Ferrocyanide adsorption on aluminum oxides

Ferrocyanide (Fe(CN)6(4-)) adsorption onto gamma-alumina ( gamma-Al2O3(s) ) and gibbsite (Al(OH)3(s)) was investigated over a wide pH range and at various solid loadings. Batch experiments were performed using 100-ml solutions (I = 0.01 M NaCl) dosed with 1.0 mgl(-1) Fe(CN)6(4-) as CN. Equilibrium adsorption-pH edges were developed for 0.3, 0.6, 1.2, and 2.0 gl(-1) gamma-Al(2)O3(s) and 25 gl(-1) Al(OH)3(s). Ferrocyanide adsorption increased as pH decreased, consistent with the general pH dependence for adsorption of anions onto oxide minerals. Ferrocyanide adsorption onto Al(OH)3(s) was approximately 300 times lower than onto gamma-Al(2)O3(s) on a unit weight basis due to the higher surface reactivity of the gamma-Al(2)O3(s). Ferrocyanide adsorption onto gamma-Al(2)O3(s) was significantly greater than has been reported for goethite (FeOOH(s)), and both gamma-Al(2)O3(s) and FeOOH(s) adsorbed ferrocyanide to a greater extent than Al(OH)3(s) . The investigation showed that ferrocyanide can adsorb significantly onto aluminum oxides spanning a range of crystallinity and properties, with the extent of adsorption highly dependent on pH, the solid crystalline structure, and associated surface reactivity.