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•Sepiolite and palygorskite have been evaluated for their potential for CO2 capture.•Sepiolite and palygorskite were modified by microwave-assisted acid treatment and impregnated with ...amines.•Raw sepiolite hashigh potential in CO2 capture at 25 °C than palygorskite due to the lower microporosity of the later.•The double functionalization of sepiolite with APTES-PEI led to the highest CO2 adsorption capacity.
Two fibrous clay minerals (sepiolite and palygorskite) have been employed as adsorbents to assess their adsorption capacity of pure CO2 in a volumetric setup. The raw sepiolite reached a CO2 uptake of 1.48 mmol g−1 due to the presence of nanocavities acting as a molecular sieve. Both sepiolite and palygorskite were modified by microwave-assisted acid treatment, which led to an increase in specific surface area and pore volume due to Mg2+ leaching, particularly in the case of sepiolite. However, the partial digestion of these fibrous structures does not improve CO2 adsorption uptake due to the progressive increase of the size of nanocavities. In a next step, both fibrous clay minerals were functionalized with amine species by different procedures (grafting with (3-Aminopropyl) triethoxysilane (APTES), impregnation with polyethyleneimine (PEI) and double functionalization by grafting with APTES and then impregnation with PEI. In all cases, it can be observed that the incorporation of amine species favors the chemical interaction between the amines species and the CO2 molecules, although it also produces obstruction of the nanochannels so the adsorption takes place mainly on the outer surface of the fibers. Finally, the incorporation of amine species by double functionalization led to the highest CO2 adsorbed concentration of 2.07 mmol g−1 at 760 mm Hg and 65 °C due to a larger proportion of available amines sites as well as the use of higher adsorption temperature, which favored the diffusion of CO2 molecules within the adsorbent.
Fluorescent water soluble carbon nanoparticles, in short carbon dots (CDs), was synthesized from lactose by microwave assisted hydrochloric acid method. Characterized by TEM and DLS to obtain the ...morphology shape (average 10nm in size), with a higher negative surface charge supported by the composition was obtained by XPS spectroscopy. The maximum of the emission was centered at 450nm with a lifetime of 2.1ns. Without further functionalization of the CDs a nanosensor was obtained that responded exponentially to HAAs in the 0.35–0.45mgL−1 concentration range by fluorescence static quenching, demonstrated by the lifetime analysis of the CDs in presence of HAAs. Some amino compounds were selected as model for interferences to evaluate the selectivity of this method, showing a notorious added value, with recoveries around 98%. The accuracy of the method was in terms of RSD about 2.5%. The results suggest their promising applications in chemical sensing.
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•Novel synthesis of fluorescent CDs from MW assisted HCl treatment.•CDs has been characterized and analyzed by DLS, XPS and fluorescence techniques.•The quenching caused by HAAs proposed analytical method.•The static mechanism was demonstrated by fluorescence lifetime analysis.•The wide range of interferences studied make suitable for sensor.
Highly luminescent nanoparticles based in Silicon quantum dots, coated by hydroxyl PAMAM dendrimer (PAMAM-OH) of 5th generation, were obtained by one step process by hydrothermal treatment of ...3-Aminopropyl)triethoxysilane (APTES) in aqueous solution. Previous to the optimization of the synthesis procedure, different dendritic molecules of 5th generation were tested to obtain the most intense fluorescence signal. The influence of different parameters such ratio APTES/PAMAM-OH, pH and ionic strength on the fluorescence intensity was studied. The fluorescence spectra showed maximum excitation and emission wavelengths at 370 and 446nm, respectively. The obtained silicon nanoparticles (SiQDs@PAMAM-OH) were characterized by TEM, DLS and XPS, and were found to detect selectively Cr(VI) in aqueous solutions at 2.7μM level of detection, sensitivity of 0.2μM with a RSD of 0.16% (n=10). To study the feasibility of the proposed system for Cr(VI) detection, it was tested in real electrochemical solution bath and a tanning effluent obtained from electrochemical industry and with two certified waters, demonstrating promising outcomes as nano-sensor.
