Henri Fauduet

Optimization by the simplex method of the separation of phenolic acids by high-performance liquid chromatography in wastewater olive and sugar beet vinasse

Optimization of a high-performance liquid chromatography separation has been developed for nine polyphenols by application of the simplex method. The nine polyphenols selected were mainly phenolic acids that can be present in wastewater and they can be removed by adsorption on activated carbon and resins. After the organic solvent (MeOH) had been chosen, a linear gradient in three stages and the furnace temperature were retained as parameters of optimization. The optimal conditions were determined by the super modified simplex and, in order to measure them a Chromatographic Response Function (CRF) was chosen. With the optimal conditions, the time of analysis was decreased from 69 to 40 min. The validation of the method was made on wastewater olive oil (WWOO) and sugar beet vinasse.

Kinetic modelling of the degradation of the α-tocopherol in biodiesel-rape methyl ester.

The aim of this work was to study the influence of three major factors (light, atmospheric oxygen, temperature) responsible for the degradation of tocopherols. The evolution of alpha-tocopherol contents was analysed by high-performance liquid chromatography. Taguchis experimental design was applied to establish a mathematical model of alpha-tocopherols degradation in function of the studied parameters especially in a domain of temperature between 50 degrees C and 150 degrees C. The results show that the major factor is the temperature, especially above 100 degrees C. Light is a negligible factor, meaning that degradation is mainly due to an autoxidation phenomenon. Moreover, only interactions between temperature and atmospheric oxygen have been observed especially above 100 degrees C. The mathematical model was validated for a temperature of 75 degrees C and permits to calculate a predictive speed of degradation in this domain.

COMPARISON OF KINETIC MODELS FOR THE AQUEOUS SOLID-LIQUID EXTRACTION OF TILIA SAPWOOD IN A CONTINUOUS STIRRED TANK REACTOR

The kinetic study of the aqueous extraction of Tilia sapwood was based on temperature, while all the other factors were kept constant. Several models were used and compared to explain the kinetics of the aqueous solid-liquid extraction of Tilia sapwood. For each model, the rate constant, the equilibrium extraction capacity, and the initial extraction rate were evaluated to analyze the suitability of these kinetic models to describe the leaching process for temperatures ranging from 313 to 363 K. The pseudo first-order model could not be applied during the whole of the process. The Elovich model provided a good degree of correlation (from 0.929 to 0.988) and could be applied all along the extraction process. The pseudo second-order model was satisfactorily applied, with coefficients of correlation over 0.998, showing that it perfectly described the process. A physical explanation of these models was finally proposed.

Interest of a chemometric approach in understanding the retention behaviour of three columns in hydrophilic interaction liquid chromatography: Application to the separation of glycerol carbonate, glycerol and urea

A chemometric approach was used to study the retention behaviour of glycerol, urea and glycerol carbonate in hydrophilic interaction liquid chromatography (HILIC). First, a simplex method was developed to optimize the sensitivity of an evaporative light scattering detector. A mixture design was then applied to model retention factors as a function of the mobile phase content in acetonitrile, water and methanol on three columns: Atlantis HILIC Silica, ZIC-HILIC and Monochrom diol. Atlantis HILIC Silica exhibits predominantly hydrophobic interactions, while retention on the other two columns is mainly ruled by hydrophilic interactions. Finally, a desirability function is applied on the resolution factors. The use of this function enables the compositions of eluent phases to be determined in order to achieve separation between the three chemicals. Monochrom diol proved to be the most efficient column.

Removal of Diethyl Phthalate from Aqueous Media by Adsorption on Different Activated Carbons: Kinetic and Isotherm Studies

The adsorption of diethyl phthalate (DEP) was studied on four activated carbons (ACs) with different chemical and microporous properties. The kinetic results showed that the non-linear form of the pseudo-second order kinetic model provided the best parameters. Results further showed that the DEP adsorption kinetics is favored by ACs which have a ratio of a specific microporous surface to a specific external surface that is relatively low. Besides, an increase in temperature induced an increase in the rate constant k 2 , but the adsorption capacity is temperature independent. Two models, (Langmuir (linear and non-linear forms) and Dubinin-Radushkevich-Kaganer (DRK)), were tested from experimental data. While the Langmuir model provided the best correlation on all the ACs studied. The surface occupied, calculated with the Langmuir parameter obtained by the non-linear form, evidenced the importance of the external surface and the mean pore size. The results show that the non-electrostatic interactions are predominant in the DEP adsorption and are essentially due to dispersion and hydrophobic interactions (for L27 and X17). In the case of F22 and S21 the DEP adsorption is only due to dispersion interaction. A comparison of the thermogravimetric analysis of the ACs washed and saturated shows that the DEP is totally desorbed between 300 and 500°C with a characteristic peak.

