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Environmental friendly method of the epoxidation of limonene with hydrogen peroxide over the Ti-SBA-15 catalyst

Abstract

This work presents the studies on the epoxidation of limonene to 1,2-epoxylimonene with hydrogen peroxide and over the titanium-silicate Ti-SBA-15 catalyst. The main object of the research was a solvent effect on the epoxidation process. The influence of solvents, such as: methanol, toluene, propan-2-ol (isopropyl alcohol), acetonitrile and ethanol has been studied. Furthermore, the influence of temperature in the range of 0-120°C and the reaction time in the range of 0.25-48 h have been investigated. Gas chromatography and iodometric titration methods were used to establish the products of this process and amount of the unreacted hydrogen peroxide. 1,2-Epoxylimonene, 1,2-epoxylimonene diol, perillyl alcohol, carvone and carveol have been determined as the main products of this process. All these compounds are very valuable raw materials for organic syntheses, medicine or cosmetic and food industry.

Open access
Flocculation efficiency of hybrid polymers with trivalent metal cations

Abstract

Acrylamide/acrylic acid copolymers (AAm/AA) have been synthesized by microemulsion polymerization in absence and presence of trivalent cations Al+3 and Fe+3. Starch materials were obtained by introducing cations Al+3 and Fe+3, in the form of aqueous solutions of sulphates(VI) (modif. starch/Me+3), into the oxidized starch (modif. starch). The flocculation performance of obtained polyacrylamide copolymers and the one based on the natural polymer was compared with the performance of the commercial AAm/AA flocculant (CF). All materials were characterized by capillary viscometry, FTIR and DSC methods. An aqueous suspension of talc was used for the flocculation studies. The flocculation effectiveness was evaluated on the basis of reduction of suspension extinction and the sludge volume. It was found that synthesized AAm/AA/Me+3 copolymers and modif. starch/Me+3 materials exhibit better flocculation properties for a model talc suspension than a commercially available floculant.

Open access
Genetic variability in Acidithiobacillus spp. – a working horse of environmental biotechnologies

Abstract

The genus Acidithiobacillus comprises 7 species of Gram-negative obligatory acidophilic chemolithotrophic bacteria that derive energy mainly from the oxidation of reduced sulphur compounds. Four of the species also catalyse the dissimilatory oxidation of ferrous iron while three (A. thiooxidans, A. albertensis, and A. caldus) do not. Bacteria from the genus Acidithiobacillus are often associated with mineral biotechnologies (biomining) and acid mine drainage. While acceleration of mineral solubilisation is a positive aspect in environmental biotechnologies, it is undesirable in acid mine drainage with strong negative ecological impact and there is profound interest in genetics and genomics of these bacteria. Representatives of Acidithiobacillus genus occur world-wide, however there are limited data on Acidithiobacillus spp. variability from Slovakia. In our work the variability of Acidithiobacillus spp., from Slovakia was analysed and the presence of A ferrooxidans was detected. In addition, for the first time we report here on the occurrence of A. albertensis as well. Comparative analyses confirmed pronounced genetic and genomic diversity within the genus, especially within A. ferrooxidans and A. thioxidans complexes. Based on data presented, several Acidithiobacillus species could be considered as a complex species and the description of several new species is very probable in the near future.

Open access
Influence of epoxy resin curing systems and aluminium surface modification on selected properties of adhesive joints

Abstract

The aim of the present study was to investigate the effect of epoxy resin curing agents and aluminium surface modification on the properties of adhesive joints which were subjected to aging under thermal shock conditions. Composites containing reinforced aramid and carbon fibres with aluminium flat profiles (alloy Al 5754) were tested under shear conditions. Epoxy resin (Araldite LY 1564) with amine curing agents (Aradur 3486, Aradur 3487 and Aradur 3405) was used as a matrix. Composites were made using vacuum-assisted contact lamination. The degree of degradation was assessed on the basis of lap shear strength of adhesive joints in accordance with EN ISO 1465:2009. The research showed that epoxy composite samples based on Aradur 3405 (accelerated aliphatic polyamine) and sanded surface of aluminium presented the best lap shear adhesive strength, because this composite has the largest roughness. The hardness of the used adhesive is slightly increased with the cycle number.

Open access
Membrane reactor for enzymatic depolymerization – a case study based on protein hydrolysis

Abstract

The efficiency of enzymatic depolymerization in a membrane reactor was investigated. The model analysis was performed on bovine serum albumin hydrolysis reaction led by three different enzymes, for which kinetic equations have different forms. Comparing to a classic reactor, the reaction yield turns out to be distinctly higher for all types of kinetics. The effect arises from increasing (thanks to the proper selectivity of the applied membrane) the concentration of reagents in the reaction volume. The investigations indicated the importance of membrane selectivity election, residence time and at non-competitive inhibition the substrate (biopolymer) concentration in feed stream. Presented analysis is helpful in these parameters choice for enzymatic hydrolysis of different biopolymers.

