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Selective Recovery of Mushistonite from Gravity Tailings of Copper–Tin Minerals in Tajikistan

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Selective Recovery of Mushistonite from Gravity Tailings of Copper–Tin Minerals in Tajikistan minerals Article Selective Recovery of Mushistonite from Gravity Tailings of Copper–Tin Minerals in Tajikistan Lei Sun, Yuehua Hu *, Wei Sun, Zhiyong Gao ID and Mengjie Tian School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China; [email protected] (L.S.); [email protected] (W.S.); [email protected] (Z.G.); [email protected] (M.T.) * Correspondence: [email protected]; Tel.: +86-731-8883-0482 Received: 31 October 2017; Accepted: 4 December 2017; Published: 7 December 2017 Abstract: Tajikistan has abundant copper–tin resources. In this study, mineralogical analysis of copper–tin ores from the Mushiston deposit of Tajikistan indicates that tin mainly occurred in mushistonite, cassiterite, and stannite, while copper mainly occurred in mushistonite, malachite, azurite, and stannite. The total grades of tin (Sn) and copper (Cu) were 0.65% and 0.66%, respectively, and the dissemination size of copper–tin minerals ranged from 4 µm to over 200 µm. Coarse particles of copper–tin minerals were partially recovered by shaking table concentrators with a low recovery rate. Based on the mineralogical analysis, flotation recovery was used for the first time on the fine particles of copper–tin minerals, including mushistonite, from shaking table tailings. Single factor flotation experiments, open circuit flotation tests, and closed circuit flotation tests were performed to determine the optimized flotation conditions. Results indicated that benzohydroxamic acid (C6H5CONHOH) and lead nitrate could effectively recover the mushistonite, cooperating with other depressants. The final concentrate contained 13.28% Sn, with a recovery rate of 61.56%, and 18.51% Cu, with a recovery rate of 86.52%. This method proved effective for the exploitation and use of this type of copper–tin resource in Tajikistan. Keywords: mushistonite; copper–tin tailings; flotation; benzohydroxamic acid 1. Introduction Tajikistan has abundant mineral resources. More than 400 different mineral deposits have been confirmed through systematic geological investigations. The main deposits of tin ores are found within the Zarafshan–Hisar geological and structural zone, in Central and South Pamir of Tajikistan. The tin resources total about 73 thousand tons [1]. The primary raw material deposit of tin in the Zarafshan–Hisar zone is found in Mushiston. This unique species of tin ore was originally discovered in the Penjikent region of Tajikistan by geologists in the 1960s, but was not named at that time [2,3]. Later, in 1984, the deposit was officially called mushistonite, after the name of the place where it was first discovered in Penjikent, Tajikistan [4–6]. Mushistonite is a malachite-green mineral with a dull luster, and recognized as a copper–tin– hydroxide mineral. Its eneral molecular formula is (Cu,Fe,Zn)Sn(OH)6, with a framework of corner- 0 linked BB (OH)6 octahedra [7]. Mushistonite has also been found in Sichuan, China and South Dakota, U.S., with slightly different chemical element content [5,8,9]. Mushistonite is a rare mineral, distributed in several areas around the world, and is not exploited on a large commercial scale currently. Few research reports have studied the exploitation and use of mushistonite [10,11]. In recent years, some companies and researchers have tentatively exploited the mine and established a small-scale minerals concentration factory. Coarse particle size fractions of cassiterite, chalcopyrite, and malachite were recovered by gravity separation using shaking tables. Minerals 2017, 7, 242; doi:10.3390/min7120242 www.mdpi.com/journal/minerals Minerals 2017, 7, 242 2 of 11 Minerals 2017, 7, 242 2 of 11 The factory attempted to recover the fine particle size fraction of copper and tin minerals, including mushistoniteThe factory attempted, using the to sulfidation recover the flotation fine particle method, size but fraction failed. of copper and tin minerals, including mushistonite,Research usingstudies the have sulfidation indicated flotation that oxide method, minerals but failed., such as cassiterite and scheelite, could establishResearch hydroxylated studies have surfaces indicated in the that flotation oxide minerals, pulp. Benzohydroxamic such as cassiterite and acid scheelite, (BHA) couldand lead establish ions reacthydroxylated with the surfaces hydroxyl in groups the flotation and co pulp.