Interactions of silver halides with metal chelates and chelating agents. II. The effects of Ni(II) and Co(III) complexes

Abstract

The critical coagulation concentration (ccc) of Ni 2+ for a negatively charged silver bromide hydrosol is decreased by about 1000 times when very small amounts of 2,2′-dipyridyl (dipy) are added to the sol. This is due to complex ion formation between Ni 2+ and dipy. The ability of the various Ni(II) chelate species to adsorb at the particle/solution interface depends on the degree to which the metal ion is coordinated to the bidentate amine chelating agent, or, alternatively, on the degree to which the central metal ion is hydrated. The stabilities of negatively charged silver iodide hydrosols were investigated as a function of the concentrations of [Co(dipy) 3] 3+ and [Co(phen) 3] 3+ (phen = 1,10-phenanthroline). The results show that these ions are very efficient coagulation and reversal of charge agents. This is attributed to the strong adsorption of the complex ions at the AgI/solution interface, which is verified by electrophoretic, infrared, and radioactive tracer measurements.