Clay Minerals in the Amakusa Pottery Stones and Some Features of Their Pottery Clays. Surface Charge of Sericite and Dispersion- Coagulation Properties of Pottery Clay in Water Hiroshi TATEYAMA, Hideharu HIROSUE, Satoshi NISHIMURA and Kinue TSUNEMATSU Government Industrial Research Institute of Kyushu. Shukumachi, Tosu, Saga 841 and Shigeki KAJI Fukuoka Industrial Research Institute, Fukuoka Prefecture, 332 Kamikoga, Chikushino, Fukuoka 818 Abstract Two kinds of pottery clays (TS-1, TS- 2) have been prep ared by pulverizing Amakusa pottery stone and two sorts of sericites (5-1, S-2) by elutriating the two pottery clays, respectively. Dispersion and coagulation properties of suspended pottery clays (TS-1, TS-2) and surface charge of sericites (5-1, S-2) have been studied as a function of ph on the basis of the data for zeta potential and the DLVO theory. Two kinds of sericites showed almost the same value of zeta potential in high ph region, however, the values of 5-1 were smaller than those of S-2 at ph below 7.
Surface potential, Stern layer and Guoy layer charges of S-1 and S-2 were calculated on the assumption that the edge potential was + 2 mv at ph 7. The surface potentials of S-1 and S-2 were-74 mv and -60 mv, respectively. In the coagulation series tests, sediments in coagulated suspensions of TS-1 were more voluminous than those of TS-2 of the same solid concentration under the conditions of ph below 7 or above 12. The difference between the structures of both sediments in coagulated suspensions was analyzed by the DLVO theory including the particle size effects. It was difficult to consider that three types of association(face-to- face, face-toedge, edge-to-edge) occurred simultaneously or to the same extent, when a suspention of very thin plate-like clay minerals coagulated in water. At the early stage of coagulation, edge-to-edge association was considered to play an important role in determining the structure of sediments because a potential energy barrier of edge- to-edge association in case of the very thin particles became much lower than the average kinetic energy of particles (15kt). It was therefore concluded that thin particles exhibited voluminous coagulation than thicker particles. Key words: Amakusa pottery stone, Sericite, Dispersion and coagulation tests, DLVO theory, Particle size effects, Zeta potential.
Fig. 1. Flow chart of sample preparation for dispersion-coaguration test and zeta potential measurement.
34 立 山 博 ら 粘土科学 S-1 Fig. 5. Electron sols. S-2 microphtographs of amixture of sericites (S-1, S-2) and positive silver と し た こ の 仮 定 を セ リサ イ ト ま で 拡 張 し て 各 セ リ サ Table 2. Zeta potential, surface surface in Stern and charge layers of rnuscovite (S-1, S-2), potential, and Guoy sericites イ トの 層 面 の ゼ ー タ 電 位 を 求 め た.そ 2に 示 す.S-1は S-2は,S-1よ り7.0mV高 こ れ ら の 値 を 基 に,各 い 値 と な っ た. セ リサ イ トの ス タ ー ン層 及 び 拡 散 層 に お け る 電 荷 密 度 を 求 め,さ 算 し た21)結 果 をTable2に は,白 の 結 果 をTable ほ ぼ 白 雲 母 と同 じ値 を 示 した が, らに表 面 電 位 を計 示 す.S-1の 表 面 電 位 雲 母 と ほ ぼ 近 い 値 を 示 す が,S-2は 較 し て 約10mV程 両者 に比 度 高 い 電 位 と な っ た.ス に お け る 電 荷 密 度 はS-1が 高 く,ま タ ー ン層 た,ス ター ン 層 と 拡 散 層 に お け る 電 荷 密 度 の 比(δ1/δ2)はS-1 が 僅 か に 大 き い.こ 状 態 の 差,特 M-1; muscovite, σ1; SternIayer σ2 were 10-4M S-1, σ2; calculated and S-2; Guoylayer, at a concentration ericites, SP, σ1, of の よ う にS-1,S-2間 で 表面 に 表面 電 位 に お いて 明 瞭 に 差 が 認 め られ た.し か し,Fig.5に は,顕 著 な 差 は 認 め ら れ な か っ た.こ 示 す よ う に銀 粒 子 の 付 着 量 に の 原 因 は,常 に 正 に 帯 電 し た 銀 粒 子 と 負 に 帯 電 し た セ リサ イ ト粒 子 間 で ヘ テ ロ 凝 集 を 起 し,そ NaCl. の と 考 え ら れ る. の 差 が 明 確 に現 れ な か った も
Fig. 9. Total potential energy of interaction (-) as a function of distance between two plates. Fig.10. Maximum total potential energy (-) as a function of layer thickness (d)