Search

Amino-functionalized monodisperse polymeric microspheres have great significance in water remediation. Herein, polypyrrole (PPy)-modified silica-coated magnetic monodispersed emulsion sphere (MES) microspheres (MES@Fe3O4@SiO2-PPy, MFSP) were successfully prepared via in situ polymerization for the adsorption of hexavalent chromium in an aqueous solution. The magnetism of MFSP enabled fast separation under an applied magnetic field. The results showed that MFSP exhibited outstanding adsorption for Cr(VI) (301.2 mg g−1 at pH 2.0), which followed the pseudo-second-order kinetic and Langmuir isotherm models. Moreover, the MFSP can be reused in the adsorption–desorption cycle by simple elution, and the removal rate of Cr(VI) by MFSP remained above 91% after five consecutive cycles. Combined with XPS, EDS, and Zeta potential measurement for adsorption mechanism analysis, it was concluded that the removal of Cr(VI) could be attributed to both adsorption and reduction. The combination of good adsorption performance and magnetic separation makes MFSP a promising candidate for the removal of low-concentration metal ions. [ABSTRACT FROM AUTHOR]

Monodisperse polypyrrole/SBA-15 composite (PPy/SBA-15) was fabricated by in situ polymerization and used for Cr(VI) adsorption from aqueous solution. PPy/SBA-15 was characterized by numerous approaches. Factors affecting the Cr(VI) adsorption process, including the pH, the dose of adsorbent and contact time, were analyzed through batch experiments. The optimum experimental conditions were pH 2, dose of 4 g L−1 and contact time of 300 min. Meanwhile, PPy/SBA-15 had strong selective adsorption of Cr(VI) in co-existing ionic solution, the adsorption kinetics matched a pseudo-second-order kinetic model, and the adsorption isotherm data followed Langmuir adsorption isotherm models with a maximum adsorption capacity of 194.17 mg g−1 at 298 K, which is higher than that found in other reports of the same type of adsorbent. Regeneration evaluation demonstrated that the adsorbent can be recycled four times, retaining 92.58% of its removal rate. Moreover, EDX indicated that PPy/SBA-15 adsorbed Cr(VI) on its surface owing to ion exchange of chloride ions with either HCrO4− or Cr2O72−. XPS further certified that part of Cr(VI) was reduced to Cr(III). Overall, PPy/SBA-15 possesses capability as an alternative adsorbent to remove Cr(VI) from aqueous solution. [ABSTRACT FROM AUTHOR]