Morphology-controlled synthesis of polystyrene-Mn3O4 nanocomposites using surfactant and their application for water treatment

In this study, the nanocomposites of polystyrene (PS) and Mn3O4 with controllable shape were synthesized by the addition of an aqueous solution including manganese salt, surfactant, and cosurfactant into the PS colloid at basic condition. By using ethanol as a solvent in the sulfonate-modified PS aqueous dispersion and NH4OH, Mn3O4 particles were immobilized onto the PS surface successfully. The surface coverage by Mn3O4 particles formed on the surface of PS could be controlled efficiently by varying the concentration of manganese salt added into the reaction medium. As the manganese salt amount increased, the extent of surface coverage of PS by Mn3O4 (loading amount of Mn3O4) also increased. Through this synthetic process, the stable decoration of Mn3O4 particles or the formation of Mn3O4 shell on the surface of PS could be achieved efficiently. In addition, the increase in crystallinity and the decreases in BET surface area and total pore volume of PS-Mn3O4 composites were observed when the more surface of PS was covered by Mn3O4 nanoparticles. The prepared composite particles were characterized by using TEM, BET, and XRD. As an application of synthesized PS-Mn3O4 nanocomposites for water treatment, their catalytic performances for the degradation of methylene blue (MB) were examined by using UV-vis spectrophotometer with the assistance of H2O2 at 25 °C. The highest efficiency was achieved by using PS-Mn3O4 catalyst having the lowest surface coverage and crystallinity because of its largest BET surface area and total pore volume among the obtained samples. From these results, it was found that the catalytic performances of Mn3O4-based composite particles were influenced by the kind of core material in comparison with those reported in our previous studies.