Nanospace engineering of methylviologen modified hectorite-like layered silicates with varied layer charge density for the adsorbents design

Nanospace engineering of porous organic-clay intercalation compounds has been conducted by ion exchange reactions of 1,1′-dimethyl-4, 4′-bipyridinium chloride (methylviologen) with different layer charged hectoritelike layered silicates (cation exchange capacity derived from the amount of the cation exchanged: 42, 74, and 85 mequivalent/100 g clay) prepared by the reaction of LiF, Mg(OH)₂, and colloidal silica. The nanospace created with silicate layers and 1,1′-dimethyl-4,4′- bipyridinium cations has been used for the adsorption of organic compounds (N,N-dimethylaniline and 2,4-dichlorophenol) in the interlayer spaces of a series of the 1,1′-dimethyl-4,4′-bipyridinium-layered silicate intercalation compounds. All of the intercalation compounds adsorbed N,N-dimethylaniline from aqueous solution. The basal spacing of the intercalates did not change by the adsorption, indicating that the adsorbed N,N-dimethylaniline existed in the interlayer nanospace. The intercalated N,N-dimethylaniline polymerized to develop a purple color when the layered silicates with the cation exchange capacities of 74 and 42 meq/100 g were used. On the other hand, the intercalation compound with a larger content of 1,1′-dimethyl-4,4′-bipyridinium (cation exchange capacity: 85 meq/100 g) suppressed the polymerization (to dimer or trimer) of N,N-dimethylaniline due to the smaller pore. The adsorption capacity of 2,4-dichlorophenol was larger when the 1,1′-dimethyl-4,4′- bipyridinium content was smaller. It is found that the volume of the nanospace formed with 1,1′-dimethyl-4,4′-bipyridinium and silicate layers is controllable by using the layered silicate with varied layer charge density.