Copper(II) Interactions with Kaolinite: Factors Controlling Adsorption

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Abstract
The adsorption of Cu2+ on kaolinite was studied at different ionic strengths following various treatments of the mineral surface in order to evaluate the conditions influencing adsorption. The data indicate a strong preference of the Na+ exchange form of kaolinite for Cu2+ but a weak affinity of the natural kaolinite for Cu2+. Protons are generated by Cu2+ adsorption, a result of the exchange of surface protons, and possibly the enhancement of Cu2+ hydrolysis at the kaolinite surfaces. The exchange of Na+ by Cu2+ on the kaolinite is not described by the mass-action equation, but can be interpreted in terms of permanent charge sites on the surfaces when the additional factors of Na+-H3O+ exchange and blockage of sites by Al ions are considered.