Abstract Activated carbon is a material that has various environmental applications, such as the adsorption of metallic lead ions (Pb2+). It can be obtained from different plant species. In this research, the seed of Persea americana (Avocado- HASS variety) was obtained from local markets in the city of Cartagena to be used in the removal of Pb2+ from wastewater from the fishing industry. To obtain activated carbon, the seed was carbonized in a Terrigeno-brand clay oven, Model DB 1200. Orthophosphoric acid at 21% w/v was used as an activating agent. The residual water was characterized following the APHA specifications. The turbidity was determined by nephelometry in a Turbiquant 300 IR turbidimeter. The Pb2+ concentration was determined by atomic absorption spectroscopy in a Thermo Scientific iCE 3300 equipment. The chemical surface of the material was performed by Fourier transform infrared spectroscopy (FTIR). The carbons were morphologically characterized using a scanning electron microscope SEM (Jeol 5910LV), visualized at 15kV. A yield of 20.38% by mass of coal is achieved. The pores are of irregular size, ranging from 16.2 to 55.98 μm. 65% of Pb2+, turbidity (57.6%), color (57%), total solids (50.2%), as well as BOD (53.12%) and COD (36%) are removed, finding statistically significant differences in values at the 95% level of significance. The seed of Persea americana (HASS avocado) can serve as plant material to obtain an adsorbent material (activated carbon) and be used in the removal of Pb2+ from wastewater.

Resumo O carvão ativado é um material que possui diversas aplicações ambientais, como a adsorção de íons de chumbo metálico (Pb2+). Pode ser obtido a partir de diferentes espécies de plantas. Nesta pesquisa, foi utilizada a semente de Persea americana (variedade abacate-HASS), proveniente de mercados locais da cidade de Cartagena, para ser usado na remoção de Pb2+ de águas residuais da indústria pesqueira. Para obtenção do carvão ativado, a semente foi carbonizada em forno de barro da marca Terrigeno, modelo DB 1200. Foi utilizado ácido ortofosfórico a 21% p/v como agente ativador. A água residual foi caracterizada seguindo as especificações da APHA. A turbidez foi determinada por nefelometria em um turbidímetro Turbiquant 300 IR. A concentração de Pb2+ foi determinada por espectroscopia de absorção atômica em um equipamento Thermo Scientific iCE 3300. A superfície química do material foi realizada por espectroscopia no infravermelho com transformada de Fourier (FTIR). Os carbonos foram caracterizados morfologicamente usando um microscópio eletrônico de varredura SEM (Jeol 5910LV), visualizado a 15kV. Obtém-se um rendimento de 20,38% em massa de carvão. Os poros são de tamanho irregular, variando de 16,2 a 55,98 μm. 65% de Pb2+, turbidez (57,6%), cor (57%), sólidos totais (50,2%), bem como DBO (53,12%) e DQO (36%) são removidos, encontrando diferenças estatisticamente significativas nos valores a 95 % Nível de significância. A semente de Persea americana (abacate HASS) pode servir como material vegetal para obter um material adsorvente (carvão ativado) e ser utilizado na remoção de metais pesados de águas residuais.

