Efficient removal of cationic dye from aqueous media using alkali-treated multilayered polymer microspheres prepared via emulsion polymerization

Abstract

Poly(styrene)/poly(styrene-co-methacrylic acid), PSt/P(St-co-MAA), and core–shell microspheres were synthesized using a facile emulsion polymerization method, and the synthesized particles were alkali treated to create rough surface microspheres. The microspheres effectively served as highly efficient adsorbents for eliminating the cationic dye methylene blue (MB) from water. The diameter of the particles was measured, and various techniques, including FT-IR, SEM, and TGA, were employed to characterize the prepared PSt/P(St-co-MAA) microspheres and MB-adsorbed microspheres, PSt/P(St-co-MAA)-MB. The influence of various factors, including initial pH, dye concentration, dyeing bath temperature and contact time, on dye adsorption capacity was thoroughly examined using the batch-adsorption method. The adsorption capacity progressively increased as the pH of the dyeing bath, dye concentration, temperature, and contact time increased. The findings revealed that the adsorption capacity could reach as high as 198.7 mg g⁻¹ at 25 °C. Additionally, adsorption kinetics suggested that the adsorption process followed the pseudo-second-order kinetic model. The equilibrium adsorption data were well represented by applying the Langmuir isotherm model. Thermodynamic analysis indicated that the adsorption process was endothermic, spontaneous, and classified as physisorption. The findings demonstrate that the PSt/P(St-co-MAA) microspheres are highly effective for the removal of cationic dyes from wastewater.