E#ects of Imogolite Addition on Colloidal Stability of Montmorillonite and Kaolinite

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1 J. Jpn. Soc. Soil Phys. No. +*1, p.-1.-,**1 *** E#ects of Imogolite Addition on Colloidal Stability of Montmorillonite and Kaolinite Yu Lu MA* and Jutaro KARUBE** * United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, -,++ Chuo, Ami-machi, Ibaraki-ken, -***-3-, Japan ** Faculty of Agriculture, Ibaraki University, -,++ Chuo, Ami-machi, Ibaraki-ken, -***-3-, Japan Abstract E#ects of imogolite addition on colloidal stability of montmorillonite and kaolinite were examined to clarify the colloidal properties of imogolite which coagulates in alkaline condition. One to one mixture of montmorillonite and imogolite coagulated at any ph. Observation through transmission electron microscope revealed that montmorillonite and imogolite, including the mixture with lower imogolite concentration, mutually flocculated (formed a domain) at any ph. Non-deferrated kaolinite coagulated below ph /.3 and dispersed above ph 0.*, whereas / imogolite added sample showed the opposite stability. Deferrated kaolinite dispersed above ph..,, whereas +* imogolite added sample coagulated at any ph. All the imogolite added samples microscopically flocculated both under acidic and alkaline conditions. In acidic conditions, it was attributed to the electrostatic attraction between permanent negative charge of crystalline clay minerals and variable positive charge of imogolite. In alkaline conditions, it was considered to be resulted by the neutralized surface charge of imogolite. Key words : imogolite, montmorillonite, kaolinite, colloidal stability, charge characteristics + Horikawa, +31/ ; Harsh et al., +33, ; Karube, +332 PZNC ph 0.* ph Clark and McBride, +32. ;,**- Horikawa +31/ Harsh et al.,**, Tsuchida et al.,**/ * * -***-3- -,++ ** -***-3- -,++ :

2 38 +*1,**1 ph 0./ Ahmad and Karube, +332 ph,**- ph,,+, Karube, +332 F Na Ahmad and Karube, , mm Na,**+ / + ms m +,,,,+ *., kg m - + : * + : *.+ + : *./ + : +* : + 2* gm - + : * + : *.*/ + : *.+ * : + 2 gm - /* cm - HCl NaOH ph ph + +/ +,. - ph,. +* cm - MODEL TY-.D ph,,, +332 Na Cl KNO - /* cm - + g *.*, M *.. M NaCl, cm - HCl NaOH ph.* cm -,. ph /* cm - + MKNO - +** cm - - Na Cl Na Cl CEC AEC,,- *.*. kg m - + mm ph + : *.+ ph,.1 ph -.* + : *./ ph -.- ph -./ + : *.+ + : + ph -.,., -+, + : *./ + ph...

when dispersed and * when coagulated. Karube, +332 ph 3.. + + : *./ + : *.

3 : 39 M:I+ : *./ ph... + Fig. + c*., kg m - M: I: + * Colloidal stability of montmorillonite, imogolite, and their mixtures. (measured using scattered light, c*., kg m - ) M : montmorillonite, I : imogolite Relative turbidity approaches + when dispersed and * when coagulated. Karube, +332 ph : *./ + : *.+ + Photo + -, M:I+ : *./ ph 3.. Transmission electron micrographs of montmorillonite-imogolite mixtures. -,+ ph /.3 ph 0.*, ph 0.* ph - ph /.3 /, + : *.+

4 40 +*1,**1, Fig., K: I: Colloidal stability of kaolinite (non-deferrated) and kaolinite-imogolite mixtures (measured using scattered light). K : kaolinite, I : imogolite Scattered light intensity increases when dispersed. Although imogolite disperses in acidic conditions, scattered light was imperceptible due to low concentration.,. +* ph.., / ph - +* ph / - Fig. - *.*, M NaCl Charge characteristics of kaolinite (nondeferrated and deferrated) (measured with *.*, M NaCl). -,, + : *./, ph... ph +*.. ph... ph +*.. Gustafsson,,**+ ph... 0

kaolinite-imogolite mixtures (measured using transmitted light).

when dispersed. Ordinate was inverted for comparison with Fig.,.

. (coagulated) Transmission electron micrographs of

5 : 41 K:I+ : *.+ ph... (dispersed). Fig.. K: I:, Colloidal stability of kaolinite (non-deferrated) and kaolinite-imogolite mixtures (measured using transmitted light). K : kaolinite, I : imogolite Transmitted light intensity decreases when dispersed. Ordinate was inverted for comparison with Fig.,., Photo, K:I+ : *.*/ ph +*.. (coagulated) Transmission electron micrographs of kaolinite-imogolite mixtures. ph +*... / Fig. / Colloidal stability of kaolinite (deferrated) and kaolinite-imogolite mixtures (measured using scattered light). ph + : + ph ph

6 42 +*1,**1 0 : ; : ; Fig. 0 Illustrations explaining the transmission electron micrographs of kaolinite-imogolite mixtures. (upper : acidic ; flocculated in microscopic and dispersed in macroscopic observation) (lower : alkaline ; flocculated both in microscopic and macroscopic observation) ph /.3 / ph ph.., +* ph Ahmad, M.M. and Karube, J. (+332) : E#ects of salts and ph on the critical coagulation concentration of montmorillonite. Trans. Jpn. Soc. Irrig. Drain. Reclam. Eng., +3/ : Clark, C. J. and McBride, M.B. (+32.) : Cation and anion retention by natural and synthetic allophane and imogolite. Clays and Clay Minerals, -, :,3+,33. Gustafsson, J.P. (,**+) : The surface chemistry of imogolite. Clays and Clay Minerals,.3 : 1-2*. Harsh, J.B., Chorover, J. and Nizeyimana, E. (,**,) : Allophane and imogolite. pp.,3+-,,. ln J.B. Dixon and D.G. Schulze (ed.) Soil mineralogy with environmental applications. SSSA Book Series No. 1. SSSA, Madison, WI. Harsh, J.B., Traina, S. J., Boyle, J. and Yang, Y. (+33,) : Adsorption of cations on imogolite and their effect on surface charge characteristics. Clays and Clay Minerals,.* : 1**1*0. Horikawa, Y. (+31/) : Electrokinetic phenomena of aqueous suspensions of allophane and imogolite. Clay Science,. :,//,0-. Karube, J. (+332) : Hysteresis of the colloidal stability of imogolite. Clays and clay minerals,.0 : /2- /2/ : +30 : +*-++*.,**- :,20,21.,**- : p -.. Tsuchida, H., Ooi, S., Nakaishi, K. and Adachi, Y. (,**/) :E#ects of ph and ionic strength on electrokinetic properties of imogolite. Colloids and Surfaces A : Physicochemical and Eng. Aspects,,0/ : ,**+ :. :,.,,.2.

7 : 43 + : + ph ph ph /.3 ph 0.* / :,**1.,* :,**1 3 1

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