Structural Study of Microporous Xerogels Prepared by Polycondensation of Pyrogallol with Formaldehyde

Microporous xerogels were prepared by polycondensation of pyrogallol with formaldehyde catalyzed by perchloric acid in aqueous medium. The samples were characterized by FTIR absorption spectra. The micro-porosity and the specific surface area are characterized by nitrogen adsorption - desorption isotherms. The obtained characteristics depend on the conditions of polycondensation

Synthesis and characterization of a new silica nanoparticles using APG/CTAB as modified agent

International audienc

Adsorption of organic matter from industrial phosphoric acid (H3PO4) onto activated bentonite

The Tunisian industrial phosphoric acid (IPA) was obtained from the phosphate rock by the wet process. However, the organic matter (OM) contained in the acid may interact with organic solvents to form stable foams, preventing phase settling, or simply by forming cross layers and organic phases, and denaturing part of the solvent. Hence, removal of these organics seems to be an important step for the production of decontaminated phosphoric acid. In the phosphoric acid plant of M'dhilla, the OM can be found as colloidal suspension and soluble forms. The colloidal organics are coagulated and deposited with the gypsum precipitation during the aging of H3PO4, while the soluble part remains behind. The purpose of this work was to study the OM adsorption onto montmorillonite bentonite. Equilibrium data are analyzed by the Langmuir, Freundlich and Redlich–Peterson adsorption isotherm models

Tuning particle morphology of mesoporous silica nanoparticles for adsorption of dyes from aqueous solution

Spherical and rod mesoporous silica nanoparticles with hexagonal mesostructure were prepared using the modified Stöber method. The morphology, size and internal pore structure can be controlled by simple changing of surfactant concentration and water:ethanol molar ratio. Monodispersed spheroid MCM-41 was obtained at 40 °C under basic conditions using cetyltrimethylammonium bromide (C16TAB) as template. Obtained materials were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), transmission electron microscopy (TEM) and scanning electronic microscopy (SEM). The results reveal that the pore volume and surface area increase when the amount of C16TAB increases whereas the pore diameter and particle size decrease. However, the use of ethanol as cosolvent led to an increase in the particles’ size. Moreover, the addition of a 3-aminopropyltriethoxysilane greatly influenced the final particle shape. The material was effectively used for the removal of two fluorescent dyes (Hoechst 33342 and rhodamine 6g) from aqueous solution. Adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. The Langmuir model was found to fit the experimental data better than others models. Keywords: MCM-41, Modified Stöber method, Adsorption, Hoechst-33342, Rhodamine-6

Water Extraction of Tannins from Aleppo Pine Bark and Sumac Root for the Production of Green Wood Adhesives

International audienceThe extraction of condensed tannins from Aleppo pine bark and sumac roots (Brown Rhus tripartitum) was examined in near industrial conditions, using a water medium in the presence of 2% NaHCO 3 and 0.5% NaHSO 3 at two different temperatures (70 • C and at 100 • C). The tannins extracts were recovered in high yields (~25% of Aleppo pine and~30% for sumac) with high phenolic contents (>75%). The tannins were characterized by 13 C-NMR and MALDI TOF and showed characteristics of procyanidin/prodelphinidin units. The tannins extracted at 100 • C were composed of smaller flavonoid oligomers (DP 10). Adhesive resin formulations were prepared using Aleppo or sumac tannins and four different cross linkers (hexamine, glutaraldehyde, furfural, and glyoxal). The resins were studied by TMA in bending and tannins-based formaldehyde-free wood particleboards were produced. The panels displayed internal bond strengths > 0.35 MPa with the four hardeners and all of them passed relevant international standard specifications for interior grade panels. The best results were observed with the tannins extracted at 70 • C with furfural as hardener (IB = 0.81 MPa for Aleppo pine and IB = 0.76 MPa for sumac)

The Development of a New Phosphogypsum-Based Construction Material: A Study of the Physicochemical, Mechanical and Thermal Characteristics

Phosphogypsum (PG) is a waste (or by-product) of the production of phosphoric acid, a basic constituent in the manufacturing of modern fertilizers. The annual production of phosphogypsum in Tunisia is currently estimated to be 10 million tons. Its storage in slag in close proximity to production plants generates pollution problems; however, valorization may be a solution. The present paper proposes a simple process for the valorization of this by-product into a construction material. Several physicochemical characterizations are used to prove the characteristics of samples. The chemical composition shows that PG is a gypsum compound with several impurities. The morphological analyses show that the powder materials are mesoporous with a lower specific area. The structural characterizations show that these solids play the role of a water pump as the degree of hydration changes from 2 to 0 and vice versa, depending on the temperature. Mechanical and thermal analyses show that the prepared formulation is brittle and insulating, which presents opportunities for it to be used as a decoration material