Statistical physics investigation on the simultaneous adsorption mechanism of Cd²⁺ and Pb²⁺ on amino functionalized activated carbon derived from coal gasification fine slag

In this study, a novel surface amino-functionalized activated carbon (T-AC) was synthesized from coal gasification fine slag (CGFS) and used as an adsorbent for heavy metal ions. T-AC exhibits excellent adsorption capacity for Cd²⁺ and Pb²⁺. The adsorption process of Cd²⁺ and Pb²⁺ onto T-AC was found to be spontaneous. The dominant adsorption process was chemisorption, primarily involving chelation and covalent bonding. In binary systems, as the initial concentration increases, the independent adsorption effect of Pb²⁺ and Cd²⁺ gradually becomes a competitive adsorption effect. Statistical physical models revealed that the adsorption of T-AC for Cd²⁺ and Pb²⁺ in single systems followed a multi-molecular adsorption process, whereas in binary systems, it involved a multi-anchorage process. The adsorption capacity was primarily influenced by the number of ions attached to the receptor sites and the density of the adsorbent receptor sites. Moreover, elevating temperature enhanced the thermal movement of heavy metal ions within the pore structure of the adsorbent, reducing their tendency to aggregate at the active sites. This work provides insights into the microscopic-level adsorption process of heavy metal ions by carbon-based materials and contributed to understand of the adsorption behavior.