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.