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The chemical recycling of used motor oil via catalytic cracking to convert it into secondary diesel-like fuels is a sustainable and technically attractive solution for managing environmental concerns associated with traditional disposal. In this context, this study was conducted to screen basic and acidic-aluminum silicate catalysts doped with different metals, including Mg, Zn, Cu, and Ni. The catalysts were thoroughly characterized using various techniques such as N2 adsorption–desorption isotherms, FT-IR spectroscopy, and TG analysis. The liquid and gaseous products were identified using GC, and their characteristics were compared with acceptable ranges from ASTM characterization methods for diesel fuel. The results showed that metal doping improved the performance of the catalysts, resulting in higher conversion rates of up to 65%, compared to thermal (15%) and aluminum silicates (≈20%). Among all catalysts, basic aluminum silicates doped with Ni showed the best catalytic performance, with conversions and yields three times higher than aluminum silicate catalysts. These findings significantly contribute to developing efficient and eco-friendly processes for the chemical recycling of used motor oil. This study highlights the potential of basic aluminum silicates doped with Ni as a promising catalyst for catalytic cracking and encourages further research in this area.

Elucidation of reaction mechanisms in forming nanostructures is relevant to obtain robust and affordable protocols that can lead to materials with enhanced properties and good reproducibility. Here, the formation of magnetic iron oxide monocrystalline nanoflowers in polyol solvents using N-methyldiethanolamine (NMDEA) as co-solvent has been shown to occur through a non-classical crystallization pathway. This pathway involves intermediate mesocrystals that, in addition, can be transformed into large single colloidal nanocrystals. Interestingly, the crossover of a non-classical crystallization pathway to a classical crystallization pathway can be induced by merely changing the NMDEA concentration. The key is the stability of a green rust-like intermediate complex that modulates the nucleation rate and growth of magnetite nanocrystals. The crossover separates two crystallization domains (classical and non-classical) and three basic configurations (mesocrystals, large and small colloidal nanocrystals). The above finding facilitated the synthesis of magnetic materials with different configurations to suit various engineering applications. Consequently, the effect of the single and multicore configurations of magnetic iron oxide on the biomedical (magnetic hyperthermia and enzyme immobilization) and catalytic activity (Fenton-like reactions and photo-Fenton-like processes driven by visible light irradiation) has been experimentally demonstrated.

A crucial challenge to face in the treatment of biofilm-associated infection is the ability of bacteria to develop resistance to traditional antimicrobial therapies based on the administration of antibiotics alone. This study aims to apply magnetic hyperthermia together with controlled antibiotic delivery from a unique magnetic-responsive nanocarrier for a combination therapy against biofilm. The design of the nanosystem is based on antibiotic-loaded mesoporous silica nanoparticles (MSNs) externally functionalized with a thermo-responsive polymer capping layer, and decorated in the outermost surface with superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs are able to generate heat upon application of an alternating magnetic field (AMF), reaching the temperature needed to induce a change in the polymer conformation from linear to globular, therefore triggering pore uncapping and the antibiotic cargo release. The microbiological assays indicated that exposure of E. coli biofilms to 200 µg/mL of the nanosystem and the application of an AMF (202 kHz, 30 mT) decreased the number of viable bacteria by 4 log10 units compared with the control. The results of the present study show that combined hyperthermia and antibiotic treatment is a promising approach for the effective management of biofilm-associated infections., This research was funded by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 814410 (GIOTTO), the European Research Council under ERC-2015-AdG Proposal No. 694160 (VERDI) and the Ministerio de Ciencia e Innovación grant number PID2020-117091RB-I00. E.Á. thanks the financial support by FPI fellowship No. BES-2016-078767 from the Ministerio de Ciencia e Innovación.