Resumen Los compuestos residuales y sus metabolitos de la industria farmacéutica son considerados contaminantes emergentes y una fuente creciente de contaminación ambiental, ya que son utilizados Por una gran cantidad de personas. Debido a sus propiedades fisicoquímicas, se transportan fácilmente a los sistemas hidrológicos y a cuerpos de agua. Así, la eliminación de este tipo de compuestos del agua mediante adsorción es una de las técnicas más prometedoras. El objetivo de éste investigación fue el estudiar la cinética y las isotermas de adsorción del ibuprofeno sobre carbones activados sintetizados a baja temperatura a partir de cáscaras de cacao (Theobroma cacao), e impregnadas con cloruro de zinc (ZnCl2) a relaciones de impregnación 1:2 (CA1: 2) y 1:3 (CA1: 3). Al material de partida y activado se le realizó una caracterización química y textural mediante análisis elemental, microscopía electrónica de barrido (SEM) y método Brunauer Emmett Teller (BET). para conocer su morfología, composición física y área superficial. Para realizar las pruebas de adsorción se utilizaron soluciones de ibuprofeno a 20, 30 y 40 ppm. La activación de la cáscara de cacao causó un aumento en la porosidad y área superficial de los carbones, como se evidencia en los resultados del análisis SEM, siendo CA1:2 el que presentó dichas propiedades en mayor proporción (297.21 m2/g), asimismo, fue el carbón que eliminó la mayor cantidad de ibuprofeno. La cantidad máxima de ibuprofeno adsorbida por CA1:2 y CA1:3 fueron de 68.27 mg/g y 65.75 mg/g, respectivamente. Los resultados sugieren que los bio-carbones activados elaborados a partir de cáscara de cacao, son considerados buenos adsorbentes de ibuprofeno, colaborando en la disminución de este contaminante en fase acuosa, contribuyendo al saneamiento ambiental.

Abstract Metabolites and residual compounds from pharmaceutic industry are considered as emerging contaminants and an increasing source of environmental pollution, as they are used by a quantity of people, and due to their physicochemical properties, they are easily transported to hydrological systems and bodies of water. Then, the elimination of this kind of compounds from water by adsorption is one of the most promising techniques. The aim of this research was to study the kinetic and isotherms of ibuprofen adsorption onto low temperature-synthetized activated carbons from cocoa husks (Theobroma cacao) and impregnated with a solution of Zinc Chloride (ZnCl2) at impregnations ratios biomass:solution of 1:2 (CA1:2) and 1:3 (CA1:3). The material source and activated underwent a chemical and textural characterization by elemental analysis, scanning electron microscopy (SEM) and the Brunauer Emmett Teller method (BET), for knowing their morphology, chemical composition, and surface area. Ibuprofen solutions at 20, 30 and 40 ppm were used to perform adsorption tests. The activation of cocoa husk caused an increase in the porosity and surface area of the charcoals, evidenced in the results of the SEM analysis, with CA1:2 being the one that presented such properties in a greater proportion (297.21 m2/g); likewise, it was the carbon that eliminated the highest ibuprofen quantity. The maximum amount of ibuprofen adsorbed by CA1:2 and CA1:3 were 68.27 mg/g and 65.75 mg/g, respectively. Results suggest that the charcoals activated from cocoa husk are considered as good adsorbents of ibuprofen, collaborating in the reduction of this pollutant in the aqueous phase, contributing to environmental sanitation.

Resumo Para determinar o papel que as substâncias húmicas (HS) desempenham como promotores do crescimento vegetal, foi avaliado o efeito do HS extraído do carvão mineral no crescimento de plantas de tomate (Solanum lycopersicum) e melão (Cucumis melo). Três concentrações de HS foram avaliadas em 200 gramas de solo. O fertilizante (uréia 0,3%) e ácido húmico nas concentrações de 0,05%, 0,1% e 0,2% foram adicionados diretamente e ao mesmo tempo na quantidade de solo, utilizando uma amostra controle sem adição de ácido húmico. As medições de aumento foram feitas em intervalos de três dias até 45 dias. Plantas tratadas com altas concentrações de HS demonstraram um aumento significativo nas raízes (p> 0,05). Em ambas as plantas, a concentração de 0,2% no HS apresentou o maior aumento de crescimento, com o melão apresentando a maior variação com o passar do tempo, com seu maior pico nos 36 dias (13,1 ± 0,05cm) do experimento, enquanto no no tomateiro o máximo crescimento ocorreu em 30 dias (9,2 ± 0,01 cm). O teste de Dunnett mostrou que não houve diferença estatisticamente significativa entre o controle e as concentrações de 0,05% e 0,1% (p> 0,05), enquanto entre o controle e a amostra de solo com concentração de 0,2% houve diferença estatisticamente significativa (p <0,05). Os resultados obtidos mostram uma notável influência do ácido húmico no crescimento das plantas estudadas, principalmente em altas concentrações.

