Performance Evaluation and Mechanism Exploration of Heavy Metal Ion Adsorption by Four Carbon Materials

In order to develop a high-efficiency adsorbent for removing trace heavy metal ions in aqueous solution, this study systematically evaluated the adsorption performance of four carbon materials. The study investigates how morphology, surface functional groups, and charge characteristics affect adsorption performance, and elucidates the dominant adsorption mechanism via modeling and thermodynamic analysis. Activated carbon and its nitrogen-modified derivative show excellent Co2+ adsorption ability adsorption performance with a maximum of 80%. The adsorption behavior conforms to monolayer adsorption mechanism. For activated carbon and beard‑shaped carbon nanotubes, Co2+ removal is mainly achieved through adsorption capacity with uptake capacity correlating positively with textural properties. In contrast, adsorption of Co2+ by N‑doped AC and OH‑functionalized CNTs involves two mechanisms: physical adsorption and chemical adsorption, and its adsorption mechanism is affected by the density of the surface hydroxyl group. In five consecutive adsorption-desorption cycles, all materials maintain stable adsorption efficiency (maintained at more than 95% of the initial adsorption capacity). In the mixed metal competitive adsorption system, N-AC exhibits the highest selectivity for Pb2+, followed by Co2+, while Cr(VI) has the lowest adsorption capacity. It is worth noting that N-AC also shows excellent universality in removing Pb2+ and Cr(VI), highlighting its great application potential in the field of actual wastewater treatment

Songhui Liu, Ting Wang, Weize Sun, Jingle Chen, Huali Chen