Adsorption of pigments and free fatty acids from shea butter on activated Cameroonian claysAdsorption of pigments and free fatty acids from shea butter on acid-activated Cameroonian local clays was investigated. The adsorption of the pigments was followed by the reduction of the absorbance of the shea butter at 295 nm. The kinetic study revealed that both the temperature at which the experiment was performed and the degree of activation of the clays influence the time of contact required to reach adsorption equilibrium of the pigments and the amount of pigments adsorbed. Thus, at 90 7C, the time required was 30 min for the clays activated with 0.5 M (A0.5M) and 1.0 M solutions (A1M) of sulphuric acid, and 45 min for the clay activated with a 2.0 M solution (A2M) of sulphuric acid. At 80 7C, the adsorption equilibrium was reached after 45 min for clays A0.5M and A1M, and 60 min for clay A2M. At 65 7C, the contact time to reach adsorption equilibrium was longer than 75 min for all the adsorbents used. At 90 7C, the amount of pigments adsorbed at equilibrium by clay A2M was about two thirds of that adsorbed by clay A0.5M, and one half of the amount adsorbed by clay A1M. For each adsorbent, the amount of pigment adsorbed decreased with temperature. A1M was the most efficient local clay for the adsorption of shea butter pigments and compared favourably with the industrial clay used as reference. The same evolution was observed with the adsorption of free fatty acids on different clays. The contact time needed for the elimination of peroxides was 40 min for all the clays used. The most efficient adsorbents for the adsorption of the pigments and free fatty acids were also the ones that gave the best results in the elimination of peroxides. The energy of activation for the adsorption of the pigments, as determined by the adsorption kinetic model of Brimberg, were 61 6 9 kJ/mol, 73 6 11 kJ/mol, 67 6 10kJ/mol, and 47 6 7 kJ/ mol for the industrial adsorbent (EN) and clays A0.5M, A1M and A2M, respectively. These values of activation energies indicate that the shea butter pigments are chemisorbed on acid-activated clays. It was found that the adsorption isotherms follow the Freundlich equation.

Alkaline activation of volcanic ash using Na 2 SiO 3 as activator showed its limits because of their low reactivity, nevertheless, phosphoric acid activation using H 3 PO 4 as activator can offer a great possibility of utilization of the latter aluminosilicate. The present study aims to determine the chemical composition of amorphous phase of volcanic ash and examine through the microstructure of the obtained cement-based phosphoric acid activation the relation between silicon and phosphorus atoms. Chemical composition of amorphous phase was determined by dissolution with NaOH and HCl. Cement fresh paste was subjected to isothermal calorimetry and temperature variation. Meanwhile, the hardened paste was characterized by X-ray diffraction, thermogravimetry analysis, scanning electron microscopy, energy dispersive spectrometry and Fourier transform infrared spectroscopy in order to study the microstructure. Also, the cement product was submitted to compressive strength test. The results obtained showed that, the amorphous phase of volcanic ash contain SiO 2 , Al 2 O 3 , Fe 2 O 3 , MgO and CaO oxides. This study allowed to understand the fact that phosphoric acid activation of volcanic ash at ambient temperature is an exothermic reaction and its described as a dissolution/precipitation process. Also, the obtained product was hydrated. Compressive strength of the cement product aged 1 and 28 days was respectively 20.6 and 30.5 MPa. Based on SEM/EDS analysis, silicon are partially replaced by phosphorus atoms and the product is made of-Si-O-Al-O-P-O-phospho-sialate network. Phosphoric acid activation is a promising route of valorisation of volcanic ash.

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Activated carbons were produced from palm nut hull, which is a waste material of palm oil extraction industries. Activated carbons having various pore size distributions and surface composition were obtained by conventional carbonization method via the sulphuric acid solution pre-treatment method. The surface areas, mesopore volume and-OH groups of activated carbons increase with the increases of sulphuric acid solution concentration. The activated carbons obtained were tested for the adsorption of pigments and free fatty acids from palm oil and shea butter. It comes out from this study that the amount of adsorbate (i.e. pigments and free fatty acids) fixed increases with the increase of the adsorption temperature and with the increases of mesopore volume. Intraparticle diffusion, pseudo-first-order and pseudo-second-order kinetics models were used to analyze the kinetics data obtained at different temperatures (temperature range 60 °C to 90 °C). Among the kinetics models used, the pseudo-second order was the best applicable model to describe the adsorption of oil pigments and free fatty acid onto activated carbons. The activation energies obtained by applying the Arrhenius equation for the adsorption of pigments were low (i.e. less than 40 kJ•mol-1 for the both vegetables oils), indicating that the adsorption could be assigned to physisorption.