No abstract

Increasing uranium exhaustion of the classical uranium ores in the last century as well as the urgent need for discovering clean nuclear energy would recently reorient research attention toward the nonconventional resources. The latter include mainly phosphate ore. This work is design to produce of citric acid by Aspergillus niger via optimization of the nutritional parameters. The medium used was supplemented with different concentrations of sucrose. It was found that sucrose (60 g/l) at pH of 3 to yield about 44.16(%) citric acid. The work is then successive to recover uranium from El-Sebaiya phosphate rock through its bioleaching which adopts on the citric acid produced from the A. niger metabolism extractant. The impure precipitate of bioleach liquor was purified via Amberlite I.R.A-400 anion exchanger resin and a marketable product of ammonium diuranate was prepared

In this investigation, a synthetic Talc Phosphogypsum ferri-silicate TPFS sorbent was prepared by thermal activation then evaluated the uranium ions removal from sulfate waste solution containing uranium. Generally, the synthetic adsorbents from raw and waste materials have a significant attention from scientists because the environmental concern and economic development, particularly, the uranium elimination from radioactive waste solutions. The uranium removal percentage and loading capacity were determined by optimization the conditions of adsorption such as the pH range, adsorbent/adsorbate ratio, uranium concentration of radioactive waste solutions, equilibrium time and temperature. The resultant adsorption efficiency and loading capacity were 87.2% and 375 mg g−1, respectively. The adsorption isothermally was in accordance with Langmuir isotherm model, in addition pseudo-second-order kinetic model, with theoretical capacity of 384.6 and 333 mg g−1, respectively. Uranium (VI) adsorption on TPFS was inhibited at elevated temperatures. The removal of uranium from sulfate waste solution by TPES sorbent according to the thermodynamic functions values was exothermic (∆H of −16.095) and non-spontaneous in nature (∆G of −17.27 at 303 K). In addition, there was a decrease in the randomness at the TPFS/uranium waste solution interface with ∆S value of 3.88.

In this study, a synthetic BaSO4·CaSO4 composite was prepared by co-precipitation technique, characterised and examined for REE sorption. The sorption parameters were; pH = 4, equilibrium time = 20 min, temperature = 303 K, and REE liquor volume to composite mass ratio of 0.2:1 L g−1. The sorption reaction was controlled by pseudo 2nd order kinetic mechanism and Langmuir adsorption isotherm with an adsorption capacity of 168.63 mg g−1. 90.14% of REE (III) was desorbed using 1 mol L−1 HNO3. The process was endothermic and spontaneous. Accordingly, 1:1 barite-gypsum (natural ingredient for BaSO4·CaSO4), with 136 mg g−1 loading capacity, was used for REEs extraction.

In the present study, thermally treated kaolinite at 600 ºC was incorporated with titanium hydroxide produced from ilmenite to prepare a novel, low-cost and a promising adsorbent (KT). Different analytical techniques such as FTIR, EDS, SEM were used to determine its structural analysis. Its applicability for uranium uptaking and desorption from its aqueous solutions was investigated by varying controlling conditions including pH, shaking time, initial concentrations, temperature and KT dose weight. Untreated kaolinite showed zero loading capacity and adsorption efficiency towards uranium ions, on the contrary thermal activation and incorporation with Ti(OH)4 improved its performance. Batch results for adsorption experiments showed that loading capacity of (KT) reached 160mgg−1; at pH 5, after only 20 min shaking time. Uranium adsorption process was much closer to a traditional Langmuir adsorption isotherm with a theoretical saturation capacity of 161.3mgg−1. From thermodynamics data, the adsorption process is endothermic in nature which emphasized by elevating temperature has an enhancement effect on uranium adsorption with uptake of 205 mgg−1 at 60 ℃. Uranium adsorption was kinetically fitted with the pseudo-second-order model. KT composite has a high applicability and reusability due to its high resistance to extreme acidity levels.