Experimental study of carbon dioxide absorption by Fe2O3@glutamine/NMP nanofluid

Facile Fabrication and Characterization of Amine-Functional Silica Coated Magnetic Iron Oxide Nanoparticles for Aqueous Carbon Dioxide Adsorption

Surface active amine-functionalized silica coated magnetic iron oxide nanoparticles were prepared by a simple two-step process for adsorbing CO2 gas from aqueous medium. First, oleic acid (OA) coated iron oxide magnetic particles (denoted as Fe3O4-OA) were prepared by a simple coprecipitation method. Then, the surface of the Fe3O4-OA particles was coated with silica by using tetraethyl orthosilicate. Finally, aminated Fe3O4/SiO2-NH2 nanoparticles were concomitantly formed by the reactions of 3-aminopropyl triethoxysilane with silica-coated particles. The formation of materials was confirmed by Fourier transform infrared spectral analysis. Transmission electron microscopic analysis revealed both spherical and needle-shaped morphologies of magnetic Fe3O4/SiO2-NH2 particles with an average size of 15 and 68.6 nm, respectively. The saturation magnetization of Fe3O4/SiO2-NH2 nanoparticles was found to be 33.6 emu g-1, measured by a vibrating sample magnetometer at ambient conditions. The crystallinity and average crystallite size (7.0 nm) of the Fe3O4/SiO2-NH2 particles were revealed from X-ray diffraction data analyses. Thermogravimetric analysis exhibited good thermal stability of the nanoadsorbent up to an elevated temperature. Zeta potential measurements revealed pH-sensitive surface activity of Fe3O4/SiO2-NH2 nanoparticles in aqueous medium. The produced magnetic Fe3O4/SiO2-NH2 nanoparticles also exhibited efficient proton capturing activity (92%). The particles were used for magnetically recyclable adsorption of aqueous CO2 at different pH values and temperatures. Fe3O4/SiO2-NH2 nanoparticles demonstrated the highest aqueous CO2 adsorption efficiency (90%) at 40 °C, which is clearly two times higher than that of nonfunctionalized Fe3O4-OA particles.

Insight into the application of supercritical water oxidation for dichlorvos degradation: experimental and simulation aspects

Dichlorvos or 2,2-dichlorovinyl dimethyl phosphate (DDVP) ( C 4 H 7 C l 2 O 4 P ) is a chlorinated organophosphorus pesticide, which is frequently detected in agricultural wastewater. Herein, a batch reactor was used to carry out the supercritical water oxidation (SCWO) of a synthetic wastewater containing dichlorvos as a very hazardous agricultural pollutant. To do so, the impact of four operating parameters including dichlorvos concentration (100-500 ppm), oxidant coefficient (0.7-2), temperature (300-500°C) and time (0-100 s) on dichlorvos removal was optimized by the response surface method (RSM). According to the obtained results, at optimal conditions (i.e. initial concentration of dichlorvos 107.5 ppm, oxidation ratio 1.9234, temperature 419.9°C and time 79.94 s), as an index for dichlorvos removal, the chemical oxygen demand (COD) was found to be about 96.34%. Also, the results of high-performance liquid chromatography test showed that dichloroacetaldehyde (C2CL2H2O) and dichloroacetic acid (C2CL2H2O2) were created as intermediate substances during the dichlorvos degradation. Further, the molecular dynamics simulation was performed using ReaxFF force field to show the reaction path and products obtained in each step of the dichlorvos removal. Finally, as an indication, the simulation results indicated a good coordination with the experimental results.

Intensification of CO2 absorption and desorption by metal/non-metal oxide nanoparticles in bubble columns

In this study, four different metal/non-metal oxide nanoparticles including CuO, Fe₃O₄, ZnO, and SiO₂ were employed to improve CO₂ absorption and desorption in methyl diethanolamine (MDEA)-based nanofluid. CO₂ absorption experiment with various nanofluids was done in a bubble column reactor at ambient temperature. Also, CO₂ stripping experiments for all nanofluids were done at 60 and 70 °C. The influence of nanoparticles type, nanoparticle concentration, and the stability of nanoparticles were studied on both CO₂ absorption and stripping. The obtained results revealed that Fe₃O₄ nanoparticles at 0.01 wt.% concentration had the best influence on CO₂ absorption and it improved the CO₂ loading up to 36%. Also, CO₂ stripping experiments for all nanofluids were done at 60 and 70 °C. The desorption experiments illustrated that metal oxide nanoparticles can be more efficient in improving CO₂ desorption. In CO₂ desorption, the CuO nanoparticles at 0.05 wt.% had higher efficiency, and enhanced CO₂ concentration at outlet gas phase up to 44.2 vol.% at 70 °C. Finally, as an indication, the chemical stability of Fe₃O₄ NPs under optimum operational conditions was studied using XRD analysis and the result showed that the proposed operational condition did not have any negative effect on the chemical nature of Fe₃O₄ NPs.

