Pickering medium internal phase emulsions based on natural clay particles: Route to a macroporous adsorbent

We synthesized oil-in-water Pickering medium internal phase emulsions (MIPEs) based on (1) natural, unmodified montmorillonite (MMT) nanoparticles as a stabilizer; (2) a trace quantity of Tween-20 (T-20) as a co-stabilizer; and (3) eco-friendly flaxseed oil as the continuous phase. We modulated the stability, rheological properties, and droplet size of the emulsion by adjusting the MMT concentration, Tween-20 concentration, and oil phase volume fraction. We used these emulsions as templates to prepare a macroporous monolithic adsorbent [poly (carboxymethylcellulose-g-acrylamide); PCAM] with a hierarchical pore structure and excellent connectivity that approximates materials derived from Pickering high internal phase emulsions (HIPEs). Even when we decreased the internal phase volume fraction to 30%, there were still interconnecting pores in the material. Compared with Pickering HIPEs, our approach reduced the oil phase volume fraction substantially (approximately 45%), which lowered the production cost of the emulsion. Our Pickering MIPE-derived macroporous monolithic material effectively adsorbed cationic dyes (methyl violet and methylene blue) from water. Our environmentally friendly method of preparing Pickering MIPEs will enable researchers to prepare absorbents with an excellent hierarchical pore structure, which will facilitate rapid mass transport and increased greater specific surface area.