Sorption of H₃BO₃/B(OH)₄⁻ on calcined LDHs including different divalent metals.
Sorption of H₃BO₃/B(OH)₄⁻ on calcined LDHs including different divalent metals.
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DOI：
10.1016/j.jcis.2014.12.093
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发表时间：
2015-05
影响因子：
9.9
通讯作者：
X. Qiu;K. Sasaki;K. Osseo-Asare;T. Hirajima;Keiko Ideta;J. Miyawaki
中科院分区：
文献类型：
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作者：
X. Qiu;K. Sasaki;K. Osseo-Asare;T. Hirajima;Keiko Ideta;J. Miyawaki
合成了含不同二价金属(Zn-LDH、Mg-LDH和Ca-LDH)的LDH，并制备了用于除硼的焙烧LDH(Zn-CLDH、Mg-CLDH和Ca-CLDH)。基于X射线衍射仪、扫描电子显微镜、BET、27Al核磁共振、CO2-TPD和11B核磁共振，系统地研究了不同CLDHs与硼物种反应前后的性质。与水化和再生有关的不同CLDH的比表面积、碱度和粒子电荷明显受二价金属性质的影响。随着时间的推移，不同CLDHs的晶相转变和吸附的硼物种种类不同。Ca-CLDH的再生所需时间最短。但Ca-LDH分解后释放出钙离子，与硼酸盐形成钙矾石。锌-乳酸脱氢酶也迅速转化为锌-乳酸脱氢酶。在重建过程中，B(OH)4-−插入到锌-水滑石的层间，这是锌-水滑石去除硼酸盐的主要机理。初始pH值的升高会引起硼酸盐与OH-−之间的竞争，从而降低了其对硼酸盐的去除效率。对于Mg-CLDH，第一阶段包括表面络合和静电吸引，第二阶段将硼酸固定在氢氧化镁中，并以层间阴离子物种的形式将硼酸盐吸引到新形成的镁-LDH中。
LDHs with different divalent metals (Zn-LDH, Mg-LDH and Ca-LDH) have been synthesized and produced calcined LDHs (Zn-CLDH, Mg-CLDH and Ca-CLDH) for borate removal. Based on XRD, SEM, BET,27Al NMR, CO2-TPD, and11B NMR, detailed characterization of different CLDHs before and after reaction with the boron species was systematically performed. The surface area, basicity and the particle charge of the different CLDHs, which are related to the hydration and regeneration, were markably influenced by the nature of the divalent metals. Transformation of crystal phases and the types of boron species adsorbed by the different CLDHs varied as time changed. The regeneration of Ca-CLDH required the shortest time. However, Ca-LDH decomposed to release Ca2+ions, forming ettringite with borate. Zn-CLDH also rapidly transformed into Zn-LDH. During this reconstruction, B(OH)4−was intercalated into the interlayer of Zn-LDHs, which is the predominant mechanism of borate removal by Zn-CLDH. Increase in the initial pH caused a competition between borate and OH−so that the removal efficiency of borate by Zn-CLDH decreased. For Mg-CLDH, surface complexation and electrostatic attraction were included in the first stage, immobilizing boric acid into Mg(OH)2and attracting borate as interlayer anionic species into the new forming Mg-LDHs in the second stage.