Calcium platinum aluminium, CaPtAl

A preliminary X-ray study of CaPtAl has been reported previously by Hulliger [J. Alloys Compd (1993), 196, 225–228] based on X-ray powder diffraction data without structure refinement. With the present single-crystal X-ray study, we confirm the assignment of the TiNiSi type for CaPtAl, in a fully ordered inverse structure. All three atoms of the asymmetric unit have .m. site symmetry. The structure features a ∞ 3[AlPt] open framework with a fourfold coordination of Pt by Al atoms and vice versa. The Ca atoms are located in the large channels of the structure

Effect of Cooking on Moisture Sorption Isotherms of Sheanut (Vitellaria paradoxa Gaertn.) Kernels: Evidence from Light and Scanning Electron Microscopy

International audienceThe standard static gravimetric method was used to determine moisture sorption isotherms of both raw and cooked sheanut kernels at 40, 50 and 60 A degrees C in the water activity range 0.11-0.96 in order to evaluate the influence of cooking on the moisture sorption capacity of the kernels. Preliminary analysis showed that the kernels lost a significant quantity of its proteins and carbohydrate during the cooking process. Results of analysis of the moisture sorption isotherms revealed that cooked kernels generally had significantly (p < 0.05) lower equilibrium moisture contents (EMC) than the raw ones for both desorption and adsorption processes. The effect of temperature on the sorption processes as portrayed by the desorption isotherms revealed that EMC decreased steadily with increase in temperature within the water activity range 0.10-0.8 a(w) but increased rapidly with increase in temperature above 0.8 a(w) resulting in the overlap of isotherms for all sorption processes. This crossing over of isotherms was attributed to the dissolution of sugars at higher water activities. The protein matrix in the kernel was observed using light microscopy and was found to have been disorientated after cooking. Studies using light and scanning electron microscopy revealed that the reduced ability of cooked kernels to sorb water could be linked to changes in the structure of the kernels brought about by the cooking of the kernels. It is concluded that cooking had a very significant effect on the amount of water sorbed by sheanut kernels

Nano-silica from kaolinitic clay used as adsorbent for anionic and cationic dyes removal: linear and non-linear regression isotherms and kinetics studies

The increasing occurrence of wastewaters associated with industrial development has begotten a permanent search for new and more efficient techniques for the removal of hazardous substances such as heavy metals and dyes. The use of natural and available resources to develop improved and sustainable commodities for this purpose remains crucial and is among promising emerging green technologies for water treatment. It offers the gradual shifting of hazardous industrial chemicals precursors to the abundant non-metallic mineral resources that receive an added value. This work investigated the uptake capacity by the adsorption process of methylene blue (MB) and azocarmine G (AG) onto nano-silica synthesized from kaolinite clay. The effects of contact time (0-30 min), the adsorbent dosage (5-100 mg), the initial pH of the solution (1-11 for MB and 1-7 for AG), and the initial dye concentration (5-50 mg/L) were studied. The selected conditions to carry out kinetic and isotherm adsorption experiments were: 15 mins, 20 mg, 11 for MB, 1.01 for AG, and 50 mg/L. Four adsorption isotherms and three kinetic models were used to model the adsorption data thanks to linear and non-linear regression methods. From the obtained results, the Freundlich isotherm model fitted well the adsorption phenomenon while the pseudo-second-order kinetic model described well the adsorption mechanism. Furthermore, the free energy of adsorption was similar for the two absorbents, 0.71 kJ, pointing physisorption as the dominant adsorption mechanism. The optimum MB and AG uptake were respectively 13.8 and 36.1 mg/g. Conclusively, the nano-silica represents a potentially viable and powerful adsorbent whose use could lead to a plausible improvement in environmental preservation