Co-recovery of manganese from pyrolusite and gold from carbonaceous gold ore using fluidized roasting coupling technology
Graphical abstract
Introduction
The pyrolusite is stable in the acidic or alkali conditions, but manganese can be acidic extracted from pyrolusite in reductive conditions due to the generation of acid-soluble manganese oxide [1]. At present, mainly reductive technologies for pyrolusite include the roasting reduction and the hydrometallurgical process. The roasting reduction can be achieved using coal-based reducer [2] or organic materials such as sawdust, cellulose, molasses, cassava, sugarcane, banyan-leaves, tea-leaves [[3], [4], [5], [6], [7], [8], [9]] at high temperature. However, the traditional reduction roasting technology has the disadvantages of high cost, great energy consumption and easy sintering. Moreover, due to the poor grindability of biomass, the long roasting time and insufficient heat transfer would be caused in roasting process [10,11]. The inorganic reductants (iron filings, SO2, Na2SO3 and H2O2) often used in hydrometallurgical process, but it would introduce difficulties concurrently in separation and purification [[12], [13], [14]].
Carbonaceous gold ore contains a large amount of carbon, organic carbon and carbonate. During the gold extracting process, the dissolved gold complex will be adsorbed by carbonaceous matter, thus causing low gold extracting efficiency. Therefore, it is essential to pre-roast to remove the carbonaceous matter from carbonaceous gold ore before the gold extraction [15].
In order to make full use of the carbon component in carbonaceous gold ore, it was used as the reductant in pyrolusite processing [16]. And the roasting coupling technology, which is to combine the oxidizing roasting process of carbonaceous gold ore with the reducing roasting process of pyrolusite in one roaster, was presented. Based on the efficient fluidized roasting technology, the leaching effect of manganese and gold, optimal technical conditions of roasting, and the roasting process analysis were investigated. The coupling processing research can not only realize the utilization of the waste and decrease the emission of harmful gases during the oxidizing roasting pretreatment of carbonaceous gold ore, but also reduce the consumption of energy and bring good economic benefits. Meanwhile, fluidized roasting, which has advantages such as large phase contact area, high heat transfer efficiency, low energy consumption, was adopted in roasting process. Thus, the cleaner and efficient production was achieved.
Section snippets
Materials
The high-grade pyrolusite and carbonaceous gold ore in Gansu were obtained as the research object in this study. Both of the ore samples were crushed, ground, and characterized by X-ray fluorecence (XRF) and X-ray diffraction (XRD). The results of multi-element analysis of pyrolusite and carbonaceous gold ore were shown in Table 1, Table 2 respectively. The XRD pattern of pyrolusite and carbonaceous gold ore were shown in Fig. 1, Fig. 2 respectively. Analysis of carbonaceous matter in
Cold gas flow experiment
As the sample was added into to the fluidized bed reactor, a certain height of the feed layer was formed above the grid plate. With the increase of bottom gas flow, feed layer underwent four different phases: the static phase, the initial phase, the fluidized phase, and the conveying phase. The gas passes through the gap between particles but the feed layer is stationary at slow gas flow rate. And the pressure drop of the feed layer increases monotonously with the increase of the gas flow rate.
Conclusions
The fluidized roasting coupling technology realizes the amalgamations of roasting process of pyrolusite and carbonaceous gold ore. The reduction process of pyrolusite ore by carbonaceous gold ore can not only maximize the utilization of carbonaceous gold ore and decrease the emission of harmful gases, but also achieve efficient extraction manganese and gold. Under the conditions mass ratio (carbonaceous gold ore to pyrolusite) at 2:3, reaction temperature at 1073.15 K, reaction time at 30 min,
Declaration of Competing Interest
This article has not been published elsewhere in whole or in part. All authors have read and approved the content and agree to submit for consideration for publication in the journal. There are no any ethical/legal conflicts involved in the article. If accepted, the article will not be published elsewhere in the same form, in any language, without the written authorization of the Publisher.
Acknowledgements
This research was supported by China Ocean Mineral Resource R&D Association under Grant No.DY135-B2-15, Major science and technology program for water pollution control and treatment under Grant No. 2015ZX07205-003, the National Natural Science Foundation of China under Grant No. 21176242 and No. 21176026.
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2022, Advanced Powder TechnologyCitation Excerpt :This result is beneficial for the improvement of roasting pretreatment technology. CO and CH4 were not detected, which is different from the thermal decomposition gas release of humic acids in carbonaceous materials and needs further analysis [17,23]. From Table 2 and Table 3, pyrite was the most important gold-locked minerals in the carbonaceous gold ores, followed by mica, kaolinite, goethite, and dolomite.