Abstract
Lithium carbonate is an important chemical raw material that is widely used in many contexts. The preparation of lithium carbonate by acid roasting is limited due to the large amounts of low-value sodium sulfate waste salts that result. In this research, bipolar membrane electrodialysis (BMED) technology was developed to treat waste sodium sulfate containing lithium carbonate for conversion of low-value sodium sulfate into high-value sulfuric acid and sodium hydroxide. Both can be used as raw materials in upstream processes. In order to verify the feasibility of the method, the effects of the feed salt concentration, current density, flow rate, and volume ratio on the desalination performance were determined. The conversion rate of sodium sulfate was close to 100%. The energy consumption obtained under the best experimental conditions was 1.4 kWh·kg−1. The purity of the obtained sulfuric acid and sodium hydroxide products reached 98.32% and 98.23%, respectively. Calculated under the best process conditions, the total process cost of BMED was estimated to be USD 0.705 kg−1 Na2SO4, which is considered low and provides an indication of the potential economic and environmental benefits of using applying this technology.
Highlights
Lithium carbonate, an inorganic compound, exists as colorless monoclinal crystals or a white powder
It can be seen that the concentrations of acid and base increased as a function of time, indicating that H+ and OH− were continuously produced by BPM and transported from the cation exchange layer (CEL) and anion exchange layer (AEL) to the acid and base compartments, respectively
More ions can be transported through the ion exchange membrane, resulting in a decrease in current efficiency at high salt concentrations
Summary
An inorganic compound, exists as colorless monoclinal crystals or a white powder. The alkaline roasting method, difficulties in operating and maintaining equipment develop due to the high energy consumption for evaporation, the high requirement for temperature control, the low recovery rate of lithium, and strong flocculability of the sludge after water leaching [6]. Sodium hydroxide is added to the calcined product to adjust the pH to neutralize excess sulfuric acid and remove impurities [5,8]. Sulfuric roasting has strong adaptability to varis added to obtain lithium carbonate. Sulfuric roasting has strong adaptability to ious raw materials and can handle many kinds of lithium-bearing ores. A large amount of sulfuric acid and NaOH is verted into into low-value sodium sulfate.
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