查看更多>>摘要：A magnetic nano-scaled composite was synthesized by self-assembly of cationic surfactant octadecyl dimethyl hydroxyethyl ammonium nitrate (SN) into natural mineral diatomite via a 'dissolution and reassembly' method. Fourier transform infrared (FT-IR), elemental analysis, scanning electron microscopy (SEM), transmission electron microscope (TEM), surface area and magnetic analysis were performed to characterize the achieved composites. The results indicated that SN and Fe3O4 nanopartilces were successfully inserted into the diatomite matrix. Under the same condition, the mixed phenols adsorption experiments showed that the maximum adsorption capacity of phenols by the composite was in order of 2,4,6-trichlorophenol > 2,6-dichlorophenol > 2,4-dichlorophenol > p-nitrophenol > m-methylphenol > phenol, the same as the competitive adsorption ability. The adsorption process obeyed the Langmuir isothermal model. 2,6-Dichlorophenol was used as a representative contaminant to further investigate the mechanism of adsorption. Electrostatic interaction and hydrophobic stacking effect might play important roles in the adsorption towards organic phenols. Owing to the embedded magnetic Fe3O4, the composite was able to be separated easily from liquid media under an external magnetic field. The further calcination of the used composites showed a possibility to deliver new magnetic mesoporous absorbents for further use. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study, low-rank lignite coal sample collected from Jining coalfield of Shandong province in China was subjected to desulphurization by using a new bacteria and Acidithiobacillus ferrooxidans isolated from the native coal mine site. The molecular identification of the 16S rRNA gene showed that the new native bacteria was Pseudomonas sp., denoted as NP22, and it is reported for the first time for the capability to remove about 46% of total sulphur from the lignite coal. In the present study, the effects of various parameters such as medium pH, incubation time, pulp density, particle size, incubation temperature on desulphurization from lignite coal with the Pseudomonas sp. NP22 and Acidithiobacillus ferrooxidans were investigated. Analytical characterization indicated that total sulphur content of lignite coal was reduced to 2.76% and 3.23% by using two microorganisms. Also, the calorific value of lignite coal was not affected adversely after two microorganisms' desulphurization but rather its calorific value increased from 6219 cal/g to 6406 cal/g and 6315 cal/g, however, the ash content of the lignite coal was eliminated. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Cemented coal gangue-fly ash backfill (CGFB, a mixture of binder, coal gangue, fly ash and water) is introduced and applied to fill underground voids in coal mines. Once placed, the CGFB mixtures should have favorable stability and environmental performance, and these are closely related to the thermal, hydraulic and mechanical properties of the CGFBs. In this study, column and block experiments are conducted to investigate the coupled evolutions of the main performance characteristics (thermal, hydraulic and mechanical) of CGFB structures. A test apparatus is designed and equipped to investigate the thermal (temperature development), hydraulic (water drainage) and mechanical (lateral expansion) performances of CGFB columns under pressure in drained and laterally constrained conditions. The CGFBs are cured at room temperature and monitored for 30 days. Additionally, water drainage and uniaxial compressive strength (UCS) of CGFB blocks at different curing temperatures (20 and 50 degrees C) are also tested. The results indicate that the hydraulic and mechanical behaviors of the CGFBs are significantly affected by thermal factors (heat generated by binder hydration and heat transfer between the CGFB and its surroundings). This study will contribute to a better understanding of the thermohydro-mechanical behavior of underground CGFB structures, and thus a better design of stable and environment-friendly CGFBs. (C) 2017 Elsevier B.V. All rights reserved.
Schoeman, E.Bradshaw, S. M.Akdogan, G.Snyders, C. A....
