STUDIA CHEMIA - Issue no.3 / 2018 - Table of contents

Nowadays the need for renewable resources becomes more and more stringent. Biomass remains one of the most important sources of energy, being used directly or by chemical conversion processes in order to produce clean energy. Relative to this aspect, the present paper proposes the direct approach, by analyzing to biomass type materials (topinambur and Romanian hemp) in order to determine their physical and chemical characteristics and their potential use in combustion processes.

Keywords: biomass, combustion, thermal and chemical analysis

Commercial beech wood char characterized by low volatile matter (5.3%) and high carbon content (94.5 %) was initially used as a potential feedstock to obtain the activated carbon for methane sorption. Micro- and mesopores volumes were determined to be at the level of 0.21 cm3∙g-1, while the specific surface area of the material was determined to be at the level of 416 m2∙g-1. Carbonization carried out at the temperature range of 750-900 oC resulted in slight increase of the pore volume (up to the value of 0.23 cm3∙g-1) and the specific surface area (up to the value of 480 m2∙g-1). Upon the steam activation (up to the 50 % loss of the organic mass) the specific surface area increased substantially and was within the range of 887 - 943 m2∙g-1 together with mico- and mesopores volumes that was within the range of 0.54 - 0.58 cm3∙g-1. The maximum methane adsorption was determined for the sample activated at a temperature of 800 oC – 17.7 g∙kg-1 with a process reversibility of 84.2%. Considering the beech wood char price, its availability and well-known methods of its surface structure improvement, the obtained active carbons are interesting for their testing on a larger scale.

Keywords: adsorption; biomass; active carbon; steam activation; carbonization

The article reports the AMS (accelerator mass spectrometry) radiocarbon investigation results of the old common ash of Aiton. Five wood samples were collected from the trunk of the tree. The deepest ends of the samples were analysed by AMS radiocarbon. We found radiocarbon dates between 165 ± 20 BP and 240 ± 18 BP, which correspond to calibrated ages of 230 – 360 years. These results, combined with a ring counting estimate, indicate an age of 330 ± 30 years for the ash of Aiton. By this value, the ash of Aiton becomes the oldest known common ash with accurate dating results.

Keywords: AMS radiocarbon dating, Fraxinus excelsior, dendrochronology, age determination

The paper is focused on the micro and nano organization of atmospheric particulate matter in Grigorescu district of Cluj-Napoca in April and May 2017. Floating particles (FP) collected from atmosphere have an increased amount of minerals such as: quartz, calcite, clays (e.g. kaolinite and muscovite), and traces of lepidocrocite. Their size varies from less than 1 to over 120 μm, established by Scherer method on an XRD pattern. PM10 contains mainly quartz and calcite followed by fractions of kaolinite and muscovite. PM2.5 contains clay in large amount and less quartz particles. Certain nanoparticles are found among PM2.5. The obtained values were in good agreement to TEM and AFM microscopy. The diameters are 42 nm for clay and 92 nm for quartz particles. Nanostructural features are organized around fine micro particles such as PM 2.5. PM10 is often found as particles around FP.

Keywords: floating particles, PM10, PM2.5, micro and nano organization

In this paper, a kinetic study about of dry flue-gas desulfurization process was investigated. Experimental thermogravimetric measurements, employing a CAHN TG- 121 system, have been performed on the reaction of sulfur dioxide and oxygen with calcined limestone. The conversions versus time of calcined limestone, ranging in particle size from 25 to 450 μm, were measured over the temperature range 973-1173 K and a gas rate of 0.046 m/s. The influence of kinetic parameters on the sulfation process has been tracked. A significant influence is the temperature at which the sulfation and the size of the adsorbent granules are achieved. Processing the experimental results in lnkI,II-T-1 coordinates allowed the determination of the activation energy and the establishment of the corresponding mechanisms. The results, Ea>42 KJ/mol for the both indicate that the sulfation process is carried out according to the macrokinetic mass transformation model, only for small granules of the solid with dp < 25 μm and temperatures T> 973 K) are the limiting ones the process. At higher granulations of the solid particles, the activation energy values Ea << 42 kJ/mol, emphasizes that limitative of the global process are the inner/outer diffusion phenomena shown that the sulfation process follows the transfer macrokinetic model.

