In this chapter, the Ni (II) removal capacity from aqueous solutions was studied using different porous solids: crude corn gut residues, corncobs treated with phosphoric and sulfuric acid and activated carbon from corncob. The effect of some variables such as pH and modification of surface chemistry on the adsorption capacity was studied. Maize leaf samples were collected from a collection center in the city of Bogotá, Colombia. After being dried, ground and brought to a workable size, they were divided into six groups: two were treated with sulfuric acid and phosphoric acid (TMSA and TMPA); four were physically activated in an inert atmosphere varying the activation time to 2, 4, and 8 hours (TM2, TM4 and TM8); and the remaining one was left as such as a raw sample (TM0). The textural results of the different solids synthesized in this study show a diversity of developed Brunauer-Emmett-Teller (BET) areas and pore volumes that generated different adsorption capacities of the divalent nickel ions. The carbon with the highest adsorption capacity was TM8, and the one with the lowest capacity was TMSA. The application of different adsorption models for the analysis of aqueous solutions demonstrated that the samples conform to the Langmuir model. As for the kinetics, the coals follow a pseudo-second-order model. In this study, several techniques were used to achieve the characterization and evaluation of synthesized solids: differential scanning microscopy, infrared spectroscopy, nitrogen adsorption isotherms and atomic absorption spectroscopy.