Correlation between eletrokinetic mobility and ionic dyes adsorption of Moroccan stevensite

This study aims at establishing a correlation between the electrical charge of Moroccan stevensite particles and ionic dyes adsorption. The electrophoretic mobility, (Ue), of the stevensite particles in water, was measured at pH 2.5–12 by microelectrophoresis. At pH between 2.5 and 8, Ue remained constant (Ue = − 1.6 10− 8 m2/(V s)), as resulting from the permanent charge of the clay mineral planar surfaces. At pH > 8, the magnitude of electrophoretic mobility increased (Ue = − 2.7 10− 8 m2/(V s)) due to the deprotonation of silanol groups on the surfaces. The anionic Orange G adsorption at the clay mineral–water interface was negligible whereas the methylene blue cations were strongly adsorbed due to the electrostatic attraction

Synthesis, characterization and photocatalytic activity of TiO2 supported natural palygorskite microfibers

This study deals with the synthesis of TiO2 supported Moroccan palygorskite fibers and their use as photocatalyst for the removal of Orange G pollutant from wastewater. The TiO2-palygorskite nanocomposite synthesis was accomplished according to a colloidal route involving a cationic surfactant as template (hexadecyltrimethylammonium bromide) assuring hence organophilic environment for the formation of TiO2 nanoparticles. The clay minerals samples were characterized before and after functionalization with TiO2. Anatase crystallizes above ca. 450 °C and remarkably remains stable up to 900 °C. In contrast, pure TiO2 xerogel obtained from titanium tetraisopropoxide (TTIP) showed before calcination a nanocrystalline structure of anatase. By increasing the temperature, anatase readily transforms into rutile beyond 600 °C. The remarkable stability at high temperature of anatase particles immobilized onto palygorskite microfibers was due to the hindrance of particles growth by sintering. Homogeneous monodisperse distribution of anatase particles with an average size of 8 nm was found by TEM and XRD onto palygorskite fibers. This anatase particle size remains below the nucleus critical size (ca. 11 nm) required for anatase–rutile transition. The TiO2 supported palygorskite sample annealed in air at 600 °C for 1 h exhibits the highest photocatalytic activity towards the degradation of Orange G compared to nanocomposite samples prepared under different conditions as well as pure TiO2 powders obtained from the xerogel route or commercially available as Degussa P25

Electrokinetic and ionic dyes adsorption studies of Moroccan stevensite Jbel Rhassoul clay

This study aims at establishing correlation between the nature of electrical charge of morocan stevensite Jbel Rhassoul clay particles and ionic dyes adsorption phenomenon. The electrical charges of the clay mineral particles were assessed by measuring zeta potential (z) using micro electrophoresis technique. Measurements were carried out onto aqueous clay dispersions by varying the pH in the range 2.5 – 12 with additions of HCl or NaOH. On the whole, the electrical charges of stevensite particles remain negative in the whole pH range. Nevertheless, depending on the pH values, two behaviours were observed. For pH ranging from 2 to around 8, the negative electrical charge remains constant (z = - 20 mV) and corresponds to permanent charges of basal surfaces formed of –O-Si-O- groups insensitive to pH variation. Beyond pH = 8, the electrical charge increases (z = - 35 mV) as a result of deprotonation of silanol edge groups. Ionic dyes adsorption experiments show that anionic orange G adsorption is negligible whereas that of cationic methylene blue is greater due to columbic interactions. In accordance with eletrokinetic measurements, the methylene blue adsorption capacity onto stevensite particles significantly increases beyond pH » 8 due to the increase of the whole electrical charge of stevensite particles evolved by silanol edge sites deprotonation

A Denotational Interprocedural Program Slicer

This paper extends a previously developed intraprocedural denotational program slicer to handle procedures. Using the denotational approach, slices can be defined in terms of the abstract syntax of the object language without the need of a control flow graph or similar intermediate structure. The algorithm presented here is capable of correctly handling the interplay between function and procedure calls, side-effects, and short-circuit expression evaluation. The ability to deal with these features is required in reverse engineering of legacy systems, where code often contains side-effects

