Polyethyleneimine (PEI) particles were synthesized by using micro-emulsion polymerization and converted to positively charged forms by modifying with various alkyl halides of variant chain lengths such as methyliodide, 1-bromoethane, 1-bromobutane, 1-bromohexane and 1-bromooctane. Furthermore, the ionic liquid colloids of PEI particles were exposed to a simple anion change procedure by treating with sodium dicyanamide (SDCA), sodium tetrafluoroborate (STFB) and ammonium hexafluorophosphate (AHFP) solutions at ambient temperature. It was demonstrated that the alky halide-modified PEI particles show antibacterial effect against different strains of bacteria such as Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 8739 and can even be used as drug delivery materials. Gallic acid (GA) absorption capacity of PEI particles increased from 200 mg to 600 mg per gram dry PEI particles by most modifications, and almost 80% of loaded GA was released in PBS in about 20 h. Interestingly, the anion-changed PEI ionic colloids were shown to be very effective in the removal of Cr(VI) ions, whereas bare PEI particles showed better UO22+ removal capability from aqueous solutions for potential environmental applications. (C) 2014 Elsevier B.V. All rights reserved.