Abstract This study evaluated the effect of HS extracted from mineral coal on the growth of tomato (Solanum lycopersicum) and melon (Cucumis melo) plants to determine the role that humic substances (HS) play as promoters of plant growth. Three concentrations of HS were evaluated in 200 grams of soil. The fertilizer (urea 0.3%) and humic acid in concentrations of 0.05%, 0.1%, and 0.2% were added directly and at the same time to the amount of soil, using a control sample without the addition of humic acid. Increase measurements were made at three-day intervals up to 45 days. Plants treated with high concentrations of HS demonstrated a significant increase in roots (p>0.05). In both plants, the concentration of 0.2% in HS showed the greatest increase in growth, with the melon plant showing the greatest variation as time passed, with its highest peak in 36 days (13.1 ± 0.05cm) of the experiment, while in the tomato plant the maximum growth occurred in 30 days (9.2 ± 0.01 cm). The Dunnett test showed that there was no statistically significant difference between the control and the concentrations of 0.05% and 0.1% (p>0.05), while among the control and the soil sample with a concentration of 0.2% there was a statistically significant difference (p<0.05). The results show a notable influence of humic acid on the growth of the studied plants, especially at high concentrations.

Resumo Este estudo tem como foco o desenvolvimento de um modelo secundário para Yarrowia lipolytica em processos de tratamento de esgoto. Os dados brutos de crescimento de Y. lipolytica foram ajustados ao modelo de Buchanan a fim de obter parâmetros de crescimento como: contagem inicial de células (Y0), taxa de crescimento específico máximo (μmax), fase de latência (λ) e população máxima de células (Ymax). Os valores µ obtidos em diferentes níveis de pH (5,0 a 8,0) foram usados para construir o modelo secundário baseado em uma equação linear. Os resultados mostraram um efeito significativo do pH nos valores de µmax. O processo de validação dos modelos desenvolvidos apresenta valores de acurácia (Af) e fator de bias (Bf) próximos a um, enquanto os valores de root mean square error (RMSE) foram baixos, confirmando que tais modelos podem prever o crescimento de Y. lipolytica em águas residuais de laticínios. Isso pode ser interessante para otimizar tratamentos de esgoto que envolvem esse tipo de microrganismo. Além disso, as águas residuais do leite eram um bom substrato para apoiar o crescimento da Yarrowia lipolytica e poderiam ser utilizadas para produzir a produção de enzimas.

Abstract This study focuses on the development of a secondary model for Yarrowia lipolytica in a sewage treatment process. The raw data of Y. lipolytica growth were adjusted to the Buchanan model in order to obtain growth parameters such as initial count cells (Y0), maximum specific growth rate (μmax), latency phase (λ) and maximum cell population (Ymax). The µ values obtained at different pH levels (5.0 to 8.0) were used to build the secondary model based on a linear equation. The results showed a significant effect of pH on µmax values. The validation process of the developed models displays accuracy (Af) and bias factor (Bf) values close to one, while the values of root mean square error (RMSE) were low, confirming that such models can predict the growth of Y. lipolytica in dairy wastewater. This can be interesting to optimize sewage treatments that involve this kind of microorganism. Moreover, the dairy wastewater was a good substrate to support the Yarrowia lipolytica's growth and could be used to produce enzymes.

