This work describes the elaboration and the electroanalytical tests of a new electrode based on a mixture of graphite and biopolymer-modified montmorillonite nanocomposite. Initially, the nanocomposite was synthesized using sodic montmorillonite (NaMT) and sodium alginate (Naalg) extracted from Tunisian algae. The resulting nanocomposite was characterized by X-ray diffraction (XRD), infrared spectroscopy (UATR), and differential scanning calorimetry (DSC). XRD analysis revealed an increase in the basal spacing d001 and the appearance of reflections (020) and (220) of guluronan groups. Infrared spectra showed characteristic polymer bands such as symmetric and antisymmetric stretching vibrations of the carboxylic group in the nanocomposite spectra indicating the modification. Thermal analysis displayed a shift in the temperature of Naalg decomposition to a higher temperature in the nanocomposite thermogram. The obtained nanocomposite was then used in the development of an electrode. The resulting hybrid electrode was tested for metronidazole (MTZ) analysis using cyclic voltammetry (CV) and square wave voltammetry (SWV). Various parameters including pH, scan rate, MTZ concentration, frequency, etc., were investigated. The results revealed the irreversibility of the studied molecule and indicated that the reduction mechanism involves both diffusion and adsorption behaviors. SWV showed a better sensitivity to detect MTZ than the CV technique. Promising results were obtained, suggesting prospects for this new hybrid electrode.

BACKGROUND: Fluorosis is an endemic disease due to an excess of fluoride intake via drinking water. In some regions of the world, removing fluoride from drinking water is a severe problem that is still to be solved. The present study focuses on the use of a natural clay to reduce fluoride concentration in Tunisian contaminated drinking water under relevant working conditions.RESULTS: Adsorption experiments were performed in batches using a fluoride aqueous solution. The Box-Behnken model design was used to define the working conditions in which three factors were controlled: clay dosage, contact time and agitation speed. The fixed parameters were the initial fluoride concentration and water pH as observed in Metlaoui, Tunisia in 2021, and experiments were performed at room temperature. Results show that 4 g(50 mL)(-1) of clay dosage, 10 min of contact time and 280 rpm of agitation speed could provide 51% fluoride removal using an untreated natural clay. Then, various adsorbents based on this clay were synthesized (chitosan-clay, C6H17NO3Si-clay and thermally treated clays purified using different methods) and tested using the same approach. Among the adsorbents tested, the thermally treated purified clays were the most effective in removing fluoride under ambient conditions with a fluoride removal of 97.5%. Tests performed on drinking water showed that the safety fluoride concentration could be achieved without modifications of the water pH.CONCLUSIONS: The thermally treated clays investigated in this study were effective for fluoride removal under relevant conditions, which can pave the way for future field applications. (c) 2023 Society of Chemical Industry (SCI).

The preparation of a hybrid containing arginine and Na montmorillonite (Na-Mt) was optimized by studying the effect of several parameters. The obtained samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), and differential scanning calorimetry (DSC). These techniques approved the modification by the increase of the basal distance and the shift of the characteristic peaks of thermal analysis. The hybrid obtained in the optimal conditions was selected, incorporated in a graphite-based electrode, and tested in the analysis of the active molecule metronidazole (MTZ) by cyclic voltammetry (CV). The best electrochemical response was obtained in the conditions (pH = 9, CEC = 2, and stirring time = 12 h) and an optimum amount of hybrid was required in the electrode composition to have a well-defined cathodic peak corresponding to the reduction of MTZ. Results showed that the elaborated electrode reaction exhibits a diffusion-controlled process which is in agreement with several studies using other types of electrodes.