-absorb Benzohydroxamic on the hydroxylated acid (BHA) surface. and leadAs a ions result, react cassiterite with the andhydroxyl scheelite groups could and be co-absorb selectively on recovered the hydroxylated by flotation surface., using As BHA a result, as a cassiterite collector andand scheelitelead nitrate could as anbe selectivelyactivator [12 recovered–16]. According by flotation, to the using chemical BHA ascomposition a collector andand leadcrystal nitrate structure as an activatorof mushistonite[12–16]. Accordingmentioned toabove, the chemicalhydroxyl compositiongroups are present and crystal within structure the mineral’s of mushistonite own natural mentioned structure. above, The strengthhydroxyl of groups the hydrogen are present bonds within betwee the mineral’sn hydroxyl own naturalgroups structure.is weak, Theand strength easily broken of the hydrogen to form hydroxylatedbonds between surfaces hydroxyl with groups grinding. is weak, We andconsidered easily broken that hydroxyl to form hydroxylatedgroups on the surfaces surface with of mushistonitegrinding. We could considered react with that hydroxylBHA and groupslead ions, on and the surfacebe selectively of mushistonite recovered couldby flotation. react with Based BHA on thisand hypothe lead ions,sis and, process be selectively mineralogy recovered and the by flotation flotation. of Based copper on–tin this tailings hypothesis, were processstudied mineralogy to recover mushistonite.and the flotation Experiment of copper–tinal results tailings confirmed were studied that flotation to recover of copper mushistonite.–tin tailings Experimental, using BHA results as the collectorconfirmed, was that feasible flotation. It of provid copper–tined an tailings,economical using and BHA realistic as the m collector,ethod for was the feasible.use of mushistonite. It provided an economical and realistic method for the use of mushistonite. 2. Materials and Methods 2. Materials and Methods 2.1. Minerals and Reagents 2.1. Minerals and Reagents The raw ore samples were collected from the crushing workshop of the Yukuang Panjakent copperThe–tin raw mine ore concentration samples were plant collected in fromNorthwest the crushing Tajikistan. workshop The samples of the Yukuangused for Panjakentflotation experimentscopper–tin mine were concentration obtained from plant the in Northwestshaking table Tajikistan. tailings The of samplesthis plant used (Figure for flotation 1). Toexperiments ensure the wererepresentativeness obtained from of the the shaking samples, table sampling tailings of work this plantwas (Figureperformed1). To during ensure the the representativenessnormal producing periodof the samples,in the plant. sampling The sampling work was work performed was sustained during for the 30 min normal each producing time, one time period every in thehalf plant. day, forThe three sampling continuous work was days. sustained All samples for 30 min were each fully time, mixed one time after every being half dried day, forin threethe natural continuous air environment.days. All samples were fully mixed after being dried in the natural air environment. The collector BHA waswas 98%98% pure,pure,and and other other reagents reagents used used in in this this study, study including, including lead lead nitrate nitrate as asactivator, activator, sodium sodium carbonate carbonate and and hydrochloric hydrochloric acid asacid pH as modifiers, pH modifiers, carboxymethyl carboxymethyl cellulose cellulose (CMC) (CMC)and sodium and sodium fluorosilicate fluorosilicate (SSF) as (SSF) depressants, as depressants as well, asas terpineolwell as terpineol as a frother, as a were frother all, analytical were all analyticalgrade. All reagentsgrade. All were reagents separately were dissolved separately into deionizeddissolvedwater into todeionized prepare thewater compound to prepare solutions the compoundused in each solutions test. used in each test. FFigureigure 1. SSamplesamples used used for for flotation flotation test testss were obtained from the shaking table tailings.tailings. 22.2..2. Analysis Methods Mineral identifications identifications of the raw ore were performed using X-rayX-ray diffraction, transmission polarized optical microscopy, and scanning electron microscopy (SEM) with energy dispersive analytical attachment attachment.. Quantitative Quantitative mineralogical mineralogical composition compositionss could could also also be calculated calculated,, but using special methods [17,18 [17,18]].. Chemical Chemical compositions compositions of of raw raw ore ore and flotation flotation ore samples were detected with X-rayX-ray fluorescencefluorescence spectrometry spectrometry and and chemical chemical analysis, analysis which, which was wa sufficients sufficient to evaluate to evaluate the result the resultof flotation. of flotation. Minerals 2017, 7, 242 3 of 11 2.3. Flotation Experiments Flotation experiments on the gravity process tailings were performed in a series of XFG type flotation machines (Jilin Prospecting Machinery Factory, Changchun, China). Single factor experiments were performed in a 3.0 L flotation cell, while open circuit and closed circuit experiments were
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