Resumo Os coagulantes podem ser extraídos de matéria vegetal e aplicados no tratamento de efluentes. Esses coagulantes são derivados de sementes, folhas, cascas, raízes e frutos. Este estudo enfoca o uso do extrato mucilaginoso de Stenocereus griseus (conhecido como Cardón Guajiro) para a remoção da demanda bioquímica de oxigênio (DBO5), demanda química de oxigênio (COD), sólidos totais, turbidez e cor em águas residuais domésticas de uma estação de bombeamento na cidade de Cartagena (Colômbia). A dose ideal de extrato de S. griseus foi determinada por um teste de jarro empregando um floculador digital E & Q F6-300. Todas as determinações físico-químicas foram realizadas seguindo as especificações dos métodos padrão para efluentes da APHA (Standard Methods for Water and Wastewater). Quando foram utilizados 1400 mgL-1 de coagulante natural no tratamento de esgoto, a turbidez obtida foi de 29,57 TNU, representando remoção de 67,24% considerando a turbidez inicial. Este parâmetro diminui até 68,61 PCU para uma remoção de 72,12% na mesma dosagem de coagulante em relação à cor. Deve-se notar que diferenças estatísticas significativas foram encontradas entre todas as doses testadas do coagulante. O extrato mucilaginoso de S. griseus, teve propriedades valiosas no tratamento primário de águas residuais domésticas.

Abstract Coagulants can be extracted from vegetal material and applied in the treatment of wastewater. These coagulants are derived from seeds, leaves, bark, roots and fruits. This study focuses on the use of the mucilaginous extract ofStenocereus griseus(known as Cardón Guajiro) for removal of biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total solids, turbidity and color in domestic wastewater from a pumping station in the city of Cartagena (Colombia). The optimal dose ofS. griseusextract was determined by a pitcher test employing an E&Q F6-300 digital flocculator. All physicochemical tests were carried out following the specifications of the standard methods for wastewater (APHA). When 1400 mgL-1 of natural coagulants were used in the sewage treatment, the turbidity obtained was 29.57 TNU, representing removal of 67.24%, considering the initial turbidity. This parameter decreases until 68.61 PCU, for a 72.12% removal at the same coagulant dosage regarding the color. It must be noted that significant statistical differences were found between all tested doses of the coagulant. The mucilaginous extract of S. griseus exhibited useful properties in the primary treatment of domestic wastewater.

RESUMEN Las sustancias húmicas son un conjunto de macromoléculas provenientes de materia orgánica biodegradada. Estas sustancias, se pueden obtener de carbones de alto rango y son importantes en la eliminación de contaminantes en soluciones acuosas. En esta investigación, se evaluó la influencia del tamaño de partículas en la extracción de ácidos húmicos, a partir de muestras de carbón bituminoso. Se realizó una oxidación en solución acuosa de las muestras con peróxido de hidrógeno, a concentraciones de 50, 40 y 30%, respectivamente, tiempos de extracción de 3 y 6 horas y tamaño de partícula a número de malla 60 y 120. Se caracterizaron las muestras de carbón por espectrometría infrarroja (FTIR). Se realizó un análisis próximo, para determinar % de humedad, % de materia volátil (%MV), % de ceniza, % de carbono fijo (%CF) y relación %CF/MV. El análisis termogravimétrico (TGA), se realizó en equipo de termografía TGA Q-500. El mayor porcentaje de extracción (76,8±3,50), se obtuvo a una concentración de 50% de agente oxidante, tiempo de extracción de 6 horas y tamaño de partícula a malla No. 120. El tiempo de extracción influye en la cantidad de ácido húmico que se puede extraer, una concentración de 40% de agente oxidante; no se encontraron diferencias estadísticamente significativas (P> 0,05), para tiempos de 3h (32,8±1,0, malla 120) y 3h (30,6±2,4, malla 60). La materia carbonácea utilizada en esta investigación puede ser un candidato potencial para obtener ácidos húmicos útiles en la industria agrícola.

