Oxygen-containing/amino groups bifunctionalized SBA-15 toward efficient removal of methylene blue: kinetics, isotherm and mechanism analysis

Abstract

Bifunctionalized SBA-15 with oxygen-containing/amino groups (NH2-SBA15-ox) has been synthesized using a sequential processing strategy: (1) direct conversion of P123 organic surfactant into a thin carbon layer on the interior framework of short-channeled SBA-15 (C-SBA-15), (2) as-prepared C-SBA-15 was then fully oxidized with (NH4)2S2O8 (C-SBA15-ox) and (3) the C-SBA15-ox was post-modified via treatment with APTMS, which created a high density of amino functional group mainly on the external surface of platelet particles. It was shown that bifunctionalized SBA-15 demonstrated much improved adsorption performance toward methylene blue under adsorption testing conditions. Specifically, the adsorption equilibrium time was significantly reduced from 180 min (initial SBA-15) to 60 min (C-SBA15-ox) and then to no more than 10 min (NH2-SBA15-ox); the maximum adsorption capacity was increased from 157 mg/g (initial SBA-15) to 379 mg/g (C-SBA15-ox) and then to 445 mg/g (NH2-SBA15-ox). In combination of short-channeled framework and bifunctionalized surface groups, the NH2-SBA15-ox should be considered as a potential adsorbent to remove other toxic substances from wastewater. Integration of oxygen-containing/amino functional surface group and platelet morphology endowed SBA-15-like sorbents with high affinity and fast adsorption kinetics toward methylene blue from aqueous solution.