A Sustainable Electrochemical Method for the Production of Vanadium Pentoxide Using Bipolar Membrane Electrodialysis

Abstract

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.

Tuning the Nucleation Rates for High-Efficiency Hydrolysis of Sodium Vanadate Solution

“…7−9 The leaching solution requires further purification and precipitation to prepare vanadium oxide (V 2 O 5 ) as the final product. 10,11 To date, many methods have been worldwide researched on vanadium enrichment and separation in leaching solutions, such as chemical precipitation, ion exchange, solvent extraction, and electrolysis. 12−14 However, the methods that can be used for large-scale industrial production involve mainly chemical precipitation, which can be further divided into hydrolysis precipitation, ammonium salt precipitation, calcium salt precipitation, and iron salt precipitation.…”

“…Vanadium is an important strategic metal with a vast range of applications in the metallurgical industry, chemical industry, battery, medicine, and other fields. − Currently, vanadium slag is the main direct raw material for vanadium extraction, which is the vanadium-containing tailings in the titanomagnetite steelmaking process. − The typical commercial process of vanadium recovery from vanadium slag involves sodium roasting–water leaching, the principle of which is to convert the insoluble spinel (FeV 2 O 4 , V 3+ ) in vanadium slag into soluble sodium metavanadate (NaVO 3 , V 5+ ) via full oxidation roasting; then it can be leached by water. − The leaching solution requires further purification and precipitation to prepare vanadium oxide (V 2 O 5 ) as the final product. , …”

Electro‐membrane reactor: A powerful tool for green chemical engineering

“…Ion transfer over electro‐membranes is essential if an electrochemical process relies on non‐Faraday reactions, such as protonation/deprotonation, metathetical reactions, and electro‐catalyzed water dissociation. Specific ion exchange membranes are assembled to create the reaction chamber, that is, one reaction unit inside a bipolar membrane reactor composes bipolar membrane|acid chamber|cation exchange membrane|feed chamber|anion exchange membrane|base chamber|bipolar membrane 21 . Acid and base could thus be produced based on cation/anion's migration across cation/anion exchange membranes and the electro‐catalyzed water dissociation on the bipolar membrane.…”

“…to create the reaction chamber, that is, one reaction unit inside a bipolar membrane reactor composes bipolar membranejacid chamberjcation exchange membranejfeed chamberjanion exchange membranejbase chamberjbipolar membrane. 21 Acid and base could thus be produced based on cation/anion's migration across cation/anion exchange membranes and the electro-catalyzed water dissociation on the bipolar membrane. By stacking the units mentioned above to thousands, acid/base production could be increased while reactions and energy consumption on the electrode chamber are negligible.…”

Phosphates Transfer in Pristine and Modified CJMA-2 Membrane during Electrodialysis Processing of NaxH(3−x)PO4 Solutions with pH from 4.5 to 9.9

“…Already, these membrane technologies are promising for the processing of fermentation broths or waste fermentation effluent [ 1 , 2 , 3 , 4 ], agricultural, industrial streams and natural waters [ 5 , 6 , 7 , 8 , 9 ], the selective separation of various acids [ 10 ]; tartrate stabilization of wine; demineralization of milk whey; reagent-free correction of the pH of juices and wines [ 11 ], or conversion of salts to polybasic acids and vice versa [ 12 , 13 ]. Citrates [ 2 , 11 , 14 , 15 ], malates [ 10 , 14 ], tartrates [ 13 ], oxalates [ 7 ], chromates [ 16 , 17 ], vanadates [ 18 ], and sulfates [ 19 ] are the most common objects of the application of processes in which ion-exchange membranes are involved. Phosphates are of particular interest, which is accompanied by an avalanche-like increase in scientific publications in recent years ( Figure 1 ).…”