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Results in Journal International Journal of Nonferrous Metallurgy: 56

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Sciprofile linkCristian Vargas, Sciprofile linkPatricio Navarro, Daniel Espinoza, Jorge Manríquez, Erica Mejía
International Journal of Nonferrous Metallurgy, Volume 8, pp 1-8; doi:10.4236/ijnm.2019.81001

Abstract:
In this work the dissolutive behavior of gold in alkaline medium using thiourea (TU), under different variables, was studied in a theoretical and experimental way, in order to determine the conditions under which it is feasible to dissolve gold in thiourea-alkaline medium. A thermodynamic study was conducted by chemical speciation using the method of Rojas-Hernández, together with an electrochemical study where the electric potential was swept in the anodic direction. The main results of the thermodynamic study were that formamidine disulfide (FDS) and sulfinic compounds (S.C.) prevail at alkaline pH; by increasing the initial concentration of thiourea at alkaline pH, the presence of the gold complex is almost zero for any initial concentration of thiourea. By including sodium sulfite in the gold-thiourea system, it was possible to obtain the Au(I)-TU complex at alkaline pH, with a presence of 95.13%. Electrochemical tests allowed verifying that in the absence of sodium sulfite the dissolution of gold in an alkaline medium is very slow but adding sodium sulfite improvements become evident in the dissolution of the metal. Therefore, sodium sulfite catalyzes the gold dissolution process and stabilizes the thiourea. With this study it was possible to establish the feasibility of using thiourea in an alkaline medium for the dissolution of gold, and the conditions under which it is possible to dissolve the gold in that medium. With these fundamentals and conditions, it is now possible to move forward to test this system for minerals and/or concentrates containing gold.
Udochukwu Mark, Charles Nwachukwu Anyakwo, Okechukwu Onyebuchi Onyemaobi, Chijioke Samson Nwobodo
International Journal of Nonferrous Metallurgy, Volume 8, pp 9-24; doi:10.4236/ijnm.2019.82002

Ogundeji Frncis Oladapo, Alabi Oladunni
International Journal of Nonferrous Metallurgy, Volume 8, pp 25-33; doi:10.4236/ijnm.2019.83003

Abstract:
Each type of a manganese deposit is a problem by itself in the matter of selection of a proper method of concentration, depending on the manganese minerals and their gangue constituents. Hence, this work studied the effect of sodium oleate concentration variation on the froth flotation of manganese ore obtained from Madaka, Niger State, Nigeria. The chemical analysis of the ore shows that it contains 48.4% MnO (37.5% Mn). Peaks were identified in XRD analysis of the crude sample as that of magnosite (MnO), hausmannite (Mn3O4), spessartine and vemuculite (Mg, Fe2+, Fe3+)3[(AlSiO4)O10](OH)2·4H2O. The ore was beneficiated by froth flotation using sodium oleate as collector at varied concentrations of 3 g/kg, 7 g/kg and 10 g/kg. Other chemical reagents used were sodium silicate, fuel oil and calcium hydroxide as dispersant, frother and pH modifier respectively. Results obtained showed percentage metal recoveries of 9.29%, 14.30% and 19.61%, assaying 65.20%, 62.03% and 61.30% Mn respectively. This indicates that at sodium oleate concentration of 3 g/kg, high grade-concentrate can be obtained.
Neeraj Kumar, Kautily Rao Tiwari, Km. Meenu, Arti Sharma, Adya Jain, Shikha Singh, Radha Tomar
International Journal of Nonferrous Metallurgy, Volume 8, pp 35-71; doi:10.4236/ijnm.2019.84004

Abstract:
In this review, we summaries the past few year work on the chemistry of CWA’s and their simulants on various heterogeneous surfaces of zeolites, composites of zeolites and doped zeolite with transition metal oxides. This review elaborates an updated literature overview on the degradation of CWA’s and its simulants. The data written in this review were collected from the peer-reviewed national and international literature.
Mohammad Hasan Omidi, Omid Salmani Nuri, Hassan Tavakoli
International Journal of Nonferrous Metallurgy, Volume 7, pp 25-38; doi:10.4236/ijnm.2018.73003

Sciprofile linkHidekazu Sueyoshi1), Kousaku Yamada, Masashi Miyazaki, Takuya Okada, Nobuyuki Ashie, Yoshiharu Kousaka
International Journal of Nonferrous Metallurgy, Volume 7, pp 1-7; doi:10.4236/ijnm.2018.71001

