Study on the adsorption performance of ZIF-8 on heavy metal ions in water and the recycling of waste ZIF-8 in cement

Water pollution caused by severe heavy metal contamination poses a significant threat to freshwater resources and aquatic ecosystems, necessitating effective removal strategies. This study focuses on the synthesis of highly crystalline ZIF-8 particles using an energy-efficient, cost-effective in-situ self-assembly method. The resulting particles exhibit exceptional specific surface area (1663.413 m2/g) and particle sizes ranging from approximately 60 to 80 nm. We conducted batch adsorption experiments using Cu(II) and Pb(II) solutions as representative models of water pollution to evaluate ZIF-8's adsorption capacity for these heavy metal ions. Remarkably, ZIF-8 demonstrated a significantly higher maximum adsorption capacity for Cu(II) (378.5 mg/g) compared to Pb(II) (92.74 mg/g) under identical experimental conditions. By employing adsorption kinetics and isotherm models, as well as density functional theory calculations, we elucidated that Cu(II) removal from water by ZIF-8 relies on ion exchange and coordination interactions, whereas Pb(II) elimination primarily occurs through surface adsorption due to ZIF-8's elevated micropore structure and specific surface area. Moreover, we proposed a sustainable solution by solidifying the waste ZIF-8 adsorbent into cement-based materials, offering an innovative and environmentally friendly alternative to landfill disposal. This methodology not only demonstrates noteworthy economic effectiveness but also ensures harm-free treatment and repurposing of waste adsorbents, providing valuable insights into secure and sustainable heavy metal removal strategies.