# Sintering with Sodium Carbonate and Leaching of Wolframite Cakes
## 4 Conclusions  
The average tungsten content in the ore of the Akchatau deposit is 0.1-0.3%. Concentrates containing 60-62% WO3 were obtained by enriching ore samples through gravity and flotation methods. The chemical and mineralogical composition of the concentrates was studied using an SPM-35 X-ray spectrometer and an Empyrean multichannel diffractometer. It was found that the reactions of tungsten minerals with sodium carbonate proceed intensively in the temperature range of 750-850 \({}^{\circ}\)C. To study the effect of sintering temperature and leaching parameters on the extraction of sodium tungstate into solutions, the concentrate was sintered with sodium carbonate at temperatures of 750, 800, and 850 \({}^{\circ}\)C, with a sodium carbonate excess factor ranging from 1.05 to 1.2. An increase in the excess coefficient of sodium carbonate during the sintering of the batch, from 1.05 to 1.2, leads to a more complete reaction for the formation of Na2 WO4. Consequently, at the leaching \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Materials Received** & **Total, g** & **WO3, g** & **Products Received** & **Total, g** & **WO3, g** \\ \hline
1. Sinter & 100 & 55.47 & 1. Cake & 32,313 & 3.023 \\ \hline
2. Water & 400 & 0 & 2. Productive solution & 242,077 & 47.47 \\ \hline  & & & 3. Process water & 225,525 & 4.966 \\ \hline Total, g & 500 & 55.47 & Total, g & 499,915 & 55.459 \\ \hline  & & & Residual, g & \(-\)0.085 & \(-\)0.011 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Calculated balance of leaching of cake. stage of the sinter, the extraction of sodium tungstate into the solution increases from 87.4% to 98.6%. Purification of the productive solution from impurities is carried out using known reagents, excluding the consumption of inorganic acids for neutralization and precipitation of H\({}_{2}\)WO\({}_{4}\). In the course of preliminary experiments the efficiency of electrodialysis application in a two-chamber cell with separation of anode and cathode spaces by a cation-exchange membrane was established, which allows to effectively purify Na\({}_{2}\)WO\({}_{4}\) solutions from impurities and to extract marketable Na\({}_{2}\)WO\({}_{4}\) at the final stage. The processes of electrodialysis of sodium tungstate solutions were investigated at continuous feeding of initial solutions and removal of electrodialysis products. The total energy costs of electrochemical processes were determined, taking into account losses in the contact network and losses due to heat generation in the electrolyte. On an industrial scale, the energy consumption depends on the plant design and the electrolyte circulation system. The possibility of using electrodialysis in a two-chamber apparatus, with separation of the anode and cathode spaces by a cation-exchange membrane, has been demonstrated for purifying sodium tungstate solutions from impurities and isolating commercial sodium tungstate at the final stage. Energy costs for electrochemical processes, within the range of current densities on the cathode of 130-524 A/m\({}^{2}\), are estimated to be 3.32-3.48 kWh per 1 kg of Na\({}_{2}\)WO\({}_{4}\). The total energy consumption also depends on losses in the contact network, as well as heat release in the electrolyte. Under laboratory setup conditions, the total energy consumption ranges from 5.72 to 13.40 kWh per 1 kg of Na\({}_{2}\)WO\({}_{4}\). In an industrial installation, the energy consumption will be determined by the design of the apparatus and the configuration of the electrolyte circulation system. Conceptualization, B.B. ; Data curation, Y.T. ; Formal analysis, A.D.; Investigation, A.T.; Methodology, G.M. ; Project administration, B.B. ; Resources, Y.Y. ; Software, Y.T. and A.Y. ; Visualization, A.Y., A.D. and A.T.; Writing--original draft, B.B. ; Writing--review and editing, Y.T. and G.M. All authors have read and agreed to the published version of the manuscript.