查看更多>>摘要：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 degrees 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 m(2)/g. (c) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：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. (c) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：The solvent extraction of iron and titanium from coal fly ash leach solution was investigated by the use of Design of Experiments. The effect of the factors: hydrogen ion concentration, Primene JMT concentration, aqueous to organic volume phase ratio and temperature on iron and titanium extraction were evaluated. A two level factorial design implemented by statistical software Design Expert 6, determined the significant factors and any associated interactive effects amongst these factors.
查看更多>>摘要：Thermomagnetic analysis was conducted on phase transformations performed for synthetic and natural hematite by reduction involving various carbohydrates (starch, glucose, fructose, sucrose, and ascorbic acid). Thermo magnetic measurements were carried out using a laboratory facility that allows the automatic registration of a sample's magnetization as the temperature changes (the rate of sample heating/cooling was 65 degrees/min). The results were then analyzed. The reduction reaction of synthetic hematite for all carbohydrates starts at a temperature of similar to 350 degrees C, while the reduction of natural hematite for all carbohydrates starts at a temperature of similar to 365 degrees C. The magnetite formed by the reaction has a Curie temperature of 565 degrees C. Both magnetite and hematite are present in all transformed samples. Saturation magnetization increases to similar to 50 Am-2/kg for the samples obtained from synthetic hematite and similar to 25 Am-2/kg for the sample obtained from natural hematite. The difference in the value of saturation magnetization is attributed to a lower magnetite content for the sample obtained from natural hematite. Synthetic hematite transforms more effective, suggesting the synthetic sample is characterized by a larger surface area compared to natural hematite. (c) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：The adsorption mechanism of octanohydroxamic acid (OHA) on monazite was studied using kinetic, isotherm, and thermodynamic adsorption tests as well as FTIR, titration, and micro-flotation experiments. The adsorption mechanism was described as a chemisorption/surface precipitation process. At low OHA concentrations, adsorption occurred by chemisorption as a result of the reaction between surface active sites and OHA molecules. With an increase in concentration and interaction time, surface precipitation occurred. For chemisorption, adsorption was an exothermic and entropy driven process and maximum adsorption was achieved at pH 9.0 due to more active sites. In an acidic environment, such as pH 3.0, adsorption was achieved via chemisorption and hydrophobic bonding. However, a strong basic and higher temperature environment contributes to surface precipitation of basic rare earth hydroxamate. FTIR tests showed the movement of -CH2 band position from 2924 cm(-1) to 2920 cm(-1) with increases in pH values from 3.0 to 6.0, 9.0, and 11.0, which corresponds to the status of chemisorbed and surface precipitated OHA, respectively. (c) 2017 Elsevier B.V. All rights reserved.
Rowson, N. A.Johnson, T. P.Deegan, D. E.Keeley, P. M....
8页
查看更多>>摘要：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. (C) 2017 Published by Elsevier B.V.
查看更多>>摘要：Mineral concentrators can be designed to support several modes of operation, which can be optimized for different geometallurgical units. Nonetheless, alternative modes often require additional equipment and processing capacity, hence an associated capital expenditure. Moreover, the concentrator designs are often based on preliminary geological data, and are therefore subject to uncertainty. The current paper describes how stochastic mine planning algorithms may be extended to quantify the net present value (NPV) of alternative operational modes in mineral processing plants, under geological uncertainty. In particular, the Variable Neighbourhood Descent method of Lamghari et al. (2014) was originally developed for open-pit mine planning, and has now been adapted to evaluate concentrator operational modes. Sample computations are presented. (C) 2017 Elsevier B.V. All rights reserved.
Galvez, Edelmira D.Sepulveda, Felipe D.Lucay, FreddyGonzalez, Jorge F....
11页
查看更多>>摘要：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. (C) 2017 Elsevier B.V. All rights reserved.
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