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Regulation of boehmite morphology is important for improving its performance in applications. In this paper, the dependence of boehmite morphology on cation ions was studied by XRD, SEM, TEM, FTIR, and zeta-potential, together with calculation of ion degree of association. Boehmite was respectively precipitated from sodium, potassium, lithium, or barium alkaline solution by adding gibbsite as seed at 180 °C for 2 h. Cation concentration and species determined the boehmite morphology. Increase in cation concentration or precipitation in K+, Na+, Li+, and Ba2+ alkaline solution correspondingly precipitated rhombic, hexagonal, and elliptical morphology for boehmite. Al­(OH)4 – was predominantly found in filtrate solution by Raman spectra, whereas red shift of FTIR was observed in alkaline solution containing Ba2+, Li+, Na+, and K+ cations. The degree of association of M n+[Al­(OH)4 –] n n− increased in the following order: Ba2+[Al­(OH)4 –]2 > Li+Al­(OH)4 – > K+Al­(OH)4 – > Na+Al­(OH)4 – in the same concentration of cation solution. This finding agreed with the variations in FTIR change and zeta potential. Meanwhile, increasing cation and Al­(OH)4 – concentration or precipitation in lithium or barium alkaline solution caused the (202) facet of boehmite to gradually disappear and the (200) facet to be exposed. Therefore, the selective adsorption of ion pairs on the (202) and (200) facet of boehmite mainly accounted for the boehmite morphology.

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Complete wolframite conversion in sulfuric acid is significant for expanding the applicability of the sulfuric acid method for producing ammonium paratungstate. In this paper, the conversion of wolframite in treating a mixed wolframite-scheelite concentrate by sulfuric acid was studied systematically. The results show that the conversion of wolframite in sulfuric acid is more difficult than that of scheelite, requiring rigorous reaction conditions. A solid H2WO4 layer forms on the surfaces of the wolframite particles and becomes denser with increasing H2SO4 concentration, thus hindering the conversion. Furthermore, the difficulty in wolframite conversion can be mainly attributed to the accumulation of Fe 2+ (and/or Mn 2+) in the H2SO4 solution, which can be solved by reducing Fe 2+ (and/or Mn 2+) concentration through oxidization and/or a two-stage process. Additionally, the solid converted product of the mixed wolframite-scheelite concentrate has an excellent leachability of tungsten in an aqueous ammonium carbonate solution at ambient temperature, with approximately 99% WO3 recovery. This work presents a route for manufacturing ammonium paratungstate by treating the mixed concentrate in sulfuric acid followed by leaching in ammonium carbonate solution.