Strategic Design of Heavy Metals Removal Agents through Zeta Potential Measurements

Industrial wastewater generally contains significant amounts of toxic heavy metals that cause a problem of contamination to the environment. In this chapter, the use of polyelectrolytic waste as new coagulant-flocculating-chelating agents in the separation of Cu, Ni, Zn, Pb, Cd, Cr by a coagulation-flocculation process is discussed. The isoelectric point (ζ = 0) of the residual water was reached with a dose of 2.5 mg chitosan and observed a clarification kinetics = 187.49% T/h, sediment kinetics = 93.96 mm/h and an efficiency of 85% in the removal of heavy metals. With the SEM-EDS analysis and the determination of heavy metals in the treated water, it is shown that the functional groups that chitosan has in its structure have the following order of affinity for the removal of heavy metals from the wastewater model: Cr = 27.64% > Ni = 21.96% > Pb = 21.28% > Zn = 14.68% > Cu = 10.96% > Cd = 3.35% > Ca = 0.12%

Innovation in the Electrophoretic Deposition of TiO2 Using Different Stabilizing Agents and Zeta Potential

Surface engineering is gaining increasing relevance in various industrial sectors and in research, and in this sense, zeta potential measurements, being a physicochemical parameter of interface, are key to linking the functionality of a coating with its application environment. In this work, different stabilizing agents with different chemical structure and electrical charge were used to improve the stability of the TiO2 particles. The influence of the electrophoretic deposition (EPD) parameters (potential and deposition time) and the concentration of chitosan and TiO2 in suspension were studied to find the best deposition performance on the titanium substrate. The composition and structure of the coatings were evaluated by infrared spectroscopies (FT-IR) and scanning electron microscopy (SEM). It was observed that the TiO2 particles were dispersed in the chitosan matrix through simultaneous deposition. Corrosion resistance was evaluated by electrochemical polarization curves, indicating a higher corrosion resistance of TiO2 and TiO2-chitosan coatings compared to the pure titanium substrate in a solution of sulfuric acid

Integral use of Nejayote: Characterization, New Strategies for Physicochemical Treatment and Recovery of Valuable By-Products

In this research, an innovative physicochemical strategy is presented to address the problem of nejayote, from two perspectives: the first focusing on sanitation and reuse of nejayote using waste from shrimp shells, thereby adding value to the recovered solids of nejayote. Zeta potential measurements are a proactive electrochemical tool to define the strategy to allow integral use of nejayote in the industry nixtamalization. The treated water can be discharged from the municipal sewer system using a process of coagulation-flocculation, with an optimal dose of 1250 mg/L chitosan at pH 5, achieving removal of up to 80% of total suspended solids and turbidity. Moreover, zeta potential measurements show that the anionic biopolyelectrolyte obtained from nejayote has potential to be applied in the area of water treatment as a green chelating agent

Chalcogenides and Carbon Nanostructures: Great Applications for PEM Fuel Cells

Nanostructured metal chalcogenides (NMCs) and carbon nanostructures (CNS) are attracting significant attention due to their features such as high stability in an acidic environment, especially if they have a significant oxygen reduction activity and remarkable superconducting properties. The broad range of CNS exhibits novel physicochemical properties, and thus it is triggering intense research about carbon nanoscience with numerous applications. In this context, new synthesis routes are designed under moderate conditions, which are definitely needed in order to simplify the process, reduce costs, and allow the production of NMCs at lower temperatures and CNS whose size and shape can be controlled. Some related studies about Pt based on sulfides and selenides, transition metal chalcogenides (TMCs), and carbon nanostructures (nanotubes and graphene) are revealed here; however, they show promise for fuel cells that these NMCs, CNS, or even NMC-CNS materials have been applied for other energy devices. Until now, a good response for cathodic reactions is employing TMCs based on tungsten and CNS without metal. According to experimental results and in terms of catalytic activity, durability, and chemical/electrochemical stability, much more research is required to produce commercially valid non-noble catalysts, electrocatalysts, or supports; however, one approach on this field is metal-free CNS