Keywords: dry desulfurization process, sulfation process, transfer and mass transformation macrokinetic model

The wet chemical synthesis of silver nanoparticles (AgNPs) by reduction of silver nitrate with sodium citrate, tannic acid, and their mixture is reported. The obtained silver nanoparticles were investigated by UV-Vis spectroscopy, scanning transmission electron microscopy (STEM), and atomic force microscopy (AFM) images and their antibacterial effect against Escherichia coli was assessed.

Keywords: silver nanoparticles, sodium citrate, tannic acid, UV-Vis spectra, STEM, AFM, antibacterial effect

This study investigates the influence of microwave field derived from wireless router and mobile telephony sources on polyphenol content and antioxidant activity of basil. The total phenolic content of basil extracts was determined by Folin-Ciocalteu method. The amount of polyphenolic compounds in basil plants exposed to microwave irradiation was higher compared to control plants. Extracts of irradiated basil exhibit higher antioxidant activity than extracts of control plants, as evidenced by the three methods of determination used: 2,2-diphenylpicrylhydrazyl radical scavenging activity, oxygen radical absorbance capacity and Trolox equivalent antioxidant capacity assays. It was determined that microwave irradiation increased both antioxidant activity and polyphenol content of basil extracts. In addition, hydroalcoholic extracts obtained from basil plants exposed to GSM microwaves showed higher antioxidant activity than hydroalcoholic extracts of plants exposed to WLAN microwaves.

Keywords: polyphenols, basil, microwave influence, antioxidant activity

Gum Arabic (GA), also known as Acacia seyal gum (ASG), is a dried exudate from trees of Acacia senegal and Acacia seyal. It provides a rich source of non-viscous soluble fiber with significant health benefits and high antioxidant properties. Tonnes of raw GA are exported annually at a high cost with limited utilization in extraction form. Techniques for the extraction of the bioactive components of GA are available but the high extraction time and the capacity and quality of extraction hinders these procedures. Ultrasonic-assisted extraction is one of the most effective techniques for the recovery of antioxidant and phenolic compounds from ASG. A comparatively low extraction time has been reported for ultrasonication, but the influence of several extraction conditions such as temperature, time and ultrasonic power on the yield of extraction has not been thoroughly studied. This study investigates the optimal ultrasonic extraction conditions for maximum recovery of antioxidant and phenolic compounds from ASG using Response Surface Methodology (RSM) under the Central Composite Design (CCD). Three ultrasonic parameters, namely time in the range of (1-3 hours), power in the range of (1-3 level or 12 to 40 kHz) and temperature from (25-60 °C) were tested for their impact on antioxidant activity. The capacity of the extracts was determined by the scavenging activity of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical, ferric reducing antioxidant power (FRAP) assay, and total phenolic compounds (TPC). The results indicated that ultrasonic time, power and temperature had a positive impact on antioxidant capacity and phenolic compounds. The optimum ultrasonic conditions were found to be a time of 3 hours, a power of 40 kHz, and a temperature of 42.50°C, under which, forty-eight bioactive compounds from the ASG extract were separated by Gas Chromatography coupled to Tandem Mass Spectrometry (GC-MS/MS).

Keywords: Acacia seyal gum, Bioactive compounds, Gum Arabic, Response Surface Methodology, Ultrasonication

