When exposed to an alternating magnetic field, superparamagnetic nanoparticles can elicit the required hyperthermic effect while also being excellent magnetic resonance imaging (MRI) contrast agents. Their main drawback is that they diffuse out of the area of interest in one or two days, thus preventing a continuous application during the typical several-cycle multi-week treatment. To solve this issue, our aim was to synthesise an implantable, biodegradable membrane infused with magnetite that enabled long-term treatment while having adequate MRI contrast and hyperthermic capabilities. To immobilise the nanoparticles inside the scaffold, they were synthesised inside hydrogel fibres. First, polysuccinimide (PSI) fibres were produced by electrospinning and crosslinked, and then, magnetitc iron oxide nanoparticles (MIONs) were synthesised inside and in-between the fibres of the hydrogel membranes with the well-known co-precipitation method. The attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) investigation proved the success of the chemical synthesis and the presence of iron oxide, and the superconducting quantum interference device (SQUID) study revealed their superparamagnetic property. The magnetic hyperthermia efficiency of the samples was significant. The given alternating current (AC) magnetic field could induce a temperature rise of 5 °C (from 37 °C to 42 °C) in less than 2 min even for five quick heat-cool cycles or for five consecutive days without considerable heat generation loss in the samples. Short-term (1 day and 7 day) biocompatibility, biodegradability and MRI contrast capability were investigated in vivo on Wistar rats. The results showed excellent MRI contrast and minimal acute inflammation.

Absorbed power of nanoparticles during magnetic hyperthermia can be well determined from changes in the quality factor ( Q factor) of a resonator in which the radiofrequency absorbent is placed. We present an order of magnitude improvement in the Q factor measurement accuracy over conventional methods by studying the switch-on and off transient signals of the resonators. A nuclear magnetic resonance console is ideally suited to acquire the transient signals and it also allows to employ the so-called pulse phase-cycling to remove transient artifacts. The improved determination of the absorbed power is demonstrated on various resonators in the 1–30 MHz range, including standard solenoids and also a birdcage resonator. This leads to the possibility to detect minute amounts of ferrite nanoparticles which are embedded in the body and also the amount of the absorbed power. We demonstrate this capability on a phantom study, where the exact location of an embedded ferrite is clearly detected.

The previously widespread mercury cell technology in chlorine production has now been replaced by more environmentally friendly membrane cell electrolysis which is a Best Available Techniques (BAT) technology. However, this requires a much cleaner brine containing contaminants (Al, Ca, Mg, etc.) in the order of ng/g at most. For this reason, it’s very important to detect trace amounts of aluminum in concentrated saline media in the simplest and fastest way. To the best of our knowledge, no one has previously developed a spectrophotometric method capable of detecting aluminum in ionic forms selectively in the order of ng/g in concentrated saline media, without any preconcentration or separation step. Our advanced analytical method provides an opportunity for this. During the analytical procedure, a colored complex ion is formed from the dissolved aluminum content of the sample with eriochrome cyanine R (ECR) ligand in buffered pH medium. The sensitivity of the measurement is increased by adding quaternary ammonium salt. The colored complex ion is formed in 15 minutes, then the absorbance measurement can be performed for 90 minutes. The effect of rock salt interference was eliminated by proper calibration. In our work the dependence of the signal on temperature, pH, time elapsed after the addition of reactants, the dosing sequence, the salinity of the medium was examined, furthermore, we studied which wavelength-absorbance values give the best fit (highest R² value) and the highest sensitivity in case of linear calibration. Surprisingly, increasing the salinity significantly improves the sensitivity of the measurement.

An efficient approach for aluminum removal was developed to produce high-purity brine feed for membrane cell electrolysis, the best available technique for chlorine production. The removal of aluminum from saturated (25 wt%) brine represented a knowledge gap. The pH dependence of precipitation and sedimentation steps was investigated. The Al-content could be reduced from 1.2 to 0.2 ppm at pH 11, meeting industrial requirements. A key factor supporting Al-removal is the presence of Ca and Mg contaminants in the mine brine. This effect was observed in the presence of at least 5 ppm magnesium and/or 150 ppm calcium. No reduction in aluminum content was observed in the absence of these alkaline earths. However, in model experiments at pH 11 and 60 °C, the aluminum content decreased to 0.21 ppm in the presence of 300 ppm calcium, 0.41 ppm in the presence of 20 ppm magnesium, and 0.07 ppm in the presence of both alkaline earths. Moreover, the presence of calcium and magnesium reduced the solubility of the resulting precipitate in acidic brines. Dynamic light scattering and photometric methods confirmed the precipitation and aggregation processes. Scanning electron microscopy and X-ray diffraction analysis of the precipitates further confirmed the phenomenon of co-precipitation, identifying the products as special Al–Ca and Al–Mg compounds. Zeta potential measurements showed that the charge of the microphases in the dense electrolyte solutions was almost completely shielded. The polyacrylamide flocculant even at a concentration of 0.1 ppm significantly accelerated the removal process. The aluminum content of the supernatant was reduced to 0.3 ppm in 10 min with 2 ppm flocculant, whereas 30 min were required in the absence of the flocculant. Graphical abstract

Magnetic hyperthermia is an adjuvant therapy for cancer where injected magnetic nanoparticles are used to transfer energy from the time-dependent applied magnetic field into the surrounding medium. Its main importance is to be able to increase the temperature of the human body locally. This localization can be further increased by using a combination of static and alternating external magnetic fields. For example, if the static field is inhomogeneous and the alternating field is oscillating then the energy transfer and consequently, the heat generation is non-vanishing only where the gradient field is zero, which results in superlocalization. Our goal here is to study theoretically and experimentally whether the perpendicular or parallel combination of static and oscillating fields produce a better superlocalization. A considerable polarization effect in superlocalization for small frequencies and large field strengths is found, which is of great importance for practical applications.

The aluminum content of concentrated (27 wt%) sodium chloride solutions could be crucial for large‐scale chlor‐alkali‐based industries applying membrane cell electrolysis. Thus, a facile method which enables a fast and reliable protocol to determine the Al content of these solutions on ppb scale in industrial environments is fundamentally important. It was demonstrated that the increased sensitivity of colorful Al‐ECR (eriochrome cyanine R) complex by the use of a cationic surfactant and specific biological buffers could effectively indicate the Al content in an extended pH interval of a concentrated saline medium under industrial conditions. The dependence of the analytical protocol on pH, temperature, time, wavelength, and the salinity of the medium was investigated. It was shown that the absorbance‐based measurements of the solution should be performed at least 2–4 h after its preparation. By applying the selected two Good's buffers (HEPES: 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid, MOPS: 3‐(N‐morpholino)‐propanesulfonic acid) and Tris (tris(hydroxymethyl)aminomethane), 32.8–38.1 % increase in the sensitivity was achieved for saturated NaCl solutions. Moreover, the limits of detection and quantification (LOD, LOQ) were also lowered by 19.0–29.8 %, and the salinity dependence of the calibration was also reduced.