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Re: Does bentonite make a good substrate additive for cation exchange? (nt)



> From: Zxcvbob at aol_com
>
> Does bentonite make a good substrate additive for cation exchange? (nt)

Just about any temperate climate clay has a much higher CEC than laterite.
I think bentonite may be a smectite clay like montmorillonite.  Laterite
is mainly or exclusively composed of hydrous oxide type clay minerals.  

Here are some numbers from a soil science book (Brady's Nature and Properties
of Soils):

	Colloid		Max CEC by weight	Max CEC by volume
			(cmol/kg)		(cmol/L)
Humus (organic)		300			 75
Vermiculite		120			150
Smectite		 90			113
Fine-grained micas	 25			 31
Kaolinite		  5			  6
Hydrous oxides		  3			  4