Preparation of phosphor-tungstic acids (H3PW12O40) by solvent extraction with 2-octanol

For more than a hundred years, extraction with ethyl ether has been the most used method for synthetizing H 3 PW 12 O 40 . However, the use of ethyl ether as the extraction agent faced many problems, such as strict regulation by public safety and environment authorities, poor operating environment, significant dissolution loss, low yields (approximately 80%), and difficulty in realizing continuous production. To overcome these problems, a new extraction method has been proposed in this paper, which uses 2-octanol as the extraction agent and water as the stripping agent. Under optimal conditions (30% 2-octanol in kerosene, O:A = 1:1, 180 g/L H 2 SO 4 , 20 g/L H 3 PO 4 , 45 °C, and a contact time of 2 min), 90.2% of H 3 PW 12 O 40 contained in the solution was extracted in a single stage; the loaded H 3 PW 12 O 40 could then be stripped completely via 3-stage continuous countercurrent stripping by maintaining O:A = 5:1, 65 °C, and t  = 5 min. Finally, the obtained strip liquor, containing more than 550 g/L H 3 PW 12 O 40 , was evaporated to obtain crystals, resulting in an increased recovery rate of 10%.