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Sepiyolite Aromatik (BDMHDA-Cl) ve Alifatik (HDTMA-Cl) Amin Adsorpsiyonu Adsorption of Aromatic (BDMHDA-Cl) and Aliphatic (HDTMA-Cl) Amine by Sepiolite
Abstract
zet Bu çalışmada, sulu ortamda aromatik ve alifatik amin türlerinden benzildimetilhegzadesil amonyum-klorür (BDMHDA-Cl) ve hegzadesiltrimetilamonyum-klorürün (HDTMA-Cl) sepiyolite adsorpsiyonu araştırılmıştır. Sepiyolite amin adsorpsiyonu volumetrik ve UV-spektrofotometrik analizleri ile belirlenmiştir. BDMHDA'nın sepiyolite olan afinitesinin (ilgi) HDTMA'ya nazaran daha yüksek olduğu belirlenmiştir. BDMHDA-sepiyolit ve HDTMA-sepiyolit sistemlerinde amin adsorpsiyonunun doğal pH'da, artan ortam sıcaklığına bağlı olarak tedricen azaldığı belirlenmiştir. Abstract It is therefore the objective of this study to investigate the adsorption of aromatic and aliphatic amines like benzyl dimethyl hexadecylammonium chloride (BDMHDA-Cl) and hexadecyl trimethylammonum chloride (HDTMA-Cl) from aqueous solutions on to sepiolite. Adsorption of amines is determined by volumetric and UV-Spectrophotometric methods on sepiolite. It was determined that the affinity of BDMHDA on the sepiolite is higher than the HDTMA. In the BDMHDA and HDTMA/sepiyolite systems, gradually decreasing of amine adsorption with the increased environmental temperature at the naturel pH was determined. © Afyon Kocatepe Üniversitesi
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Sepiolite, a magnesium hydrosilicate, is natural clay mineral which belongs to a group of layered silicates. It is used in numerous areas due to its high surface area, fibrous structure, porosity, crystal morphology and composition, surface activity, production of stable suspensions of high viscosity at low concentrations. These properties provide the basis for a variety of catalytical, sorptive and rheological application. In this study, various features of sepiolite such a its national and world-wide reserves and production figures, crystal structure, mineralogical, physical, physicochemical and rheological properties are presented along with detailed information on its diverse uses.
A B S T R A C T: The effects of dry grinding on the structure of sepiolite were studied by XRD, surface area measurement, TG-DTA and IR spectroscopy techniques. The results show that the sepiolite framework is rather resistant to mechanical stress and its alteration by dry grinding occurs through three successive, overlapping processes: (i) thinning of the fibrous particles without structural alteration; (ii) distortion of the parallel units of sepiolite fibres, affecting essentially the particle surface which transforms into an amorphous protective coating; (iii) disruption of the inner structure and a prototropy effect, producing an amorphous phase with some residual order. The effect of grinding on clay minerals is a subject of great interest because it is a very common process in industry and research. The objective of a grinding treatment is usually reduction in size, increase in surface area, or surface activation of the particles. However, a mechanical process frequently produces other physical and chemical changes which should be known. These processes have been widely studied on layer-silicates such as kaolinite and chrysotile (Miller & Oulton, 1970, 1972; Yariv, 1975; Papirer & Roland, 1981) and micas and montmorillonite (Mingelgrin et al., 1978; Henmi & Yoshinaga, 1981 ; Cicel & Kranz, 1981). These studies show that grinding of phyllosilicates causes structural degradation through a delamination mechanism, and, in some instances, a prototropy effect (Miller & Oulton, 1979; Cicel & Kranz, 1981). However, very little is known about the effects of dry grinding on sepiolite which may behave differently upon grinding because of its fibrous structure. The objective of this study was to describe the mechanism of structural changes induced during comminution of sepiolite, by means of X-ray powder diffraction (XRD), surface area measurements, TG-DTA, and IR spectroscopy techniques.
Dry grinding of pyrophyllite (Hillsboro, USA) has been studied by X-ray diffraction (XRD), specific surface area measurements (BET) and scanning electron microscopy (SEM). At the beginning of the grinding process, some effects such as delamination, gliding and folding of the layers, and decrease in particle size were detected by SEM and XRD, resulting in a large increase in specific surface area, up to a maximum of ~ 60 m 2 . g-1. Marked changes in the structure take place between 30 and 32 mins grinding. Longer grinding times increase the degree of disorder and SEM and specific surface area data suggest that aggregation occurs. XRD results indicate that some residual order persists in the degraded structure.
