International Journal of Mineral Processing最新文献

The effects of alkaline solution and calcined clays on vibrational spectra and mechanical properties were studied on geopolymer samples prepared from two alkaline solutions, calcined clays and three metakaolins. Structural evolution of the prepared geopolymers was characterized using FTIR spectroscopy and compression tests. Our results indicated high positive correlation between reactivity and compressive strength of the studied samples. Commercial potassium silicate and laboratory prepared k-silicate solutions were used to assess their effects on the prepared geopolymers. It was also observed that various secondary phases appeared, causing a slight change in the species' reactivity. Finally, it was concluded that changing alkaline solution and calcined clays decreased the mechanical properties, but increased the FTIR shift values. However, further work is needed to study the effects of alkaline solutions and natural clays from Tunisia on the properties of the prepared geopolymer. This is compulsory for prospective application of those products in various industries.

Experimental studies on the influence of scraper movement on the fluidization of air dense-medium fluidized bed (ADMFB) have been conducted. The maximum bed pressure drop is about 3% when the scraper speed changes from 0 to 0.5 m/s. The minimum fluidized velocity U_mf decreases as the scraper speed increases. At the same time, the bed density only declines by 3.7%, and the density standard deviation decreases significantly which is mainly caused by the horizontal motion of the medium. The separation tests indicated that the most appropriate scraper speed is between 0.1 m/s and 0.3 m/s and it was reasonable to move the scraper at the appropriate rate to get the better separation performance.

Reverse flotation is an effective method for separating apatite from gangue minerals (such as dolomite) in collophanite ore. However, collophanite ore flotation using traditional fatty acid collectors is uneconomical because of the relatively high cost of the raw materials. In this work, saponified gutter oil fatty acid (GOFA) was used as the collector, and its effect on collophanite ore flotation and the mechanism of adsorption were studied. The results showed that Ca^2 + is the active site for reaction with GOFA and initiates apatite flotation. The dissolution of Ca^2 + from dolomite was found to be thermodynamically more favorable than that from apatite, and the relative abundance of Ca^2 + enhanced the reaction of dolomite with GOFA. XPS analysis revealed that the interaction between GOFA and magnesium on the dolomite surface strengthened chemisorption. As magnesium is a major constituent of dolomite, but not of apatite, GOFA was selectively chemisorbed onto the dolomite surface. Closed-circuit reverse flotation tests using GOFA as the collector resulted in an excellent concentrate with 28.46 wt% P₂O₅ and 0.65 wt% MgO, corresponding to a P₂O₅ recovery of 87.2%. GOFA was demonstrated to exhibit outstanding selectivity for dolomite in the reverse flotation of collophanite ore. The use of GOFA as an environment-friendly, cost-effective, and selective collector is expected to provide new insights into low-cost collophanite ore flotation.

A novel method for Na₂SnO₃ preparation from SnO₂ and Na₂CO₃ roasted under CO-CO₂ atmosphere in a solid state has been successfully developed. In this study, the formation kinetics of Na₂SnO₃ was investigated. The formation of Na₂SnO₃ was controlled by the first-order interfacial chemical reaction at 800 °C under 10 vol% CO content; as the temperature increased to 850 °C–900 °C, it was controlled by the three-dimension (Ginstling and Brounshtein) diffusion through the product layer at the early reaction stage. The rate constant increased with the increasing of temperature. Furthermore, the rate controlling characterizations of three-dimension diffusion were also discussed.

Different factors involving in grinding of ore cause various breakage mechanisms. These different mechanisms differ the morphology of ground particles. In this study, the effect of ball mill types, feed sizes, and ball surface area have been investigated on the morphology of ground quartz particles using MBL cruise optical microscope and Olympus E-510 camera. Measured two-dimensional particle projection was expressed mathematically such as circularity, roundness and aspect ratio by ImageJ software. > 20,000 particles were morphologically measured for image analysis. Results show that circularity and roundness of ground particles are enhanced in an ordinary ball mill equipped with smooth liner (OBM). While higher aspect ratio of ground particles are achieved in cylindrical ball mill equipped with wavy liner (CBM). Consequently, the dominant breakage mechanism for OBM and CBM are abrasion and impact, respectively. Circularity and roundness values of coarse-grained ground particles are more than fine-grained particles. The increase of ball surface area causes the increase of circularity as well as roundness values and the decrease of aspect ratio value.