Evaluación de polisacáridos en floculación mediada por complejo polielectrolítico

Water is an increasingly valuable resource because its availability, primarily it is limited to precipitation and water storage; for that reason, increasing population density and climate change can interfere with water accessibility. Urban and industrial activities can produce wastewater and pollute waterbodies that could represent a significant water source; however, it needs to be treated prior to its use.  Flocculation is an important pollutants removal method to reduce a variety of organic and inorganic molecules from wastewater, using the flocculant’s intrinsic charges to stabilize/precipitate them, by different methods, one of them being via polyelectrolyte complex. Flocculant versatility depends on its capacity to remove pollutants and there are commercial flocculants with remarkable efficiencies. However, their toxicity can limit their use in waterbodies or for former human use. Research shows that polysaccharides are great option as flocculants because of their easily charged conformation and high molecular weight to neutralize pollutants and precipitate flocs, they are biocompatible, biodegradable, and easy to modify to modulate the flocculant interaction due to the functional group’s high density. This review explores the latest research on polysaccharide polyelectrolyte flocculation and derivatives and their pollutant removal capacity, the polysaccharides evaluated were the most commonly researched such as chitosan, cellulose, chitin, alginate, gums, dextran, among others. Recent research tendencies on these polysaccharides flocculation capacity, showed promising results (up to 99% removal efficiencies) with a wide variety of contaminants, making them excellent candidates for their application in green flocculation

Estudio de propiedades fotofísicas de sensores del tipo bis-fluoroforicos y su aplicación en la detección de iones metálicos

Industrialized cities like Tijuana dispose of a large amount of water with metallic elements content, as a result of by-products, which represent a health risk. A proposed alternative is the use of chemical sensors based on different mechanisms. The focus of this project is the study of bis-o-aminobenzamide macromolecules, as metal ion selector sensors with application in wastewater treatment. A series of five bis-o-aminobenzamide compounds were studied as chemical sensors capable of selecting and coordinating with metals dissolved in water, in addition to being able to remove these metals in the presence of the natural coagulant Pectin, which was extracted from the penca of the nopal. For this, different concentrations of the five compounds were prepared, the most suitable for the analyzes was selected and it was contacted with solutions of different ions. The compounds and their coordination were evaluated by fluorescence, UV-Visible and Zeta potential spectroscopies. In addition, SEM micrographs were obtained upon removal obtained. The five sensors evaluated have different fluorescence intensities. When in contact with some metal ions, a coordination was formed that reduces the emission of fluorescence. Fluorescent properties in solution were studied by varying the concentration of ligand and the study of its interaction with different metals of environmental interest was carried out. The influence of the nature of the central chain of interconnection on the fluorescent properties of the studied library was determined. These ligands have interesting fluorescent characteristics, which gives them a potential value as sensors for metals, presenting a sensitivity for the Cu +2 ion in all cases.Las ciudades industrializadas como Tijuana desechan gran cantidad de agua con contenido de elementos metálico, resultado de los subproductos, que representan un riesgo para la salud. Una alternativa propuesta es el uso de sensores químicos basados en diferentes mecanismos. El enfoque de este proyecto es el estudio de macromoléculas bis-o-aminobenzamida, como sensores selectores de iones metálicos con aplicación en el tratamiento de aguas residuales. Se estudió una serie de cinco compuestos bis-o-aminobenzamidas como sensores químicos capaces de seleccionar y coordinar con metales disueltos en el agua, además de poder remover estos metales en presencia del coagulante natural Pectina la cual fue extraída de la penca del nopal. Para ello se preparó distintas concentraciones de los cinco compuestos, se seleccionó la más adecuada para los análisis y se puso en contacto con soluciones de distintos iones. Los compuestos y su coordinación fueron evaluados por espectroscopias de fluorescencia, UV-Visible y potencial Zeta. Además, se obtuvo micrografías SEM a la remoción obtenida. Los cinco sensores evaluados presentan distintas intensidades de fluorescencia, al estar en contacto con algunos iones metálicos se formaba una coordinación que abate la emisión de fluorescencia. Se estudiaron las propiedades fluorescentes en solución variando la concentración de ligando y se realizó el estudio de su interacción con diferentes metales de interés ambiental. Se determinó la influencia de la naturaleza de la cadena central de interconexión en las propiedades fluorescentes de la biblioteca estudiada. Estos ligandos presentan características fluorescentes interesantes, lo que les confiere un valor potencial como sensores para metales, presentando una sensibilidad para el ion Cu+2 en todos los casos

