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This study deals with the removal of cationic dyes from the simulated wastewater using Fe 3 O 4 nanoparticles loaded activated carbon. Fe 3 O 4 @AC nanoparticles were synthesised using co-precipitation methods. The Fe 3 O 4 @AC nanoparticles (nps) were characterised using different techniques and data revealed that the synthesised nanoparticles were 6-16 nm in diameter. pHpzc of Fe 3 O 4 @AC nanoparticles was 7.8. BET surface area of Fe 3 O 4 @AC nps was found to be 129.6 m 2 /g by single point method and 1061.9 m 2 /g by multipoint method. Adsorption experiments were performed to optimize the effect of process conditions such as pH of solution, nanoparticles dose, temperature, concentration of dye and contact time on contaminant removal. The maximum uptake capacity of Fe 3 O 4 @AC was found to be 138 and 166.6 mg/g for methylene blue and brilliant green dyes, respectively. In order to assess dye adsorption behaviour, adsorption isotherm models viz., Langmuir, Freundlich and Temkin were applied to the data. Langmuir isotherm best fitted [R 2  = 0.993 (MB) and R 2  = 0.920 (BG)] to the experimental data of both the dyes. Further, Pseudo-second order rate equation fitted better to the experimental data. Reuse potential of the nanoparticles was also investigated for the removal of both the dyes and it is inferred from the data that the synthesised nanoadsorbent has promising reuse potential, therefore can be used for several cycles., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This study focused on the synthesis and characterization of novel magnetic iron oxide nanoparticles loaded sawdust carbon (Fe 3 O 4 /SC) and EDTA modified Fe 3 O 4 /SC (EDTA@Fe 3 O 4 /SC) nanocomposites (ncs) by low cost biogenic green synthesis approach and their application for Cd (II) removal from aqueous medium in batch mode. In isotherm studies, Langmuir and Freundlich models are best fitted to Cd (II) removal data. Langmuir maximum adsorption capacity of EDTA@Fe 3 O 4 /SC ncs was found to be 63.3, 22.4 and 25 mg/g that is greater than maximum adsorption capacity of Fe 3 O 4 /SC ncs that is 51, 18.9 and 15 mg/g at the adsorbent doses of 0.4, 1.2 and 2.0 g/L, respectively. Cd (II) adsorption rate is well explained by Pseudo-second order model. Cd (II) adsorption process is spontaneous and endothermic in nature expressed by Enthalpy, Entropy and Free Energy change. The results of regeneration studies showed that EDTA modified Fe 3 O 4 /SC ncs is promising, low cost and eco-friendly for heavy metal adsorption., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

CoxFe3-xO4-based (x=0.05–1.6) nanoparticles prepared by combustion reaction were investigated using x-ray diffraction, Raman spectroscopy, and Mössbauer spectroscopy. The Mössbauer data revealed Co2+ in both tetrahedral (site A) and octahedral (site B) sites of the cubic ferrite structure. For x≤0.4 the experimental data indicated the synthesis of a core-shell structure, with hematite as the shell and cobalt ferrite as the core of the nanoparticle. Differences in crystalline structure between the two phases support the evidences we found of a highly stressed core-shell interface, leading to symmetry reduction of the tetrahedral and octahedral sites. [ABSTRACT FROM AUTHOR]

In this study the synthesis of very small magnetite nanoparticles is reported. Analysis of the (311) X-ray diffraction line indicates nanoparticle with 2.2 nm average diameter. The as-synthesized nanosized magnetite sample was submitted to a chemical oxidation process for conversion to maghemite. However, the yielding of the chemical oxidation process, as indicated by the analysis of the Mössbauer data, was about 20%. This finding indicates a strong size-dependence of the oxidation process, reducing the yielding of the chemical process used as the nanoparticle size reduces down to extremely low values. [ABSTRACT FROM AUTHOR]

