Cocoa beans are part of the cocoa plant fruit (Theobroma cacao L.) used to prepare various products such as chocolate, cocoa butter, jelly, liqueurs, cosmetics, etc. Dark chocolate is consumed worldwide by different populations and is known for its good taste, making it one of the most favoured food products. This work aimed to determine the content of total polyphenols (TPC), total flavonoids (TFC), and the antioxidant potential measured through the ability to scavenge DPPH free radicals (DPPH), ferric reducing power (FRAP), and total antioxidant capacity (TAC), as well as major and trace elements contained in twelve commercially available dark chocolate samples, with cocoa content ranging from 40% to 99%. The total polyphenols content ranged between 10.55 and 39.82 mg/g GAE, while the total flavonoid content was from 10.04 to 37.85 mg/g CE. All applied antioxidant assays indicate that the sample with the highest cocoa percentage shows the greatest antioxidant activity (DPPH: 48.34% of inhibition; FRAP: 89.00 mg/g GAE; TAC: 83.86 mg/g AAE). Statistical methods were applied to establish the differences between the samples concerning TPC, TFC, DPPH, FRAP and TAC, as well as to differentiate the samples according to the mineral content. The results indicated that the differences in TPC and TFC between different samples depended on the cocoa content and the addition of dried fruit pieces. A good correlation between antioxidant potency composite index (ACI) and declared cocoa content was noticed (R² = 0.8034), indicating that the declared percentage of cocoa is a reliable indicator for antioxidant activity of analysed dark chocolate samples. The nutritional evaluation proved that the studied chocolate samples were an excellent source of Mg, Fe, Mn and Cu.

Newly designed mesoporous brushite-metakaolin-based geopolymer materials were examined with an idea for using this material as a potential adsorbent for Pb(II) removal from aqueous solutions. As a starting component for geopolymer synthesis, a natural raw kaolinite clay with the addition of 2 wt.%, 4 wt.%, 6 wt.%, 8 wt.%, and 10 wt.% of pure brushite was used. Phase, structural, morphological, and adsorption properties of newly synthesized mesoporous brushite-metakaolin geopolymer materials were examined in detail by the means of XRPD, FTIR, SEM-EDS, BET/BJH, and ICP-OES methods. The ICP-OES results showed that the synthesized material samples with 2 wt.%, 4 wt.%, and 6 wt.% of brushite possess significant adsorption properties and the mechanisms of the adsorption process can be attributed to chemisorption. The most notable result is that brushite-metakaolin-geopolymer with 2 wt.% of brushite have the best efficiency removal, more than 85% of Pb(II).

Electrochemical removal of organic pollutants represents an attractive methodology in water depollution. The key challenges for researchers comprise finding simple, affordable electrode materials with satisfactory efficiency in all ranges of pollutant concentration. Electrochemical oxidation of a mixture of phenol-based dyes: bromocresol green (BCG), cresol red (CR), and thymol blue (TB), in sulphate medium, at total concentration not exceeding 15 ppm, has been performed using simply prepared, low-cost composite electrodes, based on graphene nanoplatelets (GNP) and metallic oxides (TiO₂ and SnO₂) loaded on stainless steel substrate: GNP@SS, SnO₂/GNP@SS, and TiO₂/GNP@SS. Electrodes were characterised by XRD, FTIR, and electrochemical techniques. The degradation kinetics of initial dyes was tracked with UPLC and GC-MS chromatography for 6 h, at a current density of 10 mA/cm². GC-MS analysis of the degradation products revealed oxidised aromatic compounds as the main products, while TOC analysis confirmed a total mineralisation extent in the range of 30–35%. The proposed degradation mechanism involves the attack of OH-radical, as the main oxidising agent, to the hydroxyl oxygens of dye phenolic rings. Obtained results provide useful information for the further development of affordable laboratory-scale and industrial systems for the complete removal of phenol-based compounds.

This research investigated the feasibility of producing strontium-doped nanocrystalline hydroxyapatite (SrHAp) through an environmentally benign synthesis approach and evaluated the antimicrobial activity of the resulting material. The synthesized nanomaterial was subjected to comprehensive characterization. The antimicrobial efficacy of SrHAp was tested against Gram-positive and Gram-negative bacterial strains. X-ray diffraction (XRD) analysis in combination with Fourier-transform infrared (FT-IR) spectroscopy confirmed the successful formation of pure monocrystalline SrHAp. The scanning electron microscopy (SEM) examination revealed two predominant morphological structures: nanorods and prismatic configurations of the SrHAp. Transmission electron microscopy (TEM) demonstrated that the rod-like SrHAp nanocrystals aggregate into elongated grain structures with a size of about 25 nm × 10 nm. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis confirmed the presence and quantification of the concentrations of calcium, strontium, and phosphorus, while confirming the expected calcium–phosphorus ratio characteristic of hydroxyapatite. The study established that the positive surface charge of the material, with a point of zero charge near pH 10, is essential for its antimicrobial efficiency. These results suggest that SrHAp nanomaterials hold promise for biomedical applications, particularly as antimicrobial coatings for implants and scaffolds for bone tissue, where the prevention of infection is critical. Overall, despite its selective and material quantity-dependent antimicrobial efficacy, environmentally friendly synthesized SrHAp can be successfully applied as an effective controller of targeted microbial contamination, especially of Gram-positive bacterial species S. aureus, L. monocytogenes, S. Enteritidis, and A. baumanii.

Lignite and coal waste used as feed fuels in thermal power plants (TPPs) and semi-industrial fluidized bed boiler (FBB), as well as their representative fly ashes (FAs), were examined. Fly ashes were compared employing anions and cations content in correspondent water extracts, trace elements and polycyclic aromatic hydrocarbon concentrations, as well as health risk assessments of substances known to be of concern for public health. Fluoride and sulfate contents in water extracted FAs are far below the legislation limits for waste, classifying all investigated FAs as non-hazardous. Among investigated trace elements, Cd content is the lowest, while Mn content is the highest. The highest enrichment ratios are noticed for As, Pb, Hg, Cu, V and Cr. The results indicate that total PAHs content is elevated in FA from the combustion of coal waste (AFB), with fluoranthene prevailing. The cancer risk of As and the non-cancer risk of As and Ni in some FAs surpass their respective permissible limits. The incremental lifetime cancer risk of an adult population indicates a potential PAHs risk in AFB, whereas all other fly ashes are within safe limits.