ABSTRACT Humic substances are a group of macromolecules from biodegradable organic matter. These substances can be obtained from high-rank coals and are important in the removal of contaminants in aqueous solutions. In this study, the influence of particle size on the extraction of humic acids from samples of bituminous coal is evaluated. Oxidation in aqueous solution of the samples with hydrogen peroxide was carried out at concentrations of 50, 40 and 30% respectively, extraction times of 3 and 6 hours and particle size at 60 and 120 mesh number. The carbon samples were characterized by infrared spectrometry (FTIR). A close analysis was performed to determine % moisture, % volatile matter (% MV), % ash, % fixed carbon (% CF) and % CF/MV ratio. Thermogravimetric analysis (TGA) was performed on TGA Q-500 thermography equipment. The highest percentage of extraction (76.8 ± 3.50) was obtained at a concentration of 50% of oxidizing agent, extraction time of 6 hours and particle size to mesh No 120. The extraction time influences the amount of humic acid that can be extracted, a concentration of 40% of oxidizing agent, no statistically significant differences were found (P> 0.05) for times of 3h (32.8±1.0, 120 mesh) and (30.6±2.4, 60 mesh). The carbonaceous material used in this research may be a potential candidate for obtaining useful humic acids in the agricultural industry.

RESUMEN Diversos investigadores sostienen que solo a través de una conciencia de las diferencias y de las similitudes entre la educación, el ambiente y las neurociencias será posible lograr una fundamentación común necesaria para una ciencia integrada de la educación, el cerebro, la mente y el aprendizaje. El objetivo de la investigación fue determinar si el ambiente de aprendizaje y la neurociencia influyen en la atención y en la motivación de los estudiantes, que traen, como consecuencia, cambios en el rendimiento académico. El experimento, se realizó con dos grupos de estudiantes universitarios, separados en aulas, con diferente ambiente de aprendizaje, que cursaban la asignatura química general, donde el 76% fueron de género masculino y el 24%, femenino, para el grupo 1 y el 60%, masculino y 40% del sexo femenino, para el grupo 2, con edades comprendidas entre los 17 y 21 años, para ambos grupos. Para evaluar la capacidad de atención, se empleó el test d2 elaborado por Brickenkamp - Zillmer y para el análisis de la influencia de los ambientes de aprendizaje, se diseñó un test tipo Likert. El primer grupo, se le realizó el ejercicio docente en un ambiente convencional, el segundo grupo trabajó en ambientes no convencionales, con docentes formados para la aplicación de los conceptos de neurociencia. Los resultados mostraron que existe una relación estadísticamente significativa entre los resultados, respecto al rendimiento académico, para los dos grupos, a un nivel de confianza del 95%, lo cual, es importante para tener en cuenta en futuros proyectos de educación, que permitan una verdadera transformación en la enseñanza de la química, en programas de ingenierías.

SUMMARY Many researchers stated that only through conscience about differences and similarities on education, environment and neurosciences it will be possible to achieve a solid base for get an integrated science including the education, brain, mind and learning. The objective of this study was to determine if the learning environment and neuroscience influence the attention and motivation of engineering students, resulting in changes on academic performance. The tests were conducted employing two university students groups taking the subject general chemistry of which 75% were male and 25% female, with ages between 17 and 21 years. It is important to clear that both students groups had different learning environment. The first group was taught in conventional learning environments, the second one was taught in a non-conventional environments, with teachers trained to apply the concepts of neuroscience. The Brickenkamp - Zillmer test d2 was employed to evaluate the student’s attention capacity while the Likert test was used in order to evaluate the influence of learning environments. The results showed that there is a statistically significant relationship between the results with respect to academic performance, for both groups which is important to take into account in future education projects that allow a real transformation teaching of chemistry in engineering programs.

