The particle size of N-halamine biocidal polymers was methodically modified forming beads of different sizes by blending water-insoluble N-halamine polyurethane with sodium alginate as the matrix and loading heterocyclic rings onto modified silica gels. The biological activity of the prepared beads and halogenated modified silica derivatives was evaluated against examples of Grain-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The recycling possibilities and the optimum preparation conditions of the blended beads were investigated; blending prehalogenated polyurethane (5%, w/v) with sodium alginate (3%, w/v) followed by crosslinking with CaCl2 (10%, w/v) at 40 degrees C are the optimum preparation conditions for the alginate beads. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2396-2408, 2010