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Arango Hoyos, B. E., Franco Osorio, H., Valencia Gomez, E. K., Guerrero Sanchez, J., Del Canto Palominos, A. P., Larrain, F. A., et al. (2023). Exploring the capture and desorption of CO2 on graphene oxide foams supported by computational calculations. Sci. Rep., 13(1), 14476.
Abstract: In the last decade, the highest levels of greenhouse gases (GHG) in the atmosphere have been recorded, with carbon dioxide (CO2) being one of the GHGs that most concerns mankind due to the rate at which it is generated on the planet. Given its long time of permanence in the atmosphere (between 100 to 150 years); this has deployed research in the scientific field focused on the absorption and desorption of CO2 in the atmosphere. This work presents the study of CO2 adsorption employing
materials based on graphene oxide (GO), such as GO foams with different oxidation percentages (3.00%, 5.25%, and 9.00%) in their structure, obtained via an environmentally friendly method. The characterization of CO2 adsorption was carried out in a closed system, within which were placed the GO foams and other CO2 adsorbent materials (zeolite and silica gel). Through a controlled chemical reaction, production of CO2 was conducted to obtain CO2 concentration curves inside the system and calculate from these the efficiency, obtained between 86.28 and 92.20%, yield between 60.10 and 99.50%, and effectiveness of CO2 adsorption of the materials under study. The results obtained suggest that GO foams are a promising material for carbon capture and the future development of a new clean technology, given their highest CO2 adsorption efficiency and yield.
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Ashfaq, M., Talreja, N., Chauhan, D., Rodriguez, C. A., Mera, A. C., & Mangalaraja, R. V. (2022). Synthesis of reduced graphene oxide incorporated bimetallic (Cu/Bi) nanorods based photocatalyst materials for the degradation of gallic acid and bacteria. J. Ind. Eng. Chem., 110, 447–455.
Abstract: Gallic acid (GA) is a polyphenols compound commonly present in wastewater that immensely affects aquatic and human life. GA is also responsible for the inhibitory effects on the microbial activity in the soil, thereby decreasing the fertility of the soil. Therefore, the removal of GA from the wastewater is necessary to combat such issues. The present study focused on the synthesis of reduced graphene oxide (rGO) incorporated bimetallic (Cu/Bi) based nanorods (r-GO-Cu/Bi-NRs) and their photocatalytic applications. Incorporating GO within the CuBi2O4-NRs might decrease the bandgap value, thereby increasing the interfacial charge transfer. Moreover, GO increased the reactive sites and oxygen defects onto the r-GO-Cu/Bi-NRs that led to the separation rate of the photo-induced charge carriers and migration, thereby enhancing the photodegradation ability of the synthesized r-GO-Cu/Bi-NRs. The synthesis process of the r-GO-Cu/Bi-NRs is facile, novel, and economically viable for the photocatalytic degradation of organic pollutants.
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Benitez, S., Duarte, C., Opitz, T., Lagos, N. A., Pulgar, J. M., Vargas, C. A., et al. (2017). Intertidal pool fish Girella laevifrons (Kyphosidae) shown strong physiological homeostasis but shy personality: The cost of living in hypercapnic habitats. Mar. Pollut. Bull., 118(1-2), 57–63.
Abstract: Tide pools habitats are naturally exposed to a high degree of environmental variability. The consequences of living in these extreme habitats are not well established. In particular, little it is known about of the effects of hypercanic seawater (i.e. high pCO(2) levels) on marine vertebrates such as intertidal pool fish. The aim of this study was to evaluate the effects of increased pCO(2) on the physiology and behavior in juveniles of the intertidal pool fish Girella laevifrons. Two nominal pCO(2) concentrations (400 and 1600 patm) were used. We found that exposure to hypercapnic conditions did not affect oxygen consumption and absorption efficiency. However, the lateralization and boldness behavior was significantly disrupted in high pCO(2) conditions. In general, a predator-risk cost of boldness is assumed, thus the increased occurrence of shy personality in juvenile fishes may result in a change in the balance of this biological interaction, with significant ecological consequences. (C) 2017 Elsevier Ltd. All rights reserved.