Abstract:
The Mechanism of Pb removal from brass scrap by compound separation using Ca and NaF addition was investigated. Because large Ca-Pb compound particles formed by Ca addition rise to the surface of the molten brass, they can be skimmed off from the molten brass. However, fine Ca-Pb compound particles remain in the molten brass because of low buoyancy. By subsequent NaF addition, the reaction between Ca-Pb compound and NaF takes place at their contact regions, resulting in the formation of solid CaF2, liquid Pb and Na gas. Pb is mainly present at the Ca-Pb compound-CaF2 interface. CaF2 acts as a binder for aggregation of fine Ca-Pb compound particles, resulting in the formation of light and large composite compounds, which rise to the surface of the molten brass. A high Pb removal rate is achieved by skimming off.
Zhi-Xiong Liu, Lin Sun, Liang-Dong Tang, Jie Hu, Yang Xiao, Yi-Guang Chen, Zhou-Lan Yin
International Journal of Nonferrous Metallurgy, Volume 7, pp 9-23; doi:10.4236/ijnm.2018.72002

Sciprofile linkHidekazu Sueyoshi1), Masashi Miyazaki, Takuya Okada, Nobuyuki Ashie, Yoshiharu Kousaka
International Journal of Nonferrous Metallurgy, Volume 7, pp 39-55; doi:10.4236/ijnm.2018.74004

Abstract:
2 wt% Ca was added to molten brass containing 3.2 wt% Pb. The composition and grain size of the formed Ca-Pb compound were examined in detail using SEM-EDS and XRD. This revealed that the composition of the Ca-Pb compound depends on the grain size of the liquid phase Pb and the diffusion phenomenon of the Ca in the Ca-Pb compound formed on the surface of the Pb. When the Pb has a fine grain, a compound composed only of Ca-Pb compounds is formed. When the grain size of the Pb is several μm, Ca-Pb compounds containing unreacted Pb in the center are formed. These compounds aggregate into a larger compound grain. From the evaluation of the floating force (the resultant force of the weight and buoyancy of the Ca-Pb compounds formed) and the rising terminal velocity of the Ca-Pb compound within the molten brass, it was found that the floating force and rising terminal velocity depend on the composition and grain size of the Ca-Pb compound. It was found that since Ca-Pb compounds with a floating force greater than 10−6 g∙cm/s2 have a very large rising terminal velocity, they reach the surface of the molten brass in a short time after compound formation and then continue to float on the surface of the molten brass. Thus they can be removed by skimming. The effects of the grain size of the Ca-Pb compound on the floating force and the rising terminal velocity were greater than those of the composition of the Ca-Pb compound.
Qi Zhu, Sciprofile linkLing Shen, Jianjun He, Weihua Gui
International Journal of Nonferrous Metallurgy, Volume 6, pp 47-59; doi:10.4236/ijnm.2017.64004

Abstract:
The temperature of aluminum alloy work-pieces in the aging furnace directly affects the quality of aluminum alloy products. Since the temperature of aluminum alloy work-pieces cannot be measured directly, a temperature prediction model based on improved case-based reasoning (CBR) method is established to realize the online measurement of the work-pieces temperature. More specifically, the model is constructed by an advanced case-based reasoning method in which a state transition algorithm (STA) is firstly used to optimize the weights of feature attributes. In other words, STA is utilized to find the suitable attribute weights of the CBR model that can improve the accuracy of the case retrieval process. Finally, the CBR model based on STA (STCBR) was applied to predict the temperature of aluminum alloy work-pieces in the aging furnace. The results of the experiments indicated that the developed model can realize high-accuracy prediction of work-pieces temperature and it has good application prospects in the industrial field.
International Journal of Nonferrous Metallurgy, Volume 6, pp 1-16; doi:10.4236/ijnm.2017.61001

Abstract:
The purpose of this research is to develop a SolidWorks® model for transient temperature field of laser welding of PMMA/SS 304 materials for application in fabrication of the ultrasonic back-plate, with a view of optimizing the experimental conditions. The study is carried out on these materials because of the increasing application of both metals and non-metals. The work focuses specifically on these materials because they have been experimentally studied previously and as such, this study can be accepted as an assessment into feasibility of using SolidWorks® model to study the temperature field of the laser welding processes of metals and non-metals. The results of the SolidWorks® transient thermal model show that there is a concentration of high temperatures at the point of contact. It also shows that temperature decreases as we move in (between laser and the top face) to the thickness of the part. Additionally the maximum temperature occurs at the last point of the welding; this may be due to the accumulation of the temperature before arriving at the end. These findings are comparable to the previous simulated and experimental results on temperature field during laser welding of PMMA/SS 304 materials. However, SolidWorks® is shown to present a challenge in modeling a moving source of laser power.
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