In the present investigation, results obtained from the process of the biosorption of Zn(II) in synthetic wastewaters are presented, using three agricultural wastes (coffee pulp, banana pseudo-stem, and corncob). Firstly, the percentage of lignin and cellulose for each material was determined. Then, using the free software XLSTAT, the waste with the highest removal for this metal was selected and, after this, the optimum pH, kinetics, adsorption isotherm, and point of zero charge (pH_pzc) were found. Finally, a comparison with other lignocellulosic materials derived from banana, corn, and coffee crops was carried out. According to the results obtained, coffee pulp was the material that showed a high removal compared to the other two (63.58%), for which the optimum pH was 5.0 units. The kinetic model, which was adjusted to the process of biosorption, was the pseudo second order of Ho and McKay, which in turn presented an isotherm of Langmuir’s linearized model where the maximum adsorption capacity with that waste was 13.53 mg × g⁻¹, obtained with a particle size of 180 µm, contact time of 90 min at 100 RPM, temperature of 25 °C, and pH_pzc 3.95 units. Lastly, the authors state that this type of agricultural waste can be used as a green technology in the treatment of wastewater, particularly in the removal of the aforementioned pollutant, in order to fulfill goals 3.9 and 6.9 of the Sustainable Development Goals of the 2030 Agenda; to the level of challenge of the research, the authors propose for the future to carry out the implementation of this type of waste, without chemical modification, in the treatment of wastewater for the removal of the mentioned pollutant in a pilot study with different wastewaters and industries.

This research focuses on the removal of contaminants from wastewaters as a matter of great interest in the field of water pollution. The first decades of the 21st century have brought numerous approaches for the development of cheaper and more effective adsorbents capable of eliminating heavy metals. The study aims to examine the way coffee pulp (Castilla variety from Caldas, Colombia) was used as a bioadsorbent for the removal of Mn (II) from synthetic wastewater to fulfill goals 3 and 6 proposed in the Sustainable Development Goals stated for the 2030 Agenda, particularly in Sections 3.9 and 6.9. In order to achieve this objective, the agricultural residue was subjected to bromatological characterization, determination of the lignocellulosic composition, and identification of characteristic organic functional groups through IR spectrophotometry, using the ATR (attenuated total reflection) technique. Additionally, the optimal parameters for contaminant removal were identified, regarding the biomass quantity, the optimum pH, the stirring time, the adsorption kinetics, the zero charge potential (pHpzc), the adsorption isotherms, and the explanation of the possible adsorption mechanisms between the contaminant, the surface of the coffee pulp, and the capacity of maximum adsorption. The results show that lignocellulosic material presented a cellulose content of 29.93 ± 0.21% and a lignin content of 19.25 ± 0.16%. The optimum parameters found were as follows: Particle size of 180 µm, contact time from 90 min to 100 RPM, optimum pH of 4.0 pH units, room temperature; the kinetic model adjusted to the bioadsorption process was Ho and McKay’s pseudo-second-order, under an isotherm of the Langmuir model, for which the removal presented was 53.40%, with a maximum adsorption capacity of 8.01 mg·g⁻¹. Finally, the novelty of the reported research consists of using coffee pulp as a bioadsorbent without chemical modification, for the removal of heavy metals, in this case Mn (II), in industrial wastewater, which would be another application of this coffee by-product.

The present research shows the results obtained from the biosorption process of Pb, using coffee pulp as a biosorbent in synthetic waters. To do this, the lignin and cellulose content and the percentage of removal of Pb²⁺ ions was determined; additionally, the sorption’s optimal variables, such as the optimum pH, the point of zero charge (pHpzc), the kinetics and the adsorption isotherm, were determined. A comparison was made with other by-products derived from coffee crops. According to the results obtained in this research, the cellulose percentage was 29.12 ± 0.22% and the lignin percentage was 19.25 ± 0.16% in the coffee pulp, the optimum pH was 2.0 units and the kinetic model, which adjusted to the biosorption’s process, was the pseudo-second order of Ho and McKay, presenting an isotherm of Langmuir’s model and pHpzc of 3.95 units. Lastly, the removal of the pollutant was 86.45%, with a capacity of maximum adsorption of 24.10 mg·g⁻¹ obtained with a particle size of 180 µm, time of contact of 105 min and at 100 RPM. Finally, we express that (a) the coffee pulp can be used as a sustainable alternative for the removal of the pollutant mentioned in synthetic and/or industrial wastewater matrices, to meet goals 3.9 and 6.9 of the Sustainable Development Goals of the 2030 agenda, and (b) the novelty of this research is the use of an agricultural waste of easy acquisition as a sorbent, without chemical modification, since it presented a high percentage of efficiency in the removal of Pb²⁺ ions. In turn, the challenge of this research is implementing this green technology on a pilot, semi-industrial and/or industrial scale in wastewater treatment systems.

