Chemija

Title

Mon, 14 Oct 2024 00:00:00 +0300

Electrodeposition of Cu 3D structures suitable for CO2 reduction

Mon, 14 Oct 2024 00:00:00 +0300

Porous Cu foam electrodes, suitable for cathodic CO2 reduction, were deposited in an acidic sulphate solution with different additives to obtain structures with a high real surface area and an adequate mechanical stability. The influence of the electrodeposition time and solution composition on the porosity parameters, microstructure and stiffness of Cu 3D structures was evaluated. Neither ammonium acetate nor polyethylene glycol were found to be effective additives to the Cu sulphate electrolyte to achieve the main objectives. Only the presence of Cl– ions in the deposition solution resulted in a threefold increase in the real surface area and the achievement of a sufficient mechanical stability of the Cu 3D structure. The latter effect is related to the specific influence of Cl– ions during the electrodeposition process on the microstructural characteristics, such as the size of micropores in the walls of holes and crystallite aggregates that form dendritic branches. These structural changes, in contrast to the Cu samples deposited in a solution without additives, resulted in larger real surface areas, while the denser structures deposited in the presence of Cl– ions ensured the mechanical stability of the 3D structure.

Initial evaluation of waste phosphogypsum for its use as a precursor for bioceramic materials

Mon, 14 Oct 2024 00:00:00 +0300

In this study, the phosphogypsum waste taken from various places in the factory dump located in Kėdainiai (Lithuania) was reinspected and characterised by different physico-chemical characterisation methods. The results of X-ray diffraction analysis, thermogravimetric analysis and differential scanning calorimetry, Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, elemental analysis using inductively coupled plasma optical emission and X-ray fluorescence spectroscopy confirmed that the main crystalline phase of the phosphogypsum waste is gypsum (CaSO4·2H2O). The surface morphology of the investigated materials was analysed using scanning electron microscopy. The specific surface area was determined by the Brunauer–Emmet–Teller method. The pore size distribution of the material produced was obtained using the Barrett–Joyner–Halenda method. This study also demonstrated that the phosphogypsum waste could be successfully used as a precursor for the dissolution-precipitation synthesis of high quality bioceramic calcium hydroxyapatite.

Analysis of Wormwood (Artemisia absinthium L.) teas

Vida Vičkačkaitė, Julija Pronckutė, Vilius Poškus — Mon, 14 Oct 2024 00:00:00 +0300

Artemisia absinthium L., commonly known as wormwood, is a medicinal herb with deep roots in traditional medicine. Wormwood possesses numerous healing properties, including positive effects on the liver, bladder, stomach and intestines. It improves digestion, has the antidiabetic effect and exhibits antioxidant, anti-inflammatory and anticancer properties. Although wormwood can be used in various forms, the simplest and most accessible method is wormwood tea, prepared from dried raw material.
In this study, the antioxidant properties and total phenol content of wormwood teas prepared using different methods and raw materials from different manufacturers were investigated. The DPPH radical scavenging activity, expressed in Trolox equivalent antioxidant capacity, ranged from 457 to 623 mg/l, while the total phenol content, expressed in gallic acid equivalents, ranged from 112 to 224 mg/l. The findings suggest that the antioxidant properties of wormwood tea are largely influenced by phenolic compounds. It was found that teas made from wormwood leaves exhibit higher antioxidant activity and phenolic content compared to those made from wormwood stems. The main volatile components of wormwood teas were identified as β-thujone and trans-sabinyl acetate, with β-thujone content in wormwood teas ranging from 36 to 79 mg/l. Additionally, the thujone content decreases when the tea is brewed.

Optimisation of microencapsulation of isophorone diisocyanate into polyurea shell by oil-in-water interfacial polymerisation

Liepa Pastarnokienė, Ernest Potapov, Ričardas Makuška, Tatjana Kochanė — Mon, 14 Oct 2024 00:00:00 +0300

In this work, microcapsules containing isophorone diisocyanate (IPDI) encapsulated within a polyurea (PU) shell were synthesised via an oil-in-water emulsion interfacial polymerisation reaction involving tris(4-isocyanato phenyl)thiophosphate (TIPTP) and triethylenetetramine (TETA). Characterisation of the resulting microcapsules was conducted using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), optical microscopy and scanning electron microscopy (SEM). Various encapsulation parameters such as core-to-shell ratio, agitation speed, emulsifier type and concentration, and reaction time were systematically varied at four different levels. Optimisation of microencapsulation was performed using a Taguchi L16 parameter design approach, aiming to maximise desired outcomes (i.e. maximal core content and yield) while keeping the targeted microcapsule diameter of 50 µm. Under optimal conditions, the IPDI core content within microcapsules was up to 75% and the microcapsule yield was up to 49%.

Chemija

Title

Contents

Electrodeposition of Cu 3D structures suitable for CO2 reduction

Initial evaluation of waste phosphogypsum for its use as a precursor for bioceramic materials

Analysis of Wormwood (Artemisia absinthium L.) teas

Optimisation of microencapsulation of isophorone diisocyanate into polyurea shell by oil-in-water interfacial polymerisation