Resumen Este trabajo trata sobre la comparación de la asignación teórica del espectro vibracional de DADP con los desplazamientos experimentales por marcación isotópica. Para ello, se sintetizaron los isotopómeros DADP-C4 y DADP-C2, los cuales son isotopómeros parcialmente marcados. DADP-C4 y DADP-C2 fueron sintetizados a partir de acetona marcada isotópicamente en los átomos de carbonos del grupo metilo y carbonilo, respectivamente. La acetona y los compuestos isotopómeros de DADP fueron caracterizados usando espectroscopia Raman e Infrarroja. Las asignaciones teóricas fueron tomadas de estudios previos sobre la distribución de energía potencial de un modo vibracional, el cual proporciona una aproximación a las coordenadas internas relacionadas con cada banda vibracional. La marcación isotópica selectiva nos permitió acercarnos a la dependencia de cada banda, debido a que, la energía de una vibración molecular depende también de la masa recíproca de los átomos involucrados. En general, los resultados mostraron que algunas bandas asignadas experimentalmente no coinciden con las asignaciones teóricas mediante simulaciones mecánicas cuánticas.

Abstract This work deals with the comparison of the theoretical assignment of the DADP vibrational spectrum with the experimental displacements by isotopic labeling. For this, the DADP-C4 and DADP-C2 isotopomers were synthesized from acetone labeled isotopically in the methyl and the carbonyl carbon atoms, respectively. The acetone and DADP-isotopomer compounds were characterized using Raman and infrared spectroscopy. Theoretical assignments were taken from previous studies on the potential energy distribution of a vibrational mode, which provide an approach to the internal coordinates related to each band. The selective isotopic labeling allowed us to approach to the dependence of each band, because the energy of a molecular vibration also depends on the reciprocal mass of the atoms involved. In general, the results showed that some bands assigned experimentally do not coincide with the theoretical assignments by quantum mechanical simulations.

En este estudio, se describe la adsorción de plomo (Pb2+) en soluciones acuosas, a partir de carbón modificado, mediante tratamiento con CS2 y NaOH, empleando una relación 16,6:1 NaOH/Carbón p/p y 4,08:1 CS2/carbón p/p. Se realizaron pruebas de pH, cinéticas e isotermas de adsorción, para evaluar la capacidad de adsorción del carbón xantado y carbón no xantado. Los grupos azufre en el carbón xantado fueron identificados por espectroscopia infrarroja de reflectancia difusa (FTIR) y comparados con los espectros del carbón no xantado. Los resultados muestran que la mejor remoción de plomo en la solución con una concentración de 100mg de Pb2+/L y dosis de 50mg de adsorbente/10mL, respectivamente, fue a un valor de pH 5,0, logrando un porcentaje de adsorción de 98%. Los estudios cinéticos indican que el proceso de adsorción puede alcanzar el equilibrio alrededor de 120min, siguiendo una cinética de pseudo-segundo orden, para ambos materiales. El estudio de las isotermas indica que el carbón se ajusta mejor a una isoterma de tipo Langmuir y cuando se somete a la xantación, se ajusta a una isoterma de tipo Freundlich.

This study describes the adsorption of lead (Pb2+) in aqueous solutions of modified coal by treatment with CS2 and NaOH, using a ratio of 16,6:1 NaOH/coal (w/w) and 4,08 CS2/coal (w/w). Different tests such as acidity, kinetic and adsorption isotherms were carried out in order to assess the adsorption capacity of xanted and non-xanted coal. The sulfur groups presented in the xanted coal were identified by infrared spectroscopy(FTIR) and they were compared with non-xanted coal spectrum. The results show that the best lead removal in the solution (with a concentration of 100mg Pb2+/L and 50mg of adsorbent) was obtained at pH 5.0 for both coal (xanted and non-xanted) with an adsorption percentage of 98%. The kinetic studies indicate that the adsorption process can reach the equilibrium in about 120 minutes, following a pseudo-second order kinetics for both materials. The isotherms study indicates that the coal fits best to a Langmuir-type isotherm, however when the coal is xanted, it fits best to a Freundlich-type isotherm.

