Showing papers by "Centro de Investigación y Desarrollo Tecnológico en Electroquímica published in 2021"

Experimental and Theoretical Insights on Methylene Blue Removal from Wastewater Using an Adsorbent Obtained from the Residues of the Orange Industry.

Abstract: Chemical and thermochemical transformations were performed on orange peel to obtain materials that were characterized and further tested to explore their potential as adsorbents for the removal of methylene blue (MB) from aqueous solutions. The results show the high potential of some of these materials for MB adsorption not only due to the surface area of the resulting substrate but also to the chemistry of the corresponding surface functional groups. Fitting of the kinetic as well as the equilibrium experimental data to different models suggests that a variety of interactions are involved in MB adsorption. The overall capacities for these substrates (larger than 192.31 mg g−1) were found to compare well with those reported for activated carbon and other adsorbents of agro-industrial origin. According to these results and complementary with theoretical study using Density Functional Theory (DFT) approximations, it was found that the most important adsorption mechanisms of MB correspond to: (i) electrostatic interactions, (ii) H-bonding, and (iii) π (MB)–π (biochar) interactions. In view of these findings, it can be concluded that adsorbent materials obtained from orange peel, constitute a good alternative for the removal of MB dye from aqueous solutions.

Nanometric and surface properties of semiconductors correlated to photocatalysis and photoelectrocatalysis applied to organic pollutants – A review

Abstract: This review study summarizes relevant topics about the photoelectrocatalytic semiconductors for the degradation of organic pollutants. Among the topics are A) the basic concepts of photocatalysis and photoelectrocatalysis for the advanced oxidation of organics in water. B) The band theory about heterojunctions, Schottky barriers, and doping of these semiconductors being photocatalysts. C) Proposing the outlook for photocatalysts, as those systems arranging doped semiconductors with heterojunctions and having Schottky junctions, a set of tables and sections show reported cases that complement the semiconductor characteristics providing the percentage of degradation attained, such as photoanodes of Boron-doped TiO2 nanotubes, TiO2 - Sb2S3 composites, and so forth. D) The novel characteristics of graphene-based materials for improving photoelectrocatalytic systems. E) A systematic way of classifying and understanding photoelectrocatalytic semiconductors based on their relevant characteristics and photoelectrochemical mechanisms. Moreover, this work shows the photoelectrocatalytic properties of the recently reported graphene oxide - reduced graphene oxide (GO-rGO) nanohybrids, which can also be used for the degradation of organic pollutants. Finally, based on all the previously gathered and summarized information, some inferences are made about the photoelectrocatalytic properties of some GO-rGO based heterojunctions for the degradation of organic pollutants.

Thermal Energy Storage by the Encapsulation of Phase Change Materials in Building Elements-A Review.

Abstract: The energy sector is one of the fields of interest for different nations around the world. Due to the current fossil fuel crisis, the scientific community develops new energy-saving experiences to address this concern. Buildings are one of the elements of higher energy consumption, so the generation of knowledge and technological development may offer solutions to this energy demand, which are more than welcome. Phase change materials (PCMs) included in building elements such as wall panels, blocks, panels or coatings, for heating and cooling applications have been shown, when heating, to increase the heat storage capacity by absorbing heat as latent heat. Therefore, the use of latent heat storage systems using phase change materials (PCMs) has been investigated within the last two decades. In the present review, the macro and micro encapsulation methods for construction materials are reviewed, the former being the most viable method of inclusion of PCMs in construction elements. In addition, based on the analysis of the existing papers on the encapsulation process of PCMs, the importance to pay more attention to the bio-based PCMs is shown, since more research is needed to process such PCMs. To determine its thermophysical and mechanical behavior at the micro and macro levels, in order to see the feasibility of substituting petroleum-based PCMs with a more environmentally friendly bio-based one, a section devoted to the excellent PCM with lightweight aggregate (PCM-LWA concrete) is presented due to the lack of description given in other reviews.

Advances and Applications of Water Phytoremediation: A Potential Biotechnological Approach for the Treatment of Heavy Metals from Contaminated Water.

