STUDIA CHEMIA - Issue no.3 / 2023 - Table of contents

A nanocomposite made from hydroxyapatite (HAP) and silver nanoparticles (AgNPs), namely HAP-4.5 wt% AgNPs, is reported. HAP was prepared using a wet precipitation technique, and AgNPs were made by reducing silver nitrate with glucose in basic medium. HAP, AgNPs and HAP-4.5 wt% AgNPs composite were characterized by X-ray diffraction (XRD), SEM - energy dispersive X-ray spectroscopy (EDS) and different imagistic methods: TEM and AFM. The antibacterial effect of the HAP-4.5 wt% AgNPs nanocomposite was tested using diffusion technique in nutritive agar on two pathogenic species, one Gram-negative (Salmonella typhimurium) and one Gram-positive (Bacillus cereus) and promising results were obtained. This hydroxyapatite-silver nanocomposite can be employed as a potential antimicrobial coating for dental and orthopedic implants, or they can be utilized such as bone cements in clinical procedures

Keywords: hydroxyapatite, silver nanoparticles, nanocomposite, antibacterial activity, pathogens

Fuzzy linear discriminant analysis, a robust supervised method, has been successfully applied for characterization and classification of 42 Romanian medicinal plant extracts according to the total content of eight phytochemical compounds (alkaloids, polyphenols, coumarins, o-diphenols, flavonoids, anthocyanins, flavonols, flavanols) estimated by dedicated molecular absorption spectrophotometry-based methods, and their antioxidant capacity determined by DPPH* method. The obtained results (fuzzy partitions) and parameters of the class centers (robust fuzzy means) clearly demonstrated the efficiency and information power of the advanced fuzzy method in plants characterization and classification, and allow a rationale choice of a medicinal plant extract with a specified phytochemical composition and/or antioxidant activity. Previous studies have investigated the association of certain classes of phytochemicals with the antioxidant activity in plant extracts. However, most of them are limited either in the number of the plants extracts they have analyzed or in the number of the employed phytochemical classes. The distinctness of this work is the application of a fuzzy multivariate analysis on data obtained for high number of plant extracts—42 widespread medicinal plants form various plant taxa—and a high number of ubiquitous phytochemical classes in plants. The methodology developed in this paper might be also extended in the authenticity and origin control of other fruits, herbs or derived products.

Keywords: Fuzzy discriminant analysis, chemometrics, medicinal plants, phytochemical composition

Milk and cheese are important sources of macro and microelements, their amounts depend on the feeding method of the animal, the climatic and environmental conditions, the state of health and the lactation period, as well as the technology of milk processing. The purpose of this paper is to evaluate the mineral profile of raw milk and Swiss cheese produced in Ţara Dornelor in different seasons and obtained by different technologies. The results showed that during the summer season, milk is richer in K and Ca and poorer in Cu. Swiss cheese presented a lower content of Na, Ca and Mg in the summer period compared to the winter one, a similar trend being observed for Mn and Fe. The processing technology also determined significant variations (p < 0.05) in the content of micro and macro elements. The processing of Swiss cheese in a copper boiler determined an increase in the Cu content of up to 6 times compared to the product obtained in a stainless-steel boiler. These results are important both for processors interested in increasing the quality of their products, and for consumers aware of the importance of food with high nutritional value.

Keywords: micro and macroelements, dairy products technology, season, Emmental cheese

Deployment of decarbonization technologies in energy-intensive industrial applications (e.g., heat and power, metallurgy, cement, chemical sectors etc.) is of great importance for reducing CO2 emission and achieving global climate neutrality. Membrane CO2 removal systems gained relevant attention as possible energy and cost-efficient CO2 capture technology. This paper is evaluating membrane-based pre- and post-combustion CO2 capture to be applied in various industrial applications with high fossil CO2 emissions. The evaluation was geared mainly towards quantification of ancillary energy consumptions of membrane systems as well as the specification of captured CO2 in respect to its potential utilization and storage applications. As the assessment show, the membrane-based systems are promising CO2 capture technology for both pre- and post-combustion capture configurations.

Keywords: Energy-intensive industrial applications; Pre- and post-combustion CO2 capture; Membrane; Ancillary energy consumptions; Technical performance indexes

Vegetable oils are widely available in nature and are one of the most important sustainable feedstocks for biofuel production. W/Pd/γ-Al2O3-ZnZSM-5 and Nb/Pd/γ-Al2O3-ZnZSM-5 catalysts where prepared, characterized and tested in the hydrogenolysis reaction of palm oil fatty acid esters. The catalysts were characterized by determining the textural characteristics, the thermal stability, and the nature of the acidic sites. The appearance of particle agglomerations was evaluated by scanning electron microscopy (SEM). The resulting reaction products were n-aliphatic hydrocarbons, iso-aliphatic hydrocarbons, cycloaliphatic hydrocarbons, and arenes. No oxygenated organic compounds were identified in the collected liquid phase. At lower pressures, the deoxygenation process occurs to approximately 33% through the hydrogenation of the carboxylic bond and to approximately 67% through decarboxylation/decarbonylation, while at higher pressure than 60 bar the deoxygenation process proceeds preferentially through decarboxylation/ decarbonylation.

