蒙脱石中Cu^(2+)的吸附态研究

State of Cu^(2+) adsorbed by montmorillonite

对在ｐＨ ≤４．５、痕量浓度条件下吸附了Ｃｕ^（２＋）的蒙脱石的Ｘ射线衍射（ＸＲＤ）进行了研究。该蒙脱石的ｄ（００１） 由原始蒙脱石的１．４７９ ｕｍ变为 １．５２３ ｕｍ，说明水合铜离子置换了蒙脱石的层间阳离子；在该蒙脱石的 ＥＰＲ谱中记 录到了 ｇ＝ ２． ０７、 ｇ＝ ２． １４精细结构线和 ｇ为约 ２． ７～ ２． ２超精细结构线三组有关 Ｃｕ^（２＋）的信号，说明其中的 Ｃｕ^（２＋）有 三种不同的结构状态。同时，该蒙脱石热处理产物的 ＥＰＲ研究表明， ｇ＝ ２． １４信号与蒙脱石层间的水合铜离子相关， ｇ＝ ２． ０７信号和 ｇ为约 ２． ７～ ２． ２超精细结构线分别与进入了粘土矿物Ｓｉ－Ｏ四面体片复三方形孔洞和铝氧八面体空位中的 Ｃｕ^（２＋）相关。整个研究表明，在 ｐＨ ≤ ４． ５、痕量浓度条件下，蒙脱石对 Ｃｕ^（２＋）的吸附包括两种方式，即交换吸附和专性吸附。

XRD result of montmorillonite adsorbing Cu^(2+) shows its d(001) value is 1. 523 um which is different from that of the original sample with d(001 ) of 1. 479 um, suggesting that the inter-canons of montmorillonite have been replaced by hydrated copper ions. In the EPR spectra of montmorillonite adsorbing Cu^(2+), there are three signals relating with Cu^(2+). They are respectively located at g = 2. 07, g = 2. 14 which are fine lines and g ca. 2. 2 - 2. 7 which is supper fine line. It is proposed that there is three different structural state of Cu^(2+). EPR study of the thermal products of these montmorillonites shows that g = 2. 14 signal relates with hydrated copper ions existing in the interlayer of montmorillonites and g = 2. 07 signal relates with Cu^(2+) occupying the ditrigonal cavities of Si-O sheet. And, the supper fine line of g ca. 2. 2 - 2. 7 suggests Cu^(2+) migrating into octahedral vaeancies. It can be concluded that there is two adsorption styles of montmorillonite to Cu^(2+): exchangeable adsorption and special adsorption.