In this study, purification of nano-colloidal diatomaceous earth (DE) particles by acid treatment and the characterization of the structural and chemical properties important for their water treatment applications are performed. The results show that the pristine and acid treated DE material were mineralogically and chemical complex, comprising SiO2 predominantly and other oxide phases in trace to minor amounts. The crystallo-chemical structure of the purified product was similar to that of silica particles in terms of the electrokinetic zeta potentials. In aqueous media, simple alkali metal ions (K+) were observed to specifically adsorb onto the DE particles which caused shift of the isoelectric point from a pH 2 to 6 at high ionic strength. The acid treated DE particles were effective in removing 49-89% and 57-72% of the monovalent K+ ions, respectively, at pH 7.5 and 11 via specific adsorption. For the solution containing hydrolysable heavy metal ion Pb2+, on the other hand, self-nucleation lead to the removal 68%-73% and 99-100% of the species, respectively, at pH 7.5 and 11 as Pb(OH)2 precipitates with DE particles removing 3-32% of the cations via adsorption at pH 7.5. The results of interparticle forces calculations based on DLVO theory were in good agreement with the colloidal stability experiments which revealed higher settling rates at higher ionic strength. The findings highlight the importance of understanding pH-dependent hydrolysable metal ion speciation and adsorption and interactions between DE particles and the metal ions in aqueous media.