Static leaching experiments were performed to detect the heavy metals release rule of stone coal waste rocks at different solution pH levels. Results showed that solution pH exerted a significant influence on mineral dissolution. As solution pH decreased, the dissolved quantities of minerals increased gradually. With leaching time progressing, the dissolved quantities of Cr and V at each experimental pH level increased almost all the way, while As and Cd dissolved quickly at first and then the dissolution decreased. The dissolved quantities of major elements in the stone coal waste rocks were also detected.Ca and Mg dissolution increased rapidly in the beginning and then decreased slowly; however, the dissolved quantities of Al and Fe were relatively low. The maximum dissolved quantities at a solution pH of 2 were observed in the following order: Ca (2695.65 mg/kg) > Mg (510.92 mg/kg) > Al (23.64 mg/kg) > Fe (11.55 mg/kg) > V (6861 μg/kg) > Cr (1005.35 μg/kg) > Cd (751.71 μg/kg) > As (323.66 μg/kg). It can be seen that the dissolution of the elements is not correlated with their total content in the stone coal waste rocks, but is related with their content in easily soluble fraction (F1). The stone coal waste rocks were found to exhibit a relatively high neutralizing power, in that, in the range of initial solution pH at 3–9, final leachate pH stabilized at 8.3–8.5. This neutralizing ability was conducive to precipitate newly dissolved heavy metals, thus was favorable for reducing the waste rocks environmental toxicity.

Ammoniacal thiosulfate leaching of refractory oxide gold ore was investigated. According to X-ray fluorescence and fire assay analyses, the ore contained about 33.01 wt% Si, 8.53 wt% Al, 7.26 wt% K, 3.00 wt% Fe, and 2.80 ppm Au. Moreover, X-ray diffraction analysis and mineralogical studies using polished thin sections showed that the ore was composed of quartz, epidote, muscovite, and orthoclase as major minerals and goethite and jarosite as minor minerals. The effects of temperature, leaching time, and the concentrations of thiosulfate, copper ion, and ammonia on the gold extraction were studied. Maximum gold extraction of 55% was obtained using thiosulfate, ammonia, and copper sulfate concentrations of 0.1 M, 3 M, and 0.0125 M, respectively. This extraction value was achieved after room temperature leaching of a pulp with a density of 20% for 16 h. Stirring speed and the pH of the aqueous solution were 400 rpm and 10, respectively. Leaching rate using the preceding optimum conditions showed a transition after a leaching time of 2 h indicating a change in the process mechanism.

Nano zero-valent iron (NZVI) was prepared using sonochemical leaching of the obtained powder from mechanochemical treatment of natural pyrite with metal powder of aluminum. At the first step, the Fe-Al₂S₃ compound was prepared via co-milling of natural pyrite and aluminumin a planetary ball mill. At second step, the aluminum sulfide was separated from the Fe-Al₂S₃ compound to produce NZVI using sonochemical leaching method with 1.5 M NaOH solution for 45 min at 80 °C. The results from XRD and XRF analysis revealed that more than 83% of aluminum sulfide was extracted during separation step and iron phase remained as a main constituent phase in the leaching residue (NZVI). The FE-SEM images and the BET surface area verified that the produced NZVI has particles size less than 100 nm with BET surface area of 116 m²/g.

Slags produced as industrial by-products can be used to replace cement by producing alkali-activated slag (AAS) binders. Slags are produced from a variety of high temperature processes and the composition of the slag will change depending on its origin. This paper presents work which investigated the effect of the chemical composition of the slag on its silicate glass network structure and how this affects the performance of the slag during alkali-activation. Several different slag compositions were obtained and Raman spectroscopy was used to determine the silicate structure present in the slags. Mechanical strength testing and dissolution experiments were used to assess the performance of the slags during alkali-activation. The results show that the chemical composition effects the polymerisation of the slag and a decrease in polymerisation of the slag's network structure leads to an increase in the strength of the AAS binder and greater slag reactivity.

A methodology for the conceptual design of concentration circuits is presented. The methodology considers three decision levels: level I – the definition and analysis of the problem, level II – the synthesis and screening of alternatives, and level III – the final design. Level I allows setting up the problem and defining the design goals. In level II circuit alternatives are generated and evaluated using a group contribution method. Also, level II is complemented by a database that helps to select the most suitable circuit. In level III the design of each process stage is performed for the alternatives identified in level II. This final design is performed using local/global sensitivity analysis and reverse simulation. The method is illustrated with examples that demonstrate that the method is suitable for these types of problems.