8页
查看更多>>摘要：The paper discusses the elution of platinum cyanide and palladium cyanide from strong base anion exchange resins, namely Amberlite PWA5 and Minix, with the use of acidic thiourea, potassium thiocyanate and zinc cyanide. It is shown that thiocyanate ions and zinc cyanide were effective eluants for strong base resins. Acidic thiourea, however, was found to be ineffective in eluting platinum cyanide from strong base resins, but eluted palladium cyanide. The concentration of the eluting agents was found to affect the elution to a noticeable degree, with no significant effect imparted by the elution temperature and flow rate. Overall, it can be concluded that platinum cyanide and palladium cyanide can be effectively eluted from strong base anion exchange resins, with the use of potassium thiocyanate and zinc cyanide. However, split elution alternatives, such as acid washing, should be investigated to separate platinum cyanide and palladium cyanide from the base metal cyanides loaded on the resins. (C) 2017 Elsevier B.V. All rights reserved.
Schoeman, E.Bradshaw, S. M.Akdogan, G.Snyders, C. A....
9页
查看更多>>摘要：The use of ion exchange resins for the extraction of platinum and palladium from a synthetic cyanide leach solution is described in this paper. An increase in the concentrations of both platinum and palladium cyanide in solution from 0.15 to 0.45 mg/L and from 0.40 to 1.2 mg/L respectively resulted in higher equilibrium loadings while the first order constants remained constant. The solution pH did not have a significant effect on the equilibrium loading of platinum cyanide and palladium cyanide in the ranges 9 to 11. However, improvements in the loading kinetics of both these complexes were noticed with an increase in solution temperature from 30 to 60 degrees C. Changes in zinc cyanide and nickel cyanide concentrations in the range 5 to 20 mg/L did not have a significant effect on the adsorption of platinum cyanide and palladium cyanide. It was concluded that strong base anion exchange resins could effectively recover platinum and palladium cyanides from dilute synthetic cyanide solutions and that the exchange capacity and functionality of these ion exchange resins might have played an important role in their affinity for different metal anions in solutions. (C) 2017 Elsevier B.V. All rights reserved.
Lazcano, Branko ArayaDouce, Jean-FrancoisRivera, Rodolfo MarinKoltsov, Alexey...
12页
查看更多>>摘要：During iron ores granulation process minimization of the volume of water is of vital economic importance due to the associated energy cost of evaporation in the second sintering step. The optimisation of water addition demands understanding of capillarity properties of iron ore mixtures to ensure at the same time good mechanical strength of iron ore granules and just needed minimum of water in the granulation drum. Thus, in the current work wettability and capillarity properties of 7 iron ores, 7 additives and 7 mixtures of those components were studied. It was found that particles with size below 0.1 mm have a big influence on the contact angle and percentage of infiltrated water of mixtures. Particularly, the content of hematite Ore 1 had a significant effect on the contact angle. The use of calcine and dolomite additives affects slightly the magnitude of the water surface tension, but modifies the wettability of iron ores. The adaptation of the Cassie model for mixtures of iron ores of > 2-phases gave an excellent estimation of the contact angle for mixtures with size particles below 0.1 mm. A good estimation for mixtures with particles larger than 0.1 mm was also obtained. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：This study presents an optimization of the method used to quantify reactive silica (RxSiO(2)) in gibbsitic bauxites, specifically those which contain no (or insignificant) quartz. In this work they are named as Paragominas-type Bauxites. A factorial design of experiments was used. The variables included the temperature, caustic concentration and time for two cases: bauxites with low and high RxSiO(2) contents. Temperature is the most important factor and has a positive influence on RxSiO(2). First-order empirical models were properly obtained to predict the amount of RxSiO(2) as a function of temperature, caustic concentration and time, which responded to the following optimal conditions: (1) without significant amount of quartz - 180 degrees C, NaOH 10% w/v and 60 min for low RxSiO(2) and 25 min for high RxSiO(2), and (2) with significant amount of quartz - 150 degrees C, NaOH 20% w/v and 60 min for both situations. (C) 2017 Published by Elsevier B.V.