Resumen Los ácidos húmicos se producen por la descomposición de la materia orgánica de los suelos y por la oxidación de carbones minerales. En este estudio se analizó mediante superficies de respuesta el efecto de la oxidación en la extracción de ácidos húmicos de un carbón colombiano. Las variables de oxidación estudiadas fueron las siguientes: tamaño de partícula (0,063, 0,106 y 0,150 mm), concentración del agente oxidante (permanganato de potasio (KMnO4): 0,010, 0,020 y 0,050 M) y tiempo de oxidación (30, 60 and 90 minutos). El grado de oxidación se verificó con espectroscopia infrarroja. La oxidación incrementó los grupos oxigenados en la matriz carbonácea debido, principalmente, a la oxidación de componentes alifáticos. Se obtuvieron porcentajes de extracción superiores a 24 % al usar partículas de 0,063 mm y KMnO4 con 0,020 M. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat.

Abstract Humic acids are produced by decomposition of organic soil material and from oxidation of mineral coals. In this study, the effect of oxidation and the yield of humic acids extracted from a sample of Colombian mineral coal were studied by response surface methodology (RSM). The variables used were: particle size (0.063, 0.106 and 0.150 mm), concentration of the oxidizing agent (KMnO4: 0.010, 0.020 and 0.050 M) and oxidation time (30, 60 and 90 minutes). The degree of oxidation was verified by infrared spectroscopy. Oxidation increased oxygen groups in the carbonaceous matrix, mainly due to oxidation of aliphatic components. Extraction yields above 24% were obtained with 0.063 mm particle size and 0.020 M KMnO4. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat.

In this paper, two models of humic acids, the Temple-Northeastern-Birmingham (TNB) and Kolla models, were studied. Also, the complexation reaction of the structures formed by the interaction of the TNB and Kolla models with Al3+, Ca2+, Mg2+, Zn2+, K+ and NH4+ cations, common in agricultural soils, was studied. These calculations were made for the complexes, at PM6 and DFT / LANL2DZ level of theory, both in vacuum and in aqueous medium. We found a strong affinity between Kolla and TNB models, and Al3+, Ca2+, Mg2+, Zn2+, K+ and NH4+ cations, influenced by the solvent that affected the interaction sites; the solvent increased the rate of reactivity and affinity for the cations in nucleophilic regions and decreased it in electrophilic regions of the structures. Calculations of molecular electronic potential, MEP and atomic charges, the local smoothness, Fukui functions and the HSAB principle adequately described the HA/cations interactions which were affected by the number of hydrogen bonds. The most reactive sites were the hydroxyl, phenolic, carbonyls oxygens and nitrogens at both vacuum and aqueous medium, especially carbonyl oxygens. These results are consistent with the properties of HA that make them attractive as components of agricultural soils.

La combustión del carbón de bajo rango produce impactos ambientales por su bajo calor de combustión y alto contenido de heteroátomos, lo que ha promovido sus usos alternativos, como adsorbente. Un carbón subbituminoso (CS), se oxidó con aire a 150°C, en un lecho fijo, durante cuatro horas y se xantó con disulfuro de carbono en solución básica, a 30°C. Este carbón xantado (CX), se evaluó para la adsorción de Hg2+ y Cd2+ de soluciones acuosas de 0,100, 1,000, 12,48, 124,8 y 998,3mg/L; los metales, se determinaron por espectrometría de absorción atómica. CX se comparó con CS, CS sulfonado y CS activado (CAp), además de un carbón activado comercial (CAC) y una resina sintética comercial (RC), en términos de su capacidad de adsorción de metales. RC mostró la más alta capacidad de adsorción (factor de concentración 98%), seguido por CX (factor de concentración 96%). En general, el Hg2+ se adsorbió menos que el Cd2+ y las capacidades de adsorción siguieron el orden, de mayor a menor: RC, CX, CAp, CS, y CAC. CX también mostró una mejor adsorción de Cd2+, 81% vs. 15%, que un carbón xantado no oxidado, lo que muestra que la oxidación previa del carbón aumentó la cantidad de grupos oxigenados que, a su vez, aumentaron la xantación.