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Crutchik, D., Morales, N., Vazquez-Padin, J. R., & Garrido, J. M. (2017). Enhancement of struvite pellets crystallization in a fullscale plant using an industrial grade magnesium product. Water Sci. Technol., 75(3), 609–618.
Abstract: A full-scale struvite crystallization system was operated for the treatment of the centrate obtained from the sludge anaerobic digester in a municipal wastewater treatment plant. Additionally, the feasibility of an industrial grade Mg(OH) (2) as a cheap magnesium and alkali source was also investigated. The struvite crystallization plant was operated for two different periods: period I, in which an influent with low phosphate concentration (34.0 mg P . L (-1)) was fed to the crystallization plant; and period II, in which an influent with higher phosphate concentration (68.0 mg P . L (-1)) was used. A high efficiency of phosphorus recovery by struvite crystallization was obtained, even when the effluent treated had a high level of alkalinity. Phosphorus recovery percentage was around 77%, with a phosphate concentration in the effluent between 10.0 and 30.0 mg P .L- 1. The experiments gained struvite pellets of 0.5- 5.0 mm size. Moreover, the consumption of Mg(OH) (2) was estimated at 1.5 mol Mg added . mol P recovered (-1). Thus, industrial grade Mg(OH) (2) can be an economical alternative as magnesium and alkali sources for struvite crystallization at industrial scale.
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Crutchik, D., Rodrigues, S., Ruddle, D., & Garrido, J. M. (2018). Evaluation of a low-cost magnesium product for phosphorus recovery by struvite crystallization. J. Chem. Technol. Biotechnol., 93(4), 1012–1021.
Abstract: BACKGROUND: The development of a cost-effective process of struvite crystallization requires the selection of appropriate sources of alkali and magnesium. In this study, the effectiveness of two industrial grade products, MgO and Mg(OH)(2), as magnesium and alkali sources to recover phosphorus as struvite were investigated and compared in a first set of experiments. Subsequently, the use of industrial Mg(OH)(2) was compared in two different struvite crystallization systems, an upflow fluidized bed reactor (FBR) and a continuous stirred tank reactor (CSTR) coupled to a settler tank. RESULTS: At the same operational conditions, the consumption of MgO was higher than Mg(OH)(2) consumption. Moreover, industrial Mg(OH)(2) consumption for FBR and the CSTR operation was 1.6 and 1.1 1 mol Mg added mol(-1) P precipitated, respectively. This difference was caused by the high mixing intensity and the higher contact time between the Mg(OH)(2) slurry and the influent in the CSTR, favouring the conversion. CONCLUSIONS: Both industrial grade magnesium products are promising options for struvite crystallization. However, Mg(OH)(2) was more effective than the starting material, MgO, to recover phosphorus. Struvite crystallization by adding an industrial grade Mg(OH)(2) could be economically viable with regard to alternative physico-chemical P removal processes using metal salts, increasing the attractiveness of this P recovery process. (C) 2017 Society of Chemical Industry.
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Kumar, M. P., Sasikumar, M., Arulraj, A., Rajasudha, V., Murugadoss, G., Kumar, M. R., et al. (2022). NiFe Layered Double Hydroxide Electrocatalyst Prepared via an Electrochemical Deposition Method for the Oxygen Evolution Reaction. Catalysts, 12(11), 1470.
Abstract: Herein, we aimed to obtain NiFe layered double hydroxide (LDH) with a controlled phase and surface morphology as a highly active and stable oxygen evolution catalyst via the electrochemical deposition method, which was thermodynamically stable for the oxygen evolution reaction (OER) in an alkaline medium. The NiFe-LDH sample was analyzed by sophisticated instruments and tested as an electrocatalyst on Toray carbon (TC). The NiFe-LDH electrocatalyst showed an excellent performance with lower overpotential of 0.27 V at 35 mA cm(-2) and higher density of 125 mA cm(-2) for OER in the 1 M KOH electrolyte solution. Moreover, the prepared catalyst exhibited unpredictable long-time stability for 700 h. From our knowledge, NiFe-LDH is a robust highly stable electrocatalyst compared to the recent reports.