Preparación de materiales funcionalmente graduados por deposición electroforética

The objective of this work is to develop a superhydrophobic and self-healing coating with the ability to protect metal surfaces and extend the useful life of both metal and coating. By means of the electrophoretic deposition technique, titanium dioxide coatings with variable morphology and composition were created. So far two techniques have been used for the manufacture of superhydrophobic coatings: 1) Functionalization of TiO2 nanoparticles (anatase) with polydimethylsiloxane by UV irradiation and 2) Functionalization of electrophoretic deposits with polydimethylsiloxane by UV irradiation. The electrophoretic deposits vary the applied potential and the deposition times, they are observed that they are used, they are eliminated, the uniforms are uniform and homogeneous, they are minimized, they are reduced, they are diminished, they are diminished, they are diminished, they are increased, they are they increase, they increase, they increase, they decrease, they increase, they are deposited first, thus generating a homogeneous arrangement on the surface of the highly rough metal.  All deposits were characterized by FTIR, RAMAN, DLS, UV-vis- Diffuse Reflectance, AFM y FESEM.El objetivo de este trabajo es desarrollar un recubrimiento superhidrofóbico y autoregenerable con la capacidad de proteger superficies de titanio y extender la vida útil tanto del metal como del recubrimiento. Mediante la técnica de deposición electroforética se crearon recubrimientos de dióxido de titanio con morfología y composición variable. Hasta el momento se han empleados dos técnicas para la fabricación de los recubrimientos superhidrofobicos: 1) Funcionalización de nanopartículas de TiO2 (anatasa) con polidimetilsiloxano por irradiación UV y 2) Funcionalización de los depósitos electroforéticos con polidimetilsiloxano por UV. Los depósitos electroforéticos se prepararon variando el potencial aplicado y los tiempos de deposición, se observa que al utilizar potenciales menores los depósitos son más uniformes y homogéneos, se logra observar también que las grietas disminuyen significativamente con la disminución del potencial aplicado debido a que las partículas más pequeñas se depositan primero generando así un arreglo homogéneo en la superficie del metal altamente rugoso. Los depósitos fueron caracterizados por diferentes técnicas: FTIR, RAMAN, DLS, UV-vis de reflectancia difusa, AFM y FESEM

Improving the Efficiency of a Coagulation-Flocculation Wastewater Treatment of the Semiconductor Industry through Zeta Potential Measurements

Efficiency of coagulation-flocculation process used for semiconductor wastewater treatment was improved by selecting suitable conditions (pH, polyelectrolyte type, and concentration) through zeta potential measurements. Under this scenario the zeta potential, ζ, is the right parameter that allows studying and predicting the interactions at the molecular level between the contaminants in the wastewater and polyelectrolytes used for coagulation-flocculation. Additionally, this parameter is a key factor for assessing the efficiency of coagulation-flocculation processes based on the optimum dosages and windows for polyelectrolytes coagulation-flocculation effectiveness. In this paper, strategic pH variations allowed the prediction of the dosage of polyelectrolyte on wastewater from real electroplating baths, including the isoelectric point (IEP) of the dispersions of water and commercial polyelectrolytes used in typical semiconductor industries. The results showed that there is a difference between polyelectrolyte demand required for the removal of suspended solids, turbidity, and organic matter from wastewater (23.4 mg/L and 67 mg/L, resp.). It was also concluded that the dose of polyelectrolytes and coagulation-flocculation window to achieve compliance with national and international regulations as EPA in USA and SEMARNAT in Mexico is influenced by the physicochemical characteristics of the dispersions and treatment conditions (pH and polyelectrolyte dosing strategy)