The present study aims to reduce the fluoride concentration of drinking water using a novel mild adsorbent based natural clay. The natural clay was dealuminated/realuminated and dehydroxylated by intense washing and heating processes. The developed adsorbent was confirmed by X-ray diffraction (XRD), thermal analyses (ATD-TG) and nuclear magnetic resonance solid-state with magic angle spinning (MAS NMR). MAS NMR results showed that distorted tetrahedral-Al coordination and penta-Al coordination sites were responsible for fluoride adsorption. Batch adsorption experiments were investigated without any adjustment of water pH. The effect of the clay dosage over the range of 0.5-2 g/50 mL of sample solution was studied. Results revealed that the aggregation of the clay particles in the water was successfully avoided thanks to the heating process. Kinetics and adsorption isotherms were also investigated. The adsorption equilibrium was achieved on a timescale of seconds. Adsorption kinetics data followed pseudo-first-order as well as pseudo-second-order models while isotherm experimental data followed the Freundlich model. The maximum adsorption capacity was relatively small (1.2 mgmiddotg(-1)). Tests performed on Tunisian contaminated drinking water showed that water potability with respect to fluoride was successfully achieved; suggesting that the dealumi-nated/realuminated dehydroxylated clay can be a promising fluoride adsorbent for drinking water.

This study focuses on the physico-chemical characterization of an alginate extracted from seaweed (Padina pavonica) collected on the Tunisian coast. Since alginates display a broad variety of applications, especially in the food and pharmaceutical fields, their quality requires a high certain standard of purity and an accurate knowledge of their composition and structure. With this aim, once extracted the Na-alginate was purified and then characterized for comparison with a commercially available alginate. Thermal analyses (TGA and DSC) were performed to evaluate the water content, i.e. the moisture loss and the thermal stability of this polysaccharide. Spectroscopic investigations demonstrated similarities but also significant differences between the two samples. NMR spectroscopy enabled determination of the mannuronic/guluronic (M/G) ratio, which happened to be lower for the alginate extracted fromP. pavonicaalgae. SEC, performed in water as eluent, was implemented for determination of the average molecular weight of these water-soluble polymers and revealed 6-fold higher molecular weights (M(n)andM(w)) than the commercial reference. (c) 2020 Society of Chemical Industry

In recent years, there has been considerable interest in essential oils encapsulation and in developing biodegradable microparticles. The aim of this present work was to prepare clove essential oil loaded microspheres, by a modified emulsification method, using sodium alginate extracted from a Tunisian Brown seaweed Algae Padina pavonica as biopolymer. The obtained microparticles were characterized by FT-IR, DSC and SEM. Loading capacity yield, encapsulation efficiency (%EE) and in vitro release of the essential oil were also investigated. Sodium alginate microspheres were successfully prepared as confirmed by physico-chemical characterizations. %yield of microspheres and %EE of essential oil were 72.73% and 24.77% ± 7.47%, respectively. SEM showed pseudospherical microspheres with rough surface ranging, in size, from 1500 μm to 3000 μm. In vitro dissolution study indicates a controlled released of the essential oil which follows, mainly, classical Fickian diffusion. Thus, this present work highlighted the potential of this polysaccharide as a biopolymer to formulate polymeric microspheres.

Many regions in the South of Tunisia suffer from the existence of fluoride as considerable amounts (3 to 4.5 mg/L)in water resources. A Tunisian Bentonite was used for this aim. This natural and save absorbant was purified then activated. A Fe-Ben, was obtained, which shows a good potential as a cheap and efficient adsorbent for anionic micro pollutants removal from aqueous media. The modified bentonite was characterized by XRD and FTIR. The effect of pH, temperature, clay/fluoride ratio, equilibrium time and competitive ions on the adsorption of fluoride ions by batch process was studied. The obtained results revealed thata fluoride removal efficiency higher than 80%was obtained in the pH range 2- 7. The equilibrium exhibits 40 min to be reached at room temperature. Kinetics data fitted pseudo-second-order model. Batch adsorption data was better described by Langmuir isotherm model than Freundlich isotherm model. The defloridation of a Tunisian drinking water containing considerable amounts of fluoride has shown prospective results at room temperature and in neutral pH.

Cardiologists are interested in determining whether the type of hospital pathway followed by a patient is predictive of survival. The study objective was to determine whether accounting for hospital pathways in the selection of prognostic factors of one-year survival after acute myocardial infarction AMI provided a more informative analysis than that obtained by the use of a standard regression tree analysis CART method . Information on AMI was collected for 1095 hospitalized patients over an 18-month period. The construction of pathways followed by patients produced symbolic-valued observations requiring a symbolic regression tree analysis. This analysis was compared with the standard CART analysis using patients as statistical units described by standard data selected TIMI score as the primary predictor variable. For the 1011 84, resp. patients with a lower higher TIMI score, the pathway variable did not appear as a diagnostic variable until the third second stage of the tree construction. For an ecological analysis, again TIMI score was the first predictor variable. However, in a symbolic regression tree analysis using hospital pathways as statistical units, the type of pathway followed was the key predictor variable, showing in particular that pathways involving early admission to cardiology units produced high one-year survival rates.

