To improve the photocatalytic performance of Mn 0.6 Zn 0.4 Fe 2 O 4 (MZFO) and ZnIn 2 S 4 (ZIS) for organic pollutants, the p-n MZFO@ZIS heterojunctions with different weight percentage (10 ~ 40%) of MZFO are constructed from spent batteries and added indium ion via a green bioleaching and hydrothermal method. Structural, optical, and photocatalytic properties for the heterojunctions are investigated systematically by XRD, FT-IR, SEM–EDX, TEM, BET, VB-XPS, UV–vis DRS, PL, etc. The results confirm that p–n junction significantly improves the visible light adsorption and the separation efficiency of photogenerated carriers. Specifically, MZFO-25%@ZIS shows the highest photodegradation performance toward Congo red (CR), and its reactive kinetic constant is about 9.6, 7.8, and 7.0 times higher than that of P25 TiO 2 , MZFO, and ZIS, respectively, and MZFO-25%@ZIS still possesses a high reusability and simple magnetic separation after 5 cycles of reuse. The radical trapping experiments and electronic paramagnetic resonance (EPR) tests show that · O 2 − , · OH, and h + are the most important active substance for degrading CR. The pathways for the CR degradation are further proposed based on the intermediate analysis. DFT + U calculations confirm that the high charge density of Zn–O, Fe–O, and Zn–S bonds in the MZFO and ZIS molecules provides the electrons for the sufficient production of free radicals. This work also provides a novel high value-added strategy for the green utilization of spent batteries.
Songhan Hu,Mingyuan Ma,Rui Liang,Xinxin Xu,Kai Wang,Qiang Wang
Ferrite nanoparticles are widely used in magnetic resonance imaging as T 2 contrast agent particles. In this study, we propose to utilize Mn and Zn doping into ferrite to prepare Mn-Zn doped ferrite and use it as T 2 contrast agent core particles. Also, we aim to clarify the relationship between the Mn-Zn doped ferrite nanoparticles orientation and ratio of surfactant oleic acid to oleylamine as well as different solvents. The results show that high temperature thermal decomposition method can successfully prepare uniformly doped Mn-Zn ferrite nanoparticles (Mn 0.6 Zn 0.4 Fe 2 O 4 ). And the ratio of surfactant oleic acid to oleylamine has a significant impact on the orientation of Mn 0.6 Zn 0.4 Fe 2 O 4 nanoparticles growth. As the ratio of oleic acid increases, the Mn 0.6 Zn 0.4 Fe 2 O 4 nanoparticles gradually change from growing along the [110] crystal direction to growing randomly with irregular orientation, the nanoparticles morphology and size tend from rhombohedral (37 nm) to spherical (9.84 nm). In terms of solvent, benzyl ether, 1-octadecene and hexadecylamine have no influence on the action of surfactants. The Mn 0.6 Zn 0.4 Fe 2 O 4 nanoparticles in the three solvents are grown randomly without any obvious orientation changes. All nanoparticles are spherical nanoparticles, indicating that the choice of the three solvents has little effect on the orientation of the nanoparticles. However, the three different solvents affect the crystallinity of Mn 0.6 Zn 0.4 Fe 2 O 4 nanoparticles. Nanoparticles prepared with diphenyl ether as solvent show a higher crystallinity compared to those synthesized with 1-octadecene and hexadecylamine as solvents. In contrast performance, under the optimal surfactant ratio (11:1) and solvent selection (dibenzyl ether), the transverse relaxation rate r 2 value of Mn-Zn ferrite nanoparticles reach 266.24 mM −1 s −1 , while the longitudinal relaxation rate r 1 value is 10.45 mM −1 s −1 . The r 2 / r 1 ratio is significantly larger than 10, indicating that the nanoparticles with random growth orientation serve as excellent T 2 weighted contrast agents.
A facile chemical method through hydrothermal synthesis coupled with in situ polymerization to prepare the Mn 0.6 Zn 0.4 Fe 2 O 4 -carbon nanotubes (CNTs)/polyaniline (PANI) nanocomposites has been reported in this paper. The structure of samples has been characterized by the Fourier transform infrared and X-ray diffraction. The shape and size of samples have been observed by the scanning electron microscopy and transmission electron microscopy . The conductive properties of the Mn 0.6 Zn 0.4 Fe 2 O 4 -CNTs/PANI nanocomposites have been tested by a four-probe conductivity tester at room temperature . And the magnetic properties are measured by a vibrating sample magnetometer . When the mass ratio of the Mn 0.6 Zn 0.4 Fe 2 O 4 -CNTs to aniline ( m (Mn 0.6 Zn 0.4 Fe 2 O 4 -CNTs)/ m (An)) is 0.15, the M s , M r and H c achieves 15.44 emu/g, 5.06 emu/g and 308.68 Oe, respectively. At the same time the probable formation mechanism of nanocomposites is also investigated based on the experimental results.
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