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Kumar, N., Gajraj, V., Rameshbabu, R., Mangalaraja, R. V., Joshi, N. C., & Priyadarshi, N. (2022). Redox additive electrolyte assisted promising pseudocapacitance from strictly 1D and 2D blended structures of MnO2/rGO. Mater. Charact., 189, 111991.
Abstract: A promising sustainable energy storage characteristic is achieved in redox additive electrolyte by developing strict blend of one dimensional (1D) and two dimensional (2D) structures. Hydrothermal reaction is followed to obtain the desired morphology. Two dimensional (2D) reduced graphene oxide (rGO) is added into the redox reaction between potassium permanganate and sodium nitrite to obtain nanocomposite comprising 1D and 2D blended structures of MnO2/rGO. Their structures and morphologies are studied by XRD, Raman and HRTEM analyses, respectively. The pseudocapacitive behaviour is studied in a redox additive electrolyte comprising KOH and K3Fe(CN)(6). The effect of electrolytic concentration was studied by varying the concentration of K3Fe(CN)6. The specific capacity is considerably enhanced up to 1741 F/g, 8.75 A/g with increase in concentration of K3Fe (CN)6. The role of redox couple [Fe(CN)(6)](3)-/[Fe(CN)(6)](4)-played a key role in adding the charge movement across the electrode which tuned well with the manganese ions to obtain one of the most promising pseudo-capacitances from the developed 1D and 2D blended structures of MnO2/rGO. For in-depth analysis of Fe ions movement, a symmetric supercapacitor cell is constructed to achieve a commendable specific capacitance of 216 F/g at 3.75 A/g. Prolong cycling hinted decreasing electrolytic interfacial layers resulting in fast reversible ki-netics of Fe(III) -> Fe(II) ions to achieve astonishing capacity retention of 127% after 3000 cycles.
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Nandhakumar, E., Selvakumar, P., Arulraj, A., Vivek, E., Venkatraman, M. R., Sasikumar, A., et al. (2023). Investigation on rod like SnO2@CdCO3 nanocomposite-based electron transport layer for CsPbBr3 heterojunction perovskite solar cell applications br. Mater. Lett., 330, 133396.
Abstract: A novel carbonate-based nanocomposite synthesized by hydrothermal technique for planar perovskite solar cells (PPSCs) applications. According to this study, SnO2@CdCO3and SnO2/SnO2@CdCO3 performs as dual electron transporting layers for CsPbBr3 based perovskite solar cell. The fabricated PSCs with architecture of FTO/SnO2/ SnO2@CdCO3/CsPbBr3/C showed a Voc of 0.84 V, Jsc of 12.30 mA cmi 2, PCE of 6.67 % and FF of 0.64 are obtained at ambient condition.
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Pandiyarajan, T., Mangalaraja, R. V., Karthikeyan, B., Arulraj, A., & Gracia-Pinilla, M. A. (2023). Fabrication and spectroscopic investigation of sandwich-like ZnO:rGO:ZnO: rGO:ZnO structure by layer-by-layer approach. Inorg. Chem. Commun., 149, 110383.
Abstract: Transparent conducting materials (TCMs) are the heart of modern optoelectronic industries and the properties of TCMs could be improved by the introduction of 2D carbon materials. In this report, the influence of order layering on microstructural, transparency and emission characteristics of ZnO:rGO:ZnO:rGO:ZnO and rGO:ZnO: rGO:ZnO:rGO sandwich structures has been investigated. The layer-by-layer approach has been adopted for the fabrication of sandwich structured materials ZnO:rGO:ZnO:rGO:ZnO and rGO:ZnO:rGO:ZnO:rGO through the spin coating technique. The sandwich structures of ZnO and rGO exhibited hexagonal wurtzite structure of ZnO without any impurities were identified through XRD. The ordering of layer's influenced the microstructural parameters and were significantly altered. The spherical nature of the particles and the formation of the sand-wich structures were confirmed by using SEM micrograph. The reduction in an optical transparency and nar-rowing bandgap of the ZnO upon the order of layering were identified through transmission spectra. The lower energy shift of near band edge (NBE) emission and reduction in the emission intensity with respect to pure ZnO nanostructures was observed. The present work provides a simple layer-by-layer approach to fabricating sand-wich structures and improving the optical properties which have potential applications in various optoelectronic devices.