查看更多>>摘要：In this research, a zinc sulfide (sphalerite) concentrate of Angouran mine was studied by direct atmospheric leaching process. This process is an alternative to the conventional method of roast-leach-electrowinning (RLE) for zinc production by assisting ferric ions as powerful oxidant. The independent sphalerite leaching parameters investigated were ferric ions concentration (0.4-1.2 M), temperature (40-80 degrees C), particle size (21-53 pm), sulfuric acid concentration (0.5-1.5 M) and time (2-6 h). Response surface methodology (RSM) was used to optimize the process parameters. The most influencing parameter was found to be temperature and the less effective was acid concentration. Based on the results, ferric ions illustrate a complex effect on the recovery of zinc; In this regard, interaction of ferric ions with operational parameters was proposed. The optimum recovery for leaching of the zinc sulfide concentrate (e.g., 84.72%) was obtained at ferric ions concentration of 1.2 M, temperature of 80 degrees C, mean particle size of 21 pm and leaching time of 6 h. The predicted percentage recovery of zinc at the optimum condition was found to be 84.96% which was very close to the experimental value of 84.72%. Kinetic investigation was carried out in the optimum condition that obtained by RSM. Kinetic results showed that there were two stages in the sphalerite leaching. At the beginning of the leaching process, kinetics of sphalerite leaching is fast, while after about an hour the overall rate of leaching has decreased. The kinetic of leaching in the first stage is affected by both rate of chemical reaction and rate of diffusion through the sulfur layer. In this stage, the contribution of chemical reaction gradually decreases by increasing the temperature. In the second stage, the leaching rate of sphalerite is controlled only by diffusion through the product layer. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：The surface-controlled reactions and interfaces of clays and/or clay minerals are strongly determined by the adsorption of dissolved humic substances which have surface active characters. Consequently, this may lead to an improved understanding of organo-clay complexes for remediation purposes of polluted areas. The interactions between sepiolite and sepiolite-bound humic acid (HA), and its influence on the mechanism of the formation of sepiolite-humic acid complexes were examined by characterizing the structure of sepiolite through UV/Vis spectroscopy, field emission scanning electron microscopy (SEM + FEG), specific surface area, pore size and volume, and Fourier transform infrared spectroscopy (FTIR). The UV-vis spectral results of the raw sepiolite showed that there is no correlation between UV254 and the amount of humic substance released from sepiolite is dependent on increasing extraction time. The low values of humification index of the sepiolite confirmed the presence of HA with higher, and similar molecular weight, particle size, humification degree and aromaticity. Hence, it can be concluded that HA groups are presumably associated with the large quantity of silanol groups located on the sepiolite external surface preferentially through H-bonds and/or surface complexation interactions between the functional groups in HA and dissolved metal cations (Mn). This finding is in good agreement with results from FTIR and SEM-FEG investigations. EDAX analysis of the HA-extracted sepiolite illustrated a strong decrease in Mg2+, Ca2+ and K+ content indicating that electrically charged sites on HA may form metal complexes of high stability through chelation. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this work, the roles of dissolved oxygen (O-2), Fe3+ and Fe2+ and their interactions during chalcopyrite leaching in basic culture medium at normal atmospheric pressure and 45 degrees C were investigated by leaching experiments, XPS and electrochemistry analysis. Results showed that Fe3+ remarkably promoted chalcopyrite dissolution at the initial stage of leaching process, while easily caused the final passivation at the later stage. Leaching experiments showed that Fe2+ cannot promote chalcopyrite dissolution in N-2 atmosphere, while significantly promoted chalcopyrite dissolution in O-2 atmosphere. XPS and electrochemistry further proved that Fe2+ cannot directly react with chalcopyrite, Fe2+ was steadily oxidized to Fe3+ by O-2 and caused redox potential at an appropriate range (about 380-480 mV vs. Ag/AgCl), thus eliminating passivation species of polysulfide (S-n(2-)) and promoting chalcopyrite dissolution. Dissolved oxygen can directly oxidize chalcopyrite when with no addition of metal ions. In addition, Fe3+, rather than O-2 was the main oxidant in leaching system of chalcopyrite at normal atmospheric pressure. Band theory was used to further interpret the roles of oxidants and reductants in bioleaching system of chalcopyrite. This work is potentially useful in interpreting the roles of oxidants and reductants in bioleaching system of chalcopyrite at normal atmospheric pressure and 45 degrees C. (C) 2017 Published by Elsevier B.V.
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