Gemini surfactant mediated HIPE template for the preparation of highly porous monolithic chitosan-g-polyacrylamide with promising adsorption performances

In this work, a gemini-surfactant (i.e. sodium dilauramino cysteine, SDLC) stabilized high internal phase emulsion (HIPE) template was utilized to prepare monolithic polyHIPEs of chitosan-g-polyacrylamide (CT-g-PAAm) for the first time. The influences of internal phase fraction and emulsifier concentration on the porous structures were studied. The morphologies of polyHIPEs were observed via scanning electron microscope (SEM) while structure parameters were investigated by combining nitrogen adsorption/desorption measurements with mercury intrusion porosimetry (MIP). Highly porous polyHIPEs of CT-g-PAAm with porosity varying from 86 to 93% were obtained at different internal phase fractions. PoIyHIPEs were also prepared using Tween 20 as the emulsifier for comparison. It was found the polyHIPE using SDLC emulsifier (S-polyHIPE) showed higher porosity and consequent smaller foam density than that using Tween 20 emulsifier (T-polyHIPE), implying the gemini-surfactant can act as a novel type of promising emulsifier for the preparation of porous polyHIPEs. In addition, the adsorption performances of polyHIPEs were evaluated by adsorbing methylene blue (MB). At the same internal phase fraction, S-polyHIPE showed higher adsorption capacity and faster adsorption rate than T-polyHIPE. The adsorption data were analyzed by isotherm models and dynamic models, respectively. The results indicated that the adsorption occurs as a monolayer on the adsorbent surface with equal adsorption sites.