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Pugazhenthiran, N., Valdes, H., Mangalaraja, R. V., Sathishkumar, P., & Murugesan, S. (2022). Graphene modified “black {001}TiO2” nanosheets for photocatalytic oxidation of ethylene: The implications of chemical surface characteristics in the reaction mechanism. Sep. Purif. Technol., 292, 121008.
Abstract: In this work, crystal facets, bandgap, size and shape of reduced graphene oxide (rGO) modified anatase {001} black TiO2 nanosheets (rGO-B-TiO2 NSTs) were tailored for the photocatalytic oxidation of ethylene under high humidity content. XRD, Raman and HR-TEM analyses confirm that rGO-B-TiO2 NSTs have a 94 % of exposed {001} facets with high number of oxygen vacancies. In addition, rGO-B-TiO2 NSTs exhibit increased values of surface area and porosity compared to its pristine form. A 48 and 34 mu mol g(-1) of ethylene are adsorbed at the surface of rGO-B-TiO2 NSTs in the absence and in the presence of humidity, respectively. In addition, operando DRIFTS analyses provide the insight of surface interactions between ethylene molecules and adsorption sites of rGO-B-TiO2 NSTs. The photocatalytic removal efficiencies of the synthesized materials under both UV and visible light irradiation proceed as follows: rGO-B-TiO2 NSTs > B-TiO2 NSTs > TiO2 NSTs > commercial TiO2 NPs. Further, ethylene is very quickly photocatalytic oxidized when rGO-B-TiO2 NSTs is applied under UV light irradiation, having a 72 and 92 % ethylene removal in the absence and in the presence of humidity, respectively. Moreover, a 48 and 58 % of ethylene removal takes place in the absence and presence of humidity under visible light irradiation, respectively. Results indicate that rGO-B-TiO2 NSTs boost the photocatalytic activity through their virtue of visible-light absorption properties (Bandgap = 2.61 eV) and the rapid electron-hole separation at the rGO {0 0 1} black TiO2 NSTs interfaces. Such findings are confirmed through UV-visible diffused reflectance, photoelectrochemical and photoluminescence analyses. Nanosheets made of rGO modified {0 0 1} black TiO2 could be used as an effective photocatalyst for the removal of ethylene from large volume fruit storage areas by exploiting a simple light source in the presence of high content of humidity.
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Read-Daily, B. L., Sabba, F., Pavissich, J. P., & Nerenberg, R. (2016). Kinetics of nitrous oxide (N2O) formation and reduction by Paracoccus pantotrophus. AMB Express, 6, 7 pp.
Abstract: Nitrous oxide (N2O) is a powerful greenhouse gas emitted from wastewater treatment, as well as natural systems, as a result of biological nitrification and denitrification. While denitrifying bacteria can be a significant source of N2O, they can also reduce N2O to N-2. More information on the kinetics of N2O formation and reduction by denitrifying bacteria is needed to predict and quantify their impact on N2O emissions. In this study, kinetic parameters were determined for Paracoccus pantotrophus, a common denitrifying bacterium. Parameters included the maximum specific reduction rates, (q) over cap, growth rates, (mu) over cap, and yields, Y, for reduction of NO3- (nitrate) to nitrite (N2O-), N2O- to N2O, and N2O to N-2, with acetate as the electron donor. The (q) over cap values were 2.9 gN gCOD(-1) d(-1) for NNO3- to NO2-, 1.4 gN gCOD(-1) d(-1) for N2O-to N2O, and 5.3 gN gCOD(-1) d(-1) for N2O to N-2. The (mu) over cap values were 2.7, 0.93, and 1.5 d(-1), respectively. When N2O and NO3- were added concurrently, the apparent (extant) kinetics, (q) over cap (app), assuming reduction to N-2, were 6.3 gCOD gCOD(-1) d(-1), compared to 5.4 gCOD gCOD(-1) d(-1) for NO3- as the sole added acceptor. The (mu) over cap (app) was 1.6 d(-1), compared to 2.5 d(-1) for NO3- alone. These results suggest that NO3- and N2O were reduced concurrently. Based on this research, denitrifying bacteria like P. pantotrophus may serve as a significant sink for N2O. With careful design and operation, treatment plants can use denitrifying bacteria to minimize N2O emissions.
