Proton binding at clay surface in water

M. AVENA; M. M. MARISCAL; C. DE PAULI

APPLIED CLAY SCIENCE

Elsevier

Año: 2003 vol. 24 p. 3 - 3

0169-1317

his article discusses the points that have more impact in the protonation–deprotonation behavior of a phyllosilicateclay surface in aqueous media. Some concepts that are currently used to explain the behavior of the oxide–water interfaceare now applied to the clay–water interface, and a rather new interpretation of the role of structural charges on the affinityof edge groups for protons is also given. Proton binding at a phyllosilicate clay surface takes place at oxygen-containinggroups. As in the case of oxygen-containing molecules, the groups behave as monoprotic entities and undergo only oneprotonation–deprotonation step in a normal pH range. The protonation behavior depends on the intrinsic affinity of surfacegroups and long-range electrostatics. The MUSIC model confirms that the proton affinity of siloxane and gibbsite-likegroups located at the basal surfaces (001 planes) of 2:1 or 1:1 clays is very low. On the contrary, the proton affini