Electrochemical synthesis and characterization of basic bismuth nitrate [Bi6O5(OH)3](NO3)5·2H2O: a potential highly efficient sorbent for textile reactive dye removal

A new method of synthesis was developed for the preparation of basic bismuth nitrate [Bi6O5(OH)3](NO3)5·2H2O (ECBBN). Electrochemical synthesis of the material was carried out by galvanostatic electrodeposition from an acidic Bi(III) solution on a Ti substrate and further thermal treatment in air at 200 °C. Characterization of ECBBN was conducted by employing SEM–EDX, N2 adsorption, XRD and FTIR, and its pI was also determined. The analyses showed that the material obtained was pure [Bi6O5(OH)3](NO3)5·2H2O. Morphologically, ECBBN aggregates were composed of crystals, some smaller than 50 nm. Electrochemically synthesized sorbent (ECBBN) was used for the removal of the textile dye Reactive Blue 19 (RB19) from deionized water and model solutions of polluted river water, and it showed considerably superior sorption performance compared to other inorganic sorbents synthesized by conventional methods reported in the literature. A kinetic study suggests that the sorption process is both under reaction and diffusion control. Equilibration of the sorption process was attained in several minutes, i.e. the sorption process is very fast. The sorption equilibrium data were well interpreted by the Langmuir, Redlich–Peterson and Brouers–Sotolongo isotherm. Using Langmuir isotherm, the maximum sorption capacity of ECBBN was reached at pH 2 and was 1049.19 mg g−1

Laboratory Tests of a Hybrid Metal-Composite Transport Helicopter Blade Segment

Experimental acquisition and verification of structural properties of an actual helicopter main rotor blade segment have been done with an aim to validate the capability of bonded joints of these structural elements to sustain the most dominant dynamic loads in forward flight, for the assigned blade's life time. It was also one of the qualitative tests of the newly applied rotor blade hybrid structure production technology, consisting of a metal spar and 21 plastic composite segments, bonded to it after the polymerization process. Because of the structural similarity of the segments, only the most highly loaded 21st segment and adjacent spar section were investigated, as representative in this particular sense. This has enabled remarkable reduction both in time and funds required for the design and construction of the test facility. This paper is focused on the demonstration of usage of fairly low-cost experimental infrastructure for that purpose, and also provides the designers and engineers with some examples and guidelines of how it is possible to conduct experimental verifications of the properties of similar, both aeronautical and non-aeronautical hybrid structures and joints, exposed to the long-lasting dynamic loads. Tests presented in this paper were only a part of a very wide test campaign, mostly undertaken on the entire new hybrid blade structures, both on the ground and in flight, before they have been put to operational service

Initial development of the hybrid semielliptical-dolphin airfoil

Iosif Taposu has formulated a mathematical model and generated a family of airfoils whose geometry resembles the dolphin shape. These airfoils are characterized by a sharp leading edge and experiments have proven that they can achieve better aerodynamic characteristics at very high angles of attack than certain classical airfoils, with the nose geometry inclined downwards. On the other hand, they have not been applied to any commercial general aviation aircraft. The authors of this paper have been motivated to compare the aerodynamic characteristics of widely used NACA 2415 airfoil with Taposu’s Dolphin that would have the same principal geometric characteristics. A CFD calculation model has been established and applied on NACA 2415. The results were compared with NACA experiments and very good agreements have been achieved in the major domains of lift and polar curves. The same CFD model has been applied on the counterpart Dolphin 2415. Results have shown that the Dolphin has a slightly higher lift/drag ratio in the lift coefficient domain 0.1-0.35 than NACA. On the other hand, at higher and lower lift coefficients, its aerodynamic characteristics were drastically below those of the NACA section, due to the unfavorable influence of the Dolphin’s sharp nose. A series of the Dolphin’s leading edge modifications has been investigated, gradually improving its aerodynamics. Finally, version M4, consisting of about 70% of Dolphin’s original rear domain and 30% of the new nose shape, managed to exceed the NACA’s characteristics, thus paving the way to investigate the Dolphin hybrids that could be suitable for the general aviation industry

Fermentation of cow’s milk and soy milk mixture with L. acidophilus probiotic bacteria with yoghurt culture

