Fabrication of novel 3D PEI-functionalized ZIF-8@alginate aerogel composites for efficient elimination of Pb(II) and Cd(II) from aqueous solution

ZIF-8, a metal-organic framework, has large sorption capacities for a series of heavy metals. However, it is difficult to be separated from aqueous solution, limiting its practical application in wastewater treatment. Herein, ZIF-8 was in-situ grown on the polyethyleneimine-functionalized alginate to construct the ZIF-8 @ALG-PEI aerogels with a three-dimensional network structure. This synthesis strategy not only overcomes the above-mentioned defects of ZIF-8, but also provides more functional groups, pores, and channels. The synthesized ZIF-8 @ALG-PEI aerogels exhibit outstanding removal performance towards Pb(II) and Cd(II) with maximum sorption capacity values of 295.986 and 249.838 mg center dot g(-1), respectively. The sorption of Pb(II) and Cd(II) on ZIF-8 @ALG-PEI is strongly affected by pH, but little influenced by ionic strength. In the multi-component sorption systems, ZIF-8 @ALG-PEI shows better sorption affinity and selectivity for Pb(II) than for Cd(II). The three-dimensional network structure constructed by alginate makes Pb(II) and Cd(II) easier to contact with the surfaces of ZIF-8 @ALG-PEI. The strong surface complexation of the O-and N-containing functional groups provided by ZIF-8 and PEI with Pb(II) and Cd(II) makes the largest contribution to the removal of Pb(II) and Cd(II) by ZIF-8 @ALG-PEI. In summary, the experimental findings of this work prove that the synthesized ZIF-8 @ALG-PEI aerogels have promising applications in practical wastewater treatment.