Expansion property of ammonium montmorillonite
アンモニウム型モンモリロナイトの膨潤性
齋藤 彬人*; 川喜田 竜平*
; 佐久間 博*; 小田 治恵
; 本田 明; 佐藤 努*
Saito, Akito*; Kawakita, Ryohei*; Sakuma, Hiroshi*; Oda, Chie; Honda, Akira; Sato, Tsutomu*
NH
型モンモリロナイト(MMT)の膨潤挙動を明らかにするため、Na, K, NH
型MMTをそれぞれ準備し、その膨潤性の違いを相対湿度(RH)制御XRDによる分析で比較した。NH
型MMTは、RH30%以上でK型と同様の膨潤挙動を示し、RH30%以下ではNa、K型よりも膨潤性があることが示された。また、分子動力学計算では、低RH条件で、NH
型はNa、K型よりも層間に1水分子層をもつ状態に達しやすいことが示された。これはNH
のH原子とMMTの底面O原子の結合に起因すると考えられる。
To understand the swelling behavior of NH
-montmorillonite (MMT), the expandability of monoionic Na-, K- and NH
-MMT was investigated by XRD under controlled relative humidity (RH) conditions and molecular dynamics (MD) calculations. XRD results indicate that the expansion properties of NH
-MMT are similar to that of K-MMT for RH
30%. At RH
30%, however, NH
-MMT expands further and has a larger basal spacing than both Na- and K-MMT. MD calculation results showed that NH
-MMT reaches a one-layer hydration state under lower RH conditions than that of Na- and K-MMT, and was entirely consistent with the above observations by XRD. It was also confirmed that an irregular motion of interlayer NH
could result from bonds between H atoms of the NH
ion and the base O atoms of MMT. This irregular motion enabled the basal spacing of NH
-MMT to increase and consequently, to expand further under low RH conditions.