Thermal Decomposition of a Dickite-hydrazine Intercalation Complex

Key Words--Dickite, DTA-TG-DTG, HTXRD. Hydrazine, Intercalation Complex, Kaolinite. I N T R O D U C T I O N In terca la t ion of hydraz ine in the in ter layer of kaol in minera l s has been ex tens ive ly s tudied by X-ray diff rac t ion (XRD) and spect roscopic me thods (Weiss e t al . , 1963; Ledoux and Whi te , 1966; Wada and Yamada, 1968; Range e t al . , 1969; Jackson and Abde l Kader, 1978; Theng e t al . , 1984; Johns ton , 1990; Johnston and Stone, 1990; Gfibor e t aL, 1995; Frost e t aL, 1998; Kloprogge e t al. , 1999; Kr is t6f e t al . , 1997, 1999; Ruiz Cruz and Franco, 2000). Mos t of these studies invo lve the kao l in i t e -hydraz ine (K-H) complex, and especia l ly the charac ter iza t ion of kaol ini tes wi th var ious degrees of latt ice d isorder (e .g . , Range e t al . , 1969; Fernfindez Gonzfi lez e t al. , 1976; G~ibor e t al . , 1995; Kloprogge e t al . , 1999), whereas the dicki tehydraz ine (D-H) and nac r i t e -hydraz ine (N-H) complexes have rece ived less at tention. X R D analyses indica te that hydraz ine in terca la t ion in the in ter layer of the kaol in minera l s produces a basal spac ing of -10.4 A (Wada and Yamada, 1968). R a n g e e t al. (1969), however , showed that the basal spac ing of the hydraz ine-ha l loys i t e (H-H) complex is 10 .0 -10 .2 * . These authors also demons t ra t ed that a var iable f rac t ion of the start ing sample does not react wi th hydrazine , whereas some kaol ini te spec imens react s lowly and lead to complexes wi th a basal spacing of 9 .5 -9 .6 A. A s imilar spacing was obse rved by Johns ton and S tone (1990) dur ing hydraz ine loss at dec reas ing pressure, and this was in terpre ted as re la t ing to the s tructural r e a r r angemen t caused by the loss of a por t ion of the in tercala ted hydrazine . Frost e t aL (1998) and Kloprogge e t al. (1999) showed X R D patterns of K-H complexes wi th b road basa l reflections, cons is t ing of three over lapped peaks wi th d values of 10.28, 9 . 5 0 , and 8 . 8 0 A. These authors p roposed that the in terca la t ion of kaol in i tes occurs in steps and that the spacing at 10.28 A is caused by the incorpora t ion of H20 in the K-H intercalate. The o b s e r v e d di f ferences in the 001 ref lect ion profi les be tween h ighand low-defec t kaol in i tes upon in terca la t ion were att r ibuted to the defect structures. Ruiz Cruz and Franco (2000) showed that complexes wi th decreas ing d values (10.4, 9.6, and 8.5 ,~) appeared dur ing r emova l of the in terca la ted molecules wi th increas ing temperatures. They suggested that the in tercala ted H20 and hydraz ine occupy wel l -def ined posi t ions in the interlayer, wh ich al lows the ordered loss of these subs tances. The rate of loss of H20 and hydraz ine was a s sumed to be di f ferent dur ing the des t ruc t ion of the complex , as p rev ious ly sugges ted by Kris t6f e t al. (1999). However, this a ssumpt ion canno t be p roved for the K-H in terca la t ion complex because several stages of mass loss overlap. Because dickite differs f rom kaol ini te s tructural ly and the D-H in terca la t ion complex has not been prev ious ly examined in detail, we have s tudied the deintercala t ion of the D-H complex to inves t iga te the possible d i f ferences in the rmal behav io r as compared to Copyright 9 2000, The Clay Minerals Society 586 Vol. 48, No. 5, 2000 Dickite-hydrazine complex 587