The aim of the paper was to produce a functional product and to determine the physico - chemical, microbiological and sensory properties of probiotic beverages produced from different mixtures of cow’s milk and soy milk. The ratios of cow’s milk and soy milk were 100:0%, 25:75%, 50:50%, 75:25% and 0:100%. The samples were fermented with probiotic bacteria Lactobacillus acidophilus (La5) with the addition of yogurt culture. The fermentation of samples was performed at +43 °C until coagulation and pH value of 4.6. Characteristics of the obtained beverages were monitored during storage at 1st, 7th, 14th and 21st day of storage at +4 °C. Produced probiotic beverages were observed and change in active acidity, titration acidity, change in the number od probiotic bacteria, and sensory properties and acceptability of products were tracked. After fermentation, the number of lactobacilli in the samples produced gradually decreased during 21 days, but was still above the probiotic minimum (CFU 106 mL−1) so the samples had probiotic properties. Samples of fermented beverages got the best score of their sensory properties on the seventh day of preservation. The sensory properties of the samples were mainly influenced by the type and ratio of the used milk. Mixing cow’s milk with soy milk significantly improved the sensory properties of the product. The acceptance test showed good acceptance of fermented beverages samples by potential consumers, apart from the sample that was 100% soy milk

Application of new biosorbent based on chemicaly modified Lagenaria vulgaris shell for the removal of copper(II) from aqueous solutions: Effects of operational parameters

In present study a low cost biosorbent derived from Lagenaria vulgaris plant by xanthation, was tested for its ability to remove copper from aqueous solution. The effect of contact time, initial pH, initial concentration of copper(II) ions and adsorbent dosage on the removal efficiency were studied in a batch process mode. The optimal pH for investigated metal was 5. A dosage of 4 g dm-3 of xanthated Lagenaria vulgaris biosorbent (xLVB) was found to be effective for maximum uptake of copper(II). The kinetic of sorption of metal was fast, reaching at equilibrium in 50 min. The kinetic data were found to follow closely the pseudo-second-order model. The adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 23.18 mg g-1 copper(II) ions on xLVB. The presence of sulfur groups on xLVB were identified by FTIR spectroscopic study. Copper removal efficiency was achieved at 81.35% from copper plating industry wastevater

Comparison of air pollution in the working environment during in site treatment of infectious medical waste by convertor and autoclave sterilization

The aim of the present study is the comparison of ambient pollution in working environment during infectious medical waste treatment in two relevant health care institutions in the Republic of Serbia - The Blood Transfusion Institute of Serbia and The Clinical Centre of Serbia by different sterilization methods (sterilizer-convertor and autoclave, respectively). Monitoring and analysis of the following chemical compounds were performed in both institutions: water vapor, carbon dioxide, carbon monoxide, hydrochloric acid, methane, ethane, propane, hexane, formaldehyde, benzene, toluene, m-xylene, phenol, acrolein, ethanol, ethyl acetate, ethylamine, ethylene oxide, methanol, dimethyl disulphide, dimethyl sulphide, ethyl mercaptan, methyl mercaptan, freon 11 (trichlorofluoromethane), carbonyl sulphide and hydrogen chloride. The determination of vapor-phase concentrations was done by extractive Fourier transform infrared spectroscopy. Monitoring of ambient pollution during infectious medical waste sterilization has shown that mercaptans, acrolein, formaldehyde, dimethyl sulphide, and ethylene oxide are emitted in both health institutions, in concentrations which are not permitted by regulations, while increased concentrations of hydrogen chloride and phenol were found in the Clinical Centre of Serbia. A comparison of ambient pollution with two different sterilization methods has shown that higher concentrations of pollutants are emitted at higher temperatures. Considering the fact that mentioned compounds exhibit high toxicity, hence represent the risk to air quality in working and living environment, i.e. represents a risk to human health it is necessary to revise and improve the existing treatment methods. © 2020 Parlar Scientific Publications. All rights reserved

Experimental and modelling study on strontium removal from aqueous solutions by Lagenaria vulgaris biosorbent

