Preparation of polyhedral oligomeric silsesquioxane based cross-linked inorganic-organic nanohybrid as adsorbent for selective removal of acidic dyes from aqueous solution.

A cross-linked polyhedral oligomeric silsesquioxane (POSS) nanohybrid is synthesized through Schiff base chemistry by using octa-amino POSS as building blocks and glutaraldehyde as dual functional reagent. The obtained nanohybrid is characterized by FT-IR, solid-state Si NMR, SEM, TEM, TGA and N adsorption-desorption isotherm, and the results demonstrate the successful cross-linkage between POSS molecules, forming block-like irregular nanoparticles with a specific surface area of 42.8mg. As a novel solid-phase adsorbent, cross-linked POSS nanohybrid exhibits selective adsorption properties for acidic dyes, i.e., methyl orange (MO) in the present case. The strong electrostatic interactions between MO species and the nanohybrid are the main driving forces for MO adsorption. The kinetic data are well described by the pseudo-second-order kinetic model. The adsorption isotherm studies demonstrate that the data are well fit with Langmuir model at 293K and a maximum adsorption capacity of 237.5mgg is obtained. Thermodynamic studies indicate that the adsorption of MO is spontaneous and exothermal, along with reduced randomness. The adsorbed MO species could be effectively recovered by using methanol/NaOH (9/1, v/v, 0.1molL NaOH) as eluent. The practical application for textile wastewater treatment demonstrates that cross-linked POSS nanohybrid appears to be a promising material in dye removal field.