The combustion of low rank coal produces environmental impacts due to its low heat of combustion and high heteroatom content which has promoted its alternative uses as an adsorbent. A subbituminous coal (CS) was oxidized with air at 150°C on a fixed bed for 4 hours and xanthated with carbon disulfide in a basic solution, at 30°C. The resulting xanthated coal (CX) was evaluated for the adsorption of Hg2+ and Cd2+ from 0,100, 1,000, 12.48, 124.8 y 998.3mg/L aqueous solutions; metal concentrations were determined by atomic absorption spectrometry. CX was compared against CS, a sulfonated CS, activated CS (CAp), a commercial activated carbon (CAC), and a commercial synthetic resin (RC) in terms of Hg2+ and Cd2+ adsorption. RC showed the highest adsorption capacity (concentration factor 98%) followed by theCX (concentration factor 96%). The adsorption of cadmium on the sulfonated CS was 0.56meq/g, lower than that of CX, 1.85meq/g. In general, Hg2+ was less adsorbed than Cd2+; the adsorption capacities decreased in the order: RC, CX, sulfonated CS, activated CS, CS, and CAC. CX showed a better Cd2+ adsorption, 81% against 15%, than a non-oxidized 40-hours-xanthated coal, which shows that oxidation of coal increased the amount of oxygenated groups that enhanced xanthation.

The verification test, one of the most important aspects to achieve this purpose; also constitutes a key factor providing analytical services. In the present study the colorimetric evaluation of the analytical method for the determination of dissolved aluminium in treated water of eriocromocianina R, was made. The aim of this study was to confirm that the laboratory properly applied standard method for the analysis of water, generating reliable and verifiable results, strictly being followed verification protocols. Satisfactory results were found in precision and accuracy. +Original Spanish title: Evaluación analítica de las determinaciones de aluminio disuelto en aguas tratadas por método colorimétrico

Low-rank coals are an important source of humic acids, which are important in retention processes of water and nutrients in plants. In this study coal samples of Montelibano, Colombia, were oxidized with air at different temperatures and subsequently with H2O2 and HNO3. The materials were characterized by FTIR, proximate and elemental analysis, and quantification of humic acids. The oxidation process led to an increased content of oxygenated groups and humic acids in the carbonaceous structure. The solid oxidized with air at 200 ºC for 12 h and re-oxidized with HNO3 for 12 h showed the highest percentage of humic acids (85.3%).

Activated carbons were prepared with sugar cane bagasse (BC) and corn cob (ZM) to adsorb aqueous cadmium and lead. BC and ZM were carbonized at 400°C for 1 hour, activated with phosphoric acid and modified with nitric acid or hydrogen peroxide and subsequent heating. Activation increased the surface area of carbons (5 m²/g to 778 m²/g for ZM and 3 m²/g to 369 m²/g for BC). Oxygenated groups were analyzed by IR-DRIFTS. The acidity of carbons was between 1.36 and 2.12 meq/g, pH between 2.9 and 6.5, and ion exchange capacities up to 0.070 meq/g (atomic absorption).

Activated carbons were prepared with sugar cane bagasse (BC) and corn cob (ZM) to adsorb aqueous cadmium and lead. BC and ZM were carbonized at 400°C for 1 hour, activated with phosphoric acid and modified with nitric acid or hydrogen peroxide and subsequent heating. Activation increased the surface area of carbons (5 m2/g to 778 m2/g for ZM and 3 m2/g to 369 m2/g for BC). Oxygenated groups were analyzed by IR-DRIFTS. The acidity of carbons was between 1.36 and 2.12 meq/g, pH between 2.9 and 6.5, and ion exchange capacities up to 0.070 meq/g (atomic absorption).