A highly porous phosphorous-containing activated carbon derived from pistachio nutshells (PNS) was synthesis as a potential sorbent for uranium (VI) from sulfate media. The prepared phosphate activated carbon (PAC) was visualized under SEM and TEM which revealed a highly porous structure. The extraction of U(VI) from acidic media using PAC was investigated by a batch method and various parameters such as pH, equilibrium contact time, liquid to solid ratio, and initial U(VI) concentration were examined. Under the stated conditions, the optimum pH for U(VI) adsorption was found to be 3.5. The adsorption capacity of uranium upon PAC under the optimum conditions was found to be 335 mg/g. The experimental results were applied for Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. The thermodynamic equilibrium constant and the Gibbs free energy were determined (ΔG° from -4.72 to -7.65 kJ/mol) and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo second-order model.
The leaching of rare earth elements (REEs) from Egyptian Abu Tartur phosphate rock using phosphoric acid has been examined and was subsequently optimized to better understand if such an approach could be industrially feasible. Preliminary experiments were performed to properly define the design of experiments. Afterward, 24 full factorial design was implemented to optimize the leaching process. Optimum REEs leaching efficiency (96.7 ± 0.9%) was reached with the following conditions: phosphoric acid concentration of 30 wt.-% P2O5, liquid/solid ratio, mL/g, of 5:1, at 20 °C, and 120 min of leaching time. The apparent activation energy of the dissolution of REEs from phosphate rock using the phosphoric acid solution was -19.6 kJ/mol. D2EHPA was subsequently applied as an organic solvent for REEs separation from the acquired leach liquor. REEs stripping and precipitation were conducted, and finally, rare earth oxides with a purity of 88.4% were obtained. The leach liquor was further treated with concentrated sulfuric acid to recover the used phosphoric acid and produce gypsum with a purity of >95% at the same time. A flow diagram for this innovative cleaner production process was developed, and larger-scale experiments are proposed to further understand this promising approach to comprehensive phosphate rock processing.
Uranium and its compounds are radioactive and toxic, as well as highly polluting and damaging the environment. Novel uranium adsorbents with high biosorption capacity that are both eco-friendly and cost-effective are continuously being researched. The non-living biomass of the fresh water green microalga Chlorella sorokiniana was used to study the biosorption of uranium from aqueous solution. The biosorption of uranium from aqueous solutions onto the biomass of microalga C. sorokiniana was investigated in batch studies. The results showed that the optimal pH for uranium biosorption onto C. sorokiniana was 2.5. Uranium biosorption occurred quickly, with an equilibrium time of 90 min. The kinetics followed a pseudo-second-order rate equation, and the biosorption process fit the Langmuir isotherm model well, with a maximum monolayer adsorption capacity of 188.7 mg/g. The linear plot of the DKR model revealed that the mean free energy E = 14.8 kJ/mol, confirming chemisorption adsorption with ion exchange mode. The morphology of the algal biomass was investigated using a scanning electron microscope and energy dispersive X-ray spectroscopy. The FTIR spectroscopy analysis demonstrated that functional groups (carboxyl, amino, and hydroxyl) on the algal surface could contribute to the uranium biosorption process, which involves ion exchange and uranium absorption, and coordination mechanisms. Thermodynamic simulations indicated that the uranium biosorption process was exothermic (ΔH = −19.5562 kJ/mol) and spontaneous at lower temperatures. The current study revealed that C. sorokiniana non-living biomass could be an efficient, rapid, low-cost, and convenient method of removing uranium from aqueous solution.
This study focuses on the characterization and synthesis of ceramic materials that have magnetic nanoparticles (MgFe2O4) within an insulating (wüstite or magnesiowüstite) matrix (Mg1-xFexO). Ceramic Oxides were employed to absorb and elute rare-earth elements (REEs). Elements were carried out in experimental batches, including the effect of pH, adsorbent dose initial REE ions concentration, and equilibrium time. The Langmuir isotherm with a monolayer adsorption capacity surpassed 397 mg g−1 at room temperature. REE ions were effectively eluted from loaded Ceramic Oxides nanoparticles with 0.1 mol l−1 of HCl acid with an efficiency of 98%. Equilibrium modeling presented the Freundlich isotherm as the best fit model for both adsorbents and metal ions, indicating heterogeneity of the surface binding sites during adsorption. The pseudo-first order kinetic model was the best-fit model. Different qualitative techniques are used to emphasis the adsorption of REE ions onto Ceramic Oxides nanoparticles. The effect of REEs ions adsorption on the structural and morphological properties have been investigated using X-ray diffraction (XRD), porosity & surface area scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The functional groups were detected by Fourier Transform infrared spectroscopy (FTIR). By applying a magnetic field of ±20 kOe, using vibrating sample magnetometer (VSM), (M-H) hysteresis loops were formed. The difference in ionic radius and atomic weight of the REE ions is highly renovated to the fluctuations in crystallographic and magnetic parameters. Finally, Ceramic Oxides nanoparticles possessed good adsorption properties such as stability and reusability, which have potential application in wastewater treatment.
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