Distribution of naturally occurring radionuclides (U, Th) in Timahdit black shale (Morocco)

Attention has been focused recently on the use of Moroccan black oil shale as the raw material for production of a new type of adsorbent and its application to U and Th removal from contaminated wastewaters. The purpose of the present work is to provide a better understanding of the composition and structure of this shale and to determine its natural content in uranium and thorium. A black shale collected from Timahdit (Morocco) was analyzed by powder X-ray diffraction and SEM techniques. It was found that calcite, dolomite, quartz and clays constitute the main composition of the inorganic matrix. Pyrite crystals are also present. A selective leaching procedure, followed by radiochemical purification and α-counting, was performed to assess the distribution of naturally occurring radionuclides. Leaching results indicate that 238U, 235U, 234U, 232Th, 230Th and 228Th have multiple modes of occurrence in the shale. U is interpreted to have been concentrated under anaerobic conditions. An integrated isotopic approach showed the preferential mobilization of uranium carried by humic acids to carbonate and apatite phases. Th is partitioned between silicate minerals and pyrite

Preparation and characterization of a composite material based on a geopolymer binder and quartzite aggregates

We have developed a geopolymer material by alkaline reaction on thermally activated kaolin. Initially we characterized the geopolymer by different methods (rheology, DTA-TGA, etc.) and we mixed it with different amounts of natural sand to obtain a granular composite. The structural characterization of this material was undertaken by several techniques (XRF, XRD and microscopic observations). A rheological study was implemented to determine the influence of the aggregate rate on the setting kinetic. Three-point bending and compression tests were conducted for mechanical characterization. We also conducted microindentation tests to study the influence of quartzite rate on the hardness of the material. The results indicate that the integration of quartzite (up to 15 wt. %) did not alter the setting kinetic. We noted a small degradation of the mechanical behavior when the quartzite rate is increased; this effect is due to a higher density of microcracks. However, adding the aggregate has a beneficial effect on the hardness of the material. These attractive features make this material a plausible matrix whose reinforcement with plant fibers will provide a ternary composite suitable for multiple applications

Effects of Phenol Addition on Oil Extraction from Moroccan Oil Shale by Supercritical Toluene

In the present work, the effect of phenol on the supercritical extraction of the organic matter from Tarfaya's oil shale with toluene was evaluated. The experimental results showed clearly that phenol had a significant effect on the yield and the composition of the oils obtained. Moreover, it was shown that phenol was a very efficient modifier for oil shale, giving a good yield of recovery and a suitable maturation of the organic matter. The pitches prepared by mixing phenol and toluene contain more aromatics and have a high char yield at 950 °C compared to those obtained by extraction with supercritical toluene alone

Comparison of chemical and physical activation processes at obtaining adsorbents from moroccan oil shale

Within the Moroccan natural resources valorisation scheme, new adsorbents have been prepared from oil shale by chemical and physical activation processes. The activation process the authors have developed in this study give effective adsorbent materials. In view of the physico-chemical properties of these materials and application to the treatment of water loaded with a metal (Cr6+ ion) or organic (methylene blue (MB)) pollutant, it is concluded that the chemical activation process of oil shale at low temperature (250 °C) affords the best material. The material’s yield is good in comparison with the physical activation at the same temperature and the process is energy saving differently from that at 450 °C. Moreover, the chemical activation of oil shale with phosphoric acid at 250 °C produces a material with a good yield (about 70%), a high specific surface area (approximately 600 m2 /g) and a highly porous structure, which gives it a high retention of methylene blue and the Cr6+ ion

Elaboration and characterization of a new activated carbon obtained from oregano residue: Application in environmental field