Advanced oxidation processes constitute a promising alternative for the treatment of wastewater containing organic pollutants. Still, the lack of cost-effective processes has hampered the widespread use of these methodologies. Iron oxide magnetic nanoparticles stand as a great alternative since they can be engineered by different reproducible and scalable methods. The present study consists of the synthesis of single-core and multicore magnetic iron oxide nanoparticles by the microwave-assisted polyol method and their use as self-heating catalysts for the degradation of an anionic (acid orange 8) and a cationic dye (methylene blue). Decolorization of these dyes was successfully improved by subjecting the catalyst to an alternating magnetic field (AMF, 16 kA/m, 200 kHz). The sudden temperature increase at the surface of the catalyst led to an intensification of 10% in the decolorization yields using 1 g/L of catalyst, 0.3 M H2O2 and 500 ppm of dye. Full decolorization was achieved at 90 °C, but iron leaching (40 ppm) was detected at this temperature leading to a homogeneous Fenton process. Multicore nanoparticles showed higher degradation rates and 100% efficiencies in four reusability cycles under the AMF. The improvement of this process with AMF is a step forward into more sustainable remediation techniques.

[EN] Industrial effluents contain a wide range of organic pollutants that present harmful effects on the environment and deprived communities with no access to clean water. As this organic matter is resistant to conventional treatments, Advanced Oxidation Processes (AOPs) have emerged as a suitable option to counteract these envi-ronmental challenges. Engineered iron oxide nanoparticles have been widely tested in AOPs catalysis, but their full potential as magnetic induction self-heating catalysts has not been studied yet on real and highly contam-inated industrial wastewaters. In this study we have designed a self-heating catalyst with a finely tuned structure of small cores (10 nm) aggregates to develop multicore particles (40 nm) with high magnetic moment and high colloidal stability. This nanocatalyst, that can be separated by magnetic harvesting, is able to increase reaction temperatures (up to 90 ◦C at 1 mg/mL suspension in 5 min) under the action of alternating magnetic fields. This efficient heating was tested in the degradation of a model compound (methyl orange) and real wastewaters, such as leachate from a solid landfill (LIX) and colored wastewater from a textile industry (TIW). It was possible to increase reaction rates leading to a reduction of the chemical oxygen demand of 50 and 90%, for TIW and LIX. These high removal and degradation ability of the magnetic nanocatalyst was sustained with the formation of strong reactive oxygen species by a Fenton-like mechanism as proved by electron paramagnetic resonance. These findings represent an important advance for the industrial implementation of a scalable, non-toxic, self-heating catalysts that can certainly enhance AOP for wastewater treatment in a more sustainable and efficient way., This research was funded by the Spanish Ministry of Economy and Competitiveness under grant MAT2017-88148-R (AEI/FEDER, UE) and Consejo Superior de Invetigaciones Científícas PIE- 201960E062. This study was also supported by the USFQ Collaboration Grant 2018 Nº 11197 and the USFQ PoliGrants 2018–2019 Nº 12501. E.W., E.L.Jr and R.D.Z. acknowledge Argentine governmental agency ANPCyT (Project No. PICT-2016-0288 and PICT-2018-02565) and UNCuyo (Project No.06/ C527 and 06/C528) for the financial support.

Magnetic catalysts containing Fe and Ca synthesized in the presence of pectin have demonstrated to be highly efficient in the transesterification reaction for biodiesel production. Catalysts were prepared by the co-precipitation method under a N2 atmosphere with Na2CO3 from a mixture of FeSO4, FeCl3, Ca(NO3)2, and pectin followed by calcination at 550 ˚C/6h. The influence of the Fe:Ca molar ratio in the catalytic activity on the transesterification reaction with methanol was evaluated in the presence or absence of pectin. The most efficient catalyst was prepared in the presence of pectin with a Fe:Ca molar ratio of 4.5:2 (FCP2), and the best experimental conditions were at 3 % wt catalyst, 14:1 of methanol: soybean oil molar ration and 7.5 h of reaction time, which resulted in a methyl ester yield of 96.3%. It was shown that the presence of the biopolymer in the synthesis enhances the catalytic activity of the material from 20% to 99% of biodiesel production. All materials were fully characterized by TEM, FTIR, TGA, BET, XRD and DC magnetometry. It was found that catalysts present high surface areas with a nanometer size (∼20 nm), giving rise to a superparamagnetic state with a magnetic saturation high enough for separation by means of a magnet. In contrast, catalysts prepared in the absence of pectin demonstrated poor performance in the transesterification reaction of biodiesel in the optimized experimental conditions. The magnetic properties and the biopolymer role are discussed.

