Vanadium recovery from spent iron sorbent used for the treatment of mining-influenced water

Vanadium was recovered successfully from spent iron sorbent (ferric oxyhydroxide, CFH-12) using a two-step process including alkaline leaching and precipitation with CaCl2. The spent CFH-12 was collected from a field study in which a filter system was used to remove vanadium from mining-influenced water (referred to as MIWtreated CFH-12). Fresh CFH-12 was treated with synthetic vanadium solution (SVS-treated CFH-12) to compare the recovery process with the field study. First, a full factorial design was performed to optimize the precipitation process using synthetic leaching solution. The optimal conditions were found to be two times the theoretical dosage of CaCl2, a precipitation temperature of 60 degrees C, and a precipitation pH of 12.7. Vanadium desorption from the spent sorbents was conducted using 1 M NaOH, a contact time of 30 minutes and a CFH-12 solid-to-liquid ratio of 0.15 kg/L. The results revealed that vanadium could be efficiently precipitated from the leaching solution of MIW-treated CFH-12 and SVS-treated CFH-12. A higher dosage of CaCl2 was required to recover vanadium from MIW-treated CFH-12 due to the complexity of the leaching solution, which resulted in a lower vanadium content in the product. XRD analysis showed that the product recovered from SVS-treated CFH-12 mainly contained Ca-5(VO4)(3)OH and a small amount of CaCO3. TEM images revealed that the calcium vanadate hydroxide particles were round in shape, about 0.2-0.4 mu m in size and formed aggregates. The product recovered from MIW-treated CFH-12 contained amorphous calcium vanadate and crystalline Ca(OH)(2). XPS analysis confirmed that vanadium existed as V5+ in all of the recovered products.

Automated summary

Vanadium was successfully recovered from spent iron sorbent using a two-step process of alkaline leaching and precipitation with CaCl2. The optimal conditions for precipitation were determined and the differences in vanadium forms and crystalline structures in different sources of iron sorbent were identified.