Fluoroammonium method for processing of cake from leaching of titanium-magnesium production sludge

We present the results of the physical and chemical properties of cake from nitric-acid leaching of titanium production sludge. It was found that all silicon in the cake is in the form of quartz, albite, sillimanite, sodium aluminosilicate. In total, these minerals make up the majority of the cake 60.24%. Titanium is presented in the form of rutile, titanium aluminum oxide, which in total is 35.56%. Iron is part of sillimanite and hematite, the total content of which is about 4.2%. The optimal parameters of fluoroammonium processing of cake were determined: silicon distillation into sublimates at 300°С for 6 hours, sublimation of titanium in the form of titanium tetrafluoride at 800°С for 2 hours. The process of alkaline hydrolysis of sublimates of fluoride compounds and cinder was carried out. Purification of impurities and calcination of hydrated titanium dioxide were carried out. The resulting titanium and silicon dioxide products contain: 96.2% TiO2, 88 % SiО2, respectively; a niobium-containing intermediate product with a content of 11.6 % Nb2O5 was also obtained.

Deposition of Arsenic from Nitric Acid Leaching Solutions of Gold–Arsenic Sulphide Concentrates

At present, the processing of refractory gold–arsenic sulphide concentrates is becoming more relevant due to the depletion of rich crude ore reserves. In the process of the nitric acid leaching of arsenic sulphide minerals, solutions are formed containing 20–30 g/L of arsenic (III). Since market demand for arsenic compounds is limited, such solutions are traditionally converted into poorly soluble compounds. This paper describes the investigation of precipitating arsenic sulphide from nitric acid leaching solutions of refractory sulphide raw materials of nonferrous metals containing iron (III) ions using sodium hydrosulphide with a molar ratio of NaHS/As = 2.4–2.6, which is typical for pure model solutions without oxidants. The work studied the effect of temperature, the pH of the solution and the consumption of NaHS and seed crystal on this process. The highest degree of precipitation of arsenic (III) sulphide (95–99%) from nitric acid leaching solutions containing iron (III) ions without seed occurs with a pH from 1.8 to 2.0 and a NaHS/As molar ratio of 2.8. The introduction of seed crystal significantly improves the precipitation of arsenic (III) sulphide. An increase in seed crystal consumption from 0 to 34 g/L in solution promotes an increase in the degree of transition of arsenic to sediment from 36.2 to 98.1% at pH = 1. According to SEM/EDS and XRF sediment data, from the results of experiments on the effect of As2S3 seed crystal consumption, acidity and molar ratio of NaHS/As on the precipitation of arsenic (III) sulphide and the Fetotal/Fe2+ ratio in the final solution, it can be concluded that the addition of a seed accelerates the crystallisation of arsenic (III) sulphide by increasing the number of crystallisation centres; as a result, the deposition rate of As2S3 becomes higher. Since the oxidation rate of sulphide ions to elemental sulphur by iron (III) ions does not change significantly, the molar ratio of NaHS/As can be reduced to 2.25 to obtain a precipitate having a lower amount of elemental sulphur and a high arsenic content similar to that precipitated from pure model solutions.

Thermodynamics of Copper Arsenious Raw Materials Dissolution in Nitric Acid

This article describes thermodynamic study of hydrometallurgical method for processing of copper arsenious gold-containing raw material. Chemical and phase composition of the material were researched. Calculations of the Gibbs energy change were conducted for possible reactions of the main minerals, present in the raw material, with nitric acid. Eh-pH diagrams and solid/liquid equilibrium distribution diagrams, which were constructed in order to confirm the possibility of obtaining the required reaction products through nitric acid leaching of the studied raw material.

Laboratory tests of the hydrometallurgical method for processing polymetallic raw material in Central Kazakhstan

Within the scop e of this study the leaching process of Cu, Zn, Co, Mo from the complex polymetallic sulfide concentrate with high Fe, As, which was produced in Central Kazakhstan using two methods is examined. The metal concentrations in the concentrate were 0.27% Cu, 0.026% Zn, 0.464% Co, 0.057% Mo, 15.51% Fe, 7.38% As. Nitrogen oxides formed in the processes of leaching were absorbed with water, the return of absorption product to the operation of leaching allowed reducing the consumption of nitric acid. The single-stage nitric acid leaching experiment was carried out at the leach concentrate productivity of 170±20 g/h, 80±2 °С, liquid/solid mass ratio (L/S) 6/1, leach time of 10.7 h, and nitric acid (57%) consumption of 0.12±0.01 l/h. The degree of capture of nitrous gases reached 97.8%. In these conditions Cu, Zn, Co, Mo, Fe, As were obtained with dissolution efficiencies of 96.98, 64.92, 99.99, 95.39, 80.13 and 99.80% respectively. Concentrations of NO3–, H+ and redox potential in the leachate were 88.7 g/l, 1.82 mol./l and 741 mV, respectively. The two-stage counter-current nitric acid leaching experiment was carried out at the leach concentrate productivity of 170±20 g/h, 80±2 °С, L/S 6/1, leach time of 26.8 h, and nitric acid (57%) consumption of 0.06±0.006 l/h. The degree of capture of nitrous gases reached 97.8%. In these conditions Cu, Zn, Co, Mo, Fe, As were obtained with dissolution efficiencies of 99.11, 85.23, 100.00, 88.60, 77.24 and 85.56%, respectively. Concentrations of NO3–, H+ and redox potential in the leachate were 46.7 g/l, 0.35 mol/l and 658 mV, respectively. Compared to single-stage leaching, two-stage counter-current nitric acid leaching allo ws the significant economy of nitric acid (256 g of 100% HNO3 per kilogram of concentrate), which is reduction of 48%. Moreover, counter-current leaching enables reduction in concentrations of NO3–, H+ and redox potential in the leachate. The further studies should focus on possible reduction in nitric acid consumption by lowering concentration of NO3– in leachate. The authors appreciate participation of I. A. Parygin, VNIPIpromtekhnologii in this study.