Lateral flow assays may be used by minimally trained personnel for fast and inexpensive bioanalyses in decentralized non-exigent environments. Their extension to a broader catalog of applications depends on improvements in their quantification and their sensitivity. We report a strategy that combines nanomagnetic tagging of the analyte of interest with radiofrequency inductive sensing, easy to achieve in friendly and portable format. To optimize nanotag performance, we investigated the influences of their magnetic core size and agglomeration. Iron oxide nanoparticles, with sizes from 5 to 23 nm, were synthesized by thermal decomposition and then coated with dimercaptosuccinic acid and functionalized with neutravidin protein. We tested the system by immobilizing biotin in lateral flow membrane strips. When a sample containing the particles flows along the membrane, the biotin captures the neutravidin together with the magnetic nanotags, which are detected by the inductive sensor. The optimal nanotag core size is the critical threshold for superparamagnetic behavior, which maximizes both the initial magnetic permeability and the saturation magnetization. Controlled agglomeration of the nanotags increases the magnetic mass captured in the test line and further amplifies the signal.

[EN] The search for more efficient, scalable, reproducible and standardized synthesis methods able to control particle size and crystallinity is still a challenge in nanotechnology. The one-pot microwave-assisted polyol process has been optimized for the synthesis of well-defined ferrite nanoparticles. Highly uniform and crystalline γ-Fe2O3, CoFe2O4 and ZnFe2O4 nanoparticles, with diameters below 14 nm have been prepared by an easy and reproducible one-pot microwave-assisted heating procedure in a polyol medium. A pure single phase and cubic spinel structure were confirmed by powder X-ray diffraction and Raman spectroscopy. Depending on the metal precursors, nanoparticles display magnetic features from superparamagnetic behaviour (Fe- A nd Zn-ferrites) to ferrimagnetism (Co ferrite) at room temperature. The iron oxidation state of 3+ and its short-range order coordination were studied by XAS (X-ray absorption spectroscopy). External field Mössbauer spectra, recorded at low temperature, confirmed the ferrimagnetic order with a Fe3+ and M2+ partial cationic distribution within both the A and B sites in zinc and cobalt ferrite, respectively. According to these results, the ferrite stoichiometry was (Zn0.70Fe0.30)[Zn0.30Fe1.70]O4 and (Co0.28Fe0.72)[Co0.72Fe1.28]O4. This journal is, This research was funded by the Spanish Ministry of Economy and Competitiveness under grants MAT2017-88148-R, MAT2017-86540-C4-1-R, RTI2018-095303-A-C52, and PGC2018-095642-B-I00. E. M. acknowledges financial support from the Juan de la Cierva Formación (FJCI-2015-23702) and to Comunidad de Madrid – Jóvenes Doctores project (SI1-PJI-2019-00366). L. G. acknowledges financial support from the Ramón y Cajal program (RYC-2014-15512). The authors would like to acknowledge the use of the Advanced Microscopy Laboratory (INA-Universidad de Zaragoza). A. S. and A. E. acknowledge financial support from the Comunidad de Madrid for the ‘‘Atracción de Talento Investigador’’ contracts (No. 2017-T2/IND5395 and 2018-T1/IND10058). A. E. is also grateful to the 2018/NMT-4321 and SEV-2016-0686 projects. The European Synchrotron (ESRF),Ministerio Español de Ciencia, Innovación y Universidades (MCIU) and Consejo Superior de Investigaciones Cientificas (CSIC) are acknowledged for the provision of synchrotron radiation facilities. We also thank the BM25- SpLine staff for the technical support beyond their duties.

