The Removal of Zinc in an Aqueous Solution by the Phosphogypsum: Modeling and Optimizing

Background: This work is devoted to study the removal of Zn (II) by phosphogypsum which is a waste from the manufacture of phosphoric acid. Therefore we can use it in the removal of some impurities such as Zn (II). Our method is based on modeling the adsorption of Zn (II) on the phosphogypsum, by the contribution of Langmuir, Freundlich and Temkin isotherms, in the first hand. In the second hand, we are going to model and optimize with experimental design: Box-Behnken Design. The factors that affect this study are: the contact time between the adsorbate and adsorbent, the concentration of the metal ion Zn (II) and the concentration of the phosphogypsum

Modeling Soil Organic Carbon Changes under Alternative Climatic Scenarios and Soil Properties Using DNDC Model at a Semi-Arid Mediterranean Environment

Soil organic carbon (SOC) is one of the central issues in dealing with soil fertility as well as environmental and food safety. Due to the lack of relevant data sources and methodologies, analyzing SOC dynamics has been a challenge in Morocco. During the last two decades, processbased models have been adopted as alternative and powerful tools for modeling SOC dynamics; whereas, information and knowledge on the most sensitive model inputs under different climate, and soil conditions are still very limited. For this purpose, a sensitivity analysis was conducted in the present work, using the DeNitrification-DeComposition (DNDC) model based on the data collected at a semi-arid region (Merchouch station, Morocco). The objective is to identify the most influential factors affecting the DNDC-modeled SOC dynamics in a semi-arid region across different climatic and soil conditions. The results of sensitivity analysis highlighted air temperature as the main determinant of SOC. A decrease in air temperature of 4 C results in an almost 161 kg C ha?1 yr?1 increase in C sequestration rate. Initial SOC was also confirmed to be one of the most sensitive parameters for SOC. There was a 96 kg C ha?1 yr?1 increase in C sequestration rate under low initial SOC (0.005 kg C ha?1). In the DNDC, air temperature in climatic factors and initial SOC in variable soil properties had the largest impacts on SOC accumulation in Merchouch station. We can conclude that the sensitivity analysis conducted in this study within the DNDC can contribute to provide a scientific evidence of uncertainties of the selected inputs variables who can lead to uncertainties on the SOC in the study site. The information in this paper can be helpful for scientists and policy makers, who are dealing with regions of similar environmental conditions as Merchouch Station, by identifying alternative scenarios of soil carbon sequestration

Anionic templating as a versatile method to access nanostructured ionosilicas from amine and ammonium precursors

International audienceThe synthesis of new functional ionosilicas via soft templating procedures is reported. Starting from functional amine and ammonium precursors, structured materials with regular architectures on a mesoscopic length scale can be obtained only in the presence of anionic structure directing agents. This 'anionic templating route' appears as a generally applicable method to access a large variety of structured ionosilicas containing cationic groups. However, differences concerning the texture and the morphological stability of the formed materials arise from the constitution of the used silylated precursors. The as-synthesized silica hybrid/surfactant nanocomposites obtained from amine precursors often display high order but only limited morphological stability. The ordered mesostructure of the nanocomposites collapsed during surfactant elimination and low-porous and non-structured ionosilica materials were finally obtained. In contrast, the use of trisilylated quaternary ammonium precursors yielded materials displaying high porosity combined with moderate structural regularity after surfactant elimination. Finally, the formation of ionosilicas with helicoïdal morphologies was observed starting from a chiral (1R,2R)-diaminocyclohexane-precursor. All these results show that the 'anionic templating route' is a versatile strategy allowing accessing structured materials which are not accessible following classical synthetic strategies, i.e. in the presence of cationic or non-ionic structure directing agents

Synthèse et caractérisation de nanoparticules d'oxydes métalliques par voie organométallique (vers des applications biomédicales)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Silices hybrides nanostructurées par 'Liquid Crystal Templating' de précurseurs ioniques