Abstract: Potable and good-quality drinking water availability is a serious global concern, since several pollution sources significantly contribute to low water quality. Amongst these pollution sources, several are releasing an array of hazardous agents into various environmental and water matrices. Unfortunately, there are not very many ecologically friendly systems available to treat the contaminated environment exclusively. Consequently, heavy metal water contamination leads to many diseases in humans, such as cardiopulmonary diseases and cytotoxicity, among others. To solve this problem, there are a plethora of emerging technologies that play an important role in defining treatment strategies. Phytoremediation, the usage of plants to remove contaminants, is a technology that has been widely used to remediate pollution in soils, with particular reference to toxic elements. Thus, hydroponic systems coupled with bioremediation for the removal of water contaminants have shown great relevance. In this review, we addressed several studies that support the development of phytoremediation systems in water. We cover the importance of applied science and environmental engineering to generate sustainable strategies to improve water quality. In this context, the phytoremediation capabilities of different plant species and possible obstacles that phytoremediation systems may encounter are discussed with suitable examples by comparing different mechanistic processes. According to the presented data, there are a wide range of plant species with water phytoremediation potential that need to be studied from a multidisciplinary perspective to make water phytoremediation a viable method.

Energy and economic advantages of simultaneous hydrogen and biogas production in microbial electrolysis cells as a function of the applied voltage and biomass content

Abstract: Energy and economic data on gaseous biofuel production in microbial electrolysis cells (MECs) can guide their installation, operation mode and modelling. Hydrogen and methane production from waste mainly depends on the cell voltage and biomass content in a bioelectrochemical system. In the present study, the energy efficiency and economic benefits of the simultaneous dual production of gaseous biofuels in a two-chamber MEC fed with digester effluents were established. Combinations of biomass content (5–75%) from dilution of the digester effluents and cell voltage (0.30–1.20 V) were tested for the simultaneous production of biogas in the anodic compartment and hydrogen in the cathodic compartment. The biogas volume reached 33 mL (2.5 mL d−1) within 13 days and the hydrogen gas volume reached 3.5 mL (0.43 mL d−1) within 8 days each in their corresponding compartment (135 mL). The highest energy efficiency based on hydrogen produced relative to the electrical input was 854%, which was obtained at 0.3 V and 40% biomass, while the highest methane production rate was 14.4 mL L−1 d−1 with a methane purity of 87% and was obtained at 0.43 V and 65% biomass. The highest economic gain was obtained through the production of biogas with a surplus of 20% due to the simultaneous production of hydrogen, reaching 0.010 USD per kg of chemical oxygen demand (COD) removed. The data generated in the comprehensive evaluation of the operating conditions can support decision making for future techno-economic studies.

Study of a coupled adsorption/electro-oxidation process as a tertiary treatment for tequila industry wastewater

Abstract: Vinasse wastewater from tequila industry that has been conventionally treated is usually characterized by a chemical oxygen demand (COD) above 150 mg L−1, which is the maximum content permitted for discharge by Mexican Regulation. In order to increase the wastewater quality, different processes were applied, and from the experimental results, the advantages and limitations were analyzed. In this way, although Fenton experiments showed acceptable COD removal efficiencies (79–90%), operation as well as cost limit its adoption as a viable technology. Therefore, additional experiments explored electro-Fenton (EF) as well as adsorption coupled to EF in a tubular reactor. The corresponding data revealed that there was no additional increase in COD removal performance probably due to the low oxygen solubility in the electrolytic solution and the high pH that prevents the existence of Fe2+ ions necessary for the Fenton mixture. In view of these results, when an activated carbon (AC) filter was coupled to polarization at current densities between 0.5 and 2 mA cm−2, removal efficiencies from 71 to 81%, corresponding to final COD of 78 to 33 mg L−1, were achieved. Also, the adsorbent surface was continuously regenerated, promoting a more efficient adsorption and a longer service life for the AC filter. In this case, by using a current density of 0.5 mA cm−2, COD was reduced to sufficiently small values for discharge into natural water bodies, maintaining low energy consumption and therefore acceptable operation costs.

