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Carbon-based nanomaterials were prepared using a simple microwave-assisted hydrothermal carbonization method, with Chondrus crispusand Palmaria palmataalgae as a sustainable feedstock. These materials were thoroughly characterized by FTIR spectroscopy, elemental microanalysis, and XPS analysis. The resulting hydrochars effectively removed ciprofloxacin (CIP), an antibiotic, and malachite green (MG), an organic dye, both of which are pollutants posing threats to ecosystems and public health. The hydrochar derived from Chondrus crispus(HC-Cho-MW) demonstrated superior performance, following a cooperative adsorption process well-described by the Dubinin–Radushkevich isotherm. It exhibited maximum adsorption capacities of 350 mg.g−1for CIP and 136 mg.g−1for MG, at 25ºC and pH 6. These values surpass those of previously reported hydrochars and are competitive with certain activated carbons. The pseudo-second-order model provided the best fit for the kinetic data, with film diffusion predominant at specific intervals. The adsorption of CIP and MG was exothermic and entropically favorable for both hydrochars. The small ΔH values (-9.85 to -23.26 kJ.mol−1) suggest that physisorption predominantly governed the overall adsorption mechanism, although electrostatic interactions may also contribute. The hydrochars could be regenerated and reused to remove CIP and MG over three consecutive cycles. These results highlight the potential of using renewable and readily available algae biomass as a precursor for sorbents to remove pollutants from environmental water. This approach utilizes highly efficient microwave heating and avoids costly activation processes.

Ecobenign and high-temperature-stable oxides are considered a promising alternative to traditional Bi2Te3-, Bi2Se3-, and PbTe-based thermoelectric materials. The quest for high-performing thermoelectric oxides is still open and, among other challenges, includes the screening of various materials systems for potentially promising electrical and thermal transport properties. In this work, a new family of acceptor-substituted Haldane gap 1D BaGd2CoO5dense ceramic materials was characterized in this respect. The substitution of this material with calcium results in a general improvement of the electrical performance, contributed by an interplay between the charge carrier concentration and their mobility. Nevertheless, a relatively low electrical conductivity was measured, reaching ∼5 S/cm at 1175 K, resulting in a maximum power factor of ∼25 μW/(K × m2) at 1173 K for BaGd1.80Ca0.20CoO5. On the other hand, the unique anisotropic 1D structure of the prepared materials promotes efficient phonon scattering, leading to low thermal conductivities, rarely observed in oxide electroceramics. While the BaGd2–xCaxCoO5materials show attractive Seebeck coefficient values in the range 210–440 μV/K, the resulting dimensionless figure of merit is still relatively low, reaching ∼0.02 at 1173 K. The substituted BaGd2–xCaxCoO5ceramics show comparable thermoelectric performance in both inert and air atmospheres. These features highlight the potential relevance of this structure type for thermoelectric applications, with future emphasis placed on methods to improve conductivity.

Iron electrowinning offers a greener path for steel production. While alkaline media has received the most significant attention, the acidic media declined due to low Faradaic efficiency and difficulties imposed by fragile deposits. This study proposes, for the first time, prospects for acidic Fe electrowinning using a mixed-acid electrolyte (H2SO4+C2H2O4), comparing the deposition from hematite suspensions and soluble Fe2+salts (FeSO4.7H2O). Oxalic acid emerges as a key factor, facilitating Fe electrodeposition by forming iron complexes in solution, addressing the challenge associated with slow Fe2O3dissolution in H2SO4.

Iron ore represents a potential feedstock for the alkaline electrowinning of iron from suspensions. However, several difficulties can be imposed during the electrowinning due to the presence of several iron oxide types with different iron valences (e.g. hematite with magnetite), requiring further studies for establishing electrowinning as an alternative technology for iron production. In fact, an adverse effect on the Faradaic efficiency was previously reported when using magnetite as feedstock. The present study demonstrates, for the first time, the possibility of obtaining relatively high Faradaic efficiencies (66%) with hematite-magnetite mixtures at low temperature (80 °C).

One-dimensional Haldane gap materials, such as the rare earth barium chain nickelates, have received great interest due to their vibrant one-dimensional spin antiferromagnetic character and unique structure. Herein we report how these 1D structural features can also be highly beneficial for thermoelectric applications by analysis of the system CaxBaGd2-xNiO50 ≤ x≤ 0.25. Attractive Seebeck coefficients of 140–280 μV K–1at 350–1300 K are retained even at high acceptor-substitution levels, provided by the interplay of low dimensionality and electronic correlations. Furthermore, the highly anisotropic crystal structure of Haldane gap materials allows very low thermal conductivities, reaching only 1.5 W m–1K–1at temperatures above 1000 K, one of the lowest values currently documented for prospective oxide thermoelectrics. Although calcium substitution in BaGd2NiO5increases the electrical conductivity up to 5–6 S cm–1at 1150 K < T< 1300 K, this level remains insufficient for thermoelectric applications. Hence, the combination of highly promising Seebeck coefficients and low thermal conductivities offered by this 1D material type underscores a potential new structure type for thermoelectric materials, where the main challenge will be to engineer the electronic band structure and, probably, microstructural features to further enhance the mobility of the charge carriers.

The electrochemical reduction of iron oxides in alkaline media arises as a novel approach for ironmaking and iron-rich waste valorisation. Strong advantages and attractive aspects of alkaline electroreduction include lower electric energy consumption, absence of CO2emissions, and non-polluting valuable by-products such as H2and O2. Another potential advantage originates from the compatibility of this concept with intermittent renewable energies. However, to bring this technology to a competitive level, especially compared to the traditional steelmaking, innovative approaches and developments in materials processing and their appropriate integration into the electrolysis process are required. This research work explores the prospects for electrochemical reduction of a magnesium-containing ferrospinel, as a potential component in iron-containing wastes. The experimental approach considers bulk cathode- and suspension-based electrolysis concepts, which allow reaching 55% and 20% Faradaic efficiencies of the reduction to metallic iron, respectively. The effects imposed by the magnesium presence on the electroreduction kinetics, phase composition and morphology of the electroreduction products are evaluated and discussed. The obtained results open new perspectives for the recovery of metallurgical residues with low magnesium impurities content.

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