Synthèse, caractérisations et tests photocatalytiques d’un matériau argileux d’origine naturelle à base de beidellite fonctionnalisée par TiO2

Cette étude porte sur la fonctionnalisation par TiO2 d’une argile marocaine de type beidellite et sur l’évaluation de son activité photocatalytique pour l’élimination d’un colorant anionique : l’orange G (OG), utilisé dans l’industrie textile. Les échantillons argileux ont été caractérisés, avant et après fonctionnalisation, par DRX, MEB et MET couplé à l’analyse EDX, TG-ATD, FTIR, ICP et RMN du solide. La beidellite est aluminifère, dioctaédrique, de formule chimique (Si7,57Al0,43)8 (Al2,75Fe0,73Mg0,38Ti0,14)4 (Na0,37K0,23Mg0,01) avec une CEC, une surface spécifique et un volume poreux total de l’ordre de 48 méq/100 g, 72 m2/g et 0,128 cm3/g respectivement. Les matériaux argileux nanocomposites obtenus sont constitués de nanoparticules de TiO2 (taille moyenne 10 nm) supportées par les feuillets de la beidellite. Leurs surfaces spécifiques sont quasiment du même ordre de grandeur que celle de la beidellite tandis que leurs volumes poreux augmentent pour atteindre 0,226 cm3/g. L’échantillon calciné à 600 ◦C, dans lequel TiO2 est sous forme d’anatase, manifeste une activité photocatalytique remarquable vis-à-vis de l’élimination de l’OG en milieu aqueux

Flaws linked to lime in pottery of Marrakech (Morocco)

The studied clayey materials come from soil of Marrakech Haouz Plain. We discussed the influence of grain size, mineralogical and chemical composition of these raw materials on the lime behaviour in pottery shards. In this paper we propose some recommendations to inhibit lime blowing and the efflorescences responsible for flaws. The application of such recommendations will improve the quality of produced pottery and the income of potters in the region.Peer reviewe

Mineralogical and Physico-Chemical Characterizations of Ferruginous Beidellite-Rich Clay from Agadir Basin (Morocco)

The mechanism of formation of detrital, beidellite-rich clay occurring in the Agadir basin (Morocco) is well documented, but its detailed characterization is incomplete which limits its application. The aim of the present study was to provide further details of the mineralogical and physico-chemical characteristics of this clay. Bulk raw clay and its Na+-saturated, <2 mm fraction were characterized using chemical, structural, and thermal techniques. Measurements of induced streaming potential (e.g. particle charge) and of specific surface area and porous volume are reported. The raw clay contained carbonate and quartz as associated minerals along with phyllosilicates (<2 mm particle size). X-ray diffraction and scanning electron microscopy analyses showed that the <2 mm fraction was dominated by a dioctahedral smectite. Because dehydroxylation of this mineral occurred at 510ºC, and because it re-expanded in ethylene glycol after Li+-saturation followed by heating at 240ºC for 24 h, the mineral was shown to be a beidellite rather than montmorillonite. This assertion was further supported by 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectra showing predominantly negative charges in the tetrahedral sheets due to notable Al-for-Si substitutions. The chemical composition of the <2 mm fraction showed an Fe2O3 content which was ~7.52 wt.% greater than those of other beidellite occurrences but not so much that it would be identified as a nontronite. The absence of stretching and bending absorption bands corresponding to characteristic (Fe2OH) units in mid-infrared spectra and their corresponding fundamental overtones or combination bands in near-infrared spectra supported this notion. The structural formula of the beidellite in the present study was determined to be (Si7.51Al0.49)(Al2.99Fe0.68Mg0.33) (Ca0.03Na0.54Mg0.11)O20(OH)4, having dioctahedral ferruginous characteristics with almost 60% of the negative charge found in tetrahedral sheets. The cation exchange capacity determined from the structural formula was ~108 meq/100 g. The specific surface area and total pore volume were ~82.2 m2/g and 0.136 cm3/g, respectively. Interestingly, a detrital rather than a hydrothermal-alteration origin, as reported for other beidellite occurrences, explains its natural abundance and emphasizes the great interest in it

