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Effect of Adsorbed Carboxylates on the Dissolution of Boehmite Nanoplates in Highly Alkaline Solutions
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2024-01-12 , DOI: 10.1021/acs.est.3c06595
Yatong Zhao 1, 2 , Qing Guo 3 , Sichuang Xue 2 , Ping Chen 2 , Qian Zhao 4 , Lili Liu 2 , Hanna Hlushko 5 , Jay LaVerne 6 , Carolyn I Pearce 7 , Aijun Miao 1 , Zheming Wang 2 , Kevin M Rosso 2 , Xin Zhang 2
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2024-01-12 , DOI: 10.1021/acs.est.3c06595
Yatong Zhao 1, 2 , Qing Guo 3 , Sichuang Xue 2 , Ping Chen 2 , Qian Zhao 4 , Lili Liu 2 , Hanna Hlushko 5 , Jay LaVerne 6 , Carolyn I Pearce 7 , Aijun Miao 1 , Zheming Wang 2 , Kevin M Rosso 2 , Xin Zhang 2
Affiliation
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Understanding the dissolution of boehmite in highly alkaline solutions is important to processing complex nuclear waste stored at the Hanford (WA) and Savannah River (SC) sites in the United States. Here, we report the adsorption of model carboxylates on boehmite nanoplates in alkaline solutions and their effects on boehmite dissolution in 3 M NaOH at 80 °C. Although expectedly lower than at circumneutral pH, adsorption of oxalate occurred at pH 13, with adsorption decreasing linearly to 3 M NaOH. Classical molecular dynamics simulations suggest that the adsorption of oxalate dianions onto the boehmite surface under high pH can occur through either inner- or outer-sphere complexation mechanisms depending on adsorption sites. However, both adsorption models indicate relatively weak binding, with an energy preference of 1.26 to 2.10 kcal/mol. By preloading boehmite nanoplates with oxalate or acetate, we observed suppression of dissolution rates by 23 or 10%, respectively, compared to pure solids. Scanning electron microscopy and transmission electron microscopy characterizations revealed no detectable difference in the morphologic evolution of the dissolving boehmite materials. We conclude that preadsorbed carboxylates can persist on boehmite surfaces, decreasing the density of dissolution-active sites and thereby adding extrinsic controls on dissolution rates.
中文翻译：
吸附的羧酸盐对勃姆石纳米片在高碱性溶液中溶解的影响
了解勃姆石在高碱性溶液中的溶解对于处理储存在美国汉福德（WA）和萨凡纳河（SC）场地的复杂核废料非常重要。在这里，我们报告了碱性溶液中勃姆石纳米片上模型羧酸盐的吸附及其对 80 °C 3 M NaOH 中勃姆石溶解的影响。尽管预期 pH 值低于中性附近，但草酸盐吸附发生在 pH 13 时，吸附量线性下降至 3 M NaOH。经典分子动力学模拟表明，在高 pH 条件下，草酸双阴离子在勃姆石表面上的吸附可以通过内球或外球络合机制发生，具体取决于吸附位点。然而，两种吸附模型都表明结合相对较弱，能量偏好为 1.26 至 2.10 kcal/mol。通过在勃姆石纳米片上预载草酸盐或乙酸盐，我们观察到与纯固体相比，溶解速率分别降低了 23% 或 10%。扫描电子显微镜和透射电子显微镜表征表明，溶解勃姆石材料的形态演变没有可检测到的差异。我们得出的结论是，预吸附的羧酸盐可以持续存在于勃姆石表面，降低溶解活性位点的密度，从而增加对溶解速率的外在控制。
更新日期：2024-01-12
中文翻译：
吸附的羧酸盐对勃姆石纳米片在高碱性溶液中溶解的影响
了解勃姆石在高碱性溶液中的溶解对于处理储存在美国汉福德（WA）和萨凡纳河（SC）场地的复杂核废料非常重要。在这里，我们报告了碱性溶液中勃姆石纳米片上模型羧酸盐的吸附及其对 80 °C 3 M NaOH 中勃姆石溶解的影响。尽管预期 pH 值低于中性附近，但草酸盐吸附发生在 pH 13 时，吸附量线性下降至 3 M NaOH。经典分子动力学模拟表明，在高 pH 条件下，草酸双阴离子在勃姆石表面上的吸附可以通过内球或外球络合机制发生，具体取决于吸附位点。然而，两种吸附模型都表明结合相对较弱，能量偏好为 1.26 至 2.10 kcal/mol。通过在勃姆石纳米片上预载草酸盐或乙酸盐，我们观察到与纯固体相比，溶解速率分别降低了 23% 或 10%。扫描电子显微镜和透射电子显微镜表征表明，溶解勃姆石材料的形态演变没有可检测到的差异。我们得出的结论是，预吸附的羧酸盐可以持续存在于勃姆石表面，降低溶解活性位点的密度，从而增加对溶解速率的外在控制。
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