The knowledge of the risks associated with the mercury pollution and the presence of mercury in gas processing plants has motivated the development of new efficient technologies for mercury removal from natural gas streams. In this work, the results of the physicochemical characterization of a synthetic adsorbent are used to understand the gaseous mercury adsorption process. The adsorbent is a mesoporous copper sulfide (Cu Sy)hydroxyapatite with well-dispersed active sites presenting high-performance for mercury removal and fixation. Experimental results indicated that mercury migrates by diffusion into the mesopores where it is chemisorbed in two active sites located on the crystalline surface. These experimental results were considered in a phenomenological description of transport and adsorption processes resulting in a novel and more realistic mathematical model. In addition, experimental breakthrough curves at different conditions were used to validate the proposed mechanisms. The integration of experimental and modeling allowed an in-depth understanding of the adsorbents as well as the mercury removal process.