The effect of clay percentage and NaCl addition on the rheological behavior of aqueous suspensions of a purified bentonite was investigated. The solgel transition (SGT) was detected using three methods: (i) the grump of viscositywith clay percentage, (ii) the steady flowcurves and (iii) the detection of hysteresis buckle by increasing-decreasing shear stress cycles. Results showed a SGT (at 6.5%(w/w)) of clay. The effect ofNaCl addition was studied on sol suspensions (1.5%, 3.25% and 4.5% (w/w) of clay) and on gels (6.5% and 7.5% (w/w) of clay). For diluted sols the electrovisquous effect was detected at about 0.01% (w/w) of NaCl by a slight minimum of viscosity. The critical flocculation concentration (CFC) corresponded to 0.04% (w/w) of NaCl and suspensions stayed stable until 0.1% (w/w) of NaCl (maximumof viscosity) after which, sedimentationwas observed. The CFC value of the semi diluted sol was 0.05% (w/w) of NaCl and since the flocculation; the suspension became a stable gel until (0.1%(w/w)) of NaCl (max of viscosity) where a thin film of water surmounted it. For gels, the flocculation seemed to occur by stages; it started at 0.02% and continued until (0.2%(w/w)) of NaCl where a thin layer ofwater appeared.

The studied clay is collected fromthe Tataouine Douiret area of the Tunisian south. The layer contains 50%of clay fraction and 50%of impurities formed essentially from calcite and quartz. The cation exchange capacity (CEC) of purified clay is 43 meq/100g of burnt clay. The physico-chemical characterizations of the clay have shown that it is fibrous clay and particularly it is a palygorskite. The thermal analysis of rough and purified clay has demonstrated that the departure of zeolitic water is carried out at 118i‚°C. The deshydroxylation is occurred at 501i‚°C for the rough palygorskite and at 484i‚°C for the purified palygorskite. The study of the effect of the mass percentage of clay on the rheological properties has shown that the flow curves have Newtonian behaviour for clay fractions lower than 14%(w/w). The effect ofNaCl on the rheological behaviourwas studied for clay fractions 1.5, 3.25 and 14%(w/w). Concerning the first two clay fractions, the critical flocculation concentration (Ck) is noted at 0.05% of NaCl. For gel (clay 14%), a jump of viscosity is observed from 0.07% of NaCl. From 0.2% of NaCl a very rigid gel is obtained which persists even for high electrolyte percentages.

Quelques études retrouvent parmi les complications d'une capsulotomie au laser YAG la formation d'un oedème maculaire cystoïde apparaissant dans les semaines qui suivent le geste. Toutefois, on ne retrouve pas dans la littérature de mesures OCT de l'épaisseur centrale maculaire après capsulotomie. L'objectif de l'étude est de mesurer l'épaisseur maculaire après capsulotomie YAG chez 30 patients ne présentant par ailleurs aucune pathologie rétinienne connue. Il s'agit d'une étude prospective unicentrique chez des patients adressés dans le service pour capsulotomie au laser YAG. Les capsulotomies ont été réalisées par 5 ophtalmologistes différents. Les différents paramètres ont été étudiés à J0 (avant le laser), J7, J30 et J90. Ces paramètres étaient : l'acuité visuelle, le tonus oculaire et la mesure par OCT (OCT 3 de Zeiss) de l'épaisseur maculaire centrale. De plus, le nombre d'impact et la puissance du laser ont été notés pour chaque patient. Un test de Student a été utilisé pour l'étude statistique. Un « p » < 0.05 était considéré comme significatif. On ne constate pas d'épaississement significatif de l'épaisseur maculaire après capsulotomie au laser YAG (p > 0.05). Les complications connues après capsulotomie YAG sont l'oedème maculaire cystoïde, le décollement de rétine, et l'hypertonie. Dans notre série, nous n'avons pas retrouvé de telles complications, notamment pas d'oedème maculaire cystoïde. Nous avons noté une légère augmentation de l'épaisseur maculaire après laser à J7 mais non significative (p > 0.05). La capsulotomie au laser YAG n'apparaît pas, sur ce petit échantillon, comme un facteur favorisant l'épaississement maculaire.

