The explosion pressure and minimum explosible concentration (MEC) properties of metal sulfide ore dust clouds are valuable for the prevention and control of metal sulfide ore dust explosions. In this study, a 20 L explosion sphere vessel was used to investigate the effect of sulfur content, particle size, and concentration on the explosion pressure and minimum explosible concentration of metal sulfide ore dust clouds. Four samples with different sulfur contents were selected (30%–40%, 20%–30%, 10%–20%, and 0%–10%). Before and after the explosion, samples were tested by X-ray diffraction. The results indicate that the metal sulfide ore dust is explosive dust with St1 grade explosion pressure. With an increase in concentration, the maximum explosion pressure increased at first and then decreased. With an increase in sulfide content, the explosion pressure of metal sulfide ore dust increased, while the minimum explosible concentration decreased. As particle size decreased, the MEC also decreased. The sulfur content, particle size, and concentration of metal sulfide ore dust were the main factors affecting the explosion hazard.
To alleviate the environmental problem associated with rare earth wastewater, this research applied waste orange peel (OP) for the adsorption of La(III) and Y(III) from aqueous solution. The adsorption properties of orange peel are characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), and the participation of hydroxyl and other oxygen-containing groups that promote the physical-chemical interaction is verified. Batch adsorption results suggest that orange peel possesses a satisfactory adsorption performance for La(III) and Y(III). The optimal adsorption conditions were obtained at pH of 6, temperature of 40°C, appropriate dosage of 2 g/L and 3 g/L, contact time of 30 min, and initial ion concentration of 32 mg/L. Under the same condition, adsorption performance of La(III) is better than that of Y(III). The experimental data is well fitted by the Langmuir isotherm model with correlation coefficient R 2 > 0.9 and the minimum standard error values. Equilibrium results show that Langmuir monolayer adsorption capacity of La(III) and Y(III) onto orange peel is up to 37.61 and 31.10 mg/g. The fitting results of kinetics prove that the adsorption process of La(III) and Y(III) follows the pseudosecond-order model. Thus, natural orange peel as a recyclable biosorbent has potential economic and applicative benefits to remove La(III) and Y(III) from aqueous solutions.
To assess the thermal transformation process of common sulfide minerals in a nitrogen atmosphere, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and thermogravimetric mass spectrometry are employed to define the influence of the pyrrhotite content in pyrite-pyrrhotite mixtures (mixed minerals). The results indicate that an increase in pyrrhotite content decreases the temperature of the maximum mass loss rate of mixed minerals and reduces its mass loss. The solid-phase transformation of the thermal decomposition of mixed minerals is accelerated because the apparent activation energy of pyrrhotite is lower than that of pyrite and mixed minerals. However, the pyrrhotite makes the mixed minerals easier to sinter and agglomerate, which reduces the total volatilization amount of the gas product, S2; thus, the rate of mass loss decreases.
In this study, we performed a comparative analysis of the combustion behavior of pyrite, pyrrhotite, and pyrite-pyrrhotite mixture (mixed mineral) powders in an air atmosphere. To study the influence of the pyrrhotite content in mixed mineral powders on the combustion behavior in the air, thermogravimetric mass spectrometry, X-ray diffraction analysis, and scanning electron microscopy were employed. The results indicated that pyrrhotite lead to a weight gain in the mixed minerals during the combustion process. Pyrrhotite particles are more easily adsorbed on the surface of pyrite particles during mixed mineral combustion due to their strong ability to absorb oxygen, which accelerates pyrite combustion. The weight loss of mixed minerals decreased during the combustion process with increasing pyrrhotite content, resulting from pyrite encapsulation by agglomerated and sintered pyrrhotite during combustion. The calculated kinetic parameters and phase analysis results suggested that pyrite combustion is consistent with the shrinking core mechanism, and in the combustion process, the irregular pyrite particle shrank into a spherical particle; the combustion products of pyrrhotite grew in a layer-by-layer manner. Pyrrhotite combustion corresponded to the three-dimensional diffusion mechanism, and mixed mineral combustion was dominated by the shrinking core mechanism and supplemented by the three-dimensional diffusion mechanism. SO2, as the main combustion product, was continuously generated and volatilized in the reaction, signifying that the combustion reaction of pyrite is a two-phase reaction involving gas and solid.
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