Henry Zúñiga-Benítez

Degradation of ethylparaben under simulated sunlight using photo-Fenton

Ethylparaben (EPB) has been classified by different research groups as a potential endocrine-disrupting chemical, implying that it can potentially interfere with the normal balance of the endocrine system of living beings, which with its presence in different effluents, including drinking water, generates the need to seek methods that allow its removal from different water bodies. Advanced oxidation processes have been employed widely to remove organic compounds from different matrices. In this way, Fenton technology (process based on the reaction between ferrous ions and hydrogen peroxide) has been able to degrade different substrates, but due to the Fe(2+) requirements to carry out the reaction optimally, combination of the conventional Fenton process with visible light radiation (photo-Fenton) is an alternative used in the treatment of pollution due to the presence of chemicals. In this way, the effectiveness of photo-Fenton on EPB degradation was assessed using a face-centered central composite experimental design that allowed assessment of the effects of Fe(2+) and H2O2 initial concentrations on process. In general, results indicated that after 180 min of reaction almost all EPB was eliminated, the dissolved organic carbon in solution was reduced and the sample biodegradability index was increased.

Application of solar photo-Fenton for benzophenone-type UV filters removal

Benzophenones (BPs) family is one of the most frequently used groups of UV-filters. However, it has been reported by different authors that this kind of chemical compounds could be associated with some endocrine disrupting activity, genotoxicity and reproductive toxicity. In addition, different studies have evidenced the presence of BPs in several environmental matrices, indicating that conventional technologies of water treatment are not able to remove them, which generates the necessity of evaluating new alternatives of remediation. In this way, the main objective of this paper was to consider the potential removal of the benzophenone-type compounds, Benzophenone-1 and Benzophenone-2 in aqueous solutions using photo-Fenton under simulated sunlight radiation. Effects of different operational parameters, including H2O2 and Fe2+ initial concentrations, on pollutants elimination were assessed, and conditions that allow to get higher degradation rates were established. In general, results indicated that evaluated photo-catalytic system is able to remove completely the studied benzophenones, and to increase the samples biodegradability after a notable reduction of the organic carbon present in the solutions. Additionally, the identification of some of the reaction byproducts showed that hydroxylation of the substrates molecules is one of the main stages that conduct to its elimination under the evaluated experimental conditions.

Ultrasonic degradation of 1-H-benzotriazole in water.

This paper reports on the effect of different parameters of ultrasonic power, pollutant initial concentration, pH and the presence of co-existing chemical species (oxygen, nitrogen, ozone, and radical scavengers) on the ultrasonic degradation of the endocrine disruptor 1-H-benzotriazole. Increasing the 1-H-benzotriazole initial concentration from 41.97 to 167.88 μM increased the pollutant degradation rate by 40%. Likewise, a high applied ultrasonic power enhanced the extent of 1-H-benzotriazole removal and its initial degradation rate, which was accelerated in the presence of ozone and oxygen, but inhibited by nitrogen. The most favorable pH for the ultrasonic degradation was acidic media, reaching ∼90% pollutant removal in 2 h. The hydroxyl free radical concentration in the reaction medium was proportional to the ultrasound power and the irradiation time. Kinetic models based on a Langmuir-type mechanism were used to predict the pollutant sonochemical degradation. It was concluded that degradation takes place at both the bubble-liquid interfacial region and in the bulk solution, and OH radicals were the main species responsible for the reaction. Hydroxyl free radicals were generated by water pyrolysis and then diffused into the interfacial region and the bulk solution where most of the solute molecules were present.

Benzophenone-3 Removal Using Heterogeneous Photocatalysis at Pilot Scale

This paper presents the main results obtained using the heterogeneous photocatalysis with TiO2 technology in the removal of the emerging contaminant benzophenone-3 at pilot plant scale in a cylinder parabolic solar collector. In this sense, the effects of the operational parameters, pH and catalyst concentration, were analyzed, and after the use of the response surface methodology, the conditions that, under the experimental range, conduct to a higher removal of the analyte were selected. Additionally, analysis of the total organic carbon content and the biodegradability index (relationship between BDO5 and COD) of the treated samples were carried out. In general, results allowed us to infer that this kind of treatment is effective in removing a considerable percentage of the substrate, and that it could become an effective alternative to water treatment and decontamination.

Relación entre la percepción de los estudiantes sobre sus docentes y su actitud frente a la asignatura en una institución de educación superior colombiana. Relationship between the students perception on their professors and attitud.

Relacion entre la percepcion de los estudiantes sobre sus docentes y su actitud frente a la asignatura en una institucion de educacion superior colombiana. Relationship between the students perception on their professors and attitud. Resumen En la actualidad, los procesos de aprendizaje-ensenanza a nivel de educacion superior estan experimentando cambios debidos al libre acceso a la informacion y la transformacion de los mecanismos de construccion de conocimiento dentro del aula de clase. En este sentido, es importante empezar a reconocer al estudiante como actor principal de su propia formacion y al docente como guia que propicia espacios de debate y asimilacion del saber. Lo anterior y la necesidad de analizar el grado de significancia que adquiere la percepcion que desarrollan los estudiantes sobre sus docentes y su probable impacto sobre la actitud del alumno frente a sus asignaturas motivaron a la realizacion de este proyecto de investigacion, en el que a varios estudiantes pertenecientes a diferentes programas academicos de una institucion colombiana de educacion superior se les consulto sobre su percepcion general sobre sus maestros y su papel dentro del desarrollo de la clase, obteniendo como resultado que para la mayoria de encuestados factores como el dominio del tema por parte del docente, sus habilidades comunicativas y practicas metodologicas junto con la amabilidad y responsabilidad afectan de manera positiva la actitud del estudiante ante la asignatura. Palabras clave: aprendizaje, educacion superior, ensenanza, relacion docente-alumno, subjetividad. Abstract Currently, the learning-teaching processes in higher education are undergoing changes due to free access to information and the transformation of the mechanisms of knowledge construction within the classroom. In this regard, it is important to begin to recognize the student as the main actor of his own formation and the teacher as a guide that provides spaces for discussion and assimilation of knowledge. This and the need to analyze the importance acquired by the perception that students develop about their teachers and their likely impact on the students attitude over its subjects led to the realization of this research project, in which various students belonging different academic programs of a Colombian higher education institution were asked about their general perceptions of teachers and their role in the development of the class, the results indicated that for most respondents, factors such as teachers mastery of the subject , their communication skills and methodological practices together with the kindness and responsibility affect positively the students attitude to the subject. Keywords: learning, higher education, teaching, teacher-student relationship, subjectivity.