Highly efficient adsorption of uranyl ions using hydroxamic acid-functionalized graphene oxide

A chelating matrix prepared by immobilizing N-hydroxyl amine onto graphene oxide functionalized with aspartic acid (GO-HDX) was applied to recover UO2 2+ from their SO4 2− leach liquor. SEM-EDAX, FT-IR, TGA, and XRD instruments, in addition, Raman spectroscopy (IR-Raman), were used to analyze the synthesized GO-HDX. The static extraction technique optimized various physicochemical parameters that impacted the UO2 2+ extraction. The optimal pH, time of contact, initial concentration, GO-HDX dose, temp., foreign ions, and eluting agents were gained. The experimental equilibrium documents were assessed using Langmuir and Freundlich equations. The Langmuir equation model quite fits the investigational adsorption data with a maximum uptake of 277.78 mg/g, and it implied the attending of monolayer coverage of adsorbed molecules. Pseudo-first- and pseudo-second-order analyses were done to inspect the kinetic results. The data indicated that pseudo-second-order kinetics fit all concentrations. The intended thermodynamic factors were ∆G° negative values and ∆H° positive value. The data signified that the UO2 2+ extraction onto GO-HDX was spontaneous adsorption and endothermic at higher temperatures. The regeneration efficiency of GO-HDX was 98% using 1 M HCl.

Effect of accelerated solvent extraction conditions on the isolation of bioactive compounds from fennel (Foeniculum vulgare Mill.) seeds

This study focused to establish the optimal conditions of accelerated solvent extraction (ASE), i.e., temperature, static extraction time and number of extraction cycles, for the isolation of fennel (Foeniculum vulgare Mill.) seeds phenols and pigments using 96% ethanol as an extraction solvent. Hence, extraction conditions of temperature (80 and 110 °C), static extraction time (5 and 10 min) and number of extraction cycle (1, 2, 3 and 4) were varied. Obtained extracts were spectrophotometrically analyzed for the content of total phenols (TP), total chlorophylls (TCHL) and total carotenoids (TCAR). Applied extraction conditions had a significant (p<0.01) influence on the yields of analyzed compounds, except for static extraction time on TCAR (p=0.11). Based on the results of statistical analysis, the highest levels of TP and TCHL were achieved at the most invasive conditions (110 °C/10 min/4 cycles), while shorter period was sufficient to reach the highest TCAR yield (110 °C/5 min/3 cycles). In summary, ASE demonstrated to be effective extraction technique for the isolation of fennel seeds hydrophilic and lipophilic bioactive compounds.

Effect of Static Extraction Time on Supercritical Fluid Extraction of Bioactive Compounds from Phyllanthus niruri

Supercritical fluid extraction (SFE) is an effective method to extract active components from plants. SFE process can be conducted by using a static or/and dynamic extraction. Static extraction is important for the diffusion of solvated analyte to the matrix surface. Therefore, the main objective of this study is to evaluate the static extraction time influence on SFE extraction of Phyllanthus niruri and the main bioactive compounds. The extraction was conducted by using supercritical carbon dioxide (SC-CO2) with 50% ethanol-water as a co-solvent at selected operating conditions (200 bar, 60 °C, 10% co-solvent content and 3 ml/min solvent total flow rate). The static extraction time was investigated in the range of 15 min–75 min by allowing the plant matrix to immerse in a mixture of SC-CO2 and 50% ethanol-water at the operating condition. The quantification of targeted compounds, which were gallic acid (GA), corilagin (CO) and ellagic acid (EA) were analysed by using high performance liquid chromatography (HPLC). The observation on the physical characteristics of the plant matrix was performed by using the scanning electron microscopy (SEM). The best result for total extraction yield was obtained at 60 min of static extraction time, which was 20.7% g/g sample. It also gave a better result for all three targeted compounds in terms of total content percentage (0.35% g GA/g extract, 3.05% g CO/g extract, and 5.17% g EA/g extract). In conclusion, static extraction time was crucial in extracting bioactive compounds in P. niruri by using SFE method and should be considered as the main parameter other than pressure and temperature.

The Extraction of Metal Contaminants Using Supercritical Carbon Dioxide

Conventional decontamination methods utilize water-based systems, which generate high amounts of secondary wastes. Herein, the authors describe an environmentally benign decontamination method using liquid and supercritical CO2. The use of CO2 as a solvent affords effective waste reduction by its ability to be recycled, thereby leaving behind only the contaminants upon its evaporation. In this study, a CO2 solution process was assessed using t-butyl salen (t-salen), dicyclohexano-18Crown6 (DC18C6), 8-hydroxyquinoline (8-HQN), perfluoro-1-octanesulfonic acid tetra-ethylammonium salt (NEt4PFOSA), and pentadecafluorooctanoic acid ammonium salt (NEt4PFOA) to extract spiked radioactive contaminants (Nb, Zr, Co, Sr) from an inert sample matrix, namely with filter paper. With the static extraction method, Sr was extracted with a maximum extraction rate of 97%, and Nb was extracted with a maximum extraction rate of 75%. Additionally, the authors were also able to extract Co and Zr with maximum extraction rates of 73% and 64%, respectively.