The effectiveness of the adsorption of organic compounds in produced water with different residual biomass sources has been investigated. Adsorption capacities have been analyzed with palm shell, orange peel, banana peel, passion fruit peel, cocoa bean and sawdust; and compared to the commercial adsorbent walnut shell. All adsorbents undergo a pretreatment, prior to the adsorption, consisting of washing, drying and thermal conditioning. For the investigation of the adsorption capacity of the different adsorbents, synthetic produced water has been prepared with different organic compounds and expressed as the concentration of Chemical Oxygen Demand (COD). The adsorption capacities of the different adsorbents are expressed as the removal percentage of oxidizable contaminants, presented as COD concentration in the synthetic produced water. The adsorption analyses with the synthetic produced water in a batch experimental procedure show that only palm shell and sawdust actually adsorb the organic compounds in the synthetic water. Three isotherm models were considered: Langmuir, Freundlich and Temkin. Among these three models, the Langmuir model describes best the experimental data for walnut shell, palm shell and sawdust. The maximum adsorption capacity was determined and sawdust presented a maximum value of contaminant removal of 33 mg/g of dry adsorbent, while walnut shell and palm shell presented a contaminant removal of 4.9 and 5.6 mg/g of dry adsorbent, respectively. Kinetics results were best described by pseudo-first order potential law model for the experiments carried out with the walnut shell and palm shell. Breakthrough experiments show that palm shell will saturate earlier than walnut shell.

Solid phase extraction using magnetic nanoparticles has represented a leap forward in terms of the improvement of water quality, preventing the contamination of industrial effluents from discharge in a more efficient and affordable way. In the present work, superparamagnetic iron oxide nanoparticles (MNP) with different surface charges are tested as nanosorbents for the removal of chromium(VI) in aqueous solution. Uniform magnetic nanoparticles (~12 nm) were synthesized by a microwave polyol-mediated method, and tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) were grafted onto their surface, providing a variation in the surface charge. The adsorptive process of chromium was evaluated as a function of the pH, the initial concentration of chromium and contact time. Kinetic studies were best described by a pseudo-second order model in all cases. TEOS@MNP barely removed the chromium from the media, while non-grafted particles and APTES@TEOS@MNP followed the Langmuir model, with maximum adsorption capacities of 15 and 35 mgCr/g, respectively. The chromium adsorption capacities abruptly increased when the surface became positively charged as the species coexisting at the experimental pH are negatively charged. Furthermore, these particles have proven to be highly efficient in water remediation due their 100% reusability after more than six consecutive adsorption/desorption cycles., This research was funded by the Spanish Ministry of Economy and Competitiveness under grants MAT2017-88148-R, PGC2018-095642-B-I00 and Juan de la Cierva Formación FJCI-2015-23702.

[EN] The present study describes the preparation of 50.3 nm superparamagnetic nanosorbents with high surface area for the adsorptive removal of lead and methyl orange from water. This material is based on the surface modification of iron oxide superparamagnetic nanoparticles with a double-shell coating of mesoporous silica whose porosity was increased up to 570 m/g by the addition of a porogenic material and its calcination. The adsorptive performance of the nanosorbent was evaluated as a function of several parameters (e.g. solution pH, pollutant initial concentration, and contact time), concluding that pHs around 5 are needed to avoid precipitation of Pb as Pb(OH) and the equilibrium adsorption capacity is reached after 2 h in all cases. The experimental data on the adsorption capacity of lead and methyl orange onto the nanosorbent were fit to a pseudo-second order kinetic model and Langmuir isotherm model. The maximum adsorption capacity value increases from 35 up to 50 mg/g for lead removal with increasing nanosorbent surface area. Contrary, for methyl orange the maximum adsorption goes up to 240 mg/g, indicating a larger nanosorbent surface affinity for the organic matter that is able to diffuse through the silica pores as probed by the intraparticle diffusion model. In addition, we found an good reusability (100% recovering after 4 sorption/desorption cycles for methyl orange removal), which makes of this magnetic nanosorbent suitable for remediation technologies., This research was funded by the Spanish Ministry of Economy and Competitiveness under grants MAT2017-88148-R, PIE-201760E007, MAT2016-80394-R, PGC2018-095642-B-I00 and Juan de la Cierva Formación FJCI-2015-23702