María A. Villa-García

Physico-chemical characterization of steel slag. Study of its behavior under simulated environmental conditions.

The chemical and mineralogical composition of steel slag produced in two ArcelorMittal steel plants located in the North of Spain, as well as the study of the influence of simulated environmental conditions on the properties of the slag stored in disposal areas, was carried out by elemental chemical analysis, XRF, X-ray diffraction, thermal analysis, and scanning electron microscopy with EDS analyzer. Spectroscopic characterization of the slag was also performed by using FTIR spectroscopy. Due to the potential uses of the slag as low cost adsorbent for water treatment and pollutants removal, its detailed textural characterization was carried out by nitrogen adsorption-desorption at 77 K and mercury intrusion porosimetry. The results show that the slag is a crystalline heterogeneous material whose main components are iron oxides, calcium (magnesium) compounds (hydroxide, oxide, silicates, and carbonate), elemental iron, and quartz. The slags are porous materials with specific surface area of 11 m(2)g(-1), containing both mesopores and macropores. Slag exposure to simulated environmental conditions lead to the formation of carbonate phases. Carbonation reduces the leaching of alkaline earth elements as well as the release of the harmful trace elements Cr (VI) and V. Steel slags with high contents of portlandite and calcium silicates are potential raw materials for CO(2) long-term storage.

Synthesis and characterization of a novel layered titanium phosphate

A novel metastable layered titanium phosphate has been synthesized by the treatment of layered titanates (Na 2 Ti 3 O 7 and Na 4 Ti 9 O 2 0) with 1–2 M phosphoric acid solution at 120–150 °C. Based on the data of 31 P MAS NMR and IR spectroscopy, x-ray powder diffraction, and thermal and elemental analysis, the formula Ti 2 O 3 (H 2 PO 4 ) 2 · 2H 2 O was assigned to the novel compound. The layered nature of the compound was confirmed from n -alkylamine intercalation and the ion exchange behavior toward alkali, alkaline earth, and some transition metal ions.

Effect of the method of preparation on the surface area and porosity of titanium(IV) phenylphosphonate

By using three synthetic procedures we have prepared layered α-titanium phenylphosphonate samples with different degrees of crystallinity and distinct textural parameters. The solids were prepared by reacting phenylphosphonic acid with different titanium compounds used as precursors. The materials obtained have a high thermal stability as shown by TGA measurements.An analysis of nitrogen adsorption-desorption isotherms on the resulting materials allowed determination of the corresponding specific surface area and porous texture. The N2-isotherms correspond to type IV of the BDDT classification with hysteresis loops of the type H-1. The materials are essentially mesoporous and it was not detected any mensurable microporosity. Crystallinity, BET surface areas and porosity are markedly dependent on the preparation procedure.

Influence of the amination conditions on the textural properties and chromatographic behaviour of amino-functionalized glycidyl methacrylate-based particulate supports

Abstract Amino-functionalization of particulate macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate), obtained by “bulk” polymerization of a novel mixture of monomers, was carried out by reaction with concentrated ammonia, diethylamine (DEA) and the mixture DEA/THF (1:1). The influence of the amination conditions on the polymer mechanical and thermal stability, porous structure and degree of amination was analyzed; it was also found a narrow correlation between these properties and the chromatographic behaviour of the supports. The polymers functionalized with ammonia and DEA/THF were used for hen egg white proteins separation in column packed experiments; both resins carried out the separation of a mixture of lysozyme, ovalbumin and trypsin inhibitor. The DEA/THF functionalized resin showed better performance for egg white protein separation and very good retention capacity (38 mg ovalbumin/ml resin).

Functionalized glycidyl methacrylate based polymers as stationary phases for protein retention

The search for new materials for chromatographic separation of proteins is a major endeavor nowadays. In order to obtain better chromatographic separation media, poli(glycidyl methacrylate co-ethylen dimethacrylate) matrices were synthesized, milled, classified, functionalized with different reagents and then comparatively tested in batch experiments for protein retention. The Methacrylate/Dimethacrylate resin was treated in different sequences of experiments with Urea, Iminodiacetic acid, N-N dimethyl formamide and ammonia, in order to determine whether functionalization provides sufficient amino groups to capacitate them for protein retention. Fixed bed experiments with particulate resin were also carried out. Previous characterization confirms that the polymeric matrix is macroporous and exhibits a unimodal pore size distribution. The resin also presents a good thermal stability.

Textural properties of α-titanium(IV) phenylphosphonate: influence of preparation conditions

Abstract Layered α-titanium(IV) phenylphosphonate can be prepared with a broad variation in surface area and porosity. Several sources for tetravalent titanium ion and different synthetic procedures have been studied. The solids were characterized by powder X-ray diffraction (XRD), thermogravimetric (TG) analysis, IR and 31 P magic angle spinning (MAS) NMR spectroscopies, N 2 adsorption–desorption isotherms, and scanning electron microscopy (SEM). The materials obtained have a high thermal stability as shown by TG analysis. N 2 adsorption–desorption isotherms of the solids correspond to type IV of the BDDT classification and show hysteresis loops of type H-3, characteristic of solids with slit-shaped pores. The materials are essentially mesoporous, and any mensurable microporosity was not detected. BET surface areas, porosity, and crystallinity are markedly dependent on the preparation procedure.

