Search

In this study, we report the adsorption process of Congo Red (CR) dye by calcined Layered Double Hydroxide (ZAC) at 550°C. The urea hydrolysis method was applied to produce highly crystalline Zn2Al-LDH. Samples characterisation was carried out by X-ray diffraction (XRD), Thermogravimetric/differential thermal analysis (TG/DTA), and Fourier transform infrared spectroscopy (FTIR). The results show that the adsorption of CR on calcined ZnAl-LDH was accompanied by the reconstruction of the layered structure. The ZAC showed higher adsorption efficiency versus other adsorbent under investigation and optimum conditions of contact time, adsorbent dose, pH and temperature were found to be 50 min, 0.02 g, 7 and 318 K, respectively. Isotherm studies show that the Langmuir isotherm model was appropriate to describe the CR adsorption data compared with Freundlich and Temkin isotherm models, with a higher correlation coefficient (R2 > 0.99) and maximum adsorption capacity of 406.5 mg/g. The thermodynamic parameters revealed that the adsorption process was spontaneous, endothermic, and governed by chemisorption. To further facilitate the recovery process in CR adsorption, we test the feasibility of applying ZnAl-LDH and its calcined product at 550°C entrapped in alginate beads. Experimental results indicate that alginate-coated ZAC beads, which exhibited remarkable adsorption performance, were more stable and require less effort to pull and separate than the alginate/ZnAl-LDH composite beads.

Bioactive powders of the binary SiO2-CaO, ternary SiO2-CaO-P2O5 and quaternary systems SiO2-CaO-P2O5-Na2O/Mg2O were synthesized using a sol-gel route. The gels were converted into bioglasses powders by heat treatments at the temperature of 700°C. The resulting materials were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Environmental Scanning Electron Microscopy (ESEM) and in vitro bioactivity in acellular Simulated Body Fluid (SBF). The in vitro tests showed that the samples had good apatite-forming ability. Glasses doped with sodium and magnesium show good results in terms of bioactivity and mechanical properties. The results showed that the quaternary glass SiO2-CaO-P2O5-Na2O containing Na is the most bioactive, only 6 hours after its immersion in SBF; a layer of hydroxycarbonated apatite (HAC) was deposited on the glass and compressive strength of up to 233.08 MPa with a porosity of 11.02%, due to the presence of the Na2Ca2Si3O9 phase. Magnesium also affects bioactivity because it has improved from binary to ternary to quaternary doped with magnesium, bioactive from 12h of contact with the SBF.

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides). The effect of the gelling agent, such as carboxymethylcellulose (CMC) or alginate (Alg), and the drying routes (conventional drying at room temperature, or freeze-drying) on the properties and photocatalytic performances of nanostructured TiO 2 was examined. The crystallographic structures, and textural and morphological characteristics were investigated by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive spectrometry (ESEM-FEG-EDS), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS) and N 2 adsorption/desorption isotherms. The as-synthesized samples were fully crystallized and appeared to be highly phase-pure anatase or mixed titania polymorphs, and have a quasi-spherical shape with a particle size ranging from 10.34 to 18.07 nm. Phase-pure anatase was obtained by using alginate as the gelling agent, whereas CMC's gelation promotes mixed structures. The presence of rutile phase results in a lower bandgap value of 3.04 eV corresponding to 408 nm. Thus, the material absorption wavelength shifts slightly from the UV (190-380 nm) to visible region (380-750 nm). The drying process also affects TiO 2 properties. The lyophilization route improves the oxide's specific surface area, and also its photocatalytic properties verified during Orange G dye photodegradation study.

Cordierite based membranes were elaborated from a naturally Moroccan clay (Ghassoul) and algae as porosity agent (10 wt%). Specimens devoid of algae were also manufactured and used as reference samples (B1 & B2). To obtain the stoichiometry of cordierite, alumina and silica gel were added to the employed clay. After calcination at 600 °C, the mixture was heat treated according to two different thermal cycles. The first one consisted of a single thermal treatment at 1250 °C after the addition of the algae (BAL1). As for the second, two heat treatments were carried out at 1250 °C separated by the addition of the algae BAL2. Several techniques were used to characterize the cordierite membrane performances such as X-ray diffraction, thermal analysis, scanning electron microscope, Fourier-transform infrared spectroscopy and microscope impedance spectroscopy. Porosity and filtration suitability were assessed and correlated to the morphology. It has been proved that stevensite, dolomite and quartz were involved in the neoformation process and melt respectively. SEM examinations showed different features that exhibited different sized pores alongside with some melted zones. Algae addition contributed to the formation of pores in algae containing samples compared to the reference specimens. At room temperature, filtration tests were performed using textile effluent in order to reduce the turbidity, BOD and the chemical oxygen demand. The results showed that their percentages decreased by more than 60% after filtration. In addition, dielectric measurements revealed that the sintering process was effective beyond 1000 °C and it was accompanied with a low activation energy. Manufactured ceramic membranes are expected to have challenge application in the treatment of wastewater.

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides). The effect of the gelling agent, such as carboxymethylcellulose (CMC) or alginate (Alg), and the drying routes (conventional drying at room temperature, or freeze-drying) on the properties and photocatalytic performances of nanostructured TiO

This paper provides an efficient alternative way to conserve natural clays and to reduce both fired bricks costs production and wastes amounts generation. It aims to substitute natural clay by treated calamine processing wastes (TCPMT) to manufacture value added fired bricks. Different mixes containing up to 40% of TCPMT were pressed, dried and fired at various temperatures: 900, 950, 1000 and 1050 °C. The fired bricks were characterized for their physical, mechanical, mineralogical, microstructural, environmental and durability properties. The results show that the increase of temperature allows the enhancement of mechanical strength, the reduction of water absorption due to the decrease of accessible pores amount and the enhancement of potential contaminants immobilization. The mechanical strength of bricks decreases with the addition of TCPMT due to the increased formation of pores and the apparition of some coarse grains which are considered as regions of weakness of the studied bricks. The leaching behavior of reference and selected optimum bricks, assessed according to a tank leaching test, shows that almost toxic elements; Pb, Zn, As, Cr, Mo, Ba, Cd and Cu are immobilized in the sintered bricks. Finally, the experimental approach outcomes show the possibility to produce bricks containing up to 30 wt% of TCPMT with the required engineering and environmental properties when fired at 1050 °C.

International audience; Cordierite ceramic membranes were manufactured from natural clay, oxides and organic wastes as pore forming agents. Mixtures aforementioned materials with the pore-forming agents (up to 10 wt.%) were investigated in the range 1000-1200 degrees C using thermal analysis, X-ray diffraction, scanning electron microscopy, mercury porosimetry and filtration tests. Physical properties (density, water absorption and bending strength) were correlated to the processing factors (pore-forming agent addition, firing temperature and soaking time). The results showed that cordierite together with spinel, diopside and clinoenstatite neoformed. SEM analysis revealed heterogeneous aspects. The results of the response surface methodology showed that the variations of physical properties versus processing parameters were well described by the used polynomial model. The addition of pore forming agent and temperature were the most influential factors. Filtration tests were performed on the best performing sample. The results allowed to testify that these membranes could be used in waste water treatment. (C) 2017 The Ceramic Society of Japan and the Korean Ceramic Society. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

Ceramic membrane filters based on industrial by-products can be considered to be a valorization alternative of phosphate mine tailings, even more so if these ceramic membranes are used in the industrial wastewater treatment due to their good mechanical, chemical, and thermal resistance. The depollution of textile industry rejections with this method has not been studied in detail previously. In this work, ceramic membrane filters have been manufactured from natural clay and phosphate mine tailings (phosphate sludge). Blends of the abovementioned materials with a pore-forming agent (sawdust, up to 20 wt. %) were investigated in the range 900&ndash, 1100 &deg, C using thermal analysis, X-ray diffraction, scanning electron microscopy, and mercury porosimetry. Ceramic properties were measured as a function of firing temperature and sawdust addition. Filtration tests were carried out on samples with advantageous properties. The results showed that gehlenite together with diopside neoformed from lime decomposed carbonates and breakdown products of clay minerals, while calcium phosphate derived from partial decomposition of fluorapatite. Both quartz and fluorapatite resisted heating. The results of the experimental design showed that the variations of physical properties versus processing factors were well described by the polynomial model. Filtration results are quite interesting, allowing these membranes to be used in industrial effluent treatment.

