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Lanthanum aluminate-based perovskite (LaAlO 3 ) has excellent stability at high temperatures, low toxicity, and high chemical resistance and also offers wide versatility to the substitution of La 3+ and Al 3+ , thus, allowing it to be applied as a catalyst, nano-adsorbent, sensor, and microwave dielectric resonator, amongst other equally important uses. As such, LaAlO 3 perovskites have gained importance in recent years. This review considers the extensive literature of the past 10 years on the synthesis and catalytic applications of perovskites based on lanthanum and aluminum (LaAlO 3 ). The aim is, first, to provide an overview of the structure, properties, and classification of perovskites. Secondly, the most recent advances in synthetic methods, such as solid-state methods, solution-mediated methods (co-precipitation, sol-gel, and Pechini synthesis), thermal treatments (combustion, microwave, and freeze drying), and hydrothermal and solvothermal methods, are also discussed. The most recent energetic catalytic applications (the dry and steam reforming of methane; steam reforming of toluene, glycerol, and ethanol; and oxidative coupling of methane, amongst others) using these functional materials are also addressed. Finally, the synthetic challenges, advantages, and limitations associated with the preparation methods and catalytic applications are discussed.

Potassium birnessites were prepared using two methods, sol-gel or oxidation. The solids were characterised by element chemical analysis, powder X-ray diffraction, FT-IR spectroscopy, thermal analyses, and nitrogen adsorption. The evolution of the properties as a function of the preparation method was discussed. The photocatalytic performance of these solids was preliminarily tested for the degradation of 4-nitrophenol. The degradation pathway and the nature of the by-products were investigated by mass spectrometry. The solids showed good catalytic behaviour, although their preparation must be improved, mainly concerning the calcination step involved in sol-gel synthesis, which led to the formation of Mn 2 O 3 that worsened the catalytic behaviour.

The worldwide rise in biodiesel production has generated an excess of glycerol, a byproduct of the process. One of the most interesting alternative uses of glycerol is the production of solketal, a bioadditive that can improve the properties of both diesel and gasoline fuels. Even with its promising future, not much research has been performed on its toxicity in aqueous environments. In this work, solketal adsorption has been tested with two different commercial adsorbents: an activated carbon (Hydrodarco 3000) and a metal-organic framework (MIL-53). Diclofenac and caffeine were also chosen as emerging contaminants for comparison purposes. The effect of various parameters, such as the adsorbent mass or initial concentration of pollutants, has been studied. Adsorption kinetics with a better fit to a pseudo-second-order model, intraparticle diffusion, and effective diffusion coefficient were studied as well. Various isotherm equation models were employed to study the equilibrium process. The results obtained indicate that activated carbon is more effective in removing solketal from aqueous solutions than the metal-organic framework.

The use of biofuels offers advantages over existing fuels because they come from renewable sources, they are biodegradable, their storage and transport are safer, and their emissions into the atmosphere are lower. Biomass is one of the most promising sustainable energy sources with a wide variety of organic materials as raw material. Chemical, biochemical, and thermochemical methods have been proposed to obtain biofuels from raw materials from biomass. In recent years, a thermochemical method that has generated great interest is hydrothermal liquefaction. In this paper, a brief review of the main sources for liquid biofuels and the synthesis processes is presented, with special emphasis on the production of biofuels using hydrothermal liquefaction by using waste generated by human activity as raw material.

Titanium dioxide modified with Ag and Fe was synthesized using two preparation methods, characterized and applied to the photocatalytic degradation of salicylic acid in aqueous solution. The modified TiO 2 samples were prepared by the sol-gel and wet impregnation methods starting from titanium(IV) isopropoxide and using AgNO 3 and Fe(NO 3 ) 3 ·9H 2 O as precursors of the modifiers, with their content varying between 0 and 5 wt.%. Catalysts characterization was based on powder X-ray diffraction (PXRD), nitrogen physisorption at 77 K, temperature programmed reduction (H 2 -TPR), chemisorption of NH 3 at 343 K and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of salicylic acid by modified TiO 2 was investigated under ultraviolet irradiation at 298 K considering various concentrations of the catalyst, between 100 and 1000 mg catalyst /dm 3 , and of the organic molecule, between 0 and 15 mg/dm 3 . The catalysts most active in the degradation of salicylic acid were those having the highest Fe content.