Trapping nitrous gases during nitric acid leaching of sulfide concentrates

Gas-air mixtures that form in nitric acid leaching of sulfide raw materials possess the following peculiarities making a negative impact on trapping of nitrogen oxides: elevated temperature, different oxidation level of nitrogen oxides, slow oxidation of NO in region of low concentrations, and instability of the resulting gas-air mixture flow. Therefore, well-known methods of trapping nitrous gases shall be adapted to specific sulfide raw material. We propose a process flow diagram for trapping nitrous gases formed during nitric acid leaching of sulfide concentrates at atmospheric pressure on the example of Zhezkazgan concentrate. The paper addresses theoretical aspects of the use of water-ore pulp, concentrated sulfuric acid, process water and alkaline agents for trapping nitrous gases, and typical reactions of interaction of the proposed absorbents with nitrogen oxides. The choice of water-ore pulp as an absorber was made because of similarity between the mechanism of absorption of nitrogen oxides for neutral and alkali ore suspensions and the one for alkali solutions: nitrogen dioxide and nitrous anhydride are absorbed with formation of a solution of nitrates and nitrites. Due to availability in a liquid phase of ferrous iron along with NO2 and N2O3, acidic suspensions are also capable to absorb nitric oxide, to some extent, with formation of Fe(NO)SО4 complex. Process water absorbs only nitrogen dioxide, with formation of nitric and nitrous acids. Nitrous acid is an unstable compound in acidic environments and decomposes with formation of water and nitrogen oxide. At the stages of trapping nitrogen oxides with water-ore pulp and process water (circulating solution), it is recommended conditioning of gas-air mixtures by choosing the volume of additionally introduced air, in an amount to provide the highest rate of nitrogen oxide oxidation. At the stages of sulfuric acid and alkaline trapping of nitrogen oxides, it is recommended conditioning of gas-air mixtures by selecting the volume of additionally introduced air and the oxidation time of nitrogen oxide that provide an equimolecular mixture of NO and NO2. A distinctive feature of the use of water-ore pulp, concentrated sulfuric acid, process water and alkaline agents for trapping nitrous gases is possibility to use the products of absorption at the stage of sulfide concentrate leaching. The extended tests of trapping nitrous gases have been conducted. The plant capacity by the gas-air mixture ranged 17–21 m3/h, and by leached concentrate — 12–15 kg/h. In this case, the degree of capturing nitrous gases reached 96.8%. Return of the products of absorption of nitrous gases in the form of condensate, water-ore pulp, nitrosyl sulfuric acid, nitric acid solution, nitritenitrate lye allows to reduce the nitric acid consumption by 7–10 times relative the values obtained without using the trapping system. In this case, the degree of copper extraction into the leaching solution was 97.7%. The extraction degree of silver, rhenium, zinc was respectively 98.0%, 99.0%; 98.5%.

An efficient and environmentally friendly route for PbS crystal recovery from lead ash generated in tin removal section (LATR) via high-speed leaching and recrystallization method

This paper mainly investigated on synthesis of a high purity PbS crystal directly from lead ash which was collected from Tin ash removal process (LATR). The LATR was firstly disposed by nitric acid leaching system to generate the lead nitrate solution. The PbS crystal would be prepared by mixing the lead nitrate solution with the sodium sulfide at the room temperature (25 ?C). The effects of molar ratio of HNO3 to Pb in the LATR on Pb leaching efficiency was investigated, demonstrating that the Pb leaching efficiency could attain to 82.9 % at molar ratio of 3. The leaching ratio of As, Cu, Fe, and Al generally increased with increasing molar ratio of HNO3 to Pb in the LATR, while 99.99 wt% of Sn was still left in the residue. In the process of generating PbS crystal from the leaching solution, the yield of PbS crystal was increased with increasing molar ratio of Na2S to Pb in the filtrate. The yield of PbS crystal could up to 93.1% at a molar ratio of 1.5. Overall, this method proved to be an efficient and environmental friendly route for synthesis of high quality PbS crystal directly from the common lead containing waste from the lead ore or secondary smelting factory.