Separation of tungsten and molybdenum using selective precipitation with manganese sulfate assisted by cetyltrimethyl ammonium bromide (CTAB)

Abstract

In this paper, the separation of tungsten and molybdenum by selective precipitation is evaluated, and the addition of cetyltrimethyl ammonium bromide (CTAB), as complex agent, is developed to reduce Mo loss. Thermodynamic equilibrium calculations show that manganese salt has selectivity to precipitate tungsten from molybdenum. Through single factor experiments, the influence of precipitation factors is studied systematically. The results show that CTAB can enhance the separation of molybdenum and tungsten by manganese salts. Under optimal conditions (temperature 50 °C, n(Mo)/n(CTAB) = 2, n(Mo)/n(W) = 10, time 1 h), the loss rate of Mo is 0.73%, the precipitation rate of W is 89.57%, and the separation factor is 2411.67, which is much higher than the separation factor of molybdenum and tungsten without CTAB. The results of XRD and SEM show that the precipitates mainly consist of MnWO4 and a small amount of MnMoO4 with the shape of the flower cluster composed of flakes. The complex effect of CTAB is verified by the simulation of Cambridge sequential total energy package (CASTEP). The results of geometric optimization, total energy and density of states together with FTIR spectra reveal the complex mechanism of CTAB with MoO42−. As an inexpensive and green sorbent, CTAB can be used to enhance the effect of manganese salt precipitation method for selective separation of W and Mo ions.