Direct aqueous mineral carbonation of olivine minerals has been extensively investigated in the past. However, the effect of inorganic electrolytes, particularly sodium sulfate (Na2SO4), on mineral carbonation rate has not been investigated yet. In this work, we report experimental results on the CO2 uptake rate of ultrafine olivine-rich rocks using Na2SO4 and sodium chloride (NaCl) as inorganic catalysts under hydrothermal conditions. The reaction mechanism was explained using both a shrinking core model and a machine learning model. One major and unexpected finding was that the use of Na2SO4 significantly increased the carbonation efficiency compared to the baseline with and without using sodium chloride (NaCl) as an inorganic electrolyte. The results showed that an increase in the carbonation kinetics in the presence of Na2SO4 was evident, particularly at a temperature range of 145–185 °C. At this temperature range, the reaction kinetics are predominantly governed by the product layer diffusion control mechanism. The presence of Na2SO4 electrolyte likely contributed to a promoted dissolution of silica and divalent ions from the hosting rocks/minerals. Results obtained from machine learning modelling confirmed that both the temperature and Na2SO4 additive were key parameters for mineral carbonation compared with other process variables. The present study demonstrates the catalyzing role of Na2SO4 in direct aqueous mineral carbonation of olivine minerals.

中文翻译：

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橄榄石矿物的硫酸盐活化矿物碳化作用及其机制由收缩型芯模型和机器学习算法解释


橄榄石矿物的直接含水矿物碳化在过去已被广泛研究。然而，无机电解质，特别是硫酸钠 （Na2SO4） 对矿物碳化速率的影响尚未得到研究。在这项工作中，我们报道了在水热条件下使用 Na2SO4 和氯化钠 （NaCl） 作为无机催化剂的超细富含橄榄石的岩石的 CO2 吸收率的实验结果。使用收缩核心模型和机器学习模型解释了反应机制。一个出乎意料的重大发现是，与使用和不使用氯化钠 （NaCl） 作为无机电解质的基线相比，使用 Na2SO4 显著提高了碳酸化效率。结果表明，在 Na2SO4 存在下，碳化动力学明显增加，尤其是在 145–185 °C 的温度范围内。 在此温度范围内，反应动力学主要由产品层扩散控制机制控制。Na2SO4 电解质的存在可能有助于促进二氧化硅和二价离子从主岩/矿物中溶解。从机器学习建模中获得的结果证实，与其他过程变量相比，温度和 Na2SO4 添加剂都是矿物碳化的关键参数。本研究证明了 Na2SO4 在橄榄石矿物的直接含水矿物碳化中的催化作用。