Alkali Metal Cation Adsorption on Oxide Surfaces

Alkali metal cations (AMCs) have traditionally been viewed as binding non-specifically tooxide surfaces with the possible exception of Li+. This view stems from their more or less inert behavior in low to moderate ionic strength homogeneous solutions when paired with anions such as Cl-or NO3-. In fact, such solutions find widespread use as ionic strength buffers for surface charge and ion adsorption studies. However, our group, amongothers, has definitively demonstratedthat inner-sphere binding of AMCs is the rule rather than the exception for oxides as diverse as rutile and quartz. This contribution will review the experimental and computational evidence for inner-sphere binding of AMCs, and the implications of such bindingfor surface complexation models.