Coffee grounds are an organic waste consisting of the ground, roasted and processed grain for the extraction of coffee, being of great volume the waste obtained, which, if not treated and preserved for a long time, emanates unpleasant aromas and becomes an optimal means for the proliferation of flies, and other pests. Activated carbon has the characteristic of being a material that has a large surface area; because of this, it is used in adsorption, which refers to the retention of atoms, ions, and molecules on its surface. In this paper, the production of activated carbon is presented by means of the physicochemical activation of coffee waste by calcining at 900 °C and subsequent activation with sulfuric acid, as well as the Box–Behnken design of three factors for chromium (III) adsorption optimization. It is determined that the optimal conditions for performing the adsorption are pH = 3 and a contact time of 140 min. According to the analysis of variance for the experimental design, it is determined that the initial chromium formation is not significant for the adsorption process. Under the optimal adsorb conditions of 96%, an application is given to the erasure of coffee for the production of activated carbon, which serves as the adsorbent agent applied to the removal of chromium (III) aqueous. The area of activated carbon obtained is 13657.89 ± 251.09 m²/g determined by the acetic acid adsorption isotherm method.

Electronegativity is an intrinsic parameter of each chemical element that influences the response, chemical reactivity, polarity, as well as the attraction between molecules among other effects. In this sense, a didactic strategy was developed for teaching at the undergraduate level to determine the effect that electronegativity has on the vibration response of the C-Halogen bond in a molecule, through a practical experience that involved on the one hand the technique of infrared spectrophotometry and organic molecules with the presence of halogen atoms. The didactic strategy was applied to a group of students of the bachelor’s degree in industrial chemistry, which was divided into teams of 5 students who worked based on cooperative learning and with problem-based learning support, they were studying spectroscopy and who had previous knowledge of the infrared spectroscopy technique. After carrying out, the experiment and with the results obtained, the students were able to conclude that due to the strength and distance of the bond between halogen and carbon, the value of the wavenumber (cm-1) is modified, concluding that in shorter bonds a greater energy is required for it to be stretched and in longer and weaker bonds as in the case of Iodine these are stretched to a lower wavenumber. This allowed students to understand this phenomenon and the dependence of electronegativity, bond length, and bond strength on a specific response observed using infrared spectroscopy.