Mohamed Naous; Ahmed Halfadji
Abstract
In this study, maghemite and magnetite nanoparticles were functionalized with cetyl trimethyl ammonium bromide(CTAB) surfactants, in order to obtain effective chromium removal from wastewater. X-ray diffractometry (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectrophotometry ...
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In this study, maghemite and magnetite nanoparticles were functionalized with cetyl trimethyl ammonium bromide(CTAB) surfactants, in order to obtain effective chromium removal from wastewater. X-ray diffractometry (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectrophotometry (FTIR) were used to characterize the functionalized nanoparticles. Various parameters, including pH, initial chromium concentration, added salt, and adsorbent dose, were evaluated in batch experiments to evaluate chromium removal efficiency. Adsorbent dose and chromium ions show a synergistic relationship with pH and the chemical and electrostatic interactions between cationic surfactant and negatively charged Cr(VI) ions. In both types of functionalized nanoparticles, Cr(VI) was efficiently removed at low pH values with CTAB@MNPs, but the pH increased negatively impacted the removal process. Additionally, Fe3O4@CTAB mainly adsorbs chromium chemically, reducing Cr(VI) to Cr(III), with less impact from competitive ions compared with γ-Fe2O3@CTAB.At pH = 2, adsorbent dose = 5 g/L, and initial chromium concentration = 1 mg/L, maghemite@CTAB achieved a high chromium removal efficiency of 95%. In contrast, magnetite@CTAB achieved a chromium removal efficiency of 95.77% in 7 minutes and 30 seconds at pH = 4, adsorbent dose = 12 g/L, and initial chromium concentration = 98 mg/L. Notably, magnetite outperformed maghemite by a factor of 100 in chromium elimination, which can be attributed to the presence of two adsorption mechanisms, chemical and physisorption, in magnetite nanoparticles, whereas maghemite only had physisorption.
Rouhollah Hedayati; Morteza Hosseini; Ghasem Najafpour; Hosein Attar
Abstract
Cobalamins are one of the most complicated cofactors produced by the microorganisms. Propionibacterium freudenreichii has to follow the anaerobic and aerobic conditions respectively during a course of batch fermentation, for the production of the biologically active form of cobalamins. Magnetite (Fe3O4) ...
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Cobalamins are one of the most complicated cofactors produced by the microorganisms. Propionibacterium freudenreichii has to follow the anaerobic and aerobic conditions respectively during a course of batch fermentation, for the production of the biologically active form of cobalamins. Magnetite (Fe3O4) nanoparticles can modify gas-liquid volumetric mass transfer coefficient in the fermentation system to create more efficient aeration step. Initially, the modified production of Fe3O4 nanoparticle through coprecipitation method was investigated, and the smallest size of nanoparticles optimized to 13.86 nm via Box-Behnken design of response to surface methodology (RSM). The optimum condition was at the synthesis temperature of 60 °C, reaction duration of 10 minutes, and the medium agitation speed of 700 rpm. Synthesized nanoparticles characterized by SEM images, PXRD and EDS analysis while EDS spectrum reflects 39.33% of Fe and 51.8% of oxygen atomic distribution, which confirms Fe3O4 nanoparticles synthesis. Magnetite nanoparticle suspension added to the fermentation medium to compare the effect of nanoparticles incorporation and dimethylbenzimidazole addition on the cobalamin production via Propionibacterium freudenreichii. NPs incorporation in the fermentation broth was able to increase cyanocobalamin production by 20%, while there was no incorporation of external DMBI in the medium. Finally, by the central composite design analysis, cyanocobalamin production from Propionibacterium freudenreichii fermentation was optimized to 1.548 mg.L-1. Oily sludge (as a new carbon source) of 4 %w/v, magnetite nanoparticles suspension of 7.5 %v/v, and the fermentation temperature of 37 °C caused to CCD optimum condition.
Maryam Ghasemi; Somaye Mashhadi; Javad Azimi-Amin
Abstract
In this study, we have synthesized a new Fe3O4/AC nanocomposite using low cost adsorbent by microwave assisted in situ co-precipitation technique that was used as an effective adsorbent for the removal of methylene blue (MB) using the Taguchi design method as an optimization strategy. The optimum parameters ...
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In this study, we have synthesized a new Fe3O4/AC nanocomposite using low cost adsorbent by microwave assisted in situ co-precipitation technique that was used as an effective adsorbent for the removal of methylene blue (MB) using the Taguchi design method as an optimization strategy. The optimum parameters are pH 7, Fe3O4/AC nanocomposite dose 0.03 g, contact time 30 min, initial concentration of MB 25 mg/L and temperature 298 K. The obtained results of ANOVA show that their percent contribution in descending order is pH (66.81%) > adsorbent dose (25.54%) > temperature (4.83%) > initial MB concentration (1.23%) > contact time (0.32%). The kinetic data were fitted to the pseudo-first-order, pseudo-second-order and intra-particle diffusion models and adsorption of MB dye followed pseudo-second-order kinetic. The obtained values of regression coefficient for Langmuir (0.98), Frendluich (0.93) and Dubinin–Radushkevich (0.94) showed that adsorption process fits to the Langmuir isotherm and the maximum adsorption capacity is 384.6 mg/g. Moreover, the thermodynamics studies suggested the spontaneous nature of adsorption process.