Identification of Nano-Metal Oxides That Can Be Synthesized by Precipitation-Calcination Method Reacting Their Chloride Solutions with NaOH Solution and Their Application for Carbon Dioxide Capture from Air-A Thermodynamic Analysis

Several metal oxide nanoparticles (NPs) were already obtained by mixing NaOH solution with chloride solution of the corresponding metal to form metal hydroxide or oxide precipitates and wash-dry-calcine the latter. However, the complete list of metal oxide NPs is missing with which this technology works well. The aim of this study was to fill this knowledge gap and to provide a full list of possible metals for which this technology probably works well. Our methodology was chemical thermodynamics, analyzing solubilities of metal chlorides, metal oxides and metal hydroxides in water and also standard molar Gibbs energy changes accompanying the following: (i) the reaction between metal chlorides and NaOH; (ii) the dissociation reaction of metal hydroxides into metal oxide and water vapor and (iii) the reaction between metal oxides and gaseous carbon dioxide to form metal carbonates. The major result of this paper is that the following metal-oxide NPs can be produced by the above technology from the corresponding metal chlorides: Al₂O₃, BeO, CaO, CdO, CoO, CuO, FeO, Fe₂O₃, In₂O₃, La₂O₃, MgO, MnO, Nd₂O₃, NiO, Pr₂O₃, Sb₂O₃, Sm₂O₃, SnO, Y₂O₃ and ZnO. From the analysis of the literature, the following nine nano-oxides have been already obtained experimentally with this technology: CaO, CdO, Co₃O₄, CuO, Fe₂O₃, NiO, MgO, SnO₂ and ZnO (note: Co₃O₄ and SnO₂ were obtained under oxidizing conditions during calcination in air). Thus, it is predicted here that the following nano-oxides can be potentially synthesized with this technology in the future: Al₂O₃, BeO, In₂O₃, La₂O₃, MnO, Nd₂O₃, Pr₂O₃, Sb₂O₃, Sm₂O₃ and Y₂O₃. The secondary result is that among the above 20 nano-oxides, the following five nano-oxides are able to capture carbon dioxide from air at least down to 42 ppm residual CO₂-content, i.e., decreasing the current level of 420 ppm of CO₂ in the Earth's atmosphere at least tenfold: CaO, MnO, MgO, CdO, CoO. The tertiary result is that by mixing the AuCl₃ solution with NaOH solution, Au nano-particles will precipitate without forming Au-oxide NPs. The results are significant for the synthesis of metal nano-oxide particles and for capturing carbon dioxide from air.

Treatment of methyldiethanolamine wastewater using subcritical and supercritical water oxidation: parameters study, process optimization and degradation mechanism

In this examination, sub/supercritical water oxidation (SCWO) in a batch reactor was employed to degrade methyldiethanolamine (MDEA). To do so, the impact of different operating parameters including temperature (300-500 °C), time (0-100 s), initial MDEA concentration (1000-4000 ppm), oxidant coefficient (0.7-2), and pH (7.3-9.5) on MDEA degradation was separately and together investigated. Subsequently, the response surface method (RSM) was applied to optimize the operating condition of MDEA degradation. Based on the obtained results, a maximum amount of 97.4% MDEA degradation was achieved at the initial MDEA concentration of 1095 ppm in optimal condition (i.e., oxidant coefficient: 1.913, temperature: 472 °C and residence time: about 17 s). Furthermore, according to the HPLC analysis, there was a negligible amounts of formic acid (CH₂O₂) and nitrous acid (HNO₂) in the solution at the end of MDEA removal experiment. Eventually, the mechanism of MDEA degradation was acquired using molecular dynamics simulation (MDS), which had an acceptable coordination with the experimental results. In this way, the MDS results revealed that the presence of CH₂O₂ and HNO₂ compounds in the products was related to the degradation of MDEA and their production as by-products during the SCWO experiments.