Adsorption mechanism of borate with different calcined layered double hydroxides in a molar ratio of 3:1
Adsorption mechanism of borate with different calcined layered double hydroxides in a molar ratio of 3:1
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DOI：
10.5004/dwt.2019.24057
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发表时间：
2019
影响因子：
1.1
通讯作者：
Shuang Xu;Jiawen Zhao;L. Deng;J. Niu;Xuhua Zhou;Shuwang Zhang;X. Qiu;Jinyi Chen
中科院分区：
文献类型：
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作者：
Shuang Xu;Jiawen Zhao;L. Deng;J. Niu;Xuhua Zhou;Shuwang Zhang;X. Qiu;Jinyi Chen
合成了含有不同二价金属（Zn-LDH、Mg-LDH和Ca-LDH）的摩尔比为3:1的层状双氢氧化物（ldh）。在500°C （Zn-CLDH， Mg-CLDH和Ca-CLDH）下煅烧以去除硼酸盐。采用XRD、FTIR和SEM对不同CLDHs吸附硼酸前后的形貌进行表征。对于Ca-CLDH(3:1)，主要的去除机制是与硼酸盐形成钙矾石，与Ca-CLDH（2:1）相同。但后者对硼酸盐的吸附比前者高得多，因为对于Ca-CLDH(2:1)，再生过程中钙矾石的产生量大于Ca-CLDH（3:1）。对于Zn-CLDHs(3:1和2:1)，硼酸盐通过离子交换和插层完全去除。然而，尽管最终吸附量相似，但Zn-CLDH（2:1）的吸附率高于Zn-CLDH（3:1）。此外，含有聚合硼的Zn-LDH（2:1）在短时间内形成，但随着反应的进行，逐渐形成更多的含有聚合硼的Zn-LDH（3:1）。对于两种比例的Mg-LDHs，硼酸盐首先通过静电吸附固定在金属氧化物表面，然后通过插层进入Mg-LDHs中间层，导致硼酸盐浓度降低。但Mg-LDH（3:1）对硼酸盐的吸附比Mg-LDH（2:1）更快更好，且Mg-CLDH（3:1）的结构再生时间比Mg-CLDH（2:1）短。因此，在使用CLDHs除硼时，应考虑LDHs的金属类型和比例。
Layered double hydroxides (LDHs) with a molar ratio of 3:1, which contain different divalent metals (Zn-LDH, Mg-LDH, and Ca-LDH), were synthesized. They were calcined at 500°C (Zn-CLDH, Mg-CLDH, and Ca-CLDH) for borate removal. The characterization of different CLDHs before and after adsorption of boric acid was performed by XRD, FTIR, and SEM. For Ca-CLDH (3:1), the main removal mechanism was the formation of ettringite with borate, which is the same as Ca-CLDH (2:1). However, the latter has a much higher adsorption of borate than the former, because for Ca-CLDH (2:1), the amount of ettringite produced during regeneration is more than that of Ca-CLDH (3:1). For Zn-CLDHs (3:1 and 2:1), borate was removed completely by ion exchange and intercalation. However, the adsorption rate of Zn-CLDH (2:1) is higher than that of Zn-CLDH (3:1), even though the final adsorption capacity is similar. In addition, Zn-LDH (2:1) containing polymerized boron formed in a short time, but as the reaction progresses, more Zn-LDH (3:1) containing polymerized boron is gradually formed. For two ratios of Mg-CLDHs, borate was first immobilized on the surface of metal oxide by electrostatic adsorption and then entered the interlayer of Mg-LDHs by intercalation, resulting in a decrease in borate concentration. However, Mg-LDH (3:1) has a faster and better adsorption of borate than Mg-LDH (2:1), and the structure regeneration time of Mg-CLDH (3:1) was shorter than that of Mg-CLDH (2:1). Therefore, when using CLDHs for boron removal, the metal type and ratio of LDHs should be considered.