Creation of Nanosized Iron Particles Intercalated into Montmorillonite and the Effective Adsorption Sites for Low Concentrations of Arsenic in Aqueous Solution

摘要

We have conducted an investigation into the adsorption of arsenic from low concentration (50 ppb-16 ppm) test solutions using nanosized particles of FeO (OH) stabilized between layers of montmorillonite. As much as 15.3 wt percent of Fe was successfully introduced between the layers, based on the increase that was determined in the interlayer spacing due to the intercalation (12.2 ->15.7 A). It is believed that the Fe species involved were approximately four octahedral units of [FeO_6] connected in a similar way to gamma-FeO (OH) crystals, based on Fe K-edge EXAFS. The adsorption efficiency of the Fe-impregnated montmorillonite from a 50 ppb arsenite test solution satisfied the current regulations regarding As contamination in public water supplies. Trace quantities of the As adsorbed onto the active sites were analyzed using As K-edge XAFS. This was demonstrated to be bidentate dinuclear arsenate that was oxidized upon adsorption onto the Fe-montmorillonite when the concentration of the test arsenite solution was 200 ppb-16 ppm, and essentially the same arsenate structure was obtained when an arsenate test solution was adsorbed.