Abstract This work presents a study on the dissolution kinetics of a Brazilian glauconitic siltstone, known as Verdete, in the presence of sulfuric acid and in hydrothermal conditions. The objective was to verify the efficiency of the hydrothermal methodology in breaking up the structures of muscovite, glauconite and K-feldspar at low liquid/solid ratio to recover potassium. The water-soluble and insoluble products were analysed by flame photometry, XRD and SEM-EDS. The reaction rate of K extraction showed to be high, and K recovery was directly proportional to the acid concentration. K release occurred due to rupture of micas, and the reaction mechanism occurred through replacement of interlayer K+ with H+, and a partially extraction of Al3+, Fe3+, Fe2+ and Mg2+ from the 2:1 layer. With the breakup of silicate structures, the remaining solid product was amorphous silica. K-feldspar began to be dismantled at higher temperatures (> 473 K).

中文翻译：

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在热液条件下通过与硫酸反应从巴西青绿岩粉砂岩中回收钾

摘要 这项工作展示了在硫酸存在下和在热液条件下，巴西青青质粉砂岩（称为 Verdete）的溶解动力学研究。目的是验证水热方法在低液固比下分解白云母、海绿石和钾长石结构以回收钾的效率。通过火焰光度法、XRD和SEM-EDS分析水溶性和不溶性产物。K提取反应速率高，K回收率与酸浓度成正比。K 的释放是由于云母的破裂而发生的，反应机制是通过用 H+ 取代层间 K+，以及从 2:1 层中部分提取 Al3+、Fe3+、Fe2+ 和 Mg2+ 而发生的。随着硅酸盐结构的破裂，剩余的固体产物是无定形二氧化硅。钾长石在更高的温度（> 473 K）下开始分解。