Une série de précurseurs contenant des sous-structures organo-ioniques à base d'entités imidazolium, guanidinium, ammonium et zwitterionique ainsi que des précurseurs neutres contenant des sous-structures amido-thiol, amine-thiol et amine a été synthétisée. Ces précurseurs ont été utilisés pour la synthèse de matériaux silices hybrides nanostructurés par voie template. La formation de matériaux nanostructurés a été réalisée par des réactions d'hydrolyse-polycondensation par l'utilisation de différents agents de structuration. Ce travail avait pour but la détermination des principaux facteurs influençant la structuration des matériaux. Ainsi, nous avons préparé une série d'ionosilicates nanostructurés par une nouvelle méthode de structuration qui met en jeu des interactions spécifiques entre des paires d'ions précurseur cationique - surfactant anionique' et précurseur anionique - surfactant cationique'. Cette approche a permis d'accéder aux matériaux originaux de type PMO ionique. Finalement, nous avons utilisé pour la première fois des surfactants de guanidinium comme template' dans la synthèse des silices ioniques nanostructurées de morphologie sphérique. Les matériaux nanostructurés contenant des sous-structures amine, amine-thiol, ammonium et zwitterionique développés au cours de ce travail présentent des surfaces spécifiques élevées et une bonne accessibilité des sites organiques. Ces propriétés font de ces matériaux des systèmes de choix pour des applications en catalyse ou en séparation.A series of precursors containing organo-ionic substructures such as imidazolium, guanidinium, ammonium and zwitterionic entities and several neutral precursors containing thiol-amide, thiol-amine and amino groups were successfully synthesized. These precursors were used for the synthesis of nanostructured silica hybrid materials containing ionic substructures via soft templating approaches. The formation of structured materials was achieved using template directed hydrolysis polycondensation procedures in the presence of various structure directing agents. The goal of this study was the determination of the parameters influencing the structuring of the materials. Thus, we prepared a series of nanostructured ionosilicates using a new method of structuring that is based on specific interactions between cationic precursor - anionic surfactant' and anionic precursor - cationic surfactant' ion pairs. This new strategy allowed the synthesis of ionic 'periodic mesoporous organosilicas'. At the end of this thesis, we used a new guanidinium' type template in the preparation of nanostructured i-silica hybrid materials with a spherical morphology. Nanostructured ionosilicates bearing amine, amino-thiol, ammonium and zwitterionic substructures prepared in this work present high specific surface areas and a high accessibility of the organic functional sites. Due to these features, these materials have large potential in the fields of catalysis and separation.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Fate of isoproturon in two Moroccan soils

The study of the adsorption, desorption, degradation and stabilization of 14C-isoproturon in two clayey Moroccan soils of the Gharb area were investigated under laboratory conditions. Adsorption follows a non-linear isotherm. A strong affinity of clays to isoproturon was observed. Dehs soil affinity to isoproturon is stronger than that of the Tirs soil, with: KOC = 112.1 and 84.5, respectively. Non-extractible residues reached 36.3%, 35.4% and 32.0% of initial applied amounts in 60 days, respectively, for the Tirs soil, the Tirs soil treated with nitrogen and the Dehs soil. The pseudo half-life of isoproturon ranged from 31 to 50 days. Degradation products of isoproturon were N’-(4-isopropylphenyl)- N,N-dimethylurea and N’-[4-(2-hydroxyisopropylphenyl)]-N-methylurea, and other non-identified products

Pore size control and organocatalytic properties of nanostructured silica hybrid materials containing amino and ammonium groups

International audiencePeriodic mesoporous organosilicas containing amine and ammonium substructures were synthesized via soft templating approaches using anionic surfactants. Pore size control was achieved either using anionic surfactants containing alkyl groups of variable chain lengths or by addition of swelling agents such as mesitylene (1,3,5-trimethylbenzene, TMB) to the hydrolysis-polycondensation mixture. The addition of mesitylene allows to increase the pore size in the materials from 2 to 6 nm. The materials appear as versatile and recyclable heterogeneous organocatalysts in Knoevenagel and Henry reactions and in the formation of monoglycerides by ring opening reaction of glycidol. This study highlights the huge potential of silica hybrid materials containing ionic substructures (i-silica) materials in heterogeneous catalysis