International audience; In this work, the tribological behaviour of selective laser melting (SLM) processed hypereutectic Al-Si alloy is investigated by the ball on disc test with focus on the effect of silicon content (18 and 50 wt %). Different from the conventional casted sample, the SLM processed sample shows an ultra-fine microstructure with silicon size inferior to 5 μm. Indeed, the SLM processed hypereutectic Al-Si alloy illustrates a pseudo-eutectic microstructure consisted by supersaturated Al(Si) and primary silicon. Both the SLM processed Al-18Si and Al-50Si presents low wear rate about of 7.0 and 8.1◊10−4 mm3/(N◊m) respectively. Moreover, the wear mechanisms of conventional casted and SLM processed hypereutectic Al-Si alloys are compared and discussed.

In sedimentary phosphates mining operations, clayey layers are removed as mine wastes. The main objective of this paper was to investigate the feasibility to valorize these mine wastes as Lightweight aggregates (LWAs) by mixing them with organic wastes (sawdust and coffee grounds) which act as pore-forming agents. Thermal transformations and microstructural changes during heating were investigated using X-ray diffraction, thermal analysis, scanning electron microscope and Fourier-transform infrared spectroscopy. The bulk density, compressive strength and water absorption of LWAs were also determined. Neoformed mineral phases was characterized and correlated to the LWA microstructure. The results demonstrated that original aluminosilicated minerals, dolomite and part of quartz were involved in the mineralization process and melt abundance respectively. SEM observations displayed a tangled microstructure that results from merged particles and different pores sizes. The addition of pore-forming agent to clays waste enhanced the macro-pore formation process in comparison to the reference samples. LWAs with good performances (density 0.8–0.95 g/cm3 and compressive strength ∼77 MPa) were successfully manufactured by mixing 25 wt% of coffee grounds or sawdusts with clayey phosphate waste.

High amounts of mine wastes are continuously produced by the mining industry all over the world. Recycling possibility of some wastes in fired brick making has been investigated and showed promising results. However, little attention is given to the leaching behavior of mine wastes based fired bricks. The objective of this paper is to evaluate the geochemical behavior of fired bricks containing different types of coal wastes. The leachates were analyzed for their concentration of As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn and sulfates using different leaching tests; namely Tank Leaching tests (NEN 7375), Toxicity Characteristic Leaching Procedure (TCLP) and pH dependence test (EPA, 1313). The results showed that the release of constituents of potential interest was highly reduced after thermal treatment and were immobilized within the glassy matrix of the fired bricks. Moreover, it was also highlighted that the final pH of all fired samples changed and stabilized around 8-8.5 when the initial pH of leaching solution was in the range 2.5-11.5. The release of heavy metals and metalloids (As) tended to decrease with the increase of pH from acidic to alkaline solutions while Mo displayed a different trend.

International audience; Blends of a naturally occurring clay (0-30 wt.%) and phosphate sludge were heated at different temperatures and times and their microstructures were investigated using impedance spectroscopy, dilatometry, X-ray diffraction and scanning electron microscope. The weights of the effects of the change of temperature, soaking time and clay addition on some physical ceramic properties (shrinkage, water absorption and compressive strength) were assessed. For the latter purpose, the response surface methodology was used. The results showed that the sintering process was effective between 750 and 1000 degrees C and occurred by melt flow. It was accompanied with low activation energy for ionic conduction (0.20-0.35 eV). Due to the quantitative formation of gehlenite (the unique neoformed phase), the ionic conduction regressed and the melt formation was limited. Also, it was shown that the effects of the experimental factors on physical properties of the blends were well described with the adopted polynomial models, and the weights of the effects of the factors followed the order: temperature > clay content > soaking time. The effects of the interactions between the factors on the properties studied were evaluated and discussed in relation to the microstructure change. (C) 2015 The Ceramic Society of Japan and the Korean Ceramic Society. Production and hosting by Elsevier B.V. All rights reserved.

Ni0.5TiOPO4 oxyphosphate exhibits good electrochemical properties as an anode material in lithium ion batteries but suffers from its low conductivity. We present here the electrochemical performances of the synthesized Ni0.5TiOPO4/carbon composite by using sucrose as the carbon source. X-ray diffraction study confirms that this phosphate crystallizes in the monoclinic system (S.G. P21/c). The use of the Ni0.5TiOPO4/C composite in lithium batteries shows enhanced electrochemical performances compared with the uncoated material. Capacities up to 200 mAh g−1 could be reached during cycling of this electrode. Furthermore, an acceptable rate capability was obtained with very low capacity fading even at 0.5C rate. Nevertheless, a considerable irreversible capacity was evidenced during the first discharge. In situ synchrotron X-ray radiation was utilized to study the structural change during the first discharge in order to evidence the origin of this irreversible capacity. Lithium insertion during the first discharge induces an amorphization of the crystal structure of the parent material accompanied by an irreversible formation of a new phase.

In this work, we present the synthesis and the characterization of ionic conducting ceramics of NaSICON-type (Natrium super ionic conductor). The properties of this ceramic make it suitable for use in electrochemical devices. These solid electrolytes can be used as sensors for application in the manufacturing of potentiometric gas sensors, for the detection of pollutant emissions and for environment control. The family of NaSICON that we studied has as a general formula Na{sub 2.8}Zr{sub 2-y}Si{sub 1.8-4y}P{sub 1.2+4y}O{sub 12} with 0=

International audience; Microstructure of expandable lightweight aggregates (LWAs), which was composed of phosphate waste (PW), cement kiln dust (CKD) and raw clay (RC) was investigated, and the effects of processing factors (temperature, waste content, soaking time) on their physical properties were quantified by using response surface methodology (RSM). The potential use of LWAs as a phosphorus source was assessed through the use of seeds of alfalfa. It was found that the main minerals of the waste, namely carbonates and fluorapatite, were involved in the formation of labradorite/anorthite and melt respectively. Stability of mullite- the main constituent of CKD- was sensitive to the melt content. The assemblage of the identified phases was discussed based on the CaO-SiO2-Al2O3 phase diagram. The results of RSM showed that the change of compressive strength, firing shrinkage and water absorption of LWAs versus processing factors was well described with a polynomial model and the weights of the effects of the factors increased in the following order: sintering temperature > waste content (in the case of PW-RC) > soaking time. On the other hand, it was found that due to the release of phosphorus by soil-embedded pellets, the growth of alfalfa plants improved, and the rate enhanced in this order: PW-RC > PW-CKD > PW-CKD-RC. The absorbed quantity of phosphorus (0.12%) was still lower than the common uptake amount. (C) 2016 Elsevier Ltd. All rights reserved.

The effect of the composition of two steels (B and 6MnCr5) on precipitation of undesirable phases (carbides, nitrides and carbonitrides) under thermochemical treatment (low-pressure or vacuum carbonitriding) is investigated. Metallographic and x-ray diffraction studies and thermodynamic computations are performed. BMI Fours Industriels, St. Quentin Fallavier, France

BiMnO 3 synthesized at high pressure is a triclinically distorted perovskite and a ferromagnetic with T c =108 K. High-temperature X-ray diffraction analysis, thermal analysis, thermogravimetry, and magnetic measurements were used to determine stability and the melting sequence of BiMnO 3 phase in air. Structural phase transition from triclinic to tetragonal structure has been determined at 490°C in air for a polycrystalline BiMnO 3 perovskite. Two phases form immediately at the decomposition temperature of 600°C, namely Bi 2 O 3 and Bi 2 O 3 · 2Mn 2 O 3+ δ . The Bi 2 O 3 ·2Mn 2 O 3+ δ coexists with liquid up to at least 900°C.

Phosphate sludge generated from beneficiation plants of Moroccan phosphate rocks was investigated at 900–1200 °C by X-ray diffraction, scanning electron microscopy, thermal analysis and Fourier-transform infrared spectroscopy. Mixtures of the phosphate sludge and a swelling clay (up to 30 wt.%) were investigated and their properties (shrinkage, density, water absorption and compressive strength) were measured as a function of temperature and clay addition. The results showed that gehlenite neoformed from lime of decomposed carbonates and breakdown products of clay minerals and that fluorapatite (original mineral) resisted heating until fusion. The measured properties were mainly controlled by temperature, and the effect of clay addition was less regular, except for water absorption. Considering the mixtures densities (1.44–3.02 g/cm 3 ), lightweight agglomerates can be produced at 900 or 1100 °C, but their compressive strengths were relatively low (2–4.5 MPa). Based on SiO 2 –Al 2 O 3 -Fluxes diagram and taking account of the chemical composition of the materials used, the production of expanded aggregates requires clay additions as high as 80 wt.%.

not Available.

not Available.