Search Results (9)

Currently, one of the most important challenges for the conservation of stone artworks is the removal of metal corrosion products on their surfaces. Traditional cleaning methods, which typically involve the application of aqueous solutions containing chelating agents capable of complexing these metal ions, have shown some weaknesses. These weaknesses become apparent when such methods are applied to statues and other vertical surfaces or when aiming to limit the cleaning process to a specific area with controlled application times. Furthermore, the porosity of the stone surface plays a role concerning the cleaning efficiency. To address these issues, chelating agents can be incorporated into gel-like materials. This study is a proof of concept to evaluate the cleaning efficacy of various gel formulations composed of polyvinyl alcohol (PVA), borax (B), and agarose (AG), loaded with two chelators: ethylenediaminetetraacetic acid (EDTA) and potassium sodium tartrate (PST or Rochelle salt). Three types of carbonate stones (travertine, Lecce stone, and Carrara marble) characterized by different porosities were artificially stained with copper sulphates and treated with the different PVA-B-AG formulations. The effectiveness of the treatment was directly monitored on the stones using a multi-technique approach that included scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and non-invasive portable nuclear magnetic resonance (NMR). Additionally, the rheological properties of the gels were investigated, and the Fourier transform infrared attenuated total reflection spectroscopy (FTIR ATR) was used to analyse the chemical structure of the gel before and after treatment, aiming to understand the changes induced by the cleaning process. Full article

The instability of calcium tartrate (CaT) in wines occurs when the effective concentration of ions surpasses the solubility product, leading to the formation of CaT crystals. Unlike potassium hydrogen tartrate (KHT), temperature has little effect on the rate of CaT precipitation, making cold stabilization ineffective. Additives like metatartaric acid and carboxymethylcellulose (CMC) have been used to mitigate this problem, but metatartaric acid’s effectiveness is limited due to hydrolysis. Additionally, potassium polyaspartate (KPA), commonly used as a KHT stabilizer, has been reported to reduce wine stability regarding CaT instability. Therefore, exploring alternative stabilization methods is crucial. Alginic acid, permitted as a processing aid in winemaking, can be an alternative to CMC and metatartaric acid due to its strong negative charge and ability to bind calcium ions. This study aimed to assess alginic acid’s efficacy as a CaT stabilizer compared to CMC and investigate the impact of KPA on CaT instability. The results showed that KPA did not increase CaT instability and even improved its stability in some wines. Alginic acid outperformed both CMC and KPA in mitigating CaT instability, possibly due to its higher zeta potential and calcium ion complexation ability. This study is the first to investigate the use of alginic acid for CaT stability in wine. Full article

Magnesium (Mg) has been explored during the last few decades in the biomedical industry as a biodegradable implant. However, mechanical properties and corrosion resistance are still big concerns for clinical use. Therefore, this study proposes a suitable surface modification of the Mg by plasma electrolytic oxidation (PEO) to improve its corrosion resistance and biological performance. Mg samples were processed in a galvanostatic mode using an electrolytic solution of a phosphate compound supplemented with either potassium pyrophosphate or sodium-potassium tartrate. The obtained coatings were physiochemically characterized by SEM, XRD, EDS, and micro-Raman spectroscopy. The corrosion resistance of the coatings was studied using a hydrogen evolution setup and electrochemical tests. Finally, the biological performance of the material was evaluated by using an indirect test with osteoblasts. Obtained coatings showed a porous morphology with thicknesses ranging from 2 to 3 µm, which was closely dependent on the PEO solution. The corrosion resistance tests improved the degradation rate compared to the raw material. Additionally, an unreported active–passive corrosion behavior was evidence of a protective layer of corrosion products underneath the anodic coating. Indirect in vitro cytotoxicity assays indicated that the coatings improved the biocompatibility of the material. In conclusion, it was found that the produced coatings from this study not only lead to material protection but also improve the biological performance of the material and ensure cell survival, indicating that this could be a potential material used for bone implants. Full article

Atom Transfer Radical Polymerization (ATRP) is an effective catalytic process leading to well-defined polymers with desired properties. This process based on reversible deactivation of propagating chains has a lower rate in comparison with conventional radical polymerization, especially in the case of obtaining polymers with high molecular weights. Thus, the increase of the rate of this process with preserving control over molecular weight distribution is a challenging task. In this work, novel catalytic systems for Activators Generated by Electron Transfer (AGET) ATRP of acrylonitrile based on copper (II) bromide complexes were proposed. It was found that Rochelle salt (potassium sodium tartrate tetrahydrate) may be used as a reducing agent for regeneration of copper-based catalysts to increase the rate of the process. The provided UV-vis spectroscopy experiments have confirmed the reducing ability of tartaric anion. It was found that the use tandem catalytic system based on two copper complexes with different ligands also increases the polymerization rate. The performed experiments allowed us to develop a catalytic system for rapidly obtaining polyacrylonitrile polymers with desired molecular weights exceeding 100 kDa. Full article

