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2 Physicochemical Problems of Mineral Processing

2 2024

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Production of pure tantalum and niobium oxides by hydrometallurgical processing of coltan smelter cake from Tanganyika Province/RD Congo using NH4HF2-KOH flux system

Kitungwa Bertin K., Yuma Phalaris M., Kalenga Mubiayi. Pierre, Shengo Michel L., Ngubeni Grace, Moloto Nosipho, Mbayo Marsi K., Kyona Crépin W.

Physicochemical Problems of Mineral Processing

2024

Vol. 60, iss. 4

art. no. 192436

Pure tantalum and niobium oxides were produced from the molten cake after mixing oreNH4HF2-KOH in a respective mass ratio of 1/4/3. This resulted in solubilization yields of over 95% for Nb and around 92% for Ta in sulfuric acid solution 3 molar. Extraction of tantalum and niobium using octan-2-ol yielded over 95% niobium and 98% tantalum when pH is set at 0.5-1.0 and 1.5-2 respectively. The compounds K3NbOF6, K3NbO4 and K2TaF7 were identified after melting. While in aqueous solution ionic species such as NbF6 (OH) 23-, NbF6- and TaF72- are likely to be identified. Precipitation of tantalum and niobium in NH4OH solution (pH=7.50-8.0) as hydrated oxides after stripping with distilled water and crystallization identified hydrated oxides such as Ta2O5.nH2O, Nb2O5.nH2O. These two oxides were associated with a small amount of SiO2.nH2O as an impurity resulting from the extraction and precipitation of tantalum and niobium. SEM-EDS, XRD, TGA-DTG and FTIR analyses identified and characterized these compounds.

Identification of tin species released in solution during water leaching of solids from the alkaline smelting (NaOH-KOH) of stanniferous ores

Yuma Phalaris M., Kitungwa Bertin K., Mubiayi Pierre Kalenga, Shengo Michel L., Moloto Nosipho, Ngubeni Grace, Mbayo Marsi K., Kyona Crépin W.

Physicochemical Problems of Mineral Processing

2024

Vol. 60, iss. 3

art. no. 189758

Tin species were studied from Makundju ores in DRCongo. The identification of tin species released in aqueous solution during leaching of solids from the alkaline smelting (NaOH-KOH) was done to prepare added-value mining products on tin ores mined in the eastern DR Congo. Prior to alkaline fusion to have the smelting products (SP), the initial sample (IS) was processed for tests and characterization of tin species. Alkaline fusion in molten KOH-NaOH system was used and leached solution was considered for further analyses. Various physicochemical techniques including X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and FTIR spectroscopy were used to characterize the initial ore and the molten cake. Water leached cake solution at a solid/liquid ratio of 1:10 was used to identify and characterize tin species. ICP-OES analysis of the pH 11.9 solution revealed a content of 4506.3 ppm, which is equivalent to a 95.87% leaching yield. Such yield attests to the stable Sn(OH)2-6(aq) ion as confirmed by UV-Vis. Crystallizations of M2Sn(OH) 6(s) (M = Na and/or K) was studied using XRD, FTIR and TGA. As pH decreases below 9, Sn(OH) )2-6(aq) ion changes to other tin species such as Sn(OH)-5(aq), Sn(OH)4(S), Sn(OH)+3(aq), Sn(OH)2+2(aq), Sn(OH)3+(aq) and Sn4+(aq). The stability of each the tinspecies was determined at different pH values in aqueous solution. Hence, alkaline hexahydroxostannate nanoparticles, used in many electronic applications, can be produced from tin ores.