Microporous polypropylene membrane filters are modified with a cationic surfactant, dimethyldioctadecylammonium bromide (DDAB), to create a charged surface. Negatively charged nanoparticles can then be filtered by utilizing the electrostatic interaction between the charged particles and the polar heads of the surfactants adsorbed on the filters. The study focuses on particle adsorption and particle filtration. Particle adsorption studies have shown that particle adsorption can be increased significantly with this treatment due to Coulombic attraction. Filtration results for 60 nm negatively charged particles (carboxylate modified copolymer) filtered through DDAB treated filters show a significant increase in particle capture efficiency. Capture efficiency is dependent on the pH of the suspension due to competitive adsorption between the hydroxide ions and the negatively charged nanoparticles. As the mean pore diameter increases, capture efficiency decreases due to the increase in distance between the particles and the charged filter surface. Filtration efficiency can be increased from 10% to 95% by surface modification of the filters.