Surface Complexation Modeling of Copper Sorption by Hydrous Oxides of Iron and Aluminum

✍ Scribed by K.G Karthikeyan; Herschel A Elliott

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 103 KB
• Volume: 220
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1999.6507

✦ Synopsis

Surface complexation models were used to simulate adsorption (ADS) and coprecipitation (CPT) of copper (Cu) by hydrous oxides of iron (HFO) and aluminum (HAO) over a range of pH and surface-loading conditions. The generalized two-layer model was satisfactory for two very different conditions: (1) low sorbate/ sorbent ratios where metal-oxide interaction is adequately described as Cu 2؉ coordination to surface functional groups and (2) under HFO-CPT conditions which result in extremely high adsorption site density (0.425 mol of sites/mol of Fe). As the sorbate/ sorbent ratio is progressively increased, the models must account for metal hydrolysis and surface precipitate formation, and Cu interaction with both hydrous oxides could be fitted over a wide range of surface loadings using a comprehensive surface precipitation model. Similar mass law constants for sorption reactions were used for generalized two-layer and surface precipitation modeling, ADS and CPT conditions, and pH-edge and isotherm data. Corroborating sorption and spectroscopic evidence, modeling indicated that Cu precipitated on HAO, unlike HFO, has a markedly lower K sp than bulk precipitated Cu(OH) 2 (s). Results also suggest that enhanced Cu removal by CPT was not simply a manifestation of higher surface area.