The shell of Lagenaria vulgaris (LV) plant was used as biosorbent for strontium removal from aqueous solutions. Chemical structure of the biosorbent's surface was characterized by the means of FTIR and Boehm's titrations. SEM-EDX technique was used to study the morphology and elemental composition of the material. The analyses pointed out to abundance of acidic functional groups which are charged in solution and hence responsible for ionic exchange of Sr(II) ions. Sorption was examined by varying initial concentrations of Sr(II) in solutions, sorbent's loadings, pH, and contacting times. Equilibrium of the process was attained in the first 10 min of contacting and followed pseudo-second order and Chrastil's kinetic models. It was established that sorption onto aLVB was heterogenous by nature and fitted well to Freundlich and Sips isotherm models with maximum sorption capacity of 29.55 mg g(-1). Sorption potentail was kept high after six cycles when acidic desorbents were used

A New Photocatalyst Bismuth Oxo Citrate: Synthesis, Characterization, and Photocatalytic Performance

A new photocatalyst bismuth oxo citrate was synthesized by facile precipitation process with calcination at 200 8C. The photocatalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fouriertransform infrared (FTIR) spectroscopy, N2 sorptometry, and elemental analysis. Morphologically, it is composed of polyhedral particles with different, irregular shapes and sizes. The specific surface area (SSA) of the photocatalyst was 8.92 m2 g-1. It showed very good photocatalytic performance and reusability. Total decolorization of Reactive Blue 19 (RB19) was achieved in less than 10 minutes, which is much faster in comparison with TiO2 P25. Also, bismuth oxo citrate showed higher photocatalytic activity than other photocatalysts based on bismuth compounds reported by other authors. Optimal photocatalysis parameters were pH 2 and photocatalyst dose of 250 mg dm-3. The decolorization rate was found to decrease as initial dye concentration increased. The photocatalytic data best fitted to L-H kinetic model with pseudo-first order reaction rate. Chrastil diffusion model showed that diffusion has not influence on the process. Water Environ. Res., 90, 719 (2018). © 2018 Water Environment Federation

Effects of system parameters and inorganic salts on the photodecolourisation of textile dye Reactive Blue 19 by UV/H2O2 process

The photodecolourisation of textile dye Reactive Blue 19 (RB 19), an anionic anthraquinone dye of the reactive class, was investigated using UV radiation in the presence of H2O2 in a batch photo-reactor with low-pressure mercury lamps. The effects of the system parameters: initial pH, initial dye concentration, concentration of peroxide and radiation intensity, as well as the presence of salts, (NaCl, Na2SO4, NaNO3, NaH2PO4) on dye decolourisation was examined. Increasing the initial pH resulted in an increase in decolourisation efficiency. Results showed that with an increase of dye concentration from 10 to 100 mg∙ℓ–1, the efficiency of the process decreases. The highest decolourisation rates were noted at H2O2 concentrations of approximately 30 mmol∙ℓ–1. The increase of radiation intensity from 730 to 1 950 μW∙cm–2, linearly increases decolourisation efficiency. The inorganic ions investigated have inhibiting effects on RB 19 decolourisation by the UV/H2O2 process with inhibition intensities in the following order: H2PO4– > NO3– > SO42– > Cl–. This study has shown that the UV/H2O2 process is a promising technology for degradation of RB 19 in water and wastewater

Effect of irregular interproximal dental restorations on periodontal status

Introduction. Research of effects that irregular interproximal dental restoration have on supporting structures of the teeth and examination of evolution and course of changes in tissue structure is quite a poorly studied topic. Aim of this study is to examine and assess clinical and radiological changes in periodontal tissue caused by irregular interproximal dental restoration in particular group of patients with different age and sex. Methods. Irregularities which were assesed in this study are divided into two groups: a) gap (cracks) occurring between dental restorations and the gingival walls in Class II cavities, b) prominence of dental fillings out of the teeth anatomical sphere, resulting with the positive step in gum third of tooth in Class II cavities. The study was based on whether in the particular forms of irregularities of the dental restorations are differences in the degree of change in the periodontal tissue, depending on the material from which the restoration is made, and the materials used were composite fillings and amalgams. Results of this study show that irregular dental fillings significantly affect the inflammatory response in periodontal tissue. Irregularities in the form of unfilled space cause major changes in periodontal tissue. Composite fillings cause a higher degree of inflammation in relation to amalgam fillings. Conclusion. Improper tooth fillings cause periodontal tissue damages