Structure – Function Correlation of Branched and Linear Polyaramides for Removal of Pollutants from Water

Abstract

Plastic wastes in the environment degrade and release smaller particles called microplastics and nanoplastic particles. In this study, a series of polyaramides (PAs) are prepared with different structural features and used to remove plastic nanoparticles and dissolved dyes. The prepared PAs showed good thermal stability, surface area, and negative zeta potential. Among the six PAs studied, PA3 showed the highest adsorption capacity towards cationic polyvinyl chloride nanoparticles (PVC NPs) and dissolved dyes such as neutral red (NR) and methylene blue (MB). The PA adsorbents were also able to remove multi-pollutants successively from water. The adsorption isotherms, kinetics, mechanism, and reusability were also thoroughly investigated. The anionic PVC NPs or dyes were not adsorbed on the surface of the PAs and showed poor adsorption efficiency. The cationic pollutants were removed from the water due to strong electrostatic attraction with the negatively charged PA adsorbents. To understand the adsorption mechanism, the adsorption efficiencies of the branched PAs (1-3, A3B2) are compared with linear PAs (4, 5, A2B2) and a model triamide molecule (TA). PA3 showed high adsorption efficiencies compared to other polymers. After extraction of pollutants, all used adsorbents were regenerated using dilute acid washings and reused for pollutant removal from water with a minimum loss of efficiency. As a proof of concept, plastic particles from a commercial facial scrubber were removed efficiently using the PA adsorbents. Synthetic functional polymers offer potential solutions for removing emerging pollutants such as plastic micro- and nanoparticles from water.