Equilibrium and Kenitic Modeling of Cd(II) Adsorption from Aqueous Solution using Tricalcium Phosphate

The performance of adsorption of Cd(II) from aqueous solutions onto tricalcium phosphate Ca3(PO4)2 (TCP) have been determined and studied with kinetic and isotherm models. The effect of contact time, concentration of Cd(II) was studied. Extraction kinetics is very fast, Indeed t=5 mn. The amount of TCP sorbed per gram of Cd(II) qt (mg/g) increased with increasing initial Cd(II) concentration. The adsorption of Cd(II) by TCP followed pseudo-second order kinetics. Diffusion intraparticle is the only rate-controlling step. Adsorption equilibrium data were analyzed by Langmuir, Frendlich and Temkin isotherm equation using regression analysis. Langmuir found to best represent the data for Cd(II) adsorption onto TCP. The negative value of change in Gibbs free energy (?G°=-4.249 Kj/mol) indicates the feasible and spontaneous adsorption. The positive value of the variation of adsorption energy ?Q=31.48 Kj/mol indicate that the adsorption reaction is exothermic. Keywords: Cd(II) adsorption, Isotherm, Kenitic, Tricalcium phosphat

Attributs de qualité, propriétés chimiques et composés bioactifs du jus de grenade (Punica granatum L.) transformé à partir d'arilles après congélation

Pomegranate juice quality depends essentially on its chemical and nutritional components stability. The valuable nutritional components may be reduced during its processing or storage. This study examined the effect of pomegranate arils’ frozen storage on juice quality, in terms of physicochemical properties and bioactive compounds stability. The physicochemical criteria (pH, TSS, TA, color attributes) and biochemical criteria (Total Phenolic content, Total anthocyanin content and antioxidant activity) were assessed on pomegranate juice extracted from frozen arils stored at (-18°C) for 6 months. Two cultivars ‘Sefri’ and ‘Wonderful’ were subject to this study. Results showed that the pH, TSS, and TA were generally stable in frozen arils juice. However, arils freezing had a significant effect on pomegranate juice color parameters. In fact, a significant decrease of a* values were revealed in juice samples for both cultivars. Therefore, the color intensity (chroma) has decreased significantly and total color differences (ΔE∗ab) also showed a significant difference (p < 0.05) between fresh juice and frozen arils juice. Arils freezing conditions (−18 °C) for 6 months didn’t affect pomegranate juice physiochemical criteria. However, bioactive compounds of pomegranate juice were reduced significantly. In fact, total phenolic content decreased by about 27% and 31% for ‘Sefri’ and ‘Wonderful’ cultivars, respectively. Total anthocyanins content decreased by 20% and 30% for ‘Sefri’ and ‘Wonderful’ cultivars, respectively. Antioxidant activity, measured based on the juice’s radical scavenging properties using the 2,2-diphenyl-1-picrylhydrazyl method, decreased by about 50% for ‘Sefri’ cultivar and 60% for ‘Wonderful’ cultivar.La qualité du jus de grenade dépend essentiellement de la stabilité de ses propriétés chimiques et nutritionnelles. L'objectif de cette étude est d'examiner l'effet de la congélation des arilles de grenade sur la qualité du jus, en termes de propriétés physicochimiques et de stabilité des composés bioactifs. Les critères physicochimiques (pH, TSS, TA, paramètres de la couleur) et biochimiques (teneur en polyphénols totaux, teneur en anthocyanes totaux et l’activité antioxydante) ont été évalués sur le jus de grenade extrait d'arilles congelées stockées à (-18°C) pendant 6 mois. Deux cultivars 'Sefri' et 'Wonderful' ont fait l'objet de cette étude. Les résultats ont montré que le pH, le TSS et le TA étaient généralement stables dans le jus d'arilles congelé. Cependant, la congélation des arilles a eu un effet significatif sur les paramètres de couleur du jus de grenade. En fait, une diminution significative des valeurs a* a été révélée dans les échantillons de jus pour les deux cultivars. Par conséquent, l'intensité de la couleur (chroma) a diminué de manière significative et les différences totales de couleur (ΔE∗ab) ont également montré une différence significative (p < 0,05) entre le jus frais et celui d'arilles congelées. La teneur des polyphénols totaux du jus d'arilles congelées a diminué d'environ 27% pour le cultivar 'Sefri' et de 31% pour le cultivar 'Wonderful'. De plus, la teneur totale en anthocyanes a diminué de 20% pour le cultivar 'Sefri' et de 30% pour le cultivar 'Wonderful'. L'activité antioxydante, mesurée sur la base des propriétés de piégeage des radicaux du jus par la méthode du 2,2-diphényl-1-picrylhydrazyl, a diminué d'environ 50% pour le cultivar 'Sefri' et de 60% pour le cultivar 'Wonderful'. Le stockage des arilles dans des conditions de congélation (-18 °C) pendant 6 mois n'a pas affecté les critères physico-chimiques du jus de grenade, cependant, les composés bioactifs du jus de grenade ont été réduits de manière significative

Atmospheric rivers and associated extreme rainfall over Morocco

Atmospheric rivers (ARs) are long, narrow, and transient corridors of enhanced water vapour content in the lower troposphere, associated with strong low-level winds. These features play a key role in the global water cycle and drive weather extremes in many parts of the world. Here, we assessed the frequency and general characteristics of landfalling ARs over Morocco for the period 1979–2020. We used ECMWF ERA5 reanalysis data to detect and track landfalling ARs and then assessed AR association with rainfall at the annual and seasonal scales, as well as extreme rainfall events (defined as a daily precipitation amount exceeding the 99th percentile threshold of the wet days) at 30 gauging stations located across Morocco. Results indicate that about 36 ARs/year make landfall in Morocco. AR occurrence varies spatially and seasonally with highest occurrences in the autumn (SON) and Winter (DJF) in the northern part of the country and along the Atlantic across northern regions. AR rainfall climatology indicates up to 180 mm/year recorded in stations located in the north west. High fractional contributions (~28%) are recorded in the north and the Atlantic regions, with the driest regions of the south receiving about a third of their annual rainfall from ARs. For extreme rainfall, the highest AR contributions can attain over 50% in the southern dry regions and along the Atlantic north coast and Atlas highlands