This study focuses on the valorization of extraction residues of medicinal plants which represent approximately 80% of the gross weight of the plant. In this context we proceeded to the transformation of “marc oregano” to a material adsorbent type activated carbon. The oregano marc, obtained after extraction of essential oils and organic compounds, has undergone a chemical activation using the phosphoric acid 85% (H3PO4). It is well known as precursors of lignocellulosic activating agent, allows the development of a large porosity in the activated material. The activated product has subsequently underwent heat treatment in the temperature range from 200 to 350 °C. The optimum temperature for development was set at 300 °C. The results obtained showed that the adsorbent material O300 has developed the interesting textural properties. It is an adsorbent material like activated carbon, which presents, according to the BET method, a specific surface of 1200 m2·g−1 (specific surface area of commercial activated carbon is of about 905 m2·g−1). The application of adsorbent material developed O300 in microbial decontamination of urban waste water, has revealed its effectiveness and its important adsorptive properties against pathogens pollutants from wastewater

Oxidative conversion of lignin over cobalt-iron mixed oxides prepared via the alginate gelation

The depolymerization of polymer lignin model to low molecular weight products was studied in water, at 200 °C under 100 MPa of 10% O2 using cobalt-iron mixed oxides as catalysts. These nanostructured oxides with different Co/Fe ratios were prepared via alginate gelation. X-ray diffraction, scanning electron microscope, and size exclusion chromatography were used to study the influence of the Fe/Co ratios on the structure and the proprieties of the oxides as well as the morphology, the structure, and the composition of the obtained degraded products. The results showed that the oxides used in this study were versatile catalysts with a high catalytic activity for lignin depolymerization. Furthermore, these oxides demonstrated high yield and high selectivity towards aromatic compounds

Punica granatum leave extract as green corrosion inhibitor for mild steel in Hydrochloric acid

Leave of Punica granatum extract (LPGE) as green inhibitor for the corrosion of mild steel in 1M HCl solution was studied using weight-loss and potentiodynamic polarization measurements. The results obtained revealed that LPGE has fairly good inhibiting properties for mild steel corrosion in 1M HCl solution, with efficiency of around 94 % at a concentration of 1 g/l. The inhibition was of a mixed anodic–cathodic nature. The film which is formed over the metal surface was analysed by FT-IR spectroscopy. Further examination using X-ray diffraction confirms the role of LPGE as an effective corrosion inhibitor for mild steel in acid media

Properties of metakaolin based geopolymer incorporating calcium carbonate

International audienceAn alkaline solution, thermally activated kaolinite clay and a mineral additive (calcium carbonate) were mixed with the aim to elaborate a geopolymer material with physical and mechanical properties comparable to those of classical construction materials. The starting reagents were characterized by quantitative chemical analyses (XRF), mineralogical analyses (XRD), thermal gravimetric analyses (TGA), and grain size distribution measurements. The setting of the mixture (polymerization) was implemented by measuring the evolution of the viscosity as a function of time at different temperatures. The geopolymers were synthesized at a temperature of 40 degrees C. The investigation of the mechanical behavior reveals that these materials display acceptable characteristics the flexural and compression strength are around 4.6 and 26 MPa respectively, for an added calcium carbonate over dry matter ration up to 12% by weight. The promising results exposed in this paper show that the geopolymer formulations can be adapted for applications in construction and civil engineering structures as an alternative to conventional materials. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

Properties of metakaolin based geopolymer incorporating calcium carbonate

International audienceAn alkaline solution, thermally activated kaolinite clay and a mineral additive (calcium carbonate) were mixed with the aim to elaborate a geopolymer material with physical and mechanical properties comparable to those of classical construction materials. The starting reagents were characterized by quantitative chemical analyses (XRF), mineralogical analyses (XRD), thermal gravimetric analyses (TGA), and grain size distribution measurements. The setting of the mixture (polymerization) was implemented by measuring the evolution of the viscosity as a function of time at different temperatures. The geopolymers were synthesized at a temperature of 40 degrees C. The investigation of the mechanical behavior reveals that these materials display acceptable characteristics the flexural and compression strength are around 4.6 and 26 MPa respectively, for an added calcium carbonate over dry matter ration up to 12% by weight. The promising results exposed in this paper show that the geopolymer formulations can be adapted for applications in construction and civil engineering structures as an alternative to conventional materials. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved