Extraction of Lithium from Lepidolite Using Mixed Grinding with Sodium Sulfide Followed by Water Leaching

Mixed grinding with Na2S followed by water leaching was performed to extract Li from lepidolite. The leachability of Li increases dramatically in the ground mixture, regardless of the mixing ratio over the range of 1:1 to 3:1, while only 4.53% of Li was extracted in lepidolite ground without Na2S. The leachability increased with an increase of the grinding time, and ultimately, 93% of the Li was leached by water from the ground mixture with a weight ratio of 3:1 (Na2S:Lepidolite). In the process of the mixed grinding, the Li-contained lepidolite was destructured crystallographically, and it might have changed to different compounds. This process enables us to extract Li from lepidolite via a water leaching treatment

Extraction of Lithium from Lepidolite Using Mixed Grinding with Sodium Sulfide Followed by Water Leaching

Mixed grinding with Na2S followed by water leaching was performed to extract Li from lepidolite. The leachability of Li increases dramatically in the ground mixture, regardless of the mixing ratio over the range of 1:1 to 3:1, while only 4.53% of Li was extracted in lepidolite ground without Na2S. The leachability increased with an increase of the grinding time, and ultimately, 93% of the Li was leached by water from the ground mixture with a weight ratio of 3:1 (Na2S:Lepidolite). In the process of the mixed grinding, the Li-contained lepidolite was destructured crystallographically, and it might have changed to different compounds. This process enables us to extract Li from lepidolite via a water leaching treatment

Leaching Kinetics of Zinc from Metal Oxide Varistors (MOVs) with Sulfuric Acid

The leaching kinetics of zinc from zinc oxide-based metal oxide varistors (MOVs) was investigated in H2SO4 at atmospheric pressure. Kinetics experiments were carried out at various agitation speeds, particle sizes, initial H2SO4 concentrations, and reaction temperatures. It was determined that the leaching rate of zinc was independent of agitation speed above 300 rpm and also independent of particle size below 105 μm, whereas it dramatically increased with an increasing H2SO4 concentration. Except for when the H2SO4 concentration was varied, the m-values were almost constant at varying agitation speeds (m-values: 0.554–0.579), particle sizes (m-values: 0.507–0.560) and reaction temperature (m-values: 0.530–0.560) conditions. All of the m-values in these experiments were found to be below 0.580. Therefore, it is proposed that the extraction of zinc is a diffusion-controlled reaction. The leaching kinetics followed the D3 kinetic equation with a rate-controlling diffusion step through the ash layers, and the corresponding apparent activation energy was calculated as 20.7 kJ/mol in the temperature range of 313 K to 353 K

A New Recycling Process for Tungsten Carbide Soft Scrap That Employs a Mechanochemical Reaction with Sodium Hydroxide

WC soft scrap, including Co used as a binder, thermally oxidized at 600 °C, was subjected to grinding with NaOH in a mechanochemical reaction, followed by water leaching to establish an effective recycling process. Na2WO4 was synthesized through a mechanochemical (MC) reaction with oxidized scrap, and Na2CO3 was formed when the mixing ratio of NaOH increased. These as-synthesized compounds were water-soluble. When the weight ratio of soft scrap to NaOH was 1:0.5, 99.2% W was extracted by water leaching, while the extraction yield of Co was limited to 3.57% under the same conditions

Leaching Behavior of Al, Co and W from the Al-Alloying Treated WC-Co Tool as a New Recycling Process for WC Hard Scrap

The Al-alloying treated tungsten carbide (WC)-Co tool was subjected to grinding using a jaw crusher and planetary mill followed by three wet chemical treatment steps to establish an effective recycling process for WC scraps, especially those generated as bulky and hard scrap. This alloyed WC tool was readily ground to a powder of 1 mm or less and divided into two portions that were 150 µm in size. The wet chemical treatments enabled us to recover W to 69.44% from the under-sized 150 µm and also obtain WC powders from the over-sized 150 µm with a high purity of 98.9% or more

Effect of Mechanical Activation on the Kinetics of Copper Leaching from Copper Sulfide (CuS)

The effect of mechanical activation on the copper leaching of copper sulfide, CuS, in 1 M HNO3 (slurry density: 10 g/L) was investigated by analysis of the leachability and the apparent activation energy. Mechanical activation produced an increase in the leachability and a decrease of the activation energy in this leaching reaction. The leachability increased proportionally to the degree of mechanical activation, reaching 96.6% leaching within 60 min at 80 °C from CuS ground at 700 rpm for 15 min. This leaching process was controlled by surface chemical reaction following the shrinking-core model. The apparent activation energy of leaching for CuS (71.5 kJ/mol) in the range of 50 to 80 °C decreased with an increase of the degree of mechanical activation, reaching 44.3 kJ/mol for Cu leaching from CuS ground at 700 rpm for 15 min

Platinum recycling from fuel cell-spent electrocatalysts using oxidative leaching in HCl solution

The recovery of platinum (Pt) from electrocatalysts in spent proton exchange membrane fuel cells is promising and important for the sustainable development of such a noble metal. Conventional leaching of Pt in the aqueous phase typically requires the use of high concentration of mineral acids and the presence of strong oxidants owing to its thermodynamic stability and non-reactive properties. In the present study, the dissolution of Pt from a Pt/C fuel cell electrocatalyst was investigated using a simple and efficient process under moderate conditions in chloride media. Notably, the leachability of Pt was high ∼76% in a solution of low concentration HCl 2.0 M at 90 °C for 120 min in the absence of an oxidant. The enhancement of Pt leaching efficiency can be obtained using various oxidizing agents HNO3, H2O2, NaClO and NaClO3, and NaClO3 shown the most effective improvement from 76% to 88%. The dissolution of Pt in a solution of 2.0 M HCl and 3.0 wt% NaClO3 improved to 98% by the increase in leaching temperature from 50 to 90 °C. Kinetic studies indicated that Pt leaching in HCl in the presence of NaClO3 followed a chemical-controlled mechanism with an activation energy (Ea) of 40.6 kJ/mol. Based on the findings of this study, an efficient process is proposed to recover and reuse Pt from an electrocatalyst sample of spent fuel cells, including oxidative leaching, chemical precipitation and laser reduction

Dual-species Bose-Einstein condensates of ^{23}Na and ^{41}K with tunable interactions

We report the creation of dual-species Bose-Einstein condensates (BECs) of ^{23}Na and ^{41}K. Favorable background scattering lengths enable efficient sympathetic cooling of ^{41}K via forced evaporative cooling of ^{23}Na in a plugged magnetic trap and an optical dipole trap. The 1/e lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about 3×10^{5} ^{23}Na atoms surrounding 5×10^{4} ^{41}K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest s-wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic ^{23}Na^{41}K molecules as well as the exploration of many-body physics in bosonic ^{23}Na-^{41}K mixtures