Adsorption of phenols by magnetic polysulfone microcapsules containing tributyl phosphate

Porous polysulfone (PSF) microcapsules containing both tributyl phosphate (TBP) as extractant and magnetic nanoparticles (Fe3O4) that help the isolation operation have been successfully prepared for the first time using a phase inversion method. Several techniques, including Fourier transform infrared (FT-IR), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA) have been used to characterize the microcapsules. The adsorption of four kinds of phenols (4-chlorophenol, 4-CP; 2-chlorophenol, 2-CP; 4-nitrophenol, 4-NP; phenol, Ph) from aqueous solutions on to the magnetic microcapsules has then been studied in a batch system as a function of contact time (5–60 min), initial phenols concentrations (about 99–1050 mg/L) and pH (2–12). The results show that increasing the initial concentration of the phenols and the adsorption time favored the adsorption. In contrast, the adsorption decreased for pH > 6. Adsorption data were modeled using Freundlich and Langmuir adsorption isotherms and the appropriate parameters were calculated. The Freundlich equation provided a better fit for the four phenols than the Langmuir equation. Simultaneously, various kinetic models including pseudo-first-order, pseudo-second-order and intraparticle diffusion were investigated to determine the mechanism of adsorption. The experimental data fitted the pseudo-second-order kinetic model well, and showed that intraparticle solute diffusion was not the only rate-controlling sorption step. In an investigation of potential industrial applications, it is demonstrated that the final concentration of phenols treated with the novel magnetic microcapsules will be within allowed limits. After six extraction and regeneration cycles, the microcapsules were unchanged and showed almost the same adsorption ability. These results demonstrate that these novel magnetic microcapsules have potential applications in the treatment of environmental pollution caused by phenols. This study broadens the application of microcapsules, which are, at the moment, mainly used to remove heavy metals from water.