The current study analysed the dynamics of oxidative stress markers in patients with acute ST-elevation myocardial infarction treated by primary percutaneous intervention. Excessive reactive oxygen species production is known to induce myocardial reperfusion injury. There are few studies that evaluated oxidative stress markers in the interventional era, the historical papers were all based on thrombolysis as a mean of reperfusion. Thirty-seven patients were included. Peripheral venous blood samples were obtained prior to coronary angioplasty, at 1 hour and 24 hours after that. Plasma malondialdehyde, reduced glutathione / oxidised glutathione ratio and total antioxidant capacity were determined. Malondialdehyde was significantly lower at 1 hour (3.1 ± 0.96 nmol/ml vs 2.68 ± 0.81 nmol/ml, p < 0.01) and 24 hours (3.1 ± 0.96 nmol/ml vs 2.15 ± 0.95 nmol/ml, p < 0.01). Also, reduced glutathione / oxidised glutathione ratio dropped significantly at 1 hour (3.25 Q1-Q3 2.17-5.19 vs 2.33 Q1-Q3 1.53-2.82, p < 0.01) and at 24 hours (3.25 Q1-Q3 2.17-5.19 vs 1.96 Q1-Q3 1.28-2.85, p < 0.01). Total antioxidant capacity had non-significant variation. There was no correlation between these markers and time from symptom-onset or left ventricular ejection fraction. Reperfusion of the occluded coronary artery by percutaneous coronary intervention in acute myocardial infarction led to a rapid decrease of reduced glutathione / oxidised glutathione ratio, that may indicate a depletion of antioxidants as a consequence of overproduction of reactive oxygen species in the damaged area. However, the malondialdehyde level significantly decreased after vessel opening. This may suggest low reperfusion injury after angioplasty.

Keywords: Oxidative stress, acute myocardial infarction, malondialdehyde, glutathione, total antioxidant capacity

Gold nanoparticles have been functionalized with the biologically active MUC-1 peptide conjugated to KLH and the obtained bio-nanostructure was characterized using an array of techniques such as: UV-Vis and ATR-FT-IR spectroscopy, dynamic light scattering (DLS) and atomic force microscopy (AFM). A 54 nm monodisperse bio-nanostructure with high aqueous stability was obtained.

Keywords: gold nanoparticles, functionalization, MUC-1 peptide

The aim of this study was the preparation and characterization of different biomorphic implants based on calcined cattle bones coated with hydroxyapatite (Hap) based nanocomposites in different ratios. For comparison, molded nanocomposites were also produced as biomorphic implants. The obtained nanocomposite/implants were characterized using X-ray diffraction, light microscopy and scanning electron microscopy, Brunauer-Emmett-Teller surface area and apparent porosity. The release of Ca and P in simulated body fluid was monitored by X-ray fluorescence. The adsorption capacity and extended-release dosage of implants were investigated with ibuprofen, an anti-inflammatory drug, by UV-VIS spectroscopy. The highest adsorption efficiency and stability were obtained for sintered (S) (Hap-) and 20% gelatin (G) nanocomposite (Hap-20G-S) and bone parts coated with Hap-S and Hap-20G-S nanocomposite, respectively. The best results (high adsorption efficiency and slow release - low desorption capacity) were obtained for molded Hap-20G-S composite, without bone. In summary, the cattle bones with hydroxyapatite coatings show great promise in production of inexpensive and patient-specific bone implants.

Keywords: biomorphic implants, hydroxyapatite, gelatin, carbon nanotubes, ibuprofen

For this study, a natural ionic exchanger (zeolitic volcanic tuff) and a synthetic anionic exchanger were considered, to remove iron and manganese ions, reduce COD, chlorides and conductivity values from water. It was worked with a zeolitic volcanic tuff cropped out from Macicas area, Romania, and a synthetic anionic exchanger Amberlite A-21. A groundwater and surface sources of drinking water from Ialomiţa-Muntenia (Romania) catchment were analysed, with iron and manganese contents (0.2527–0.3059 mg Fetot/L, 0.0234 mg Mn/L), COD (14.530–17.064 mg KMnO4/L), chlorides contents (170.95 mg/L), pH=7.70, and with electrical conductivity of 1433-1451 μS/cm. The ionic exchange process has been achieved in batch and continuous-flow conditions. The process was realized in static regime, with good results, the highest efficiencies for iron and manganese ions removal being 99% and 79-95%, respectively.

Keywords: municipal water source, food water, zeolitic volcanic tuff, ionic exchange