Batch sorption experiments were performed to study the adsorption of six emerging pollutants from aqueous solutions using a commercial granular activated carbon as adsorbent. Caffeine, clofibric acid, diclofenac, gallic acid, ibuprofen and salicylic acid were selected as representative contaminants. The activated carbon was characterized by nitrogen adsorption at 77 K, and through the determination of point of zero charge. The effects of several operational parameters, such as pH, initial concentration of organic molecules, mass of adsorbent and contact time, on the sorption behaviour were evaluated. The contact time to attain equilibrium for maximum adsorption was found to be 40 min. The kinetic data were correlated to several adsorption models, and the adsorption mechanism found to follow pseudo-second-order and intraparticle-diffusion models with external mass transfer predominating in the first 15 min of the experiment. The equilibrium adsorption data were analysed using the Freundlich, Langmuir and Toth isotherm equation models. The similar chemical structure and molecular weight of the organic pollutants studied to make the adsorption capacity of the activated carbon used very similar for all the molecules.

The effect of high pressure on the reducibility and dispersion of oxides of Co and Fe supported on γ-Al 2 O 3 , SiO 2 , and TiO 2 has been studied. The catalysts, having a nominal metal content of 10 wt.%, were prepared by incipient wetness impregnation of previously calcined supports. After drying at 60 °C for 6 h and calcination at 500 °C for 4 h, the catalysts were reduced by hydrogen at two pressures, 1 and 25 bar. The metal reduction was studied by temperature-programmed reduction up to 750 °C at the two pressures, and the metal dispersion was measured by CO chemisorption at 25 °C, obtaining values between 1% and 8%. The physicochemical characterization of these materials was completed by means of chemical analysis, X-ray diffraction, N 2 adsorption-desorption at -196 °C and scanning electron microscopy. The high pressure lowered the reduction temperature of the metal oxides, improving their reducibility and dispersion. The metal reducibility increased from 42%, in the case of Fe/Al 2 O 3 (1 bar), to 100%, in the case of Fe/TiO 2 (25 bar).

In this study, industrial wastes, which remain after aluminum extraction from saline slags, were used as adsorbents. The aluminum saline slags were treated under reflux with 2 mol/dm 3 aqueous solutions of NaOH, H 2 SO 4 , and HCl for 2 h. After separation by filtration, aqueous solutions containing the extracted aluminum and residual wastes were obtained. The wastes were characterized by nitrogen adsorption at -196 °C, X-ray diffraction, scanning electron microscopy, and ammonia pulse chemisorption. The chemical treatment reduced the specific surface area, from 84 to 23 m 2 /g, and the pore volume, from 0.136 to 0.052 cm 3 /g, of the saline slag and increased the ammonia-adsorption capacity from 2.84 to 5.22 cm 3 /g, in the case of acid-treated solids. The materials were applied for the removal of Acid Orange 7 and Acid Blue 80 from aqueous solutions, considering both single and binary systems. The results showed interesting differences in the adsorption capacity between the samples. The saline slag treated with HCl rapidly adsorbed all of the dyes present in solution, whereas the other materials retained between 50 and 70% of the molecules present in solution. The amount of Acid Orange 7 removed by the nontreated material and by the material treated with NaOH increased in the presence of Acid Blue 80, which can be considered as a synergistic behavior. The CO 2 adsorption of the solids at several temperatures up to 200 °C was also evaluated under dry conditions. The aluminum saline slag presented an adsorption capacity higher than the rest of treated samples, a behavior that can be explained by the specific sites of adsorption and the textural properties of the solids. The isosteric heats of CO 2 adsorption, determined from the Clausius-Clapeyron equation, varied between 1.7 and 26.8 kJ/mol. The wastes should be used as adsorbents for the selective removal of organic contaminants in wastewater treatment., Competing Interests: The authors declare no competing financial interest.

This study aimed to assess the capacity of saponite modified with n-hexadecyltrimethylammonium bromide (CTAB) and/or 3-aminopropyltriethoxysilane (APTS) to adsorb and remove caffeine from aqueous solutions. Powder X-ray diffraction (PXRD) revealed increased basal spacing in the modified saponites. Small-angle X-ray scattering (SAXS) confirmed the PXRD results; it also showed how the different clay layers were stacked and provided information on the swelling of natural saponite and of the saponites functionalized with CTAB and/or APTS. Thermal analyses, infrared spectroscopy, scanning electron microscopy, element chemical analysis, and textural analyses confirmed functionalization of the natural saponite. The maximum adsorption capacity at equilibrium was 80.54 mg/g, indicating that the saponite modified with 3-aminopropyltriethoxysilane constitutes an efficient and suitable caffeine adsorbent.

