Tris(2,2′-bipyridine)ruthenium(II)-clays as adsorbents for phenol and chlorinated phenols from aqueous solution

The adsorptive properties of tris(2,2′-bipyridine)ruthenium(II)-clay intercalation compounds, which were synthesized through cation exchange reactions from synthetic saponite (Sumecton SA), synthetic fluoro-tetrasilicic mica and montmorillonite (Kunipia F) for phenols were investigated. The adsorption isotherms of phenols for the tris(2,2′-bipyridine)ruthenium(II)-clays from aqueous solutions followed Langmuir type, indicating strong adsorbate–adsorbent interactions. The basal spacings of the tris(2,2′-bipyridine)ruthenium(II)-clays did not change through the adsorption of phenols. This means that the adsorbed phenols existed in the interlayer nanopore created by the tris(2,2′-bipyridine)ruthenium(II) in the interlayer space of the tris(2,2′-bipyridine)ruthenium(II)-clays. The adsorbed amounts of phenols varied depending upon the nature of clays. One of the factors responsible for the variation in the adsorbed amounts is the layer charge density of smectites. Relatively low-layer charge density of saponite led to relatively large pore volume in the interlayer space. The adsorbed amounts of 2,4-dichlorophenol for the tris(2,2′-bipyridine)ruthenium(II)-saponite and the tris(2,2′-bipyridine)ruthenium(II)-montmorillonite were the largest among three phenols. It is thought that the interactions between tris(2,2′-bipyridine)ruthenium(II) cation and phenols played an important role in the adsorption of these phenols.