Structure and functional group regulation of plastics for efficient ammonia capture

Activated carbon and metal organic frameworks have been tested as NH₃ recovery adsorbents, however, they are limited due to low NH₃ adsorption capacity and high cost, respectively. In this study, ethylene glycol dimethacrylate (EGDMA) polymers as the representative ester plastics were tested, and their structure and adsorption sites were regulated using HNO₃, HCl, or H₂SO₄ with varied H⁺ concentrations. The results showed that the EGDMA polymers all used hydrolysis which promoted NH₃ adsorption via different mechanisms. With HNO₃ and HCl optimization, an increased surface area promoted NH₃ adsorption via physical forces. H₂SO₄ optimization resulted in -COOH, -OH, and -SO₃H formation, which reacted with NH₃ by chemical adsorption and hydrogen bonds. This significantly increased the NH₃ adsorption capacity (85.99 mg·g^-1) compared to the material before optimization (0.36 mg·g^-1). This study presents a novel low-cost and efficient method to recycle waste plastics as NH₃ adsorbents.