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•Novel synthesis of fluorescent SiQDs@PAMAM-OH from APTES assisted by hydrothermal treatment.•SiQDs-PAMAM-OH has been characterized and analyzed by DLS, XPS and fluorescence techniques.•The quenching caused by Cr(VI) proposed analytical method.•The static mechanism was demonstrated by fluorescence lifetime analysis.•The wide range of interferences studied make suitable for sensor.
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•High selectivity to ethylene is obtained on both Ti- or Nb-promoted NiO catalysts (ca. 90 wt% NiO).•High selectivity is also attained over TiO2-supported NiO (ca. 20 wt% NiO).•Low ...selectivity is observed when working with Nb2O5-supported NiO.•The elimination of electrophilic oxygen species stands as the key factor to improve the catalytic performance.
Ti- and Nb- containing NiO catalysts have been synthesized by two different preparation methods: i) by precipitation (Me-Ni-O oxides, Me = Nb or Ti), in order to prepare promoted NiO catalysts; and ii) by wet impregnation on TiO2 or NbOx supports, in order to prepare diluted/supported NiO catalysts. The catalysts have been also characterized and tested in the oxidative dehydrogenation of ethane. The catalytic performance of Ti- and Nb-promoted catalysts strongly depends on the composition, although in both cases the optimal one is found at similar Ti or Nb loadings (ca. 90 wt% NiO), showing similar ethylene selectivity in the ODH of ethane (ca. 90% at 10–20% ethane conversion). However, in the case of diluted catalysts, the catalytic behavior of Ti- and Nb-containing catalysts is drastically different. Then, over TiO2-diluted NiO catalyst, the highest selectivity to ethylene (ca. 90% selectivity) is achieved at NiO loading of 20 wt.%. However, over Nb2O5-diluted NiO catalyst, selectivity to ethylene was lower than 70%. A discussion on the characteristics of selective catalysts is done. In this case, the best catalysts must present a low concentration of free NiO and TiO2 or Nb2O5 phases, maximizing the Ni-O-Ti or Ni-O-Nb interaction. Interestingly, this takes place at different NiO loading depending on the preparation method and the nature of promoted/diluter. The low selectivity to ethylene achieved by NiO diluted with Nb2O5 has been related to the low interaction of NiO with the surface of Nb2O5, which hinders the elimination of unselective electrophilic O species.
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•Porous Clays Heterostructures (PCH) favours dispersion of iron species.•Fe/PCH presents high activity in toluene oxidation and in H2S conversion.•Fe/PCH higher activity than pure ...Fe2O3 and Fe/silica.•High selectivity to S in the H2S oxidation and good stability.
Porous Clays Heterostructures (PCH) from natural pillared clays (bentonite with a high proportion of montmorillonite) have been used as supports of iron oxide for two reactions of environmental interest: i) the elimination of toluene (a representative compound of one of the most toxic subsets of volatile organic compounds, aromatics) by total oxidation and ii) the selective oxidation of H2S to elemental sulfur. For both reactions these catalysts have resulted to be remarkably more efficient than similar catalysts prepared using conventional silica as a support. Thus, in the total oxidation of toluene it has been observed that the catalytic activity obtained using siliceous PCH is two orders of magnitude higher than that with conventional silica. The catalytic activity has shown to be dependant of the capacity of the support for dispersing iron oxide in a way that the higher the dispersion of iron oxide on the surface of the support, the higher is the activity. In the case of the selective oxidation of H2S to S both higher catalytic activity and higher selectivity to S have been observed using siliceous porous clays heterostructures than using conventional silica. Highly dispersed FeOx species have been shown as highly selective towards elemental sulfur whereas more aggregated FeOx species favour the formation of sulphur oxides decreasing the selectivity to S. Analyses of the surface by XPS have shown the predominance of sulfate species in the catalysts presenting low selectivity to elemental sulfur.