The catalytic efficiency of takovite-aluminosilicate-chromium catalysts obtained by adsorption of Cr(3+) ions from aqueous solutions by a takovite-aluminosilicate nanocomposite adsorbent is reported. The adsorbent was synthesized by the coprecipitation method. The catalytic activity of the final Cr-catalysts depended on the amount of adsorbed chromium. (Z)-cyclooctene conversion up to 90% with total selectivity for the epoxide was achieved when the oxidation was carried out with hydrogen peroxide, at room temperature. After five consecutive runs, the catalysts maintained high activity, although after the sixth reuse, the epoxide yields strongly decreased to 35%. The catalysts were also efficient for cyclohexane oxidation, reaching up to 18% conversion, with cyclohexanone/cyclohexanol selectivity close to 1.2. On the whole, their use as catalysts gives a very interesting application for the solids obtained by adsorption of a contaminant cation such as Cr(3+).

The preparation, characterization, and application in oxidation reactions of new biomimetic catalysts are reported. Brazilian Sao Simao kaolinite clay has been functionalized with [meso-tetrakis(pentafluorophenyl)porphinato]iron(III), Fe(TPFPP). To obtain the functionalized clay, the natural clay was purified by dispersion-sedimentation, expanded by insertion of dimethyl sulfoxide (DMSO), and functionalized with amino groups by substitution of DMSO with ethanolamine. These previous steps allowed clay functionalization with Fe(TPFPP), leading to a layered material with a basal spacing of 10.73 A. Clay functionalization with the porphyrin was confirmed by formation of the secondary amine, as demonstrated by FTIR bands at 3500-3700 cm(-1). UV-vis spectroscopy revealed a red shift in the Soret band of the iron porphyrin in the functionalized material as compared to the parent iron porphyrin catalyst in solution, indicating Fe(III)P --> Fe(II)P reduction. The catalytic performance of the functionalized clay was evaluated in the epoxidation of cyclooctene, with complete selectivity for the epoxide (100% epoxide yield), and ketonization of cyclohexane, cyclohexanone being the major product. The novel catalyst was also evaluated in the Baeyer-Villiger (BV) oxidation of cyclohexanone, with 85% conversion of cyclohexanone in epsilon-caprolactone, with total selectivity to epsilon-caprolactone.

The aim of this work is to use magnetic measurements as a research tool in the study of possible metal-support interactions in nickel and cobalt nanoporous catalysts. Several physicochemical techniques, namely nitrogen adsorption, X-ray diffraction, temperature-programmed reduction and chemical analysis, were used to analyze the role of the preparation method and the nature of the support on the existence of such metal-support interactions and to relate them with the magnetic response of these nanoporous systems. The catalysts were prepared by incipient wetness impregnation and precipitation-deposition with two commercial oxides, gamma-Al2O3 and SiO2, as supports. The magnetic behavior of the catalysts is drastically affected by the existence of interactions between the metal and the support during the preparation procedure. The samples with weak metal-support interactions have characteristic magnetic behavior of antiferromagnetic metal oxide nanoparticles, while the ones having strong interactions display spin-glass like behavior.

The aim of this work is to study the effect of the platinum content (0-1.8 wt % Pt) on the microstructure of an alumina-pillared clay. For this purpose, the nitrogen physisorption data at -196 degrees C, the micropore size distributions of the supported platinum catalysts, and the hydrogen chemisorption results at 30 degrees C have been analyzed and compared. The preparation of the catalysts has modified the textural properties of the Al-pillared clay support, giving rise to a loss of surface area and micropore volume. After reduction at 420 degrees C, the presence of dispersed metallic platinum with mean crystallite size in the 22-55 A range has been found by hydrogen adsorption. Comparison of all results reveals that the platinum species block the micropore entrances by steric hindrance to nitrogen access as the platinum content increases.

A new method for the characterization of the pore size distribution of microporous solids is applied on data obtained for activated carbon molecular sieve samples. In this method, based on the Dubinin-Astakhov equation, a simple numerical algorithm is used for the reconstruction of the micropore size distribution from the integral equation that represents the experimental nitrogen adsorption isotherm. The results are compared with the ones obtained on the basis of the well-known Horvath-Kawazoe method. The samples used in this study come from a carbon molecular sieve that has been treated with solutions of concentrated HNO3 at various temperatures and with solutions of H2O2 of various concentrations.