A remarkable adsorbent for removal of bisphenol S from water: Aminated metal-organic framework, MIL-101-NH2

Purification of water contaminated with organics has recently attracted much attention. In this study, the adsorptive removal of bisphenol S (BPS) from water was studied by using a metal-organic framework (MOF) MIL-101 with or without –NH2 functionality. In order to understand the adsorption of BPS in detail, adsorption of other relevant materials, such as bisphenol A (BPA) and sulfamethoxazole (SMZ), was also carried out. The adsorbed quantity increased significantly for SMZ and BPS (different from BPA adsorption) with the introduction of –NH2 groups onto MIL-101 even though the surface area of MIL-101-NH2 is much smaller than that of the pristine MIL-101. Moreover, adsorption of BPS was carried out over a wide pH range in order to understand the adsorption mechanism. It could be suggested that hydrogen bonding (with six-membered ring structure) between –S(O)2 and NH2 of MIL-101-NH2 could be an important contribution to the adsorption of BPS and SMZ. Moreover, H-bonding between –NH2 of the MOF and –OH (of BPS and BPA) or –NH2 (of SMZ) might also be possible. SMZ adsorption could remarkably be increased by loading –NH2 on MIL-101, because of another mechanism of ion-dipole interaction between the anionic N of SMZ and the –NH2 of MIL-101-NH2. Finally, MIL-101-NH2 showed the highest adsorption capacity for BPS (513 mg/g, at pH 7), compared with any reported results, and was recyclable after simple ethanol washing, suggesting the possible application of aminated MOFs in the adsorption of organics with sulfonyl group like BPS.