Mössbauer and magnetic characterization of polymer-dispersed γ-Fe2O3 nanoparticles treated under different chemical processes are reported in this work. X-ray powder diffraction analysis provides a mean particle size of D ~ 8.0 nm. Whereas Mössbauer spectroscopy data suggest the presence of only Fe3 + ions, magnetization measurements indicate the occurrence of a freezing phenomenon in agreement with the thermal evolution of Mössbauer spectra. A core–shell model was used to determine a magnetically disordered layer (shell) of d ~ 1.0 nm covering a region of collinear magnetic moments (core). The chemical treatments with H2O2 and Na2S2O8 modify notoriously the magnetic response of the polymer-dispersed nanoparticles. [ABSTRACT FROM AUTHOR]

The chemical co-precipitation process was used to synthesize (in situ) spherical iron-oxide nanoparticle in sulfonated styrene-divinylbenzene polymeric template. X-ray diffraction technique supports the magnetite phase formation with a mean particle diameter of about 19 nm. The analysis of Mössbauer spectra is consistent with two magnetic splitting patterns assigned to A- and B-iron sites of magnetite, with no visible magnetic relaxation effect even at 297 K. Considering the different experimental time window between Mössbauer spectroscopy and DC magnetization, the results obtained from both techniques are in very good agreement. Magnetic data suggest hosting magnetite nanoparticles interacting antiferromagnetically. [ABSTRACT FROM AUTHOR]

Biocompatible magnetic nanocomposite consisting of bovine serum albumin-based nanosized spheres hosting maghemite nanoparticle has been investigated by Mössbauer spectroscopy, X-ray diffraction, and electron microscopy. The 77 K Mössbauer spectrum was curve-fitted to two sextets whereas one doublet plus one sextet was used to fit the 300 K Mössbauer spectrum. The temperature evolution of the hyperfine parameters indicated two Mössbauer components; one associated to the core maghemite nanoparticle and the other associated to the maghemite surface shell. The 300 K quadrupole splitting value indicated strong interaction between the surface of the maghemite nanoparticle and the hosting template. [ABSTRACT FROM AUTHOR]

Mössbauer spectroscopy was used in this study to investigate magnetite nanoparticles, obtained by spray pyrolysis and thermal treatment under H2 reduction atmosphere. Room temperature XRD data indicate the formation of magnetite phase and a second phase (metallic iron) which amount increases as the time of reduction under H2 is increased. While room temperature Mössbauer data confirm the formation of the cubic phase of magnetite and the occurrence of metallic iron phase, the more complex features of 77 K-Mössbauer spectra suggest the occurrence of electronic localization favored by the different crystalline phase of magnetite at low temperatures which transition to the lower symmetry structure should occur at T ∼120 K (Verwey transition). [ABSTRACT FROM AUTHOR]

Mössbauer spectroscopy was used in this study to investigate magnetite-based nanocomposites, using mesoporous styrene-divinylbenzene (Sty-DVB) microspheres as the hosting template. The magnetite content was increased in the polymeric template by performing several in situ chemical reactions (one to six cycles) in the hosting material. We found the Mössbauer linewidth associated to site-A increasing with the relative increase of iron in site-A. The Mössbauer linewidth associated to site-B decreases with the relative decrease of iron in site-B. We explain our findings by assuming local change in the homogeneity associated to changes in the relative iron population in sites A and B. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy were used in the characterization of a nanocomposite containing magnetic nanoparticles dispersed in a glycolic acid-based template. Maghemite nanoparticles were identified as the iron oxide phase dispersed in the polymeric template. From the low-temperature Mössbauer data the amount of the iron-based, non-magnetic material at the nanoparticle surface was estimated as roughly one monolayer in thickness. [ABSTRACT FROM AUTHOR]

CoxFe3-xO4-based (x=0.05–1.6) nanoparticles prepared by combustion reaction were investigated using x-ray diffraction, Raman spectroscopy, and Mössbauer spectroscopy. The Mössbauer data revealed Co2+ in both tetrahedral (site A) and octahedral (site B) sites of the cubic ferrite structure. For x≤0.4 the experimental data indicated the synthesis of a core-shell structure, with hematite as the shell and cobalt ferrite as the core of the nanoparticle. Differences in crystalline structure between the two phases support the evidences we found of a highly stressed core-shell interface, leading to symmetry reduction of the tetrahedral and octahedral sites. [ABSTRACT FROM AUTHOR]