Some of the diverse agro-industrial waste generated in primary or secondary stages have proved to be promising biomaterials for treating aqueous effluents contaminated, in this case, with heavy metals. Therefore, it is necessary to know their optimal operating conditions and the regeneration or reusability of the solid by-product, an aspect related to desorption. Considering the above, this article presents the findings of a preliminary study related to the desorption process of coffee pulp without physicochemical modification (Castilla variety), an agricultural waste used as a sorbent of Cr(III and VI) ions in synthetic wastewater. The desorption efficiency of four eluting agents at defined concentrations (0.10M)—HC1, HNO₃, H₂SO₄, and EDTA—was evaluated in a time interval of 1 to 9 days. Likewise, the proposals for the sorption and/or desorption mechanisms proposed and reported in the literature with respect to the use of biosorbents derived from the coffee crop are presented. With respect to the results, the coffee pulp used in previous studies of the adsorption of chromium species mentioned (optimal conditions in synthetic water of particle size 180 μm, dose 20 g·L⁻¹, agitation 100 RPM, room temperature, time of 90 to 105 min) showed efficiencies in the removal of Cr(III) and Cr(VI) of 93.26% and 74.80%, respectively. Regarding the extracting substances used, H₂SO₄ 0.10 M was the one that presented the highest desorption percentage in both chromic species, with a desorption of 45.75% Cr(VI) and 66.84% Cr(III) in periods of 5 and 9 days, respectively, with agitation of 100 RPM and room temperature. Finally, the dissemination of preliminary results on the desorption of coffee pulp contaminated with chromic species without physicochemical modification is novel in this study, as similar work with this specific material has not yet been reported in the literature. On the other hand, the limitations of the study and future research are related to the evaluation at different concentrations and of other extractor solutions that allow improving the efficiency of desorption of these chemical species in a shorter time from the coffee pulp (with and without modification) as well as the reuse cycles. As a result, the desorption of coffee pulp used as an adsorbent material in real water could help researchers identify the possible interfering factors that affect the process (foreign anions and cations, organic matter, environmental conditions, among others).

La Educación para el Desarrollo Sostenible, proporciona a los educandos valores, actitudes, conocimientos en pro de dar alternativas de solución a los desafíos sociales, ambientales y económicos que posiblemente se estén dando en el presente y a futuro. El objetivo del presente artículo pretende ilustrar el proceso del fortalecimiento de la competencia para el desarrollo sostenible Análisis Crítico la cual está conformada por los componentes del pensamiento crítico, compromiso ético e intelectual; este desarrollo se realizó mediante la implementación de un Ambiente Virtual de Aprendizaje, el cual estuvo constituido por tres módulos que relacionaba: la contaminación del río Tunjuelo, la Industria de Curtiembres en San Benito y el Método Híbrido (que involucra el uso de la precipitación química con Oxido de Magnesio y la utilización de un residuo solido proveniente de la industria de curtiembre Wet-Blue para la remoción de cromo en aguas residuales de la etapa de curtido). El tipo de paradigma investigativo fue de tipo cualitativo, con un alcance descriptivo, la cual se desarrolló con un grupo de Profesores en Formación Inicial, pertenecientes a la Licenciatura en Ciencias Naturales y Educación Ambiental de la Universidad Pedagógica Pública de Kennedy; para evaluar el fortalecimiento de dicha competencia, se presentan tres indicadores (1- Comprende que el conocimiento es incompleto y está teñido de subjetividad; 2- Comprende que todo sistema (económico, social y ambiental) presenta disfunciones que pueden ser identificadas y corregidas 3- Reconoce las disfunciones sociales, económicas y ambientales que se oponen al desarrollo sostenible, Propone alternativas de mejora) y sus respectivos niveles, en función a las respuestas suministradas por la población participante. Dentro de los resultados obtenidos se evidencia una progresión en los niveles de aprobado a sobresaliente, que componen los indicadores. ABSTRACT. Education for Sustainable Development provides students with values, attitudes and knowledge in order to provide alternative solutions to the social, environmental and economic challenges that may be occurring in the present and in the future. The objective of this article is to illustrate the process of strengthening the competence for sustainable development Critical Analysis, which is made up of the components of critical thinking, ethical and intellectual commitment; this development was carried out through the implementation of a Virtual Learning Environment, which consisted of three modules related to: the pollution of the Tunjuelo River, the Tannery Industry in San Benito and the Hybrid Method (which involves the use of chemical precipitation with Magnesium Oxide and the use of a solid residue from the Wet-Blue tannery industry for the removal of chromium in wastewater from the tanning stage). The type of research paradigm was qualitative, with a descriptive scope, which was developed with a group of Initial Teacher Training, belonging to the Bachelor's Degree in Natural Sciences and Environmental Education of the Public Pedagogical University of Kennedy; to evaluate the strengthening of this competence, three indicators are presented (1- Understands that knowledge is incomplete and is tinged with subjectivity; 2- Understands that every system (economic, social and environmental) presents dysfunctions that can be identified and corrected 3- Recognizes the social, economic and environmental dysfunctions that oppose sustainable development, Proposes alternatives for improvement) and their respective levels, according to the answers provided by the participating population. Within the results obtained there is evidence of a progression in the levels from passing to outstanding, which make up the indicators. KEYWORDS. Critical Analysis, Virtual Learning Environment, Competence for Sustainable Development, Education for Sustainable Development, Teachers in Initial Training.