The main objective of this work is to evaluate the organofunctionalization of the expanded perlite with orthophenanthroline. Thermogravimetry was used to quantify the orthophenanthroline content incorporated in the material. The thermogravimetric analysis showed that, for very low concentrations, there is no incorporation. However, by increasing the concentration of orthophenanthroline, the process becomes possible. The results also indicated the concentration of 0.1 mol/L as the optimum concentration for the functionalization. As a way to prove the applicability of the thermogravimetric analysis in the evaluation of such a process, the liquid residue, called wash water, was analyzed by molecular absorption spectrophotometry in the UV-vis region. The results obtained allowed to quantify the mass of orthophenanthroline not incorporated during the process. Finally, the adsorption process was carried out to remove the acidic black dye from eriochrome T using as adsorbent the material that had the highest content of orthophenanthroline incorporated.