Extraction of tantalum and niobium from tin slags by chlorination and carbochlorination

Abstract

Chlorination and carbochlorination of tantalum and niobium low-grade concentrate (LGC) and highgrade concentrate (HGC), obtained by leaching of tin slag, were studied using Cl 2 ϩ N 2 and Cl 2 ϩ CO ϩ N 2 gas mixtures. Thermogravimetric analysis and conventional boat experiments were performed between 200 ЊC and 1000 ЊC. Chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the samples and reaction products. Chlorination of LGC led to the recovery of about 95 pct of tantalum and niobium compounds at 1000 ЊC. However, the tantalum and niobium chlorinated compounds were contaminated by chlorides of Fe, Mn, etc. For HGC, chlorination at 1000 ЊC allowed the extraction of about 84 and 65 pct of the niobium and tantalum compounds, respectively. The recovered condensates were composed of pure tantalum and niobium chlorinated compounds. The apparent activation energies E a for the chlorination of LGC and HGC, between 850 ЊC and 1000 ЊC, were 166 and 293 kJ/mole, respectively. At temperatures lower than 650 ЊC, the apparent activation energies for the LGC and HGC carbochlorination were 116 and 103 kJ/mole, respectively. Total extraction of the tantalum and niobium compounds was achieved by the carbochlorination of the LGC at 1000 ЊC. The generated tantalum and niobium chlorinated compounds were contaminated by the chlorides of Fe, Mn, Al, and Ca. The carbochlorination of the HGC at 500 ЊC allowed complete extraction and recovery of pure tantalum and niobium compounds. These results confirm the importance of obtaining an HGC from tin slag before its subsequent chlorination. The carbochlorination of such a concentrate could be an efficient process for the recovery of relatively pure tantalum and niobium chlorinated compounds at low temperatures.

Chlorination kinetics of ZnO with Ar-Cl2-O2 gas and the effect of oxychloride formation

“…The measured weight loss per unit gas volume was independent of the gas flow rate in the gas flow rate range between 50 and 130 cm 3 /min STP, which means that samples were equilibrated with gaseous atmosphere and the average weight loss of sample was approximately 12.45 g/m 3 STP. Reactions [7] to [9] were considered to calculate the partial pressure of chlorine from experimental results. [8] The relationship between weight loss of metallic tin and the partial pressure of chlorine was expressed as Eq.…”

“…[7] to [9] and mass balance in the reaction system: The calculated partial pressure of chlorine of premixed Ar-Cl 2 gas was approximately 238 Pa. Experiments with ZnO pellets were conducted at three experimental conditions as shown in Table VI.…”

“…Recovered heavy metal chlorides could be used as raw materials and the chlorinated residue, mainly iron oxide, also could be used as an ironmaking resource. The efficiency of selective chlorination has been investigated for extraction of metals, [9][10][11][12] mutual separation of rare earth elements, [13][14][15][16][17][18] and recovery of metals from spent catalysis, [19,20] polishes, [21] or bottom ash of incinerated municipal waste. [22] Son and Tsukihashi measured vapor pressures of ZnCl 2 between 823 K and 873 K [23,24] and of PbCl 2 between 923 K and 1023 K [25] by the transpiration method in Ar-O 2 stream and reported that vapor pressures decreased with the increase of partial pressure of oxygen.…”

Upgrading tantalum and niobium oxides content in Bangka tin slag with double leaching

“…At recent research, Indonesian tin slags, that have (TaNb) 2 O 5 at about 0.97%, dissolved with HF, can be increased to 2.0% of (TaNb) 2 O 5 , while dissolved with HCl followed by NaOH, can be increased to 1.71% of (TaNb) 2 O 5 [15]. Methods used to increase TNO contents of tin slags in previous researches are: electromagnetic separation [19], dissolution in hydrochloric acid and hydrofluoric acid followed by decalcination at 800C, then by final melting with carbon [9], alkaline and acid washing, then concentrates is applied by selective carbochlorination at temperature lower than 500C [10], dissolved with HF-H 2 SO 4 [12], Chlorination (Cl 2 +N 2 or Cl 2 +CO+N 2 ) at 500-1,000C [11], in situ carbothermic reduction using coarse concentrates powder with collie coal reductor and metallurgical cokes at 1,200-1,400C [13], chlorination with chlorine gas in front of hydrochloric acid leaching and chlorination with carbon tetrachloride vapor at a relatively low temperature [14], separation with magnetic properties is choosed in increasing tantalume and niobium contents due to their low magnetic properties [20].…”

Kinetics of hematite chlorination with Cl2 and Cl2+O2: Part I. Chlorination with Cl2

“…The extraction of these metals and / or upgrading of their ores by chlorination process depends on the amount and nature of the iron compounds content. In some cases, such as from laterites [4], jarosites [5], steel making waste dusts [6], slags from tin metallurgy [7], etc., selective separation of nonferrous metals are desirable, while in other cases, for example in the upgrading of chromite [8], bauxite [9], ilmenite [10], etc., removal of Fe as volatile chlorides has been proved to be highly beneficial. Selectivity in the processes, as mentioned above, is greatly dependent on the nature of interaction between iron oxides and different chlorinating agents.…”