Keywords: fatty acids methyl esters, W/Pd/γ-Al2O3-ZnZSM-5, Nb/Pd/γ-Al2O3-ZnZSM-5, catalyst, hydrogenolysis

The paper investigates the corrosion inhibition property of the Valerian (Valeriana officinalis) extract for carbon steel in acid and neutral solutions. The extracted natural compounds from plants have been reported in the literature as efficient corrosion inhibitors due to their stability to different environments, eco-friendly character, and their low cost. The usefulness of a different type of valerian species, in corrosion protection, by inhibiting the anodic oxidation reaction due to the improvement of the development of a passivating film, has been reported earlier for the Valeriana wallichii root extract in the corrosion of mild steel in different acidic media. Based on the latter findings, our studies have been performed in three different media, H2SO4, HCl and NaCl. An array of electrochemical techniques such as Tafel polarization, cyclic voltammetry, as well as chronopotentiometry have been employed to elucidate the corrosion behavior of carbon steel within the investigated media, containing various amounts of Valeriana officinalis extract. Quantum chemical calculations have been employed in order to assess the adsorption capacity of the mentioned extract onto the metal surface. The latter extract exhibits inhibitory effects in the studied media, even at small concentrations.

Keywords: natural extracts; green corrosion inhibitor; Tafel linear polarization; molecular modelling, sustainability

This work evaluates the chemical impact of polyethylene terephthalate (PET) as plastic waste material used in clayey soil improvement. The purpose of this work is to study the behaviour of PET added in different percentages in soil, and how it affects the chemical composition of soil by applying rapid ageing cycles. The thermal stability of the clay-PET mixtures using the thermogravimetric method was studied, and the impact of PET quantity on pH was measured. To detect the migration of PET degradation products to the soil gas chromatography with mass spectrometry (GC-MS) was used. The GC-MS analysis results indicate the presence of DIBP, the concentration increased proportionally with the amount of PET added to the clay. The thermogravimetric analysis shows a thermal degradation of the polymeric chain starting from 200 °C.

Keywords: soil, PET waste materials, thermal stability, GC-MS analysis, additives migration

Benzyl decanoate was successfully synthesized by the direct esterification of decanoic acid with benzyl alcohol mediated by lipase B from Candida antarctica immobilized by entrapment in a sol-gel matrix in a solvent-free system, using a ternary mixture of silane precursors and glycerol as additive. The most active (LS-6, 92.1% conversion after 90 minutes) and stable biocatalyst (95% of the initial activity after 7 reaction cycles) yielded 2.2 g of benzyl decanoate in a scaled-up process (91% isolation yield).

Keywords: benzyl decanoate, esterification, solvent free system, lipase, additive, sol-gel, biocatalysis, aroma ester

The article discloses the AMS (accelerator mass spectrometry) radiocarbon dating results of the Egg baobab, a superlative Grandidier baobab (Adansonia grandidieri) from the Andomiry Forest, Atsimo-Andrefana region, Madagascar. The investigation of the baobab shows that it consists of 5 perfectly fused stems and exhibits a closed ring-shaped structure with a very large false cavity inside. The calculated overall wood volume of the Egg baobab is 450 m3. Two wood samples were collected from the exterior of the stems, out of which nine tiny segments were extracted and dated by radiocarbon. The oldest sample segment had a radiocarbon date of 921 ± 24 BP, which corresponds to a calibrated age of 840 ± 25 years. According to this value the Egg baobab is 875 ± 75 years old.

Keywords: AMS radiocarbon dating, Adansonia grandidieri, tropical trees, multiple stems, false cavity.

Adenosine triphosphate (ATP) has a high affinity for the organic phosphate binding site of hemoglobin (Hb), affecting the affinity for oxygen. Periodate-oxidized-ATP (oATP) behaves as an affinity tag for several enzymes that use ATP as a substrate and has the ability to form intermolecular aldimine bonds by reaction with free amino groups on proteins. Due to its unique structure, oATP has been used to produce structural and functional modifications of Hb to obtain a compound with a low affinity for oxygen that could be used as a blood substitute. However, the oATP-Hb derivative was shown to present a notable increase in pro-oxidative reactivity compared to Hb in vitro, and accordingly exhibited toxicity in in vivo studies. This pro-oxidant reactivity was alleviated by crosslinking Hb with bovine serum albumin (BSA) in an oATP-Hb-BSA copolymer. We now show that oATP and oATP-Hb-BSA display high-affinity toxicity towards cancer cells, and may hence deserve further investigation as adjuvants in anti-cancer therapy.

Keywords: hemoglobin, cells, oATP, blood substitute, cancer

The volatile oil composition and secondary metabolite content in different parts of S. mollis ssp. mollis and S. mollis ssp. szowitzii were investigated in this study. Based on their chemical composition, the components of the S. mollis ssp. mollis and S. mollis ssp. szowitzii plant species could be distinguished in the current study. Using GC-MS analysis, 70 distinct volatile oil components could be found in various plant sections of this species. Avicularin, Biapigenin, and Hyperoside were found in the highest concentrations in all plant parts of both species. Further, Catechine and Chlorogenic acid could be detected in all plant parts of S. mollis ssp. mollis.The volatile oil composition and secondary metabolite content of different parts of this investigated two species revealed high variability, displayed by Biplot Analysis. Different components of medicinal importance could be detected in different parts of this species. These compounds could be isolated and used for further basic investigations.

Keywords: Scorzonera mollis, volatile oil, secondary metabolites, Türkiye

The present work completes information reported previously on Chrystal violet adsorption from aqueous solutions onto Salvinia natans powder. It identifies intraparticle diffusion as the rate determining step within the sequence of four individual stages of the adsorption mechanism. It also demonstrates, that even is somewhat faster, the film diffusion at the solid-liquid boundary is also slow enough to contribute to the overall process rate. The novel use of a simple kinetic model, consisting of two parallel and competing first-order steps, as well as of an algorithm familiar to pharmacokinetics (the method of residuals), individual rate coefficients of both the film and the intraparticle diffusion were calculated simultaneously from the same kinetic curves. The dependence of their values with employed operating conditions consolidates previous findings and conclusions.

Keywords: Adsorption; Rate determining diffusion; Method of residuals; Competing first-order processes