Efficiency of integrated electrooxidation and anaerobic digestion of waste activated sludge

Abstract: Most of the organic content of waste activated sludge (WAS) comprises microbial cells hard to degrade, which must be pre-treated for energy recovery by anaerobic digestion (AD). Electrooxidation pre-treatment (EOP) with boron-doped diamond (BDD) electrode have been considered a promising novel technology that increase hydrolysis rate, by the disintegrating cell walls from WAS. Although electrochemical oxidation could efficiently solubilize organic substances of macromolecules, limited reports are available on EOP of WAS for improving AD. In this endeavour, the mathematical optimization study and the energy analysis of the effects of initial total solids concentrations [TS] of WAS and current density (CD) during EOP on the methane production and removal of chemical oxygen demand (COD) and volatile solids (VS) were investigated. Because limited reports are available on EOP of WAS for improving biogas production, it is not well understood; however, it has started to attract interest of scientists and engineers. In the present work, the energy recovery as biogas and WAS conversion were comprehensively affected by CD and [TS], in an integrated EOP and AD system. When working with WAS at 3% of [TS] pre-treated at current density of 24.1 mA/cm2, the highest COD and VS removal were achieved, making it possible to obtain the maximum methane (CH4) production of 305 N-L/kg VS and a positive energy balance of 1.67 kWh/kg VS. Therefore, the current densities used in BDD electrode are adequate to produce the strong oxidant (hydroxyl radical, ·OH) on the electrode surface, allow the oxidation of organic compounds that favours the solubilization of particulate matter and VS from WAS. The improvement of VS removal and COD solubilization were due to the effects of pre-treatments, which help to break down the microbial cells for faster subsequent degradation; this allows a decomposition reaction that leads to biodegrade more compounds during AD. The balance was positive, suggesting that even without any optimization the energy used as electricity could be recovered from the increased methane production. It is worth noting that this kind of analysis have not been sufficiently studied so far. It is therefore important to understand how operational parameters can influence the pre-treatment and AD performances. The current study highlights that the mathematical optimization and energy analysis can make the whole process more convenient and feasible.

Effects of Ce Doping on the Photocatalytic and Electrochemical Performance of Nickel Hydroxide Nanostructures

Abstract: Ni(OH)2 doped with cerium cations was synthesized by a hydrothermal method and its electrochemical, photoelectrochemical and photocatalytic behavior was determined by the corresponding suitable techniques. Ni(OH)2 films doped with different Ce proportions were evaluated in a KOH support electrolyte solution by cyclic voltammetry. Scan-rate dependent voltammograms displayed pseudo-capacitive behavior while the charge transfer resistance of Ce-doped samples was determined through electrochemical impedance spectroscopy. The calculated charge transfer resistance value was 132 Ω for Ni(OH)2 containing 350 μmoles of Ce. Chronoamperometry under intermittent UV light was employed to measure the photo-response of nanomaterials. The experimental results indicated that the photocurrent of Ni(OH)2 containing 350 µmoles of Ce was ten times greater than that of pure Ni(OH)2. Photocatalytic activity of the powders was demonstrated under UV light irradiation accomplishing 83% of methyl orange degradation after 140 min of reaction with pseudo-first-order kinetics and the calculated degradation rate constant was 0.0125 min− 1. The results evidenced the electrochemical, photoelectrochemical and photocatalytic activity of the synthesized materials, which sets them as suitable materials for a wide range of promising photo-based applications.

Improving plasma bonding of PDMS to gold-patterned glass for electrochemical microfluidic applications

Abstract: Plasma-treated poly(dimethylsiloxane) (PDMS) bonds irreversibly to Si-containing substrates In electrochemical microfluidic cells, commonly used gold electrodes are inert to this bonding method, causing leaks in the PDMS $$\vert$$ Au interface In this work, the effect of the electrode connector width on the leak was studied Leak pressure tests show that higher leak pressures can be obtained using narrower electrode connectors A 4 $$\upmu$$ m connector width presents a leak pressure of 238±22 kPa, comparable to the typical failure pressures reported for PDMS $$\vert$$ glass devices without electrodes Finite element modeling suggests that the deformation of the PDMS under the pressure in the channel is the mechanism responsible for the sharp increase in leak resistance observed at narrow gold structures To ensure that narrow connectors are suitable for faradaic electrochemical measurements, a model analyte was evaluated in cells with different electrode connector width Voltammograms show that even when using the 4 $$\upmu$$ m structure, ohmic drop is negligible We propose the use of narrow electrode connectors to reliably use the simple and widespread plasma bonding method while minimizing the solution leaking