Synthesis and reactivity of dithiodiphenylphosphinato-derivatives of rhodium. Crystal structure of the square-pyramidal rhodium(III) complex [RhI(η2-S2PPh2)(COMe)(PPh3)]

Abstract The complexes [Rh 2 (μ-Cl) 2 L 4 ] (L 2 = 1,5-cyclooctadiene (COD); L  CO) react with Na[S 2 PPh 2 ] to give the mononuclear derivatives [Rh(S 2 PPh 2 )L 2 ] (L 2  COD, 1 ; L  CO, 2 ). Treatment of complex 2 with PPh 3 affords [Rh(S 2 PPh 2 )(CO)(PPh 3 )]( 3 ). Complex 3 reacts with iodine to give a mixture of two isomers of [RhI 2 (S 2 PPh 2 )(CO)(PPh 3 )] ( 4 ). A similar reaction of 3 with methyl iodide gives the pentacoordinate rhodium(III) acyl derivative [RhI(S 2 PPh 2 ) (COMe)(PPh 3 )] ( 5 ), which has a square-pyramidal geometry with the acyl group in the apical position, as determined by X-ray diffraction. The cationic nitrosyl derivative [Rh(S 2 PPh 2 )(NO)(PPh 3 )]BF 4 ( 6 ) has been prepared by reaction of complex 3 with NOBF 4 . Neither complex 1 nor complex 3 is a catalyst precursor for the homogeneous hydrogenation of alkenes and alkynes.

Synthesis of the Ion-Exchanger Based on 2-(diethylamino)ethyl Methacrylate-co-Ethyleneglycol Dimethacrylate Beads: Physico-Chemical Characterization and Chromatographic Performance for Sulfonamide Adsorption

Sulfonamide antibiotics are persistent pollutants of aquatic environments, known to induce high levels of bacterial resistance and potential human health and ecological risks. We synthesized copolymeric beads of 2-(diethylamino)ethyl methacrylate-co-ethyleneglycol dimethacrylate (DEAEM-co-EGDMA) and further conducted batch and column-packed experiments to systematically examine their adsorption properties toward sulfamethoxazole, the sulfonamide most frequently detected in municipal sewage. The polymeric beads were obtained by suspension polymerization of a monomer mixture consisting of 40% DEAEM and 60% EGDMA dissolved in acetonitrile (ACN). Polyvinylpyrrolidone (PVP) was used as stabilizer of the suspension system. Cyclohexanol and poly(ethylene glycol) (PEG) of 1 kDa were used as porogens. Physical characterization showed that the polymers consist of macroporous micro spheres exhibiting a unimodal particle size distribution and good thermal stability. The copolymer showed very good retention capacity, 101 mg SMX/g wet resin, which is equivalent to 220 mg SMX/g dry resin. The Langmuir model described the successful SMX removal. Equilibrium and kinetic parameters were determined using the pore diffusion model. Several cycles of loading and elution were performed in a fixed bed column. Total SMX recovery was achieved in all elution cycles. The resin showed good performance to concentrate the antibiotic in the initial stages of elution, thus facilitating the removal of this compound.

Characterization of sinter flue dust to enhance alternative recycling and environmental impact at disposal

Dust emission is one of the main environmental pollution impacts associated with steelmaking. In this sense, electrostatic precipitators (ESP) are regarded as the best available technique for treating this type of emission, thus generating two differentiated fractions: coarse and fine. Thorough chemical and structural characterization of both materials was carried out to recycle these byproducts in either the sintering process or other steps of pig iron production. Both types of dusts are crystalline heterogeneous materials mainly composed of sepiolite (Mg8Si12(OH)2·12H2O), hematite (Fe2O3) and calcite (CaCO3), the coarse fraction containing low amounts of Na (0.38 ± 0.04%) and K (0.17 ± 0.02%), which adversely affect blast furnace operation. Hence, the coarse fraction is suitable for recycling, whereas the fine one presents higher concentrations of these alkali elements. Besides, textural characterization revealed that dust particulates are essentially macroporous materials, with specific surface area values of 21.6 m2/g for the coarse fraction and 33.7 m2/g for dust fines. In order to ensure inoffensive dumpsites, the environmental behavior associated with dust particles accumulated in disposal areas was also evaluated by performing leaching studies simulating different rainfall scenarios. It was found that the specific leaching rates of Ca, Mg, K and S varied between 0.072 ± 0.001 and 0.75 ± 0.01 µgelement/(gdust·d), whereas slower leaching rates were obtained for heavy metals (Fe, Mn and Cu), the values ranging from (1.20 ± 0.1) × 10-4 to (1.8 ± 0.1) × 10-3 µgelement/(gdust·d). These low rates indicate that the leaching of sinter dusts compounds has minimal environmental impact.

STEPWISE INTERCALATION OF PIPERIDINE IN LAYERED ALPHA - AND GAMMA - HAFNIUM PHOSPHATE

The mechanism of intercalation of piperidine in α-hafnium phosphate, Hf(HPO4;V) 2H2O (dooz = 7.6 [Adot]) and γ-hafnium phosphate, Hf(P04)(H2P04) 2H20 (doo2 - 12.1 [Adot]), has been investigated by ...