Abstract It was hypothesized that bauxite digestion may be improved by using microwave heating as it has been shown in literature that some material processes have improved efficiency. To test this hypothesis, a set of digestion experiments were conducted using gibbsite, one of the major minerals in bauxite. Gibbsite was digested at various temperatures (50, 75, and 95 °C) in either 1 M or 6 M sodium hydroxide solutions for 30 min using either a convection oven or a 2.45 GHz microwave applicator. Results show that microwave heating provided an increase of 5–7% in the digestion after 30 min and required around 1/10th the time to heat the solutions compared to conventional heating. Electromagnetic simulations show that preferential heating occurs at the solution surface creating a temperature gradient within the solution. Although vigorous stirring of the solution was used to minimize the temperature gradient, it could still be responsible for the observed difference in digestion. Digestion of bauxite itself yielded similar results to the gibbsite.

中文翻译：

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三水铝石和铝土矿在氢氧化钠中的微波消解

摘要 假设铝土矿消化可以通过使用微波加热来改善，因为文献中已经表明一些材料工艺提高了效率。为了验证这一假设，使用铝土矿中的主要矿物之一三水铝石进行了一系列消化实验。三水铝石在不同温度（50、75 和 95 °C）中使用对流烘箱或 2.45 GHz 微波施加器在 1 M 或 6 M 氢氧化钠溶液中消解 30 分钟。结果表明，与传统加热相比，微波加热在 30 分钟后使消化增加了 5-7%，并且加热溶液所需的时间大约是其 1/10。电磁模拟表明，优先加热发生在溶液表面，从而在溶液内产生温度梯度。尽管使用剧烈搅拌溶液来最小化温度梯度，但它仍然可能是观察到的消化差异的原因。铝土矿本身的消化产生与三水铝石相似的结果。