Sonication induced redox reactions of the Ojén (Andalucía, Spain) vermiculite (original) (raw)
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Ultrasonics Sonochemistry, 2014
This paper describes the effect of temperature, time, solvent and sonication conditions under air and Argon for the preparation of micron and sub-micron sized vermiculite particles in a Rosetttype reactor. The resulting material were characterized via X-ray powder diffraction (XRDP), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) Spectroscopy, BET surface area Analysis, chemical analysis (elemental analysis), thermal analysis (TGA) and Laser Granulometry. The sonicated vermiculites displayed modified particle morphologies and reduced sizes (observed by scanning electron microscopy and laser granulometry). Under the conditions used in this work, sub-micron sized particles were obtained after 5 h of sonication, whereas longer times promoted aggregation. Laser granulometry data revealed also that the smallest particles were obtained at high temperature while it is generally accepted that the mechanical effects of ultrasound are optimum at low temperatures. X-ray diffraction results indicated a reduction of the crystallite size along the basal direction (001); but structural changes were not observed. Sonication at different conditions also leads to the surface modification of the vermiculite particles brought out by BET surface measurements and Infrared Spectroscopy. The results indicate clearly that the efficiency of ultrasound irradiation was significantly affected by different parameters such as temperature, solvent, type of gas and reactor type.
Effect of sonication on the particle size of montmorillonite clays
Journal of Colloid and Interface Science, 2008
This paper reports on the effect of sonication on SAz-1 and SWy-1 montmorillonite suspensions. Changes in the size of the particles of these materials and modifications of their properties have been investigated. The variation of the particle size has been analyzed by DLS (dynamic light scattering). In all cases the clay particles show a bimodal distribution. Sonication resulted in a decrease of the larger modal diameter, as well as a reduction of its volume percentage. Simultaneously, the proportion of the smallest particles increases. After 60 min of sonication, SAz-1 presented a very broad particle size distribution with a modal diameter of 283 nm. On the other hand, the SWy-1 sonicated for 60 min presents a bimodal distribution of particles at 140 and 454 nm. Changes in the properties of the clay suspensions due to sonication were evaluated spectroscopically from dye-clay interactions, using Methylene Blue. The acidic sites present in the interlamellar region, which are responsible for dye protonation, disappeared after sonication of the clay. The changes in the size of the scattering particles and the lack of acidic sites after sonication suggest that sonication induces delamination of the clay particles.
How does sonication affect the mineral and organic constituents of soil aggregates?—A review
Application of ultrasound to disperse soil aggregates has been critical in enabling researchers to separate and analyze aggregate building blocks that include organic and mineral particles as well as mineral associated organic matter. But the forces generated in the process may also alter the dispersion products and, thus, potentially interfere with the interpretation of experimental results. This review summarizes present knowledge on experimental conditions that may lead to physical damage and chemical modifications of aggregate building blocks. The energy level at which physical disintegration of organic particles could be detected was as low as 60 J mL -1 . Physical damage of sand-and silt-sized mineral particles was observed to commence at energy levels exceeding 700 J cm -3 . No evidence was found for the disintegration of particles within the clay-size fraction of soils even though studies analyzing pure minerals such as kaolinite revealed particle breakage after application of energy amounts > 12,000 J cm -3 . Here we outline a strategy to minimize artifacts such as physical damage of mineral or organic particles resulting from ultrasonication by adopting a stepwise dispersion protocol involving successively higher energy levels, accompanied by a sequential separation of organic and mineral compounds. Sonification effects on soil aggregate constituents 489 Ahmed, M., Oades, J. (1984): Distribution of organic matter and adenosine triphosphate after fractionation of soils by physical procedures. Soil Biol. Biochem. 16, 465-470. Asano, M., Wagai, R. (2014): Evidence of aggregate hierarchy at micro-to submicron scales in an allophanic Andisol. Geoderma 216, 62-74. Amelung, W., Zech, W. (1999): Minimisation of organic matter disruption during particle-size fractionation of grassland epipedons. Geoderma 92, 73-85. Baisden, W. T., Amundson, R., Cook, A. C., Brenner, D. L. (2002): The turnover and storage of C and N in five density fractions from California annual grassland surface soil. Glob. Biogeochem. Cycles 16, 1117-1132. Balesdent, J., Petraud, J.-P., Feller, C. (1991): Effets des ultrasons sur la distribution granulométrique des matières organiques des sols. Sci. Sol. 29, 95-106. Balesdent, J. (1996): The significance of organic separates to carbon dynamics and its modelling in some cultivated soils. Eur. J. Soil Sci. 47, 485-493. Beckett, M. A., Hua, I. (2001): Impact of ultrasonic frequency on aqueous sonoluminescence and sonochemistry. J. Phys. Chem. A 105, 3796-3802. Bird, J. A., Kleber, M., Torn, M. S. (2008): 13 C and 15 N stabilization dynamics in soil organic matter fractions during needle and fine root decomposition. Org. Geochem. 39, 465-477. Brotchie, A., Statham, T., Zhou, M., Dharmarathne, L., Grieser, F., Ashokkumar, M. (2010): Acoustic bubble sizes, coalescence, and sonochemical activity in aqueous electrolyte solutions saturated with different gases. Langmuir 26, 12690-12695.