A B S T R A C T: A sepiolite from Vallecas (Spain) was treated with solutions of HCI (1.25, 2.5, 5.0, 10.0 and 20.0 wt%) at 25~ for 2, 6, 24 and 48 h, respectively. The resulting solids were characterized by XRD, FT-IR and thermal analyses, along with SEM, TEM and nitrogen adsorption isotherms at 77 K. The free silica was digested and determined in all samples. Several samples were seen to have specific surface areas up to 450 m2/g, with a maximum value of 549 m2/g in the sample treated with 1.25 wt% HCI for 48 h. A sudden decrease in specific surface areas was observed when free silica was digested.
Anionic surfactants constitute the main ingredients of detergents and a number of surfactant formulations used in a spectrum of diverse industries. The aim of this study is to examine the amenability of natural sepiolite to the adsorption of anionic surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS). Adsorption isotherms exhibit three regions with distinctly different slopes. The first region is characterized by the complexation of anionic surfactants with Mg2+ ions at the octahedral sheet or hydrogen bonding between the oxygen groups of anionic head groups of surfactant and H+ of the bound or zeolitic water. The Mg2+ ions released from sepiolite leads to the precipitation of magnesium salt of surfactant in the second region. The third region marks both the beginning of plateau region and micellar dissolution of the precipitate. The effect of temperature on surfactant adsorption for SDS/sepiolite system was utilized to calculate such thermodynamic parameters as the free energy of adsorption (DeltaG(ads)(degrees)) and the heat of adsorption (DeltaH(ads)(degrees)). The low value of DeltaH(ads)(degrees) (1.87 kJ/mol) is an evidence for the physical adsorption of anionic surfactants onto sepiolite. The relatively large value of entropic contribution (-TDeltaS(ads)(degrees)) indicates that the adsorption of anionic surfactants onto sepiolite is entropically governed.
A series of adsorption tests examined the uptake of typical quaternary cationic surfactants, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide from water by a clay mineral, sepiolite. Adsorption tests conducted under different conditions revealed that sepiolite is highly receptive to adsorption of cationic surfactants. Adsorption of cationic surfactants on sepiolite exhibits two distinct regions. The first stage is characterized by low rate and is governed through an ion-exchange process between ammonium ions and magnesium ions in the octahedral sheet. The second stage is ascribed to a combination of chain–chain interactions through van der Waals forces and ion-exchange process. The incorporation of surfactant ion is elaborated on the basis of experimental data and thermodynamic equations.
Systematic adsorption tests were carried out to determine the uptake of typical quaternary amines, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide and a primary amine, dodecylamine hydrochloride by sepiolite. Bottle adsorption tests conducted with untreated, acid- and heat-activated sepiolites exhibit two distinct regions. The first stage is characterized by low rate and governed through an ion exchange process between ammonium ions and magnesium ions in the octahedral sheet. The second stage is ascribed to a combination of chain-chain interactions through Van der Waals forces and ion exchange process. Despite several-fold increases in surface areas upon activation, surprisingly no improvement in adsorption is observed. The observed differences are explained on the basis of partial collapse of the sepiolite crystal structure, the removal of zeolitic and bound waters and modification of the pore size distribution of sepiolite upon treatments.
Çeşitli amin türleri kullanılarak sepiyolitin adsorpsiyon mekanizmasının açıklanması, Doktora Tezi, Eskişehir Osmangazi Üniversitesi Fen Bilimleri Enstitüsü
- E Sabah
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adsorpsiyon mekanizmasının açıklanması, Doktora
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Enstitüsü, Eskişehir, 245.
Acid activasion of a Spanish sepiolite, physicochemical charakterization, free silica content and surface area of the solids obtained
- V M A Rodriguez
- L J D Gonzales
- B M A Munoz
Rodriguez, V.M.A., Gonzales, L.J.D. and Munoz, B.M.A.,
1994. Acid activasion of a Spanish sepiolite,
physicochemical charakterization, free silica content
and surface area of the solids obtained. Clay Minerals,
29, 361-367.