Carbon nanomaterials possessing a high specific surface area, electrical conductivity and chemical stability are promising electrode materials for alkali metal-ion batteries and supercapacitors. In this work, we study nitrogen-doped carbon (NC) obtained by chemical vapor deposition of acetonitrile over the pyrolysis product of calcium tartrate, and activated with a potassium hydroxide melt followed by hydrothermal treatment in an aqueous ammonia solution. Such a two-stage chemical modification leads to an increase in the specific surface area up to 1180 m² g⁻¹, due to the formation of nanopores 0.6–1.5 nm in size. According to a spectroscopic study, the pore edges are decorated with imine, amine, and amide groups. In sodium-ion batteries, the modified material mNC exhibits a stable reversible gravimetric capacity in the range of 252–160 mA h g⁻¹ at current densities of 0.05–1.00 A g⁻¹, which is higher than the corresponding capacity of 142–96 mA h g⁻¹ for the initial NC sample. In supercapacitors, the mNC demonstrates the highest specific capacitance of 172 F g⁻¹ and 151 F g⁻¹ at 2 V s⁻¹ in 1 M H₂SO₄ and 6 M KOH electrolytes, respectively. The improvement in the electrochemical performance of mNC is explained by the cumulative contribution of a developed pore structure, which ensures rapid diffusion of ions, and the presence of imine, amine, and amide groups, which enhance binding with sodium ions and react with protons or hydroxyl ions. These findings indicate that hydrogenated nitrogen functional groups grafted to the edges of graphitic domains are responsible for Na⁺ ion storage sites and surface redox reactions in acidic and alkaline electrolytes, making modified carbon a promising electrode material for electrochemical applications. Full article

In this study, the preservation of As(III) in model solutions and natural groundwater samples from four locations in Croatia was conducted. Model laboratory samples were spiked with As(III) and As(V), and different complexing agents. Solutions were analysed in intervals of 24, 48 h and during ten days after preparation. Model samples containing citric acid, sodium citrate, sodium oxalate and potassium sodium tartrate in combination with acetic acid, spiked with As(III)and As(V), showed good species preservation. As(III), in model samples, was preserved for 7 days with citric acid, and citric acid in combination with acetic acid, as well as with tartrate. As(III), in natural samples, was preserved for 6 to 12 days with potassium sodium tartrate, citric acid, and citric acid in combination with acetic acid and showed improvement, compared with unpreserved samples (oxidation in 3 days). The results showed that acetic acid alone was not successful in preserving As speciation. Good resolution of inorganic arsenic species was achieved using differential pulse anodic stripping voltammetry technique (DPASV). Since this technique is comparatively cheaper and more convenient to use than other available techniques it could become a method of choice for arsenic speciation in water. Full article

The concentration dependencies of diffusion permeability of homogeneous (AMX-Sb and AX) and heterogeneous (MA-41 and FTAM-EDI) anion-exchange membranes (AEMs) is obtained in solutions of ampholytes (sodium bicarbonate, NaHCO₃; monosodium phosphate, NaH₂PO₄; and potassium hydrogen tartrate, KHT) and a strong electrolyte (sodium chloride, NaCl). It is established that the diffusion permeability of AEMs increases with dilution of the ampholyte solutions, while it decreases in the case of the strong electrolyte solution. The factors causing the unusual form of concentration dependencies of AEMs in the ampholyte solutions are considered: (1) the enrichment of the internal AEM solution with multiply charged counterions and (2) the increase in the pore size of AEMs with dilution of the external solution. The enrichment of the internal solution of AEMs with multiply charged counterions is caused by the Donnan exclusion of protons, which are the products of protolysis reactions. The increase in the pore size is conditioned by the stretching of the elastic polymer matrix due to the penetration of strongly hydrated anions of carbonic, phosphoric, and tartaric acids into the AEMs. Full article

Glulisine is a US Food and Drug Administration (FDA) approved insulin analogue, used for controlling hyperglycaemia in patients with diabetes mellitus (DM). It is fast acting which better approximates physiological insulin secretion, improving patient outcome. Crystallisation of Glulisine was analysed by its crystallisation phase diagram and nucleation-inducing materials. Both the hanging drop vapour diffusion and microbatch-under-oil methods were used and compared. We have shown that the same protein can have different solubility behaviours depending on the nature of the salt in the precipitating agent. In the case of Glulisine with magnesium formate, lowering the precipitant concentration drove the system further into supersaturation resulting in the formation of crystals and precipitation. This was the opposite effect to the usual scenario where raising the precipitant concentration leads to supersaturation. Glulisine with sodium potassium tartrate tetrahydrate (NaKT) followed the expected trend of forming crystals or precipitate at higher concentrations and clear drops at lower concentrations of the precipitant. The outcomes of crystallisation using the different crystallisation methods is also described. Glulisine was successfully crystallised and the crystals diffracted up to a resolution limit of 1.4 Å. Full article

Olive leaves (OLL) represent a major waste generated during the production of olive oil, but there is a great potential for their valorization, because they provide important content in polyphenolic phytochemicals, which possess several bioactivities. In spite of the high number of studies dealing with polyphenol recovery from olive leaves, green processes involving environmentally benign solvents are scarce. In this study, a novel renewable natural low-transition temperature mixture (LTTM), composed of glycerol and sodium-potassium tartrate, was tested for its efficient ability to extract polyphenolic substances from OLL. The extraction process was optimised by using response surface methodology and the maximum yield in total polyphenols was 26.75 ± 3.22 mg caffeic acid equivalents per g dry weight, achieved with 50% (v/v) aqueous LTTM, liquid-to-solid ratio of 45 mL g⁻¹ and at 73 °C. The LTTM was proven to be equally effective with 60% aqueous methanol, but it displayed inferior antioxidant properties. Liquid chromatography-diode array-mass spectrometry analyses revealed no significant qualitative differences between the LTTM and the aqueous methanolic extract. Full article