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•Ni2P catalyst is much more active than CoP one for Cl-removal.•Benzene is the main reaction product for Ni2P catalyst.•The activity followed the order ...ClB>1,4-DClB≈1,2,4-TClB>1,3-DClB>1,2-DClB for Ni2P.•The activity followed the order ClB>1,4-DClB>1,3-DClB>1,2-DClB>2,4-TClB for CoP.•Active phase dispersion, P-concentration on the surface and H-species on the surface explain the results.
Ni2P and CoP catalysts (5wt.% of metal) supported on a commercial SiO2 were tested in the gas phase catalytic hydrodechlorination (HDCl) of mono (chlorobenzene-ClB) and polychlorobenzenes (PCBs) (1,2- dichlorobenzene (1,2-DClB), 1,3-dichlorobenzene (1,3-DClB), 1,4-dichlorobenzene (1,4-DClB), and 1,2,4-trichlorobenzene (1,2,4-TClB)) at atmospheric pressure. It was investigated how the number and position of chlorine atoms in the molecule influence the HDCl activity. The prepared catalysts were characterized by X-ray diffraction (XRD), CO chemisorption, N2 adsorption–desorption at −196°C, and X-ray photoelectron spectroscopy (XPS). Characterization results indicated better active phase dispersion and greater amount of P on the Ni2P catalyst surface. Catalytic results showed that the Ni2P was more active and stable in this type of reactions. The hydrodechlorination activity decreased by increasing the number of chlorine atoms in the molecule and chlorine substituents in close proximity. The observed trend in the HDCl activity was: ClB>1,4-DClB>1,3-DClB>1,2-DClB>1,2,4-TClB. The exception was the catalytic response after 24h on stream observed for the Ni2P in the HDCl reaction of 1,2,4-TClB, which was equal to that observed for the 1,4-DClB molecule, and also yielding benzene as the main reaction product.
This paper presents the catalytic activity of ruthenium phosphides supported on SBA-15 material as hydrodesulfurization (HDS) catalysts of gasoline model compounds. It was studied the influence of ...the P/Ru molar ratio of 0.5, 1, 2, 3, and 4.5 (samples were labeled as 0.5-P/Ru, 1-P/Ru, 2-P/Ru, 3-P/Ru and 4.5-P/Ru) in the hydrodesulfurization of 3-methyl-thiophene as a model molecule and evaluated under mild reaction conditions. The ruthenium phosphide phase was synthesized from a conventional phosphate reduction method using RuCl3 and (NH4)2HPO4 as precursors. The catalysts were characterized by XRPD, N2 adsorption–desorption isotherms, TEM, EDS, XPS, NH3-TPD, H2-TPD and CO chemisorption. All catalysts maintained the mesoporous structure characteristic of the SBA-15 support, although pore blockage occurred at high P loadings. TEM images and EDS mapping showed well dispersed active phosphide phases, mainly RuP and Ru2P, as evidenced by XRPD. 3-P/Ru catalyst became to be the most active in the HDS reaction, with a high isomerization ability, which was assigned to its medium acidity and higher amount of active species on the surface that activates H2 species.
•The ruthenium phosphide catalysts are effective for the HDS for selective sulfur removal of gasoline model compounds.•The phosphorus load leads the formation of Ru2P active phase, optimizing a P/Ru molar ratio of 3.•The ruthenium phosphide catalysts displayed medium acidity properties that led to a high isomerization ability.
The substantial sludge, composed of organic compounds, was detected in sediments samples of Anzali wetland. Photocatalysts have a great potential for decomposing organic compounds. In the present ...research, an attempt was made to decompose the sludge of Anzali wetland using titanium dioxide nanoparticles (TiO
2
NPs). For this purpose, Luzchem’s CCP-4 V photoreactor, which is equipped with 12 UV lamps, was used. The influences of UV intensity, TiO
2
concentration and exposure time were investigated for the removal of sludge. The statistically analysis showed that exposure time was the most effective factor in removal of sludge. The results also revealed that 10-µg/L TiO
2
after long-term exposure (5 days) would decompose about 37% of organic contents of sludge. Further detailed studies revealed that due to the decomposition of organics, about 2100, 1700, 1650, 270 and 181 µg/L of Sr, Mn, Si, Al and P would be released into the water column, respectively.
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