Effect of ultrasound on the fine fraction in aqueous medium of Mn-oxide ore
The fine fraction (< 2 mm) of the high grade Mn-ore from the world class Moanda deposit, Francevillan basin, in Gabon, contains up to 30 wt. % of manganese and about 0.4 wt. % phosphorous. A pilot study at laboratory scale integrating mineralogy and geochemistry before and after ultrasonic treatment was conducted on the fine fraction (< 2 mm) of oxidized Mn ore in order to reduce the phosphorous content and enrich this fraction in manganese. The fine fraction was dried, crushed at 2 cm and sieved at 2 mm. The two fractions (< 2 mm and 2 mm -2 cm) were investigated by X-ray diffraction and scanning electron microprobeelectron dispersive spectroscopy analyses. Both fractions contain lithiophorite, cryptomelane and pyrolusite as Mn carrier, and goethite, muscovite, illite and quartz as contaminants. The Mn hydroxide nsutite was only found in the fraction 2mm -2 cm.The < 2 mm fraction is significantly richer in goethite, muscovite/illite, and quartz. Phosphorous carriers are mainly goethite (up to 2.8 wt. % P 2 O 5 ), while the Mn minerals contain up to 0.8 wt. % P 2 O 5 . The Mn minerals are partly included in an agglomerate of goethite, muscovite/illite, and quartz. The < 2 mm fraction was treated by ultrasound for 30 s in normal water. Mineralogical and chemical analyses after ultrasound treatment showed that the Mn-minerals were largely liberated from the goethite-muscoviteillite agglomerate. Mass balance calculations show that after ultrasonic treatment the < 2 mm fraction was ≈ 50 % enriched in Mn and ≈50 % impoverished in P.
Aerosol Science and Technology, 2014
In aerosol research, a common approach for the collection of particulate matter (PM) is the use of filters in order to obtain sufficient material to undertake analysis. For subsequent chemical and toxicological analyses, in most cases the PM needs to be extracted from the filters. Sonication is commonly used to most efficiently extract the PM from the filters. Extraction protocols generally involve 10-60 min of sonication. The energy of ultrasonic waves causes the formation and collapse of cavitation bubbles in the solution. Inside the collapsing cavities the localized temperatures and pressures can reach extraordinary values. Although fleeting, such conditions can lead to pyrolysis of the molecules present inside the cavitation bubbles (gases dissolved in the liquid and solvent vapors), which results in the production of free radicals and the generation of new compounds formed by reactions with these free radicals. For example, simple sonication of pure water will result in the formation of detectable levels of hydroxyl radicals. As hydroxyl radicals are recognized as playing key roles as oxidants in the atmosphere the extraction of PM from filters using sonication is therefore problematic. Sonication can result in significant chemical and physical changes to PM through thermal degradation and other reactions. In this article, an overview of sonication technique as used in aerosol research is provided, the capacity for radical generation under these conditions is described and an analysis is given of the impact of sonicationderived free radicals on three molecular probes commonly used by researchers in this field to detect reactive oxygen species (ROS) in PM.
Influence of ultrasound on nanostructural iron formed by electrochemical reduction
Ultrasonics Sonochemistry, 2004
A method for control of particle dimensions of nanostructural amorphous iron powder obtained by electrochemical reduction under the effect of ultrasonic oscillations in reaction medium is described in this paper. Depending on the character of ultrasonic oscillations nanostructural powders were obtained differing both in average dimension and distribution of particle dimensions. In the case of simultaneous sonocation using ultrasonic vibrations with frequencies differing from each other by a factor of ten (20 and 200 kHz), the effect is complex, but includes narrowing of the average particle dimension.
Réactivité de surface des minéraux mous à l'échelle atomique
2019
Identifying reaction mechanisms of minerals is fundamental to understand diagenesis, i.e, sedimentary rock formation, construction material, like cement or gypsum, hardening, and biomineralization. The macroscopic reaction rates of minerals are generally deduced from solution chemistry measurements. Beside the measurement of macroscopic reaction rates, the study of the reactivity of minerals includes now the investigation of the atomic mechanisms involved in the reactions. This has been made possible for two decades by the use of tools resolving nanometric objects, such as vertical scanning interferometry (VSI) and atomic force microscopy (AFM). Gypsum and calcite are among soft minerals. They are extremely widespread mineral that can be found naturally in sedimentary rocks. They are also used in many industrial fields. Gypsum (CaSO4,2H2O) is an evaporate mineral. Gypsum uses include: manufacture of wallboards, plaster of Paris, soil conditioning, and hardening retarder in Portland ...
Characterization of Particles from Ferrate Pre-oxidation
Environmental Science & Technology, 2015
Studies were conducted evaluating the nature of particles that result from ferrate reduction in a laboratory water matrix and in a natural surface water with a moderate amount of dissolved organic carbon. Particle characterization included size, surface charge, morphology, X-ray photoelectron spectroscopy, and transmission Fourier transform infrared spectroscopy. Characteristics of ferrate resultant particles were compared to particles formed from dosing ferric chloride, a common water treatment coagulant. In natural water, ferrate addition produced significantly more nanoparticles than ferric addition. These particles had a negative surface charge, resulting in a stable colloidal suspension. In natural and laboratory matrix waters, the ferrate resultant particles had a similar charge versus pH relationship as particles resulting from ferric addition. Particles resulting from ferrate had morphology that differed from particles resulting from ferric iron, with ferrate resultant particles appearing smoother and more granular. X-ray photoelectron spectroscopy results show ferrate resultant particles contained Fe 2 O 3 , while ferric resultant particles did not. Results also indicate potential differences in the mechanisms leading to particle formation between ferrate reduction and ferric hydrolysis.