Mechanism of Enhancing Extraction of Vanadium from Stone Coal by Roasting with MgO
In this paper, the extraction of vanadium from stone coal by roasting with MgO and leaching with sulfuric acid has been investigated, and the mechanism analysis of stone coal roasting with MgO was studied. The results indicated that under the conditions that the mass fraction of the particles with grain size of 0–0.074 mm in raw ore was 75%, the roasting temperature was 500 °C, the roasting time was 1 h, MgO addition was 3 wt %, the sulfuric acid concentration was 20 vol %, the liquid-to-solid ratio was 1.5 mL/g, the leaching temperature was 95 °C, and leaching time was 2 h, resulting in a vanadium leaching efficiency of 86.63%, which increased by 7.73% compared with that of blank roasting. The mechanism analysis showed that the degree of calcite decomposition was low and, thus, magnesium vanadate was more easily formed than calcium vanadate below 500 °C. Moreover, magnesium vanadate was easier to dissolve than calcium vanadate during the sulfuric acid leaching process. Thus, the vanadium leaching efficiency was enhanced by using MgO as a roasting additive below 500 °C. Additionally, at high temperature the formation of tremolite would consume calcium oxide produced from the decomposition of calcite, thus, the formation of calcium vanadate was hindered, and V2O5 would react with MgO to form magnesium vanadate. Therefore, the vanadium leaching efficiency of roasting with MgO was higher than that of blank roasting at high temperature.
Efficient Extraction of Vanadium from Vanadium–Titanium Magnetite Concentrate by Potassium Salt Roasting Additives
In this paper, potassium salt roasting additives were applied to extract vanadium from vanadium–titanium magnetite concentrate. Meanwhile, the mechanisms of potassium salt roasting and acid leaching kinetics were investigated. The results indicate that potassium salt roasting additives are more efficient than sodium and calcium salt and that K2SO4 works best. Under certain conditions (a dosage of K2SO4 of 4 wt %, a roasting temperature of 900 °C, a roasting time of 1 h, a leaching temperature of 95 °C, a sulfuric acid concentration of 10% (v/v), and a leaching time of 1.5 h with a liquid to solid ratio of 3 mL/g) the vanadium leaching efficiency reached 71.37%, an increase of 30.20% compared to that of blank roasting. Additionally, XRD and related SEM-EDS analyses indicated that K2SO4 fully destroyed the structure of vanadium-bearing minerals such as magnetite, and promoted the generation of soluble KVO3 to inhibit the formation of insoluble Ca(VO3)2 in the roasting process. Furthermore, it promoted the dissolution of sphene and the release of its vanadium in the leaching process, which increased the vanadium leaching efficiency significantly. Meanwhile, leaching kinetics analyses showed that the leaching process was controlled by internal diffusion; the apparent activation energy decreased from 37.43 kJ/mol with blank roasting to 26.31 kJ/mol with potassium salt roasting. The reaction order, with regards to the sulfuric acid concentration, decreased from 0.6588 to 0.5799. Therefore, potassium salt roasting could improve mineral activity, accelerating the leaching process and reducing the dependence on high temperature and high acidity.
Calcium signaling mechanisms in dedifferentiated cardiac myocytes: comparison with neonatal and adult cardiomyocytes.
Our studies focused on calcium sparking and calcium transients in cultured adult rat cardiomyocytes and compared these findings to those in cultured neonatal and freshly isolated adult cardiomyocytes. Using deconvolution fluorescence microscopy and spec trophotometric image capture, sequence acquisitions were examined for calcium spark intensities, calcium concentrations and whether sparks gave rise to cell contraction events. Observations showed that the preparation of dedifferentiated cardiomyocytes resulted in stellate, neonatal-like cells that exhibited some aspects of calcium transient origination and proliferation similar to events seen in both neonatal and adult myocytes. Ryanodine treatment in freshly isolated adult myocytes blocked the calcium waves, indicating that calcium release at the level of the sarcoplasmic reticulum and t-tubule complex was the initiating factor, and this effect of ryanodine treatment was also seen in cultured-dedifferentiated adult myocytes. However, experiments revealed that in both neonatal and cultured adult myocytes, the inositol triphosphate pathway (IP3) was a major mechanism in the control of intracellular calcium concentrations. In neonatal myocytes, the nucleus and regions adjacent to the plasma membrane we re major sites of calcium release and flux. We conclude: (1) culturing of adult cardiomyocytes leads them to develop mechanisms of calcium homeostasis similar in some aspects to those seen in neonatal cardiomyocytes; (2) neonatal myocytes rely on both extracellular and nuclear calcium for contractile function; and (3) freshly isolated adult myocytes use sarcoplasmic reticulum calcium stores for the initiation of contractile function.