Outstanding performance of core–shell structured chitosan-sodium alginate decorated ZIF-90 beads for the synchronous purification of Pb and Co from industrial effluents

Abstract

Efficient elimination of heavy metals contaminations can be extensively concerned by utilizing environmental-friendly adsorbents with pursuing high adsorption capacity and reducing the treatment costs of industrial sewage. Herein, the core–shell structured chitosan/sodium alginate polysaccharide polymers loading zeolite imidazolate framework-90 beads (ZIF-90@CS/SA) were successfully synthesized and analyzed to obtain efficient enrichment performances for Pb and Co. The ZIF-90@CS/SA beads were multifariously characterized through the superficial micropore structures, which included both before and after adsorption performance of Pb and Co from the macroscopical experiments. The optimal weight ratio of chitosan/sodium alginate was chosen 1:2 to prepare ZIF-90@CS/SA beads by drop-method, and then adsorption experiments of Pb and Co were also conducted under various water chemistry conditions. The especial adsorption equilibrium time for the elimination of Pb and Co through the ZIF-90@CS/SA beads was 2.5 h and 3.5 h respectively, which was in accordance with pseudo-second order pattern. The maximal adsorption capacity was respectively 1.24 × 10−3 mol/g for Pb and 1.69 × 10−3 mol/g for Co, which considerably improved in comparison with many previously reported adsorbents. The adsorption mechanisms of ZIF-90@CS/SA beads with Pb and Co were dominated by the surface complexation, ion exchange and electrostatic attraction. According to macroscopical experimental studies, the ZIF-90@CS/SA beads have promising applications in the field of sewage treatment with highly efficient enrichment, advantageous regeneration and purfication of numerous heavy metal contaminants.