In order to correlate rheological and filtration parameters of clay-aqueous suspensions, the effect of acidic pH and ionic strength have been investigated. Two clays, a bentonite and a palygorskite were used to emphasize the contribution of the nature of the clay. Rheological results show that at a given bentonite percentage, when the pH of the suspension decreases, the yield stress and dynamic viscosity increase and reach a maximum at weakly acidic media before decreasing again in highly acidic medium where the structure of the clay is probably attacked. The NaCl addition to palygorskite suspensions causes an abrupt increase in viscosity at the critical flocculation concentration (CFC) revealing the beginning of the flocculation. When the ionic strength increases further, the viscosity reaches a maximumthen decreases when the suspension becomes unstable. The effect of the pH on the filtration properties for the bentonite appears to be the same as on the rheological properties. When the pH decreases, the thickness (e), the weight (m) and the water retention (WR) of the cake increase, reach a maximum for weakly acidic pH before decreasing again. The permeability of the cake increases below the pH corresponding to the observedmaximumfor the other filtration parameters.However, the addition of NaCl and the flocculation phenomenon seem to have no effect on the filtration properties of the palygorskite. There is no correlation between rheological and filtration parameters for the non swelling and fibrous clay.

The extraction of cadmium from phosphoric media has been Studied. The D(2)EHDTPA was used as extractant and dodecane as diluent. No third phase was observed in the investigated conditions.A continuous micro-pilot scale mixer-settler was successfully tested for both extraction and stripping. More than 99% extraction rate was obtained in steady-state conditions with a flow rate ratio Aqueous/Organic equal to 1.1. Continuous stripping was performed using HCl 4 M. More than 96% of the cadmium was stripped in one continuous mixer-settler stage for flow rate ratio equal to 0.7. Results were in good agreement with the predicted values based on the McCabe-Thiele method. Experimental mixer-settler stages behave as ideal ones (Murphree efficiency >98%).An optimal flow sheet is proposed to purify the Wet Phosphoric Acid (WPA) and to recover a relatively concentrated cadmium solution (1 g L-1). Two ideal stages operating at phase ratio A/S equal to 5/1 are required for the extraction step leading to a very depleted raffinate (<0.2 mu g L-1). For the stripping step, six stages are required (S/A=5/1). The recovered organic phase contains less than 2 mu g L-1 and could be recycled in the extraction step. (C) 2008 Elsevier B.V. All rights reserved.

Di(2-ethylhexyl) dithiophosphoric acid (D(2)EHDTPA) was examined for cadmium removal from phosphoric acid solutions. High extraction performance was achieved. By means of slope and saturation methods, the stoichiometry of the complex was postulated. Both methods indicated the presence of anhydrous CdR(2) as being the metallic extracted complex, HR denoting the D(2)EHDTPA molecule. The stripping of cadmium from the organic phase was ensured by aqueous solutions of HCl; quantitative stripping was achieved with either HCl (4M) or an HCl-NaCl mixture.

We have as input two portfolio of stocks managed by ING bank (North Holland). Each portfolio and each stock is described by several variables every open day of a week and during eight weeks. A portfolio is characterised by variables as its value, its performance, a stock is characterised by variable as its value, its number in the portfolio and its performance. In this paper, we study a symbolic data table where each row represents one of the eight weeks and each column represents a variable which value is an interval [min, max] corresponding to the minimum and maximum values taken during this week. Hence each cell of the data table contains an interval instead a number as usual. The SODAS software aim to extend standard data analysis to more complex data like financial data. In this paper we use it in order to study the performance of two portfolio in relation with their stocks. It results from this study that Sodas is able to study the internal variation of classes (here, the weeks) by giving explanations and graphics.