Flow-Through Polyethylenimine/ZnS Supermacroporous Composite for Hg(II) Uptake at ppb Concentrations

Abstract

Flow-through supermacroporous monoliths (cryogels) for Hg(II) ion uptake have been fabricated by cross-linking polyethylenimine (PEI) at subzero temperature and in situ functionalization with zinc sulfide nanoparticles to enhance the efficiency of sorption performance. The synergetic effect of Hg(II) chelation by the PEI matrix and ion exchange on ZnS allowed one to reach with a composite cryogel the decontamination factor of >10 5 and the Hg(II) residual concentration of <2 μg/L, which are set by U.S. EPA for mercury discharge to the aqueous environment. Under the same sorption conditions, an unmodified PEI cryogel allowed reducing the Hg(II) concentration down to 3.9 ± 0.3 μg/L, which complies with WHO requirements for drinking water. The effective dynamic sorption capacity at the Hg(II) breakpoint of 6 μg/L was more than twice higher for the PEI/ZnS cryogel than for the unmodified PEI cryogel, while the static sorption capacities of both the PEI cryogel (1214 mg/g) and PEI/ZnS cryogel (1478 mg/g) were significantly higher in comparison with previously reported materials.

Polyethylenimine as a Non-Innocent Ligand for Hexacyanoferrates Immobilization

“…This route is typical for the HCFs immobilization in polymer matrices or ion-exchange resins [ 14 ], when the content of inorganic phase in the composite is determined by the ion-exchange capacity of the matrix. The sorption capacity of PEI decreases in the order Cu(II) > Zn(II) > Ni(II) > Co(II) [ 26 ], so that copper and zinc salts were used as precursors providing potentially highest content of HCFs in the material. Another reason to choose these metal ions consists in significantly higher binding constant for Cu(II) over Zn(II) ions in PEI solution [ 27 ] that can be used to verify our hypothesis that formation of highly stable PEI complexes with metal ions prevents formation of crystalline HCFs.…”