Highly Efficient and Selective Extraction of Gold from Thiosulfate Leaching Solution Using Functionalized Dicationic Ionic Liquids

Thiosulfate leaching has been regarded as a promising alternative to cyanidation, but it still faces the challenge of the recovery of low content of gold from high concentrations of thiosulfate solutions. Liquid-liquid extraction is a method to address this issue but is still limited by the use of volatile and toxic organic solvents. To overcome this limitation, this work synthesized some functionalized dicationic ionic liquids (DILs) to serve as extraction solvents for the recovery of the gold-thiosulfate complex, [Au(S2O3)2]3-, from thiosulfate solutions. Experimental results indicated that the DILs showed higher extraction rates toward [Au(S2O3)2]3- compared with their monocationic-based counterparts, likely due to the stronger electrostatic interaction between the dications of the ILs and [Au(S2O3)2]3-. The transfer of [Au(S2O3)2]3- from the water phase to the IL phase was identified as an anion exchange and endothermic process. The rate of extraction was limited by the anion exchange process occurring at the IL-water interface. The extraction ability of ILs highly depended on the type of anion; specifically, the ILs with anions that had strong hydrogen-bonding ability exhibited high extraction ability toward [Au(S2O3)2]3-. Finally, DILs proved effective in the recovery of [Au(S2O3)2]3- from an actual gold leaching solution and exhibited high selectivity toward coexisting ions, indicating their potential as environmentally friendly solvents for gold recovery.

Study on preparation and thermal properties of new inorganic eutectic binary composite phase change materials

It is important to improve phase change materials (PCMs) with appropriate temperature and excessive latent heat to accelerate the application of latent heat energy storage technology in solar energy storage systems. In this paper, the eutectic salt of NH₄Al(SO₄)₂·12H₂O (AASD) and MgSO₄·7H₂O (MSH) was prepared and the performance was studied. The DSC results show that the optimum content of AASD in the binary eutectic salt is 55 wt%, the melting point was 76.4 °C, and the latent heat is up to 189.4 J g^-1, which is suitable for solar power storage systems. Four nucleating agents (KAl(SO₄)₂·12H₂O, MgCl₂·6H₂O, CaCl₂·2H₂O, CaF₂) and two thickening agents (sodium alginate, soluble starch) are added to the mixture in varying proportions to improve its supercooling. The best combination system was 2.0 wt% KAl(SO₄)₂·12H₂O/1.0 wt% sodium alginate with a supercooling degree of 24.3 °C. After thermal cycling tests, the best formulation of the AASD-MSH eutectic salt phase change material was determined to be 1.0 wt% CaCl₂·2H₂O/1.0 wt% soluble starch. The latent heat was 176.4 J g^-1 and the melting point was 76.3 °C. The supercooling was still lower than 30 °C after 50 thermal cycles, which served as a benchmark for the next investigation.

Superhydrophilic Modified Elastomeric RGO Aerogel Based Hydrated Salt Phase Change Materials for Effective Solar Thermal Conversion and Storage

As a typical phase-change material (PCM) with high heat storage capacity and wide distribution, hydrated salts play broad and critical roles in solar energy utilization in recent years. However, the leakage and supercooling problems of hydrated salts have been a constraint to their further practical applications. In the current work, the super-hydrophilic reduced graphene oxide (RGO) aerogels modified by konjac glucomannan (KGM) as supporting structural materials are prepared by the hydrothermal reaction-freeze-drying, which can effectively absorb and convert visible sunlight energy into thermal energy. In addition, the super-hydrophilic aerogels compounded with PCMs can ameliorate the shortcoming of leakage and suppress the supercooling temperature as low about 0.2-1.5 °C in the freezing process. Under 1 sun irradiation, the prepared sodium acetate trihydrate/KGM-modified graphene oxide aerogel (SAT/KRGO) composite PCM achieves a high photothermal conversion efficiency (86.3%) due to its good light absorption property. The number of cycles has no apparent effect on the supercooling of the composite materials, suggesting their stable thermal cycles and thermal storage.

Nanoencapsulation of phase change materials for advanced thermal energy storage systems

Phase change materials (PCMs) allow the storage of large amounts of latent heat during phase transition. They have the potential to both increase the efficiency of renewable energies such as solar power through storage of excess energy, which can be used at times of peak demand; and to reduce overall energy demand through passive thermal regulation. 198.3 million tons of oil equivalent were used in the EU in 2013 for heating. However, bulk PCMs are not suitable for use without prior encapsulation. Encapsulation in a shell material provides benefits such as protection of the PCM from the external environment and increased specific surface area to improve heat transfer. This review highlights techniques for the encapsulation of both organic and inorganic PCMs, paying particular attention to nanoencapsulation (capsules with sizes <1 μm). We also provide insight on future research, which should focus on (i) the development of multifunctional shell materials to improve lifespan and thermal properties and (ii) advanced mass manufacturing techniques for the economically viable production of PCM capsules, making it possible to utilize waste heat in intelligent passive thermal regulation systems, employing controlled, "on demand" energy release/uptake.

Graphene-decorated silica stabilized stearic acid as a thermal energy storage material

Graphene-decorated silica stabilized stearic acid composites with interesting thermal energy storage behaviors.