Currently, agricultural waste is proposed as a sustainable alternative in the removal of heavy metals present in industrial wastewater, to fulfill some of the goals proposed in the Sustainable Development Goals stated for the 2030 Agenda, in particular in Sections 3.9 and 6.9. Considering this context, the coffee pulp (Castilla variety) of Caldas municipality (Colombia) was used in study for the removal of one of the most toxic chemical species of chromium: Cr (VI). Therefore, the agricultural residue was subjected to a bromatological characterization, determination of the lignocellulosic composition and elucidation of characteristic organic functional groups by IR spectrophotometry. Additionally, the optimal parameters for contaminant removal were identified, regarding particle size, biomass quantity, optimum pH, stirring time, temperature, adsorption kinetics, zero charge potential (pHpzc) and adsorption isotherms, to analyze the kinetic model that fitted the process, the explanation of the possible adsorption mechanism between the contaminant, the surface of the coffee pulp and the capacity of maximum adsorption, respectively. Finally, the innovation of the research is discussed considering two criteria: First, when a mixture was made in different proportions between two agricultural residues (coffee pulp and plantain pseudostem) to show if there was an increase in the removal of the contaminant under the same optimal conditions found experimentally; and the second criterion, the comparison of the maximum adsorption capacity, with the percentages of removal carried out by other authors using the pulp of unmodified coffee.

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.

Objetivo: El presente artículo de revisión tuvo como objetivo realizar una indagación bibliográfica de artículos científicos en revistas locales, nacionales e internacionales en el periodo de 2010 a 2019, con relación a las tecnologías no convencionales (biopolímeros, biorremediación y residuos agroindustriales) que se han empleado en la remoción de plomo (Pb), presente en aguas residuales sintéticas o industriales. Metodología: La investigación adoptó un modelo investigativo de corte cualitativo, de tipo exploratorio. Los aspectos metodológicos correspondieron a la indagación y elección de artículos científicos (para cada una de las tecnologías no convencionales seleccionadas) del periodo 2010-2019, teniendo como criterio palabras clave; posteriormente, se realizó un análisis de esos contenidos y se diligenciaron dos matrices realizadas en Excel. Resultados: La revisión bibliográfica permitió observar que: en primer lugar, con relación a las tecnologías no convencionales con mayor tendencia en investigación, empleadas en la remoción de plomo, se encuentran los residuos agroindustriales, seguidos por la biorremediación y por último los biopolímeros, para lo cual se hallaron y seleccionaron 19 para el primero, 13 para el segundo y 9 para el último. De igual forma, los países que han reportado resultados investigativos alrededor de las tecnologías no convencionales seleccionadas, corresponden a: China, Colombia, Corea, Egipto, España, Francia, India, Indonesia, Irán, Nigeria, Malasia, México, Perú, Romania, Serbia, Singapur y Zimbabue; en contraste, las publicaciones seleccionadas se encuentran en su gran mayoría ubicadas a nivel internacional. Por último, los porcentajes de remoción más alto del orden del 100 % se presentaron con los residuos agroindustriales (para lo cual se han investigado 24); seguido del 98 %, con la biorremediación (donde se han investigado algas rojas y seis cepas de bacterias), y finalmente, los biopolímeros, con 95,32 % (donde el quitosano, el almidón, la queratina, las conchas de caracol y las plumas, se han investigado). Conclusiones: Las tecnologías no convencionales con mayor tendencia en investigación y aplicación en matrices de aguas residuales industriales, de acuerdo con periodo 2010-2019, corresponden a los residuos agroindustriales; de igual forma, la mayoría de aguas residuales en las que han sido aplicados estos métodos corresponde a las sintéticas, lo que conlleva a exponer que estas deben comenzar a ser implementadas a nivel industrial o un pilotaje, para observar su eficiencia en la remoción de metales pesados, y de forma particular el plomo. Financiamiento: La investigación llevada a cabo no recibió financiación.  

La pulpa de café (variedad caturra) proveniente de Manizales (Colombia) se ha empleado como abono orgánico, en la lombricultura como un suplemento del alimento para el ganado y como cultivo de hongos comestibles (Pleurotus ostreatus). Adicionalmente, en esta investigación se empleó como biadsorbente para la remoción de Cr (III) en aguas sintéticas y aguas problema provenientes de la etapa del curtido de una de las curtiembres San Benito. Para ello, se realizó la caracterización físico-química del agua residual y se evaluó la eficiencia del bioadsorbente realizando primero los ensayos con las aguas sintéticas y luego con las aguas reales. Se determinó que a un pH 5,0 en aguas sintéticas el modelo cinético que se ajustó fue al de pseudo segundo orden de Ho y Mackey y con una isoterma del modelo linealizado de Langmuir. La capacidad de máxima adsorción fue de 7,41 mg/g. Las remociones fueron del 93.3% en aguas sintéticas y 36, 52 % en aguas reales del sector de San Benito.

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 (pHpzc) 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 pHpzc 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.