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Shanmugaraj, K., Vinoth, V., Pugazhenthiran, N., Valdes, H., Salvo, C., Sepulveda, E., et al. (2023). Ferrihydrite- Graphene oxide foams as an efficient adsorbent for Arsenic (III) removal from an aqueous solution. Inorg. Chem. Commun., 153, 110892.
Abstract: We report the synthesis of a new range of ferrihydrite-graphene oxide (FH-GO) foams using chitosan as cross linker, with varying iron content (5 wt%, 10 wt%, and 20 wt% of FH) as highly efficient adsorbents for the removal of arsenic (III) (As(III)) in an aqueous solution. The sonochemical methods were adopted to synthesize various FH-GO foams and were further characterized by XRD, SEM, TEM, FTIR, Raman, and XPS techniques. The synthesized materials were used for the removal of As(III) in both batch and fixed bed absorbent column methods. The adsorption isotherm results showed that the 10 wt% of FH-GO foams demonstrated a superior adsorbent for the As(III) with high adsorption capacities than that of the other two FH-GO foams (5 wt% and 20 wt% of FH). Moreover, 10 wt% of FH-GO foams was also demonstrated to be nearly a complete (>98.4%) removal of As(III) ions at neutral pH 7. The adsorption isotherm fitted very well with the Langmuir model with the highest accuracy data for all the synthesized adsorbent materials. In addition, the fixed bed absorbent column method was also adopted for the removal of As(III) ions in the water sample, which showed > 99.2% of removal efficiency. The outstanding adsorption capabilities, along with their easy and low-cost synthesis, make these kinds of adsorbents extremely capable for commercial applications in wastewater treatment and drinking water purification.
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Suresh, R., Alvarez, A., Sandoval, C., Ramirez, E., Santander, P., Mangalaraja, R. V., et al. (2023). Fe2O3/NiO nanocomposites: synthesis, characterization and roxarsone sensing by Fourier transform infrared photoacoustic spectroscopy. New J. Chem., 47(27), 12806–12815.
Abstract: The Fe2O3/NiO nanocomposite was prepared through facile mixing of pure Fe2O3 and NiO nanoparticles. Pure metal oxides were synthesized by the glycine aided hydrothermal method. The crystal structure was determined by X-ray diffraction (XRD) analysis. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) clearly show that the NiO nanospheres were homogeneously distributed on Fe2O3 nanoplates. Fourier transform infrared (FTIR) spectra reveal that functionalization by glycine induces carboxylic and amino groups on the surface of nanoparticles. The optical properties such as light absorption behavior and band gap of the Fe2O3/NiO nanocomposite were determined by UV-Visible diffuse reflectance spectroscopy (DRS UV-Vis). The roxarsone (ROX) sensing behavior of the Fe2O3/NiO nanocomposite was evaluated by using Fourier transform infrared (FTIR) – photoacoustic spectroscopy (PAS) that allowed quantitative sensing of the ROX@Fe2O3/NiO complex. The photoacoustic signals of ROX were clearly observed in the FTIR-PAS spectra, particularly in the range of 1700 to 1000 cm(-1) without spectral interference from the composite. Furthermore, principal component analysis (PCA) and partial least square (PLS) regression models were applied to calibrate and validate ROX quantification. The PLS model exhibited the best performance in predicting the ROX concentration through ROX@Fe2O3/NiO samples. This proof of concept suggests that the Fe2O3/NiO nanocomposite has improved adsorption and spectral features by FTIR-PAS for sensing of organometallic compounds such as ROX.
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