Volume 95, Issue 5

The modern synthetic chemistry heavily relies on the use of stoichiometric organometallic reagents to react with various electrophiles. The dependence on stoichiometric quantities of metals and often organic halides as precursors, in turn both produces copious amounts of metal halide wastes as well as leads to concerns on future metal sustainability. Inspired by the classical Wolff-Kishner reduction, our lab has recently developed a general strategy of HOME-Chemistry , directly using naturally abundant alcohols/aldehydes and ketones as feedstocks with the releasing of innocuous water and nitrogen gas. These reactions include 1,2-carbonyl/imine addition, conjugate addition, carboxylation, olefination, cross-coupling arylation/allylation, alkylation, hydroalkylation and C-heteroatom formations. This article provides a brief summary on this chemistry.

Interest in fossil-free, bio-based materials capable of protecting against the harmful effects of UV radiation is constantly growing. The functional groups within lignin are able to effectively absorb light in the visible and UV range, making lignin a good candidate as a bio-additive in UV-protective polymer coatings. In this work, unmodified and modified (by methacrylation) lignin of different origins (softwood [spruce] and hardwood [eucalyptus]) was used as a bio-additive within epoxy resin to develop UV-blocking coatings. Methacrylation of the lignin, as well as the presence of appropriate functional groups in the coatings was confirmed by FTIR spectroscopy. The colour properties of the coatings were additionally investigated whereby the chemical modification of lignin was found to significantly influence the colour of the biocomposite coating. The thermal properties and morphology were investigated by DSC and confocal microscopy, respectively. The results demonstrate that methacrylated lignin is a promising environmentally friendly UV-protective bio-additive for polymer coatings.

Pyrolysis of ASR is an emerging technology which may increase circularity in End-of-Life Vehicle (ELV) waste recycling. To scale up from the current pilot scale, physiochemical characterisation of the by-products is required to determine their utilisation. This paper explored how the physiochemical properties of char from different pyrolysis fractions influence secondary uses. ASR was pyrolysed in a pilot-scale unit capable of processing 100 kg h −1 at 900 °C, producing 480 kg of char from which samples were taken for analysis. Three types of pyrolysis char were identified: (i) coarse char (CC) (ii) medium char (MC) and (iii) fine char (FC). Physical (particle size, moisture content and surface analysis) and chemical (calorific value, organic and inorganic elemental analysis) analysis was conducted. Physical and chemical differences were determined between char fractions: CC had the highest particle size (800 µm; mean 353.5 µm) calorific value (14,544 kcal g −1 ) and metal concentration; the relationship was CC > MC > FC. Organic elemental analysis indicated %C was highest under FC (80.29 %) and %S was highest in CC (1.04 %). Findings from this experiment provided initial insight into the differences in properties of char fractions from ASR pyrolysis. Potential future uses in char commercial markets were evaluated, with upgrading recommendations provided.

Metal oxide nanoparticles have a wide range of potential applications due to their unique properties, including their high surface area-to-volume ratio, enhanced reactivity, and unique electronic and magnetic properties. They are widely used in industries such as electronics, energy, catalysis, and medicine, where their small size and unique properties can be utilized for a variety of purposes. Fabrication of bi-metal oxide nanocomposite through green synthesis routes is of great importance. The plant leaves are being used as a prominent source for reducing/capping or functionalization of metal oxide nanoparticles. Thus, engineering of CuO/NiO nanocomposite has been carried out via exploiting Java plum leaves’ extract as reducing and capping source. After successful green synthesis, the CuO/NiO nanocomposite was directed for characterization through advanced analytical tool viz XRD, FTIR and TEM. The FTIR spectra confirm the stretching frequencies of Cu–O and Ni–O bonds at 587.1 and 647.3 cm −1 which witnesses the surface functionalities of prepared nanocomposite. XRD analysis confirms the diffraction patterns of CuO/NiO nanocomposite with exceptional crystalline structure and phase purity. TEM images evaluate the nanometric size of fabricated CuO/NiO nanocomposite with nanoflower like internal texture having size below 100 nm. The as-prepared CuO/NiO nanocomposite was used as green electrocatalyst for the determination of vanillin (VN) in food samples. The redox current response and charge transfer kinetics of CuO/NiO/GCE was examined via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions such as potential window (0.2–1.3 V), PBS electrolyte pH 7, scan rate 60 mV/s, the engineered modified electrode exhibited excellent response for VN. The LOD of prepared electrocatalyst for VN was examined as 0.0087 µM. The potential of applicability of CuO/NiO/GCE was tested in ice-cream and chocolate samples. The obtained recovery values of real samples were found in acceptable range which highlights analytical potential of prepared modified electrode for VN.

The paper studies thermal characteristics of new polycarbonates obtained using the bisphenol A-free technology. Thermal tests of polycarbonates were carried out in a wide temperature range using the DSC (diffrential scanning calorimetry) and TG (thermogravimetry) analyses. The DSC data confirmed that all materials are homogeneous whereas the endothermic peaks are responsible for melting. Additionally, the analysis of the released gases was made by means of the infrared spectroscopic analysis. Our research proved that the new polycarbonates are relatively heat resistant. In the range of the thermal destruction of the studied materials there can be considered, two types of degradation reactions. The first step around 200 °C and the second one around 300 °C. Gel permeation chromatography were performed to determined molar masses of polymers. XRD analysis showed that the obtained polycarbonates showed a partially crystalline structure.