Open access
Non-alcoholic beer production – an overview

Abstract

Through years beer became one of the best known alcoholic beverages in the world. For some reason e.g. healthy lifestyle, medical reasons, driver’s duties, etc. there is a need for soft drink with similar organoleptic properties as standard beer. There are two major approaches to obtain such product. First is to interfere with biological aspects of beer production technology like changes in mashing regime or to perform fermentation in conditions that promote lower alcohol production or using special (often genetic modified) microorganism. Second approach is to remove alcohol from standard beer. It is mainly possible due to evaporation techniques and membrane ones. All these approaches are presented in the paper.

Open access
Numerical investigation of the turbulent flow generated with a radial Turbine using a converging hollow blade

Abstract

The aim of this study is to investigate the effect of the blade shape on the characteristic of the flow patterns in a stirred tank. A new impeller blade design has been proposed. It is characterized by a converging hollow. The investigations of the flow structure generated in the vessel are made by using the computer code ANSYS CFX (version 16.0). The analysis has shown that the converging hollow blade yields highly radial flows which gave an increase in the radial velocity by 35% with less power consumption than the flat blade. Also, the effectiveness of the energy dissipation and the quality of mixing has been obviously noted. A validation test of our predicted results with other literature data was done, and a satisfactory agreement has been found.

Open access
Oxidation of cyclic ketones to dicarboxylic acids

Abstract

This paper reports the results of studies concerning an alternative method of obtaining dicarboxylic acids, which consist of the oxidation of cyclic ketones with oxygen or air. The raw materials used were cyclopentanone, cycloheptanone, cyclooctanone, cyclododecanone, 1-tetralon, 2-methylhexanone, 3-methylcyclohexanone and 4-methylcyclohexanone. Oxidation reactions were conducted at 70-100°C, under pressure of 0.1 or 0.4 MPa, for 6 h, utilizing the salts of transition metals as catalyst and acetic acid as solvent. For example, when cyclopentanone was oxidized in the presence of Mn(II) salt, a conversion above 98% and selectivity to glutaric acid up to 68% were obtained. Among synthesized dicarboxylic acids, 1,12-dodecanoic acid was obtained with the highest selectivity of 76%.

Open access
Permeability of P and K-nutrient through polystyrene membrane from aqueous solutions of urea + KH2PO4

Abstract

With the polymer-coated fertilizer as background, the permeability of P- and K-nutrient through a representative polymer membrane-polystyrene membrane were investigated by measuring their permeability in the solutions of KH2PO4-water and urea-KH2PO4-water at nominal temperature of 298 K using the Ussing chamber method. To analyze and interpret the variation of permeability with solute concentration, the solubility of permeate in polymer membrane were determined experimentally and the permeate diffusion coefficient were assessed by the measurements of density and apparent molar volume of the aqueous fertilizer solutions. An interesting “increase-decrease” trend for the permeability of both phosphorous (P)-nutrient, and potassium (K)-nutrient fertilizer with permeate concentration was observed, in which the increases in permeability at low concentrations of permeate could be attributed to the increase in solubility of KH2PO4 in polymer while the decreases in permeability at high concentrations was due to the decrease in diffusion coefficient of permeate in polymer membrane. Finally, the release kinetics of these nutrients from a PS-coated urea-KH2PO4 compound fertilizer granule was predicted using the Shaviv’s model along with the permeability data of P- and K-nutrient generated.

Open access
Preparation, Characterization, and Application of N,S-codoped TiO2/Montmorillonite Nanocomposite for the Photocatalytic Degradation of Ciprofl oxacin: Optimization by Response Surface Methodology

Abstract

An N,S-codoped TiO2/Montmorillonite nanocomposite, as a photocatalyst, was synthesized in the sol-gel method and used for the degradation of ciprofloxacin (Cip) in an aqueous solution. N,S-codoped TiO2/Montmorillonte was characterized by powder X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), and X-ray fluorescence (XRF) analyzes. A central composite design (CCD) was used to optimize the variables for the removal of Cip by the N,S-codoped TiO2/Montmorillonite. A maximum decomposition of 92% of Cip was achieved in optimum conditions. The band gap value for the nanocomposite was 2.77 eV. Moreover, with the use of nanocomposite in the four consecutive runs, the final removal efficiency was 66%. The results show that the N,S-codoped TiO2/ Montmorillonite under simulated sunlight irradiation can be applied as an effective photocatalyst for the removal of Cip from aqueous solutions.

Open access