Preparation of polystyrene based porous nanocomposite materials via pickering emulsion method and investigation of their adsorption properties

In this study, nano-sized montmorillonite (MMT) and halloysite (HL) fillers, which have different geometries, were used as solid particles to contribute to stabilization of high internal phase emulsions (HIPEs) for preparation of porous composites. PolyHIPEs were obtained by polymerization of continuous phase of HIPEs. For this purpose, immobilization of suitable agents, which have functional groups (Spirulina microalgae and cetyl trimethyl ammonium bromide) onto the selected nanoparticles' surfaces, was performed by using physical adsorption and cryoscopic expansion methods. This provides changes in hydrophobic-hydrophilic properties of nanoparticles and adsorption onto interface of water/oil emulsion droplets. The resulted modified fillers were used as a quasi-costabilizer for providing stabilization of prepared water/oil type HIPEs. Different parameters which are effective in preparation and properties of polyHIPE composite materials were evaluated. Moreover; morphological, thermal and dye (Nile blue) adsorption properties of porous organic-inorganic hybrid materials were investigated. The advantages of porous nanocomposites prepared with modified fillers over neat polyHIPE were discussed in terms of their thermal and adsorption performances. The effects of the modified filler percentage and surfactant concentration on the HIPE stability were also investigated. The minimum amount of surfactant needed for stability of neat HIPE in the absence of modified fillers was found to be 5 vol%. On the other hand, by usage of the modified MMT and HL fillers in the range of 0.25-1.00 wt%, the necessary amount of surfactant for stabilization of HIPEs was reduced to below 5 vol%. The minimum surfactant amount for the stability was found to be 2% for the emulsions consisting Sp modified MMT filler, whereas this value was further decreased to 1% for the emulsions having CTAB modified MMT filler. However, the required surfactant amount was reduced to 2% by usage of Sp-modified nanotubes acting as stabilizer like particles. On the other hand, for the CTAB modified nanotube containing HIPEs, only 1 % of surfactant was found to be enough for their stabilization. When the adsorption performances of neat polyHIPE and its composites including MMT and HL fillers were compared, it was observed that all porous composites exhibited higher adsorption performances than neat polyHIPE material. Among the composites, 0.50Sp-XP-MMT and 0.75CTAB-XP-MMT exhibited about 578% and 589% higher adsorption capacities, respectively than neat polyHIPE. Moreover, the improvements in glass transition temperatures were achieved for porous composites including modified MMT and HL fillers. Finally, the fillers used in the preparation of the porous composites were found to not only behave as a quasi-stabilizer, but also provide improvement in thermal and adsorption properties. If the toxic effect of dye-containing waste-waters for organisms are taken into consideration in nowadays, the improvement obtained in dye adsorption can be accepted as an advantage of the porous composites for the environment.