摘要 :
Despite the existence of many single ion sorption studies on iron and aluminum oxides, fewer studies have been reported that describe cosorption reactions. In this work, we present an in situ ATR FIR study of synergistic adsorptio...
展开
Despite the existence of many single ion sorption studies on iron and aluminum oxides, fewer studies have been reported that describe cosorption reactions. In this work, we present an in situ ATR FIR study of synergistic adsorption of sulfate (SO_4) and copper (Cu) on goethite, which is representative of the minerals and ions present in mine wastes, acid sulfate soils, and other industrial and agricultural settings. Sulfate adsorption was studied as a function of varying pH, and as a function of increasing concentration in the absence and presence of Cu. The presence of Cu ions in solution had a complex effect on the ability of SO_4 ions to be retained on the goethite surface with increasing pH, with complete desorption occurring near pH 7 and 9 in the absence and presence of Cu, respectively. In addition, Cu ions altered the balance of inner vs outer sphere adsorbed SO_4. The solid phase partitioning of SO_4 at pH 3 and pH 5 was elevated by the presence of Cu; in both cases Cu increased the affinity of S0_4 for the goethite surface. Complementary ex situ sorption edge studies of Cu on goethite in the absence and presence of SO_4 revealed that the Cu adsorption edge shifted to lower pH (6.3 → 5.6) in the presence of SO_4, consistent with a decrease of the electrostatic repulsion between the goethite surface and adsorbing Cu. Based on the ATR FIR and bulk sorption data we surmise that the cosorption products of SO_4 and Cu at the goethite-water interface were not in the nature of ternary complexes under the conditions studied here. This information is critical for the evaluation of the onset of surface precipitates of copper-hydroxy sulfates as a function of pH and solution concentration.
收起
