Solid-State Recrystallization Pathways of Sodium Aluminate Hydroxy Hydrates.,Inorganic Chemistry

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Solid-State Recrystallization Pathways of Sodium Aluminate Hydroxy Hydrates.
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-04-07 , DOI: 10.1021/acs.inorgchem.0c00258
Trent R Graham ₁ , Rafal Gorniak ₂ , Mateusz Dembowski ₁ , Xin Zhang ₁ , Sue B Clark _{2,

3,

4} , Carolyn I Pearce ₃ , Aurora E Clark ₂ , Kevin M Rosso ₁

Affiliation

Crystallization of Al3+-bearing solid phases from highly alkaline Na2O:Al2O3:H2O solutions commonly necessitates an Al3+ coordination change from tetrahedral to octahedral, but intermediate coordination states are often difficult to isolate. Here, a similar Al3+ coordination change process is examined during the solid-state recrystallization of monosodium aluminate hydrate (MSA) to nonasodium bis(hexahydroxyaluminate) trihydroxide hexahydrate (NSA) at ambient temperature. While the MSA structure contains solely oxolated tetrahedral Al3+, the NSA structure is a molecular aluminate salt solely based upon monomeric octahedral Al3+. Spontaneous recrystallization of MSA and excess sodium hydroxide hydrate into NSA over 3 days of reaction time was clearly evident in X-ray diffractograms and in Raman spectra. In situ single-pulse 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and 27Al multiple quantum (MQ) MAS NMR spectroscopy showed no evidence of intermediate aluminates, suggesting that transitional states, such as pentacoordinate Al3+, are short-lived and require spectroscopy with greater time resolution to detect. Such research is advancing upon a detailed mechanistic understanding of Al3+ coordination change mechanisms in these highly alkaline systems, with relevance to aluminum refining, corrosion sciences, and nuclear waste processing.

中文翻译：

铝酸钠羟基水合物的固态重结晶途径。

从高度碱性的Na2O：Al2O3：H2O溶液中结晶含Al3 +的固相通常需要从四面体到八面体的Al3 +配位变化，但是中间配位态通常很难分离。在此，在环境温度下将铝酸钠水合物（MSA）固态重结晶为六水合双（六羟基铝酸盐）三水合壬醇钠（NSA）期间，研究了类似的Al3 +配位变化过程。尽管MSA结构仅包含含羟基的四面体Al3 +，但NSA结构是仅基于单体八面体Al3 +的分子铝酸盐。在X射线衍射图和拉曼光谱中，在3天的反应时间内MSA和过量的氢氧化钠水合物自发地重结晶为NSA。原位单脉冲27Al幻角旋转（MAS）核磁共振（NMR）光谱和27Al多量子（MQ）MAS NMR光谱显示没有中间铝酸盐的证据，这表明过渡态（如五配位Al3 +）是短暂的并需要具有更大时间分辨率的光谱进行检测。这些研究是基于对这些高碱性系统中Al3 +配位变化机理的详细机械理解而进行的，与铝精炼，腐蚀科学和核废料处理有关。寿命短，需要光谱法具有更大的时间分辨率才能进行检测。这些研究是基于对这些高碱性系统中Al3 +配位变化机理的详细机械理解而进行的，与铝精炼，腐蚀科学和核废料处理有关。寿命短，需要光谱法具有更大的时间分辨率才能进行检测。这些研究是基于对这些高碱性系统中Al3 +配位变化机理的详细机械理解而进行的，与铝精炼，腐蚀科学和核废料处理有关。

更新日期：2020-04-07

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