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Ultrastrong Anion Affinity of Anionic Clay Induced by Its Inherent Nanoconfinement
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-12-30 , DOI: 10.1021/acs.est.0c03775 Chen Tian 1, 2 , Jingwei Tu 1, 3 , Peipeng Qiu 1, 2 , Shuting Wang 1, 2 , Han Song 1, 2 , Yunyun Xu 1, 2 , Xu Yan 4 , Zhang Lin 1, 2, 4 , Liyuan Chai 4
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-12-30 , DOI: 10.1021/acs.est.0c03775 Chen Tian 1, 2 , Jingwei Tu 1, 3 , Peipeng Qiu 1, 2 , Shuting Wang 1, 2 , Han Song 1, 2 , Yunyun Xu 1, 2 , Xu Yan 4 , Zhang Lin 1, 2, 4 , Liyuan Chai 4
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Layered double hydroxide (LDH), the only anionic clay in the environment, plays a key role in natural ion transportation. The ion retention effect of LDHs was traditionally attributed to ion exchange with low affinity. Here, we demonstrated an ultrastrong interaction between anions and LDHs induced by their inherent nanoconfinement using chromium ore processing residue (COPR) that contained several Cr(VI)-bonded LDHs as a probe. Hydrocalumite (Ca/Al–Cl LDH) was verified as the primary phase for Cr(VI) retention through two types of interactions such as ion exchange and Cr–Ca coordination. More significantly, the confined spacing between two layers of hydrocalumite provided spatial restriction and shielding effects to the intercalated Cr(VI), which enhanced Cr–Ca coordination by shortening the bonding distance and modulating the binding angle to achieve the lowest bonding energy. Such enhancement boosted Cr(VI) affinity up to 3.2 × 105 mL/g, which was 1–3 orders of magnitudes higher than ion exchange. The universality of this mechanism was verified using another Mg/Al–Cl LDH and various anions. This study broke the traditional awareness of low ion affinities of LDHs limited by single ion exchange and disclosed an essential mechanism for unexpected ion retention effects of anionic clays in nature.
中文翻译：
固有的纳米约束诱导阴离子粘土的超强阴离子亲和力
层状双氢氧化物（LDH）是环境中唯一的阴离子粘土，在天然离子运输中起关键作用。LDHs的离子保留效果传统上归因于低亲和力的离子交换。在这里，我们展示了使用铬矿石加工残留物（COPR）包含几个Cr（VI）键合的LDHs作为探针，由阴离子和LDHs固有的纳米约束诱导的超强相互作用。通过两种类型的相互作用（例如离子交换和Cr-Ca配位），氢钙铝石（Ca / Al–Cl LDH）被证明是Cr（VI）保留的主要相。更重要的是，两层水钙铝石之间的有限间距为插层的Cr（VI）提供了空间限制和屏蔽作用，通过缩短键合距离和调节键合角度以实现最低的键合能量，从而增强了Cr-Ca配位。这种增强将Cr（VI）亲和力提高到3.2×105 mL / g，比离子交换高1-3个数量级。使用另一种Mg / Al–Cl LDH和各种阴离子验证了该机制的普遍性。这项研究打破了传统上对LDHs受单一离子交换限制的低离子亲和力的认识，并揭示了自然界中阴离子粘土具有意想不到的离子保留效果的基本机制。
更新日期：2021-01-19
中文翻译：
固有的纳米约束诱导阴离子粘土的超强阴离子亲和力
层状双氢氧化物（LDH）是环境中唯一的阴离子粘土，在天然离子运输中起关键作用。LDHs的离子保留效果传统上归因于低亲和力的离子交换。在这里，我们展示了使用铬矿石加工残留物（COPR）包含几个Cr（VI）键合的LDHs作为探针，由阴离子和LDHs固有的纳米约束诱导的超强相互作用。通过两种类型的相互作用（例如离子交换和Cr-Ca配位），氢钙铝石（Ca / Al–Cl LDH）被证明是Cr（VI）保留的主要相。更重要的是，两层水钙铝石之间的有限间距为插层的Cr（VI）提供了空间限制和屏蔽作用，通过缩短键合距离和调节键合角度以实现最低的键合能量，从而增强了Cr-Ca配位。这种增强将Cr（VI）亲和力提高到3.2×105 mL / g，比离子交换高1-3个数量级。使用另一种Mg / Al–Cl LDH和各种阴离子验证了该机制的普遍性。这项研究打破了传统上对LDHs受单一离子交换限制的低离子亲和力的认识，并揭示了自然界中阴离子粘土具有意想不到的离子保留效果的基本机制。
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