Enhanced heavy metal piezocatalytic adsorption and antibacterial activity using kaolin-modified PVDF nanofiber mats for water treatment

Water pollution, caused by both organic and inorganic contaminants, poses a significant threat to the environment and public health. This study investigates the piezocatalytic adsorption of heavy metals (Ag, Cr, Pb, Zn) and antibacterial activity (against E. coli, S. aureus, and P. aeruginosa) using polyvinylidene fluoride (PVDF) nanofiber mats blended with varying amounts of kaolin (KA and KHW). The crystalline structure of kaolin enhances the piezoelectric properties of PVDF, facilitating the generation of reactive species (hydroxyl radicals and superoxides) under ultrasound. These reactive species effectively degrade pollutants, inhibit bacterial growth, and prevent surface passivation. Using a membrane dosage of 9 cm² and an initial contaminant concentration of 1 mg/L, the study revealed that 0.5 % KA/PVDF and 1 % KHW/PVDF mats exhibited the highest adsorption efficiencies, particularly at pH 4 within 60 min. The 0.5 % KA/PVDF mat achieved removal efficiencies of 78 %, 100 %, 93 %, and 72 % for Ag, Cr, Pb, and Zn, respectively. Stability tests confirmed reusability for up to three days. Kinetic studies followed pseudo-second-order kinetics, with KA-modified mats demonstrating superior performance compared to KHW. Furthermore, antibacterial assays showed that 0.5 % KA/PVDF significantly inhibited S. aureus and P. aeruginosa but was less effective against E. coli. Overall, kaolin-modified PVDF nanofiber mats offer promising potential for water purification and antibacterial applications.