Molecular recognition of 4-nonylphenol on a layered silicate modified with organic functionalities

A layered alkali silicate, octosilicate (Na₂Si₈O ₁₇), modified with the controlled amount and ratio of octadecyl and phenyl groups was synthesized to control the spatial distribution of the two functional groups and then achieve the effective and selective adsorption of 4-nonylphenol from aqueous solution. Octosilicates modified with the varied amount and ratio of the attached octadecyl/phenyl groups (0.7/0.7, 0.4/0.4, 0.3/0.3, and 0.4/1.0 groups per Si₈O₁₇ unit, respectively) were prepared by the reaction of the dodecylammonium-exchanged octosilicate with a controlled amount of octadecyltrichlorosilane and phenyltrichlorosilane sequentially. The adsorption of 4-nonylphenol from water on the four silylated octosilicates was investigated to find that the adsorption isotherm for the silylated octosilicate bearing the surface coverage with octadecyl/phenyl groups of 0.7/0.7 groups per Si₈O₁₇ unit was H-type, while the other silylated octosilicates gave S-type adsorption isotherms. The silylated octosilicate having surface coverage with octadecyl/phenyl groups of 0.7/0.7 groups per Si₈O₁₇ unit selectively adsorbed 4-nonylphenol from aqueous mixture of 4-butylphenol, 4-hexylphenol, and 4-nonylphenol.