Comprehensive physicochemical study of dioctahedral palygorskite-rich clay from Marrakech High Atlas (Morocco)

This study is devoted to the physicochemical and mineralogical characterizations of palygorskite from Marrakech High Atlas, Morocco. The raw clay and its Na?-saturated\ 2 lm fraction were characterized using chemical, structural, and thermal analytical techniques. Measurements of specific surface area and porous volume are reported. The clay fraction was found to be made up of 95 %of palygorskite and 5 % of sepiolite. An original feature of this palygorskite is its deficiency in zeolitic H2O. The half-cell structural formula of its dehydrated form was determined on the basis of 21 oxygens to be (Si7.92Al0.08)(Mg2.15Al1.4Fe0.4Ti0.05h1)(Ca0.03 Na0.08K0.04)O21, while the hydrated form could be formulated as (Si7.97Al0.03)(Mg2.17Al1.46Fe0.40Ti0.05)(Ca0.03Na0.07K0,03) O20.18(OH)1.94(OH2)3.8812.43H2O. These formulas showthat the (Al3??Fe3?)/Mg2? ratio is around 0.84, revealing a pronounced dioctahedral character. Further, inside its octahedral sheet, it was determined that the inner M1 sites are occupied by vacancies, whereas the M2 sites are shared between 90 % of trivalent cations (78 % for Al3? and 22 % for Fe3?), 7.5 % of Mg2+, and 2.5 % of Ti4+, all of them linked to 1.94 of structural hydroxyls. The two remaining Mg2+ by half-cell occupy edge M3 sites and are coordinated to 3.88 molecules of OH2. Channels of this palygorskite are deficient in zeolitic H2O since they contain only 2.43 H2O molecules.A correlation was found between these results and the observation of very intense and well-resolved FTIR bands arising from dioctahedral domains (mainly Al2OH, Fe2OH, and AlFeOH) along with very small responses from a trioctahedral domain (Mg3OH). Accordingly, a schematic representation of the composition of the octahedral sheet was proposed. The cation exchange capacity, specific surface area, and total pore volume were also assessed to be ca. 21.2 meq/100 g, 116 m2/g, and 0.458 cm3/g, respectively

Comment la composition chimique peut influencer la couleur des roches magmatiques et sédimentaires: Cas des roches du Haut Atlas de Maroc

peer reviewedIn spite of color being one of the physicochemical parameters most commonly used to characterize a rock, very limited studies have studied the correlation between the nature, chemical composition, and color of a rock. This study presents a new approach for quantitatively assessing the relationship between these three parameters for specific rocks (example of igneous and sedimentary rocks) collected from the High Atlas of Morocco. A spectrophotometer was used to measure the color of samples, and the measurements were expressed in CIE L*a*b* color system units then converted to Hex color codes. Whereas, the chemical composition of samples was carried out by X-ray fluorescence. The most abundant oxides in magmatic rock samples are SiO2, Al2O3, Fe2O3, MgO, and CaO, while K2O, Na2O, TiO2, and P2O5 are generally found in trace concentrations. Two categories of clays were studied, non-calcareous raw materials without carbonate contents ( 10%). Phosphate samples are rich in phosphorus (4.4%-17.5%) and CaO (11.2%-42.7%) with relatively low contents of SiO2 (28.5%-52.2%), Al2O3 (3.1%-17.5%), and Fe2O3 (1.1%-6.6%). Results show that the change in the content of these elements from one rock type to another may be indicative of rocks with particular characteristics that do have an impact on color. The main coloration agent of clays was iron, Fe2+, and Fe3+ ions can color clay minerals either red or green or in various shades of orange and brown. However, in marls and phosphates, the high concentration of carbonates inhibits this iron effect by affecting a* (red) and b* (yellow) color parameters, which leads to grayish materials. The same applies to magmatic rocks rich in Fe2O3 and CaO