Direct 3D printing of zero valent iron@polylactic acid catalyst for tetracycline degradation with magnetically inducing active persulfate.

Catalyst stability has become a challenging issue for advanced oxidation processes (AOPs). Herein, we report an alternative method based on 3D printing technology to obtain zero-valent iron polylactic acid prototypes (ZVI@PLA) in a single step and without post etching treatment. ZVI@PLA was used to activate persulfate (PS) for the removal of Tetracycline (TC) in recirculating mode under two different heating methodologies, thermal bath and contactless heating promoted by magnetic induction (MIH). The effect of both heating methodologies was systematically analysed by comparing the kinetic constant of the degradation processes. It was demonstrated that the non-contact heating of ZVI by MIH reactivates the surface of the catalyst, renewing the surface iron content exposed to the pollutant solution, which makes the ZVI@PLA catalyst reusable up to 10 cycles with no efficiency reduction. In contrast, by using a conventional thermal bath, the kinetic constant gradually decreases over the 10 cycles, because of the superficial iron consumption, being the kinetic constant 5 times lower in the 10th run compared to MIH experiment. X-ray diffraction and Mössbauer spectroscopy confirmed the presence of metallic iron embedded in the ZVI@PLA prototype, whose crystalline structure remained unchanged for 10th cycles of MIH. Moreover, it was proven that with no contact heating technology at low magnetic fields (12.2 mT), the solution temperature does not increase, but only the surface of the catalyst does. Under these superficial heated conditions, kinetic rate is increased up to 0.016 min-1 compared to the value of 0.0086 min-1 obtained for conventional heating at 20 °C. This increase is explained not only by PS activation by iron leaching but also by the contribution of ZVI in the heterogeneous activation of persulfate.

Electrochemical Synthesis and Magnetic Properties of MFe2O4 (M = Fe, Mn, Co, Ni) Nanoparticles for Potential Biomedical Applications.

In this study, we evaluate the magnetic properties and cytotoxic effect of magnetic nanoparticles (MNPs) based on magnetite and Mn, Co and Ni ferrites, obtained by electrochemical synthesis. These nanoparticles have almost spherical shape and an mode size of 9±1 nm. The electrochemical synthesis produces a single crystallographic phase with a spinel-like structure in all cases. Magnetization saturation at room temperature varies with the composition of the ferrites from MS (Fe3O4) > MS (MnFe2O4) > MS (CoFe2O4) > MS (NiFe2O4). Ferrite MNPs present low magnetic remanence indicating a superparamagnetic-like response at room temperature. However, the different values of magnetic anisotropy and size produce variations in the values of coercivity and susceptibility of the ferrite MNPs. The cytotoxicity of the different ferrites was evaluated by internalizing MNP in HeLa cancer cells. Although magnetite and Mn ferrite present low toxicity for all the concentrations studied, significant cytotoxic effect were observed when incubating the cells with high concentration of Co and Ni ferrites.

Synthesis and characterization of CoFe2O4 ferrite nanoparticles obtained by an electrochemical method.

Uniform size cobalt ferrite nanoparticles have been synthesized in one step using an electrochemical technique. Synthesis parameters such as the current density, temperature and stirring were optimized to produce pure cobalt ferrite. The nanoparticles have been investigated by means of magnetic measurements, Mössbauer spectroscopy, x-ray powder diffraction and transmission electron microscopy. The average size of the electrosynthesized samples was controlled by the synthesis parameters and this showed a rather narrow size distribution. The x-ray analysis shows that the CoFe(2)O(4) obtained presents a totally inverse spinel structure. The magnetic properties of the stoichiometric nanoparticles show ferromagnetic behavior at room temperature with a coercivity up to 6386 Oe and a saturation magnetization of 85 emu g(-1).

Electrodeposition of polythiophene assisted by sonochemistry and incorporation of fluorophores in the polymeric matrix.

This work studies the effect of an ultrasonic field of 530 kHz frequency on the electrodeposition of polythiophene in an acetonitrile solution using lithium perchlorate as background electrolyte. The results obtained show an increase in the polymer mass transfer produced and a more compact and homogenous morphology of the films yielded by sonoelectrochemistry. Electrodeposition of the polymer was also carried out in the presence of the fluorophores Harmane (1-methyl-9H-pyrido[3,4-b]indole) or BCCM (9H-pyrido[3,4-b]indole-3-carboxylic acid methyl ester). Confocal microscopy measurements performed on the films synthesised in the presence of these compounds showed that the latter are embedded in the polymer when it is sonoelectrogenerated at a potential of 2.2, 2.5 or 2.8 V. Films generated in the absence of ultrasound showed no fluorescence.