Improvement of Magnetic Saturation in Fe3O4@Y2O3:Eu3+ Nanocomposites Through the Manipulation of Eu3+ Activators

Fe3O4@Y2O3:Eu3+ nanocomposites and Y2O3:Eu3+ nanophosphors were synthesized using the hydrothermal method. Nanocomposites were analyzed using X-ray diffraction (XRD), Rietveld refinements, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, photoluminescence (PL), vibrating sample magnetometer (VSM), and high-resolution transmission electron microscopy (HRTEM). Nanocomposites exhibit superparamagnetic behavior that improves with Eu3+, resulting in increased magnetic saturation. In contrast to Y2O3:Eu3+ nanophosphors, the Fe3O4@Y2O3:Eu3+ nanocomposites display a distinctive characteristic whereby the photoluminescence intensity increases with a reduced concentration of Eu3+. The requirement of increasing the thickness of the Y2O3:Eu3+ outer layer to achieve improved light emission can be circumvented by solely manipulating the concentration of activators, without compromising the magnetic saturation of the nanocomposites. The luminescent and magnetic characteristics of Fe3O4@Y2O3:Eu3+ nanocomposites can be readily optimized using straightforward synthesis parameters, making them promising candidates for potential applications in theranostic medicine.

Recyclable magnetite-enhanced electromethanogenesis for biomethane production from wastewater

Improving the yield and methane content of biogas is of great concern for wastewater treatment by anaerobic digestion. Herein we developed a nanomagnetite-enhanced electromethanogenesis (EM_nano) process for the first time, the sustainable utilization of which improved the biomethane production rate from dairy wastewater. The maximum CH₄ production rate in the EM_nano process is 2.3 ± 0.3-fold higher than it is in the conventional methanogenesis (CM) process, and it is accompanied by an almost delay-free start-up. The technical-economic evaluation revealed that an 82.1 ± 5.0% greater net benefit was obtained in the third generation of the EM_nano process compared with the CM process. The improved methanogenesis was attributed to the formation of dense planktonic cell co-aggregates that are triggered by nanomagnetite, which facilitated the interspecies electron exchange during acetoclastic methanogenesis. Simultaneously, a cathode biofilm with high viability and catalytic activity was also formed in the EM_nano process that decreased the biofilm resistance and facilitated the electron transfer during electromethanogenesis. This study is a worthwhile attempt to combine recyclable conductive materials with an electromethanogenesis process for wastewater treatment, and it effectively achieves energy recovery with high stability and cost-effectiveness.

Combined effects of polyacrylamide and nanomagnetite amendment on soil and water quality, Khorasan Razavi, Iran

Nanotechnology is increasingly being used to remediate polluted soil and water. However, few studies are available assessing the potential of nanoparticles to bind surface particles, decrease erosion, and minimize the loading of water pollutants from agricultural surface discharge. To investigate this potential, we treated in situ field plots with two practical surface application levels of anionic polyacrylamide (PAM only) with and without nanomagnetite (PAM-NM), examined soil physical properties, and evaluated the impact of this amendment on contaminant sorption and soil erosion control. Polyacrylamide and PAM-NM treatments resulted in 32.2 and 151.9 fold reductions in Mn²⁺, 1.8 and 2.7 fold for PO₄^3--P, and 2.3 and 1.6 fold for NH₄⁺-N, respectively, compared to the control. Thus, we found that the combination of PAM and NM, had an important inhibitory effect on NH₄⁺-N and PO₄^3--P transport from soil-pollutants which can contribute substantially to the eutrophication of surface water bodies. Additionally, since the treatment, especially at a high concentration of NM, was effective at reducing Mn²⁺concentrations in the runoff water, the combination of PAM and NM may be important for mitigating potential risks associated with Mn²⁺ toxicity. Average sediment contents in the runoff monitored during the rainfall simulation were reduced by 3.6 and 4.2 fold for the low and high concentration PAM-NM treatments when compared to a control. This treatment was only slightly less effective than the PAM-only applications (4.9 and 5.9 fold, respectively). We report similar findings for turbidity of the runoff (2.6-3.3 fold for PAM only and 1.8-2.3 fold for PAM-NM) which was caused by the effects of both PAM and NM on the binding of surface particles corresponding to an increase in aggregate size and stability. Findings from this field-based study show that PAM-modified NM adsorbents can be used to both inhibit erosion and control contaminant transport.

Selected Fe and Mn (nano)oxides as perspective amendments for the stabilization of As in contaminated soils

An amorphous Mn oxide (AMO), nanomaghemite, and nanomagnetite were used as potential amendments reducing the mobility of As in three contrasting contaminated soils differing in origin of As contamination. Adsorption experiments and XPS analyses combined with incubation batch experiments and pH-static leaching tests were used. The AMO showed excellent adsorption capacity for As(V) reaching a maximum of 1.79 mmol g(-1) at pH 7 and 8. Interestingly, the adsorption capacity in this case decreases with decreasing pH, probably as a result of AMO dissolution at lower pH values. Chemical sorption of As(V) onto AMO was further confirmed with XPS. Both Fe nano-oxides proved the highest adsorption capacity at pH 4 reaching 11 mg g(-1) of adsorbed As(V). The AMO was also the most efficient amendment for decreasing As concentrations in soil solutions during 8 weeks of incubation. Additionally, pH-static leaching tests were performed at pH 4, 5, 6, 7, and natural pH (not adjusted) and AMO again proved the highest ability to decrease As content in leachate. On the other hand, strong dissolution of this amendment at lower pH values (especially pH 4) was observed. For that reason, AMO appears as a promising stabilizing agent for As, especially in neutral, alkaline, or slightly acidic soils, where As(V) species are expected to be more mobile.