Alkali treatment of polymer microspheres to efficiently remove rhodamine 6G from aqueous media

Core-shell microspheres composed of poly(styrene)-poly(styrene-methacrylic acid) (PSt-P(St-MAA)) are prepared using a simple emulsion polymerization technique. After synthesis, the particles are subjected to an alkaline treatment to create a rough surface on microspheres. The microspheres demonstrate high efficiency as an adsorbent for removing the cationic dye rhodamine 6G (Rh6G) from water. Several methods, such as FT-IR, SEM, TGA and particle size analysis, are used to characterize both the synthesized PSt-P(St-MAA) microspheres and the microspheres after Rh6G adsorption (PSt-P(St-MAA)/Rh6G). The effects of factors such as initial pH, dye concentration, temperature of the dyeing solution and contact time on dye adsorption capacity are systematically investigated using the batch adsorption method. The adsorption capacity is increased steadily with higher pH levels, dye concentration, temperature and extended contact time. The findings reveal that the adsorption capacity could reach as high as 214.2 mg/g at 25 degrees C. Furthermore, the adsorption kinetics indicate that the process adhered to a pseudo-second-order kinetic model. The equilibrium adsorption data fit well with the Langmuir isotherm model. Thermodynamic analysis reveals that the adsorption process is endothermic, spontaneous and characterized as physisorption. The results confirm that PSt-P(St-MAA) microspheres are highly efficient in removing cationic dyes from wastewater.