Dr. Salgado-Mendoza, Pablo

2021, Henríquez, Adolfo, Dr. Salgado-Mendoza, Pablo, Albornoz, Milenka, Melín, Victoria, Mansilla, Héctor, Cornejo-Ponce, Lorena, Contreras, David

Advanced oxidation processes (AOPs) are chemical systems characterized by the production of hydroxyl radicals and other reactive oxygen species. One of the most important AOP systems are the Fenton and Fenton-like reactions. The main limitation in the reactivity of these systems is the solubility and redox equilibria of Fe3+/Fe+2 species. In this way, the use of iron ligands (redox active or redox inert) is one of the most common ways to modulate the Fenton reaction. These systems are called Chelated Mediated Fenton (CMF) reaction. The 1,2-dihydroxybenzene (1,2-DHB) type ligands are one of the most used redox active compounds to drive a Fenton reaction because these ligands can chelate Fe3+ and reduce it to Fe2+ enhancing de ability of Fenton systems to generate hydroxyl radicals. These systems are called the dihydroxybezene driven Fenton reaction. In this study, the effects of five 1,2-DHBs (substituted in position 4) for driving the Fenton reaction were evaluated. The DHBs utilized were: 3,4-dihydroxybenzoic acid and 3,4-dihydroxybenzonitrile (electron-withdrawing substituents), 4-tert-butylcatechol and 4-methylcatechol (electron-donating substituents) and catechol (without substituent). The degradation of rhodamine B by different Fe3+/H2O2/1,2-DHB systems were determined at pH values between 1 and 9. These values were correlated (by a multivariate model) with the Fe+3 speciation at these pH values. To determine the Fe+3/1,2-DHB complex concentration, the stability constants for the mono, bis and tris complexes were experimentally determined. The log β1, log β2 and log β3 for the assayed 1,2-DHB were 19.30, 27.21, 45.69 for catechol; 19.52, 28.90, 44.66 for 4-methylcatechol; 19.93, 27.16, 44.77 for 4-tert-butylcatechol; 15.57, 23.46, 42.03 for 3,4-dihydroxybenzonitrile and 17.68, 29.79 and 46.27 for 3,4-dihydroxybenzoic acid, respectively. From the multivariate model (R2 = 0.994), it was determined that only Fe+3 aquocomplex, [Fe(OH)2]+ and [FeDHB]+ were significant (p < 0.05) for rhodamine B degradation, which is independent of the nature of the DHB utilized.

2024, Nashira Figueroa, Naily, Dr. Brante-Ramirez, Antonio, Leclerc, Jean-Charles, Dr. Salgado-Mendoza, Pablo, Dr. Oyarzo-Vera, Claudio

In pursuit of a more sustainable construction material with the potential to improve bioreceptivity in marine environments, this study investigates the feasibility of incorporating three industrial residues—steel sludge (“Conox”), mytilid mussel shells, and wheat straw fibers—as partial substitutes for cement and sand. The research focuses on evaluating the physical and mechanical properties of mortar and concrete mixtures containing these residues, both individually and in combination. Additionally, it assesses the metal leaching potential of concrete incorporating Conox sludges into the environment. The results show that mixture containing 10% Conox sludges as a sand substitute exhibit the highest mechanical strength but also increased porosity, water absorption, and chloride ion diffusion. The addition of mussel shells and straw fibers generally reduced mechanical properties and increased porosity in mortars, though a 20% mussel shell substitution maintained mechanical strength and chloride ion diffusion in the concrete. The combination of mussel shells with Conox sludges allowed the concrete to retain its mechanical properties, although it also increased porosity and chloride ion penetration, which may limit its use where impermeability is key. However, this increased porosity could benefit coastal erosion control structures like breakwaters and revetments, and sea walls. Moreover, metal leaching from concrete incorporating Conox sludges remained within established safety limits. Despite these challenges, the materials show promise for non-structural applications or projects where sustainability is prioritized. Our research lays the foundation and opens new possibilities for future investigations that innovate in the combination of industrial wastes, aiming to create more sustainable construction materials with a reduced impact on biodiversity.

