Add time:07/30/2019         Source:sciencedirect.com

In (NH4)2CO3 solution, leaching Ca3WO6-bearing product converted from tungsten concentrate can directly obtain ammonium tungstate solution, and thus eliminates high-salinity wastewater discharge in ammonium paratungstate manufacture. Possible reactions of Ca3WO6 leaching in aqueous ammoniacal AMMONIUM CARBONATE (cas 10361-29-2) solution under atmospheric pressure were investigated thermodynamically and experimentally. The results show that tungsten in Ca3WO6 can be efficiently leached out by forming CaCO3(s) and (NH4)2WO4 (aq) in aqueous ammoniacal ammonium carbonate solution, while raising ratio of total ammonia to total carbon in solution and forming calcite are beneficial to increase the WO3 leaching ratio. Whereas the secondary reactions of Ca3WO6 with H2O and/or Ca (OH)2/CaCO3 with (NH4)2WO4 may occur and thus CaWO4 forms in the leaching, decreasing WO3 leaching ratio especially in concentrated (NH4)2WO4 solution and in case of forming vaterite. In addition, a three-layer cover was observed on the unreacted Ca3WO6 and hinders the leaching process. Through simultaneous grinding and leaching, both high WO3 leaching ratio and high WO3 concentration leachate can be achieved by increasing ratio of total ammonia to total carbon in NH3-(NH4)2WO4- (NH4)2CO3-H2O system. These results are helpful to optimize the leaching process of the converted product with Ca3WO6 by roasting tungsten-containing materials.

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