DETERMINATION OF THE METASTABLE ZONE WIDTH OF GLYCINE AQUEOUS SOLUTIONS FOR BATCH CRYSTALLIZATIONS

The aim of this study was to determine the metastable zone width of aqueous solutions of glycine for non-seeded batch crystallizations. The saturation curve was determined by studying the heating rate influence on the apparent saturation temperatures of several solutions. A linear regression was then applied to obtain the saturation temperatures. The spontaneous nucleation curve was obtained by measuring the crystallization temperatures of several solutions at different cooling rates. The results show that the apparent nucleation order of the glycine aqueous solutions was around 3.5 ± 0.5. Moreover, from the experimental data, a second-order polynomial model was established by using the experimental design method. This model enables the expression of crystallization temperature to be defined as a function of concentration and cooling rate. The results show that the model fits well (R2 > 0.99; Q2 > 0.98) and that the cooling rate is the most influential parameter.

Setup of glycine continuous synthesis by ammonolysis of monochloroacetic acid

This article describes the continuous production of glycine by catalytic ammonolysis of monochloroacetic acid in an aqueous medium. The synthesis and crystallization of glycine are carried out in a battery of three stirred double-jacketed reactors while temperature and pH values are controlled. The results of the kinetic study allow one to calculate the residence time in each tank for a desired conversion ratio and are first checked with the setup. Then, some parameters (concentration of reagents, regulation of pH, residence time, catalyst) are modified to improve the final yield in crystallized glycine. The best yield resulting from a flow process (96.6%) is better than that resulting from a batch process (93%) and is obtained in the following conditions: the first step is performed at 75°C and pH 5.4 with a 10 mol L−1 monochloroacetic acid solution and a 17 mol L−1 ammonia aqueous one with a 0.2 molar ratio of hexamethylenetetramine; the second step is carried out at 75°C and pH 8.0; the optimal residence times are respectively 1 and 4 hours. Replacement of hexamethylenetetramine by formaldehyde can also be considered even if the yield is slightly lower.

Evolution of Toxicity and Mineralization during the Treatment of Diethylphthalate in Water by Ozone and Activated Carbon Coupling

Ozone/activated carbon coupling could be an efficient method to remove micropollutants, such as phthalates, that are refractory to classical treatments. However, this wastewater-treatment process can lead to the formation of oxidation by-products that may be toxic and which also need to be removed. The aim of this work was to study the evolution of the mineralization and the toxicity of the effluent during the treatment process so as to determine the efficiency of this method and the required time of treatment. Analyses (Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analyses, N2 adsorption isotherms) of the adsorbent material were performed to understand the role of activated carbon during the treatment. It is shown that depending on the activated carbon properties and the experimental conditions, a fast and complete removal of diethylphthalate, and total mineralization and detoxification of the treated solution can be obtained. Moreover, it is demonstrated that the activated carbon acts more as a reaction site than as an adsorbent, leading to an in situ renewal of the material during the process. DOI: 10.1061/(ASCE)EE.1943-7870.0000671.

Modelling of influential parameters on a continuous evaporation process by Doehlert shells.

The modelling of the parameters that influence the continuous evaporation of an alcoholic extract was considered using Doehlert matrices. The work was performed with a wiped falling film evaporator that allowed us to study the influence of the pressure, temperature, feed flow and dry matter of the feed solution on the dry matter contents of the resulting concentrate, and the productivity of the process. The Doehlert shells were used to model the influential parameters. The pattern obtained from the experimental results was checked allowing for some dysfunction in the unit. The evaporator was modified and a new model applied; the experimental results were then in agreement with the equations. The model was finally determined and successfully checked in order to obtain an 8% dry matter concentrate with the best productivity; the results fit in with the industrial constraints of subsequent processes.

Optimization of glycine crystallization by the golden section search

The yield and the purity of glycine obtained after ammonolysis of monochloracetic acid with hexamethylenetetramine followed by a crystallization in a hydromethanolic medium depend on the fraction of methanol in the mixture. Influence of the solvent composition on the solubility of a restored reaction mixture as a function of temperature was first studied for diverse methanol weight fractions in the medium. The results showed that the best conditions for crystallization should be located in a 70-100% methanol weight fraction range with a temperature lower than 10°C. These conditions were then optimized by the golden section search. The results obtained confirmed previous trials and indicated that the optimal methanol weight fraction is 80%. In these conditions, the yield of pure glycine obtained by crystallization was about 92.3% (for a final temperature of 7°C) and the crystals were 98% pure.