Bioadsorbents prepared by chemical activation (H 3 PO 4 ) of the residue of supercritical extraction of green tea leaves and marigold flowers were characterized by elemental analysis, Boehm titration, adsorption/desorption isotherm and scanning electron microscopy (SEM). The adsorption performance aimed at the removal of malachite green, nitrogen oxide and hydrogen sulfide was investigated. The impacts of various influential parameters of malachite green adsorption such as: contact time (8 h), initial dye concentration (20–140 mg/L), temperature (25–65 °C) and adsorbent mass (0.015–0.025 g) were investigated. The adsorption kinetic follows pseudo second-order reaction kinetics ( R 2  > 0.99). The adsorption process was best described by the Langmuir isotherm and the maximum capacity of the monolayer was from 126.58 mg/g to 333.33 mg/g for the biocarbons obtained. The negative values of Gibbs free energy indicate the spontaneous character of the process. The presence of steam in the stream of the mixture of gases had a positive effect on adsorption of nitrogen oxide and hydrogen sulfide by the bioadsorbents obtained. The most effective adsorbent of malachite green and toxic gas pollutants proved to be the biocarbon obtained from the residues of supercritical extraction of green tea leaves.

Biochars and activated carbons obtained from the nettle and the sage herbs were used for Cd(II), As(V), poly(acrylic acid) and polyethylenimine simultaneous adsorption from the multicomponent aqueous solutions. Electrokinetic studies proved that both activated carbons show acidic character of the surface. The point of zero charge of the sample obtained from the nettle herb occurs at pH 3.1, whereas that of the adsorbent obtained from the sage herb at pH 4.0. Cd(II) adsorption causes the decrease in the surface charge density and the zeta potential of both activated carbons, whereas As(V) addition results in the increase of solid surface charge density and its impact on the zeta potential value depends on adsorbent type. In case of the simultaneous presence of metals and polymers, the adsorbed macromolecules have greater influence on the surface charge density and the zeta potential values than the metal ions. Cd(II) and As(V) are well adsorbed on the examined activated carbons irrespective of the solution pH (changing in the range 3–9). Maximum adsorption were 218.27 mg/g for Cd(II) and 205.53 mg/g for As(V). The polymers presence causes a decrease (80–90 %) of both metal ions adsorbed amounts, whereas the poly(acrylic acid) and polyethylenimine adsorption mechanism in the presence of cadmium and arsenic ions depends on the adsorbent type and polymer-metal interactions.

This study presents the preparation and flammability characteristics of polymeric composites based on the epoxy resin Epidian ® 601. The triethylenetetramine (TETA) and commercial curing agents based on polyamines (IDA and PAC) were used as crosslinking compounds. Moreover, two flame retardant compounds were added to this composition, the commercial Fire Retardant (FR) and triphenyl phosphate (TP). The chemical structure of the composites and the course of curing processes were confirmed by the ATR/FT-IR (Attenuated Total Reflection–Fourier Transform Infrared) analysis. The influence of different amounts of FR or TP on the flammability and thermal resistance was discussed in detail. After the flammability test the samples were also studied to assess their thermal destruction. In addition, the composites were subjected to the swelling tests, solvent resistance, and microscopic observations. The DSC curves revealed that all materials were characterized by good thermal properties. All materials were temperature resistant up to 300 °C. Furthermore, the measurements of the hardness of the composite demonstrated that the material EP601 + TETA + 10 %FR is the hardest. The addition of FR and RP influenced the flammability of the composites increasing the thermal resistance. The ageing tests in methanol, acetone, hydrochloric acid, and potassium hydroxide were also carried out.

A headspace high sorptive extraction (HS-HiSorb) Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) method was developed and optimized for the determination of the volatile profile of extra virgin olive oil (EVOO). The HS-HiSorb extraction parameters of temperature, sample mass, stirring rate, and adsorption time were optimized by applying the one-factor-at-a-time (OFAT) approach. A total of 21 multi-varietal olive oil samples were collected from four different olive mills in Cyprus during the harvesting period 2020–2021. Seventy-six volatile organic compounds (VOCs) were identified and semi-quantified, belonging to several chemical categories such as hydrocarbons (31) three of which are terpenes, aldehydes (22), carboxylic acids (6), ketones (5), esters (4), alcohols (3), ethers (2), furans (2), and others (1). Aldehydes (40.20 %) and hydrocarbons (41.08 %) represented the main components of olive oil’s volatile profile. The overall concentrations of VOCs in the samples ranged from 8.73 to 39.81 mg/kg. The HiSorb-TD-GC-MS method was evaluated in terms of repeatability and linearity for selected VOCs. Repeatability was performed at three different concentrations (1, 10, and 100 ppb v ), and the relative standard deviation (RSD) ranged from 2.21 to 15.86 %. The calibration curves of (E)-2-hexenal, 1-penten-3-one, nonanal, and hexanal were developed to evaluate the linearity range. The results were satisfactory, with the correlation coefficient ( R 2 ) greater than 0.98. Finally, the limitations of the method are mentioned and discussed.

The synthesis and characteristics of composites based on bisphenol A diacrylate with the addition of 2-ethylhexyl acrylate, butyl acrylate, or methyl methacrylate were carried out. Benzethonium chloride and zinc oxide were used as special additives in amounts of 1, 2, and 5 % by weight of monomers. These are compounds that exhibit antimicrobial properties. The composites were produced by the UV polymerization method with the addition of Irgacure 651 as a photoinitiator. Aging and swelling tests were carried out in water, solutions of hydrochloric acid and sodium hydroxide, and acetone. To confirm the changes in the structure of the composites, ATR/FT-IR spectra were performed before and after the degradation process. The hardness of the composites was also tested. The antimicrobial properties against Escherichia coli , Staphylococcus aureus , Aspergillus niger, and Candida albicans were checked. The conducted study also showed the significant changes in the Cerrena unicolor fungus secretome caused by the presence of the composites.