Polylactic acid/multi walled carbon nanotubes (PLA/MWCNT) nanocomposite for 3D printing of medical devices

In recent years, the composite nanomaterials area has had a great development impact in health sciences. Biomaterials depict as one of the most promising since they are compatible with additive manufacturing (AM) techniques. It is also possible to use them to mold specific medical parts. Composite nanomaterials have shown good biocompatibility and low toxicity to have benefits equal to or greater than metals (i.e., Co-Cr alloy). The purpose of this study is to develop a nanocomposite biomaterial (PLA/MWCNTf) from Polylactic Acid (PLA) and functionalized Multi Walled Carbon Nanotubes (MWCNTf) to evidence its potential application in 3D printing of orthopedic fixation devices. PLA/MWCNTf nanocomposite was prepared by solution blending technique, incorporating a proportion of 0.5 wt% of MWCNTf to the PLA matrix. TGA analysis of the PLA/MWCNTf was used to determine the thermal stability, a slight increase was found compared to the PLA.  FTIR spectroscopy confirmed the presence of carboxylic acid groups in the MWCNTf which improves good incorporation of the nanotubes in the PLA matrix. Additionally, Raman spectroscopy, SEM, and AFM micrographs were used to verify MWCNTf reached the PLA surface homogeneously. Additive manufacturing preparation was done by extrusion molding of PLA/MWCNTf as well as its 3D printing. 

Evaluación de compuestos bis-fluorofóricos en agua del río Tijuana

This work focuses on the use of bis-fluorophore compounds in real water for the detection and removal of metal ions present in the Tijuana river, for this, a previous work of chemical and bacterial analysis of 6 different samples that were taken from the River was used Tijuana. All the sampling sites were carefully selected to obtain an accurate understanding of the current state of the river throughout its course. The TOC, COD, BOD, Nitrogen and phosphorus results showed that dams do not contain high amounts of these parameters, but in the city, center these values are increased due to the possible interversion of city sewer connections to the river (55, 189, 131, 11.9 and 1.1 mg / L, respectively). The points with the highest amount of organic matter were in the city center, so that specific point was chosen for the test of bis-fluorophoric compounds, to ensure the presence of metal ions in the water and it was shown that the water containing fluorescent compounds and in the presence of these bis-fluorophoric compounds there is a lowering of fluorescence. The bacterial analysis showed that the last point of the city, near the border of the USA and Mexico, concentrates a high number of bacteria and that the discharge goes directly to the Pacific Ocean, being a health and environmental problem.Este trabajo se centra en el uso de compuestos bis-fluorofóricos en agua real para la detección y remoción de iones metálicos presentes en el río Tijuana, para esto se utilizó un trabajo previo de análisis químico y bacteriano de 6 muestras diferentes que se tomaron del Río Tijuana. Todos los sitios de muestreo fueron seleccionados cuidadosamente para obtener una comprensión precisa del estado actual del río a lo largo de su curso. Los resultados de TOC, DQO, DBO, Nitrógeno y fósforo mostraron que las presas no contienen cantidades elevadas de estos parámetros, pero al centro de la ciudad estos valores se incrementan por la posible interversión de conexiones del alcantarillado de la ciudad al río (55, 189, 131, 11.9 y 1.1 mg/L, respectivamente). Los puntos con mayor cantidad de materia orgánica fueron en el centro de la ciudad, por lo que se eligió ese punto en específico para la prueba de los compuestos bis-fluorofóricos, para asegurar la presencia de iones metálicos en el agua y se mostró que el agua que contiene compuestos fluorescentes y en presencia de estos compuestos bis-fluorofóricos hay un abatimiento de la fluorescencia. El análisis bacteriano mostró que el último punto de la ciudad, cerca de la frontera de USA y México, se concentra una cantidad elevada de bacterias y que la descarga va directo al océano pacífico, siendo un problema de salud y ambiental