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在75℃和pH=1.04～2.46时采用间歇型实验方法测定了天然白钨矿在HCl溶液中的溶解速率,揭示了溶解反应的动力学机理。结果表明,Ca的释放速率随反应时间保持稳定,并随pH降低而增大。W的释放行为则更为复杂,在反应初期与Ca呈一致溶解,之后由于钨酸表面层(中间产物)的形成,W的释放量和释放速率明显下降。这说明白钨矿的溶解作用由早期的表面化学反应转变为化学反应-扩散控制过程,从而导致W、Ca呈不一致溶解。pH越小,不一致溶解出现的时间越早。酸性溶液中白钨矿的溶解速率方程为v=k[H+]n,以W和Ca计算的速率常数k分别为0.65×10-5mol/m2s和1.04×10-5mol/m2s,反应级数n则分别为1.20和1.26。结合他人研究结果,白钨矿的溶解反应相对于H+可能为一级反应。
The dissolution rate of natural scheelite in HCl solution was determined by batch experiments at 75 ℃ and pH = 1.04 ~ 2.46, revealing the kinetic mechanism of the dissolution reaction. The results showed that the release rate of Ca remained stable with the reaction time and increased with the decrease of pH. The release behavior of W was more complicated and dissolved uniformly with Ca during the initial reaction, and then the release and release rate of W significantly decreased due to the formation of tungstic acid surface layer (intermediate product). This shows that the dissolution of scheelite from the early surface chemical reaction into chemical reaction - diffusion control process, resulting in W, Ca were inconsistent dissolution. The smaller the pH, the earlier the inconsistent dissolution occurs. The dissolution rate equation of scheelite in acidic solution is v = k [H +] n. The rate constants k calculated by W and Ca are 0.65 × 10-5mol / m2s and 1.04 × 10-5mol / m2s respectively. The reaction order n Then 1.20 and 1.26 respectively. Combined with the results of other studies, the dissolution reaction of scheelite relative to H + may be a first-order reaction.