The leaching of industrial polycrystalline diamond (PCD) blanks in aqua regia at atmospheric pressure between 60 °C and 80 °C was performed using an ultrasound to improve the rate of cobalt removal in order to be able to reuse very expensive polycrystalline diamond. Because cobalt (20 wt.%) is used as a solvent catalyst in the production of PCD, its recovery is very important. The cleaned PCD are returned to the production process. Kinetic models were used in the study of cobalt dissolution from polycrystalline diamond blanks by measuring the declining ferromagnetic properties over time. For a better understanding of this leaching process, thermochemical aspects are included in this work. The lowest free Gibbs energy value was obtained with a low solid/liquid ratio and the full use of an ultrasound. A transition from a reaction-controlled to a diffusion-controlled shrinking core model was observed for PCD with a thickness greater than 2.8–3.4 mm. Intermittent ultrasound doubles the reaction rate constant, and the full use of ultrasound provides a 1.5-fold further increase. The obtained maximum activation energy between 60 °C and 80 °C is 20 kJ/mol, for a leaching of diamond blank with grain size of 5 µm.

中文翻译：

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通过超声辅助浸出法从多晶拉丝模坯中回收金刚石和钴粉—第2部分：动力学和机理

为了提高钴的去除率，超声波能够在60°C至80°C的大气压下于王水中浸出工业多晶金刚石（PCD）坯料，以便能够重新使用非常昂贵的多晶金刚石。由于钴（20 wt。％）在PCD生产中用作溶剂催化剂，因此其回收非常重要。清洁的PCD返回生产过程。通过测量随时间下降的铁磁特性，动力学模型被用于研究钴从多晶金刚石坯料中的溶解。为了更好地了解此浸出过程，这项工作包括热化学方面。在低固/液比和充分利用超声波的情况下，获得了最低的吉布斯自由能值。对于厚度大于2.8–3.4 mm的PCD，观察到了从反应控制到扩散控制的收缩核模型的转变。间歇性超声使反应速率常数增加一倍，并且充分利用超声可将反应速率进一步提高1.5倍。对于浸出粒度为5 µm的金刚石毛坯，在60°C和80°C之间获得的最大活化能为20 kJ / mol。