are the determining species within the degradation mechanism.

The influence of ZrO2 semiconductor content (0.3–5 wt%) supported on a Layered Double Hydroxides (LDH) system for photodegradation of 4-chlorophenol (4-CP) in water was studied. Complete removal of 4-CP is achieved in two stages: first, 4-CP was adsorbed on the photocatalyst in darkness, until equilibrium was reached. Afterwards, the light was turned on, and the photodegradation process started. Adsorption and photodegradation were analyzed both individually, and combined. The adsorption process of 4-CP on the synthesized samples is well described by fitting a pseudo-second-order equation. The UV photodegradation rates were 2.6 times higher than the 4-CP removal rates achieved by adsorption. The photodegradation process was analyzed by means of hydroxyl radical production displaying zeroth order behavior. The photocatalyst with 1 wt% ZrO2/LDH had the highest hydroxyl radical production rate, achieving 99 % of 4-CP degradation and 87 % of mineralization, while maintaining its photocatalytic activity during ten reaction cycles. At wt%ZrO2/ LDH higher than 1 wt%, clustering is observed, promoting charge recombination, hindering photodegradation efficiency and thus, decreasing mineralization rates. The monoclinic phase of ZrO2, identified by XRD, was responsible for the high photocatalytic activity. The distances between cations within the LDH layers were not modified after ZrO2 impregnation, thus suggesting that zirconia was supported on the external surface of LDH. Characterization was done by N2 physisorption, TGA, XRD, AAS, UV-DRS TEM, and SEM-EDS.

In this work there was studied the structural, textural and effect that has treat thermal on the removal of Cr (VI) of nanoMg/Al hydrotalcite (NHT) synthesized by the sol-gel method with a ratio of Mg/Al=3. These present the characterization of the nanoMg/Al hydrotalcite before and after Cr (VI) removal, as well as the kinetic studies and of balance. In agreement with the results, when the NHT are thermal treated to 350 °C the hydrotalcite crystalline structure remains but the textural properties are improved and structural. The NHT synthesized by the sol-gel method present a good capacity of removal with values of 91 mg of Cr (VI) removed / g of NHT. The above mentioned capacity of removal gets improved after thermal treating the material, reaching values of removal of 124 mg of Cr (VI) removed / g of NHT. The NHT with the Cr (VI) absorbed show decrease of the crystalline structure, as well as a saturation of the pores that annuls the porosity due to the fact that the Cr (VI) lodges both at the pores and at the intersheets. The time that him takes the HLM to remove the Cr (VI) of the watery solution is alone of 2 minutes, with which it is possible to conclude that the NHT have an excellent aptitude to remove Cr (VI) of watery solutions in an interval of very short time.

En este trabajo se determinan las fórmulas estructurales de minerales arcillosos contenidos en arcillas provenientes de localizaciones geológicas de los municipios de Comonfort, Jerécuaro, Victoria y San Francisco del Rincón, pertenecientes al Estado de Guanajuato, México. El método utilizado fue el propuesto por Moore y Reynolds, mediante el análisis de la fórmula resultante, se deducen tanto el tipo de especie (dioctaédrica o trioctaédrica) como el origen y el valor de la carga de capa con lo cual se identifican los minerales arcillosos presentes. Se obtienen dos minerales tipo montmorillonita, uno tipo beidellita y otro más tipo vermiculita, éste último con tendencia a formar parte de la serie esmectita-vermiculita. In this this article structural formulas of clay minerals are determined from clays coming from the geologic localizations at Comonfort, Jerécuaro, Victoria and San Francisco del Rincón, in the state of Guanajuato, México. After applying, the Moore and Reynold’s method of chemical composition, it was deduced dioctahedral or trioctahedral type, layer charge origin and value, and the specific clay mineral from the analysis of the resulting formula. Two montmorillonites type minerals, a beidellite type and a vermiculite type mineral were obtained, and the last one showed a trend to be a part of the esmectite-vermiculite series.

Aluminum lithium hydroxide carbonate hydrate, also known as Al/Li layered double hydroxide or Al-Li hydrotalcite-like compound [Al2Li(OH)6]2CO3•nH2O, was prepared by reaction of lithium carbonate with ammonium dawsonite [NH4Al(OH)2CO3]. The reaction of ammonium dawsonite with a lithium carbonate satured solution at different temperatures and lithium carbonate concentrations was studied. The obtained solids were characterized by differential thermal analysis (DTA), thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). By this method, crystalline Li/Al LDH [Al2Li(OH)6]2CO3·3H2O can be obtained at 60 °C and 4 h reaction time.

