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.

Vanadium is an important soft metal that is widely used for various industrial sectors. However, the traditional ammonium precipitation of vanadium generates a large amount of waste salt, which is a great burden to the environment. In this study, an electrochemical method for the production of vanadium pentoxide was proposed using the bipolar membrane electrodialysis (BMED) technique. By precisely regulating the pH and vanadium salt concentration, the vanadate salt, predominantly V 2 O 7 4− , could migrate through the anion-exchange membrane and combine with protons generated by water splitting in the bipolar membrane. The effects of current density, initial NaVO 3 concentration, and volume ratio between the acid and salt chambers on the BMED performances were investigated. It was found that successful completion of the experiment was highly dependent on the migration of V 2 O 7 4− and the generation of H + /OH − by water splitting in the bipolar membrane. The competition between OH − and V 2 O 7 4− across the anion-exchange membrane is advantageous to help the acid compartment to become not too much acidic but is also a disadvantage to the vanadium BMED performance. Additionally, the quick supply of protons or the fast migration of vanadate might lead to the easy conversion of the polyvanadate H 2 V 10 O 23 4− into the suspended solid V 2 O 5 . Under the current density of 30 mA/cm 2 , the NaVO 3 concentration of 0.3 mol/L, and the volume ratio between acid and salt compartments of 1:2, the vanadium concentration in the acid chamber reached 0.168 mol/L with the conversion rate of 17.29%. The energy consumption could be as low as 13.52 kWh/kg V 2 O 5 . The purity of the V 2 O 5 product via the BMED method was 98.05%, which meets the industrial standards for practical use. Therefore, the proof-of-concept experiment well proved that BMED is capable of one-step converting the vanadium salt into vanadate acid, creating possibilities for the avoidance of the vanadium ammonium precipitation procedure.