2021, Dr. Salgado-Mendoza, Pablo, Salazar-Nores, Claudio, Melin, Victoria, Thiam, Abdoulaye, Henríquez, Adolfo, Mansilla, Héctor, Yáñez, Jorge

Amitriptyline (AMT) is the most widely used tricyclic antidepressant and is classified as a recalcitrant emergent contaminant because it has been detected in different sources of water. Its accumulation in water and soil represents a risk for different living creatures. To remove amitriptyline from wastewater, the Advanced Oxidation Processes (AOPs) stands up as an interesting option since generate highly oxidized species as hydroxyl radicals (OH) by environmentally friendly mechanism. In this work, the oxidation and mineralization of AMT solution have been comparatively studied by 3 Electrochemical AOPs (EAOPs) where the OH is produced by anodic oxidation of H2O (AO-H2O2), or by electro-Fenton (EF) or photoelectro-Fenton (PEF). PEF process with a BDD anode showed the best performance for degradation and mineralization of this drug due to the synergistic action of highly reactive physiosorbed BDD (OH), homogeneous OH and UVA radiation. This process achieved total degradation of AMT at 50 min of electrolysis and 95% of mineralization after 360 min of treatment with 0.5 mmol L1 Fe2þ at 100 mA cm2. Six aromatic intermediates for the drug mineralization were identified in short time of electrolysis by GC-MS, including a chloroaromatic by-product formed from the attack of active chlorine. Short-chain carboxylic acids like succinic, malic, oxalic and formic acid were quantified by ion-exclusion HPLC. Furthermore, the formation of NO3 ions was monitored. Finally, the organic intermediates identified by chromatographic techniques were used to propose the reaction sequence for the total mineralization of AMT.

2023, Salgado-Mendoza, Pablo, Bustamante, Luis, Carmona , Danilo, Meléndrez, Manuel, Rubilar, Olga, Salazar, Claudio, Pérez, Andy, Vidal, Gladys

The present study reports on phenolic compounds profile of Eucalyptus globulus leaf extracts and exhibiting their role in obtaining silver nanoparticles (AgNP) by a green method on paper and fabric supports with or without addition of NaOH. To know the mechanism involved in the formation of AgNP, FTIR, UV–Visible spectrophotometry and UHPLC-QTOF-MS analyzes were carried out of E. globulus extracts before and after the synthesis of AgNP. The FTIR, UV–Visible spectrophotometry analyzes identified phenolic compounds, and to a lesser extent reducing sugars mainly participate as reducing agents in the formation of AgNP, while phenolic compounds would participate as stabilizing agents. UHPLC-QTOF-MS analyzes identified derived from gallic acid play an important role in AgNP formation. AgNPs were characterized in their morphology and structure by SEM-EDS, TEM-SAED, XRD, UV–Vis diffuse reflectance and TGA. The results indicate the formation of Ag and/or Ag2O nanoparticles depending on the influence of NaOH in the reaction system. Furthermore, the support used (paper or fabric), it would influence the concentration of AgNPs formed, the consumption of phenolic compounds, the antibacterial activity and band-gap of AgNPs synthesized. This study provides evidence of a simple process to support AgNP on cellulose and providing key information towards the definitive clarification of the mechanism of formation of AgNP by green synthesis.

2023, Márquez, Katherine, Jiménez-Aspee, Felipe, Márquez, Nicole, Salgado-Mendoza, Pablo, Contreras, David

Wood is a complex material whose main chemical constituents are cellulose, hemicellulose, and lignin. These components are studied in various industries after the wood has been processed by chemical or mechanical methods. For the paper industry, it is relevant to determine the pentosan content in cellulose pulp because it indicates the degree of retention of hemicellulose. Hemicellulose contributes to the resistance, increasing the yield of the pulp, and therefore, high pentosan content is desirable. In this way, this research focused on the determination of the pentosan content in hard and softwood pulps between 0.81 to 18.4%. The pentosan content can be directly determined by a chemical method, although these conventional methods are long, expensive, generate a high amount of corrosive waste, and are not recommended for routine analysis. Therefore, in this research, an alternative method was developed using near-infrared spectroscopy together with partial least squares regression to predict the pentosan content in pulps. This new method is fast, inexpensive, analysis is direct and non-destructive. Finally, the pentosan calibration model was validated by cross-validation and the predicted external samples were quantified with precision between 0.008 and 0.043 and accuracy between 3.9 and 12.2%, while SEP has a variability of 1.267% of pentosan for this model.