Preparation and characterization of carboxyl-functionalized chitosan magnetic microspheres and submicrospheres for Pb2+ removal

• The chitosan magnetic microspheres (EDCMM) and submicrospheres (EDCMSM) were prepared for Pb2+ removal.
• Both of them were comprehensively characterized by SEM, TEM, FTIR, BET and VSM techniques.
• EDCMSM had more rapid adsorption rate and EDCMM had higher absorbability, while both of them had excellent reusability.
• EDCMM and EDCMSM were promising novel adsorbents for the sorption of heavy metal ions.

The present work aimed to develop two kinds of novel adsorbents, carboxylated chitosan magnetic microspheres (EDCMM) and submicrospheres (EDCMSM), for comparative study of Pb2+ removal. Several techniques, including SEM, TEM, FTIR, BET and VSM, were applied to characterize the adsorbents. Batches of tests were conducted to investigate the Pb2+ adsorption at different pH values, contact time, initial Pb2+ concentrations and temperatures. EDCMSM with higher specific surface area and a lower content of carboxyl had faster initial absorbing rate but lower adsorption capacity for Pb2+ than that of EDCMM. The adsorption processes for both EDCMM and EDCMSM fitted well with pseudo-second-order model and were dominated by chemical reaction process. The isotherm data for both adsorbents were well described by the Langmuir model, which suggested monolayer adsorptions. Thermodynamics analysis suggested that the adsorption processes of both EDCMM and EDCMSM were endothermic and spontaneous in nature. Both adsorbents still exhibited good adsorption performances after the fifth adsorption–regeneration cycle. All these results indicated that both EDCMM and EDCMSM might be promising adsorbents for the Pb2+ removal.

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