Removal and Separation of Heavy Metal Ions from Multicomponent Simulated Waters Using Silica/Polyethyleneimine Composite Microparticles.

Composite solid surfaces with high content of functional groups (FGs) are useful materials in different types of applications requiring stimuli-responsive "hard/soft" architectures, their improved properties rising from the combination of organic-inorganic parts. Among different types of weak polyelectrolytes, poly(ethyleneimine) (PEI) is of great interest in the construction of composite systems with thin layer-by-layer (LbL) organic films due to the large number of amino groups per unit mass of polymer. Herein, the spherical silica microparticles were modified with linear (L) or branched (B) PEI chains using LbL deposition of a copper complex (PEIL-Cu or PEIB-Cu) and poly(acrylic acid) (PAA), glutaraldehyde selective cross-linking, followed by copper and PAA extraction from the multilayer. The newly formed silica/(PEIL) and silica/(PEIB) composites were used in batch and column sorption/desorption experiments of four heavy metal ions (Cu, Ni, Co, and Cd). In noncompetitive conditions ([FG]/Σ[M] > 9), all heavy metal ions were retained on composites, demonstrating the potential application of the prepared functional microparticles in surface water treatment. However, in competitive conditions ([FG]/Σ[M] < 9), only Cu is sorbed in high amount (∼2.5 mmol·g PEI) on composites, with simultaneous displacement of already sorbed ions, demonstrating the solid-phase extraction and chromatographic properties of the synthesized silica/(PEIL) and silica/(PEIB) composites.