Influence of Glycine on Cu²⁺ Adsorption by Microcrystalline Gibbsite and Boehmite

Abstract

Abstract--The adsorption of Cu E+ on microcrystalline gibbsite and boehmite from aqueous solutions having 2/1 and 5/1 glycine/Cu ratios has been studied using electron spin resonance (ESR). The presence ofglycine inhibited metal adsorption on gibbsite above pH 5, apparently by reducing Cu hydrolysis. The preferred adsorbed species on gibbsite and boehmite, based upon the ESR parameters, were probably Cu(gly) § and Cu(gly)2 ~ respectively. In both experiments, rigidly-bound ternary complexes formed with Cu2+ simultaneously bonding to the surface and one or more ligands. A large excess ofglycine destabilized the ternary complex and caused the desorption of Cu 2 § The preferred orientation of the Cu complex on gibbsite suggests that the adsorption occurred at crystal steps and that the glycine molecule hydrogen bonded to hydroxyls of the (001) surface.

Reaction of aqueous Cu–Citrate with MnO2 birnessite: Characterization of Mn dissolution, oxidation products and surface interactions

“…This similarity suggests that Cu-Citrate1:1 (oxic) may form initial ternary surface complexes through the octahedral coordination sphere of the citrate coordinated Cu instead of through the citrate ligand. exchange with surface oxygen or hydroxyl groups, similar to other (hydr)oxides, such as alumina (McBride, 1985). An illustration of this process can be observed in Fig.…”

Reactions Controlling Heavy Metal Solubility in Soils

“…These ternary complexes include oxide-Cu1± ammonia and oxide-Cu1± phosphate associations (Davis and Leckie, 1978;Bourg et aI., 1979;McBride, 1984, 1985;McBride, 1985aMcBride, , 1985b. If the metal ion were not strongly bonded, one would expect some of these complexing ligands to "strip" the metal from the surface.…”

Spectroscopic Evidence for Ternary Surface Complexes in the Lead(II)–Malonic Acid–Hematite System

“…While macroscopic results can be used to infer reaction mechanisms and molecular structures, direct evidence is only found through the application of spectroscopic and microscopic techniques. To date, relatively few studies have applied spectroscopic techniques to study metal sorption to mineral surfaces in the presence of organic acids (8)(9)(10)(11).…”