A Study for Leaching Synthetic Scheelite in H2SO4 And H2O2 Solution: An Investigation and Optimization
Creators: Mutlu Tuncer, Idil
Publisher: name: University of Alberta Library
Year: 2023

<p>Canada&#39;s 2021 Critical Minerals Strategy underscores the prominence of tungsten as a rare and critical element. Today, tungsten production relies on scheelite, categorized as a secondary resource due to its complex ore composition and lower-grade nature. This phenomenon stems from the depletion and utilization of high-grade wolframite reserves. In response to this context, the significance of synthetic scheelite has ascended, primarily due to its inherent advantages such as its low impurity content and enhanced accessibility, particularly in ongoing laboratory-based leaching investigations.</p>

<p>The most recent advancements in laboratory-scale research have yielded a feasible and environment-friendly approach for leaching synthetic scheelite utilizing a mixed acid solution of H2SO4 and H2O2. This process is carried out under normal pressure and moderate temperatures. Despite this notable progress, there persists a dearth of comprehensive inquiries into this novel leaching method. Furthermore, a comparative analysis between processes involving natural and synthetic ores remains underexplored. This existing gap in the literature underscores the need for a collaborative endeavor to achieve a comprehensive understanding of the novel leaching technique and a rigorous evaluation of the possibilities for optimizing operational parameters. Ultimately, the objective is to offer valuable insights and enhancements concerning the utilization of reagents, thereby fostering a more efficient, economically viable, and environmentally sustainable leaching process. To achieve this, a promising 2-step method for scheelite leaching was explored, aiming to minimize the thermal decomposition of H2O2 and subsequently reduce its concentration. The results showed that the 2-step method is infeasible as it requires a longer reaction time compared to the synergistic leaching approach, resulting in reduced productivity and energy efficiency.<br>
Subsequently, a detailed investigation into the thermal decomposition process ensued, seeking to extract tungsten without compromising leaching efficiency. This was achieved by optimizing the operational conditions based on established literature for natural ore. The findings unveiled the potential for multiple recycling of lixivium, supplemented with depleted chemicals, thereby promoting an eco-friendly approach while reducing operational expenses. Notably, for an L/S (mL/g) ratio of 10, enhanced H2WO4 crystallization efficiency was achieved by optimizing the thermal decomposition duration, extended up to 6 hours. Moreover, experiments conducted without H2SO4 supplementation revealed the inherent optimization potential within the leaching system. Finally, optimization was undertaken in terms of reagent concentration, involving a reduction of H2SO4 concentration from 3 mol/L to 1 mol/L, an increase in temperature from 45°C to 60°C, and an additional 30-minute leaching duration. This collective effort culminated in proposing an environmentally conscious and cost-effective process for synthetic scheelite leaching in the solution of H2SO4 and H2O2. </p>