In this work there was studied the effect of nano-Mg/Al hydrotalcite (NHT) as filler on maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). NHT was synthesized by the coprecipitation method with a ratio of Mg/Al=6 and nanocomposites were prepared using 1, 3 and 5 %wt of filler via melt-blending.Morphological and structural analysis of NHT were performed and for nanocomposites, tensile tests and thermal properties were measured. Results showed that filler was well dispersed in the LLDPE matrix, mechanical properties were enhanced in most of the cases and thermal stability improvements were achieved in the nanocomposites.

In the present study the synthesis and physicochemical characterization of Mg/Al hydrotalcite as well as its arsenic removal capacity is described. The adsorbent materials were synthesized by the coprecipitation method and characterized to identify its structure. Adsorption isotherm studies of As (III) from aqueous solution are described using the Langmuir, Freundlich, and Dubinin–Radushkevich models. The As (III) adsorption isotherm data fit best to the Freundlich model. The maximum As (III) adsorption efficienciesare 791.92 mg As (III)/g Mg/Al Hydrotalcite = 2, 642.56 mg As (III)/g Mg/Al Hydrotalcite = 3, 963.79 mg As (III)/g Mg/Al Hydrotalcite = 2 at 350 °C and 827.54 mg As (III)/g Mg/Al Hydrotalcite = 3 at 350 °C, in contact times less than 2 min. These results shown that Mg/Al hydrotalcite phases have a great capability to remove arsenic from aqueous systems in comparison with Fe-oxides-hydroxides, which are generally considered between the most efficient arsenic removers. This capacity can be attributed to a combination of anionic exchange, surface capture, and precipitation processes occurring over Mg/Al hydrotalcite, which made it as a potential material to remove arsenite efficiently.

En este trabajo se determinan las fórmulas estructurales de minerales arcillosos contenidos en arcillas provenientes de localizaciones geológicas de los municipios de Comonfort, Jerécuaro, Victoria y San Francisco del Rincón, pertenecientes al Estado de Guanajuato, México. El método utilizado fue el propuesto por Moore y Reynolds, mediante el análisis de la fórmula resultante, se deducen tanto el tipo de especie (dioctaédrica o trioctaédrica) como el origen y el valor de la carga de capa con lo cual se identifican los minerales arcillosos presentes. Se obtienen dos minerales tipo montmorillonita, uno tipo beidellita y otro más tipo vermiculita, éste último con tendencia a formar parte de la serie esmectita-vermiculita.

Arsenic is one of the most toxic elements that can be found. Arsenic is mainly emitted by the copper, lead and zinc production, in agriculture as pesticides and herbicides. Two forms of arsenic are common in natural waters: arsenite (AsO33−) and arseniate (AsO43−), referred to as As(III) and As(V). The nano-Mg/Al-hydrotalcites present ionic exchange and adsorbent capacities. In this work, the physic-chemical characterization of nano-Mg/Al-hydrotalcites and his arsenic removal capacityis described. The solids were synthesized by the sol-gel method with Mg/Al=2 and 3 ratio. The solids and their thermal treated products were characterized by XRD, FTIR, DTA, TGA and N2 adsorption. The solids were used as adsorbents As(III) in aqueous solutions. Adsorption isotherm studies of As(III) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin–Radushkevich adsorption isotherm models. The As(III) adsorption isotherm data fit best to the isotherm Freundlich model. The maximum As(III) uptake capacity by nano-Mg/Al-hydrotalcites and the heated solids were determined using the Freundlich equation and were found to 547.46, 660.15, 799.88 and 739.12 mg As(III)/g HT-Mg/Al=2, HT-Mg/Al=3, HT-Mg/Al=2 at 350°C and HT-Mg/Al=3 at 350°C respectively. In the kinetic studies using 40 mg/L concentration of As(III) solutions was obtained an excellent removal capacity in contact times less at one minute.

Aluminum lithium hydroxide carbonate hydrate, also known as Al-Li double hydroxide or Al-Li hydrotalcite-like compound [Al2Li(OH)6]2CO3•nH2O, was prepared from basic aluminum sulfate. This compound was prepared by precipitation in homogeneous solution of an aluminum bisulfite solution. A sodium aluminate aqueous solution was prepared by dissolving basic aluminum sulfate in 1M sodium hydroxide. The Al-Li double hydroxide was obtained after addition of lithium carbonate satured solution to the sodium aluminate solution, at 60 °C. The synthesized powder was characterized by thermal analysis (TG, DTG and DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By this method crystalline Li-Al hydrotalcite like compound with composition near to Al4Li2(OH)12CO3 •3H2O was obtained.

In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio=2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N(2) adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.