Surface modification of polypropylene non-woven fibers with TiO sub(2) nanoparticles via layer-by-layer self assembly method: Preparation and photocatalytic activity

Polypropylene (PP) meltblown fibers were coated with titanium dioxide (TiO sub(2)) nanoparticles using layer-by-layer (LbL) deposition technique. The fibers were first modified with 3 layers of poly(4-styrenesulfonic acid) (PSS) and poly(diallyl-dimethylammonium chloride) (PDADMAC) to improve the anchoring of the TiO sub(2) nanoparticle clusters. PDADMAC, which is positively charged, was then used as counter polyelectrolyte in tandem with anionic TiO sub(2) nanoparticles to construct TiO sub(2)/PDADMAC bilayer in the LbL fashion. The number of deposited TiO sub(2)/PDADMAC layers was varied from 1 to 7 bilayer, and could be used to adjust TiO sub(2) loading. The LbL technique showed higher TiO sub(2) loading efficiency than the impregnation approach. The modified fibers were tested for their photocatalytic activity against a model dye, Methylene Blue (MB). Results showed that the TiO sub(2) modified fibers exhibited excellent photocatalytic activity efficiency similar to that of TiO sub(2) powder dispersed in solution. The deposition of TiO sub(2) 3 bilayer on the PP substrate was sufficient to produce nanocomposite fibers that could bleach the MB solution in less than 4 hr. TiO sub(2)-LbL constructions also preserved TiO sub(2) adhesion on substrate surface after 1 cycle of photocatalytic test. Successive photocatalytic test showed decline in MB reduction rate with loss of TiO sub(2) particles from the substrate outer surface. However, even in the third cycle, the TiO sub(2) modified fibers are still moderately effective as it could remove more than 95% of MB after 8 hr of treatment.