On the Intensification of Selective Flotation of Sulfide Polymetallic Ores by Electric Pulse Discharges
Abstract Generated abstract
This paper examines the use of high-voltage electric pulse discharges to prepare collective sulfide polymetallic ore concentrates for selective flotation. The authors argue that discharge-induced ionization and oxidation alter xanthate collectors, heavy-metal xanthates, dissolved gases, and sulfide mineral surfaces, producing sulfate ions, hydroxides, oxides, and sulfo-oxides in the pulp. Experimental observations indicate that the treatment affects minerals differently: galena flotation is almost completely depressed after 100 pulses, sphalerite recovery decreases substantially with increasing pulse number, while chalcopyrite largely retains flotation activity. These selective changes in surface chemistry suggest that electric pulse discharge treatment may intensify the separation of polymetallic sulfide concentrates.
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ON THE INTENSIFICATION OF SELECTIVE FLOTATION OF SULFIDE POLYMETALLIC ORES BY ELECTRIC PULSE DISCHARGES
G. L. LOBANOVA, S. A. BABENKO, I. I. KALYATSKII, V. I. KURETS
One of the principal tasks in the flotation of polymetallic ores is the separation of collective concentrates. For this purpose, a number of technological operations are used that ensure a change in the surface properties of sulfides with respect to the common collector reagent—xanthate. The main operations of this technology are the desorption of flotation reagents from the surface of the minerals constituting the collective concentrate, and the selective activation or depression of sulfides.
The easy oxidizability of xanthate [1] and the ability of oxygen to act as a regulating reagent in the flotation of sulfides [2] made it possible to assume the possibility of using high-voltage pulse discharges for preparing the pulp of the collective concentrate of polymetallic ore for selection.
The ionization processes involved in the development of a discharge in water [3], and the large amount of energy released in the discharge channel [4], lead to the ionization of gases dissolved in the water, and of hydrogen and oxygen formed during its decomposition.
As our studies have shown, ionized oxygen reacts practically completely with substances prone to oxidation—reagents, minerals, and electrode material. In this case the evolved gas contains 74% hydrogen, 22% nitrogen, carbon oxides and gases not identified chromatographically, and 4% oxygen.
A consequence of such a large consumption of oxygen, in particular, is a decrease in the concentration of the potassium xanthate solution under the action of electric pulse discharges and the decomposition of heavy-metal xanthates formed through the interaction of potassium xanthate with sulfide minerals.
On the other hand, sulfate ions and iron hydroxides accumulate in the pulp as a result of oxidation of sulfide minerals and steel electrodes during treatment of the pulp of sulfide minerals with electric discharges. The quantitative ratios of ions in the pulp before and after treatment with electric pulse discharges are presented in Table 1.
The accumulation of sulfate ions in the pulp most likely occurs through dissolution of the oxidation products of sulfide minerals. As mineralogical analysis showed, part of the newly formed products produced under the action of electric discharges becomes fixed on the surface of the minerals. These products are most clearly visible in the region of the breakdown channel. X-ray-
X-ray diffraction analysis makes it possible to identify newly formed products on galena, pyrite, and sphalerite as oxides and sulfo-oxides; on chalcopyrite, in addition to these, covellite is also formed.
A consequence of changes in the surface of sulfides during treatment of the pulp with high-voltage pulsed discharges is a change in the flotation properties of the minerals. Moreover, the change in the flotation activity of sulfide minerals occurs to different degrees for different minerals.
Table 1
| Mineral | pH before treatment | $\mathrm{SO_4^{--}}$ initial, mg/l | pH after treatment | $\mathrm{SO_4^{--}}$ final, mg/l |
|---|---|---|---|---|
| Galena | 7.0 | 6.8 | 5.8 | 104.2 |
| Sphalerite | 6.8 | 7.2 | 5.5 | 115.3 |
| Chalcopyrite | 7.0 | 7.3 | 5.0 | 202.0 |
Chalcopyrite, under the experimental conditions, retains its flotation activity. The recovery of sphalerite, as the number of pulses increases from 0 to 200, decreases from 81 to 51%. The most significant change in flotation activity is observed for galena. After treatment of the pulp with 100 pulses, flotation of galena is almost completely suppressed.
Strong oxidation of the galena surface is accompanied by sloughing of sulfate that had become fixed on its surface [5], owing to their crystallographic mismatch. When galena is treated at this moment with xanthate, a decrease in sorption of the latter is observed, which reduces the flotation activity of galena under the conditions of our experiment.
Chalcopyrite is oxidized with the formation of copper sulfate and iron sulfate. At a pulp pH of 5.7—5.0, which occurs when the pulp is treated with electrical discharges, iron sulfate passes into solution. Copper sulfate reacts with chalcopyrite to form bornite, and then chalcosine and covellite [6]. These phenomena contribute to the preservation of the flotation activity of chalcopyrite.
The differing influence of electrical pulsed discharges on the flotation properties of sulfide minerals may promote the selective flotation of polymetallic ores.
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