Selective adsorption of bisphenol A by organic-inorganic hybrid mesoporous silicas

Organic-inorganic hybrid mesoporous material (Ph-MS) was synthesized by co-condensation of phenyltriethoxysilane and tetraethoxysilane. Ph-MS, which had pore size of 0.96 nm and surface area of 750 m²/g, exhibited mesoscopic orderness and suitable textural properties to act as a potential adsorbent for bisphenol A (BPA), which is one of the endocrine disrupting chemicals. Ph-MS adsorbed most amount of BPA faster than powder activated carbon (PAC), and the kinetic adsorption data for Ph-MS was fitted well with the pseudo-second-order kinetic model. Maximum adsorption capacities of adsorbents were estimated from isotherm data using Langmuir model. Ph-MS exhibited high adsorption affinity to BPA showing large adsorption capacity of 351 mg/g, while showing little adsorption affinity to phenol (40 mg/g). PAC, which is one of the general adsorbents for organic compounds, showed large adsorption capacity for both BPA (337 mg/g) and phenol (253 mg/g). Adsorption selectivity of Ph-MS, defined as a relative equilibrium distribution coefficient, K_RD, for BPA against phenol, was at least 5 times larger than that of PAC, showing high adsorption selectivity for BPA. The selective adsorption behavior of Ph-MS was discussed using the results of material characterizations including X-ray diffraction, N₂ adsorption/desorption measurements, and Fourier transform infrared spectroscopy, and the results of adsorption experiments.