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The interaction ability of cellulosic materials as a function of fine structure and Helmholtz surface energy
Tatjana Kreže, Karin Stana-Kleinschek, Volker Ribitsch, Zdenka Peršin, Majda Sfiligoj-Smole, 2005, izvirni znanstveni članek

Opis: Many chemical or physical modification processes significantly influence the accessibility of fiber forming polymers by causing structural changes. The wettability and sorption ability improvements of polymeric materials are major tasks during finishing processes. Different pre-treatment processes are used in order to improve the accessibility of dissociable groups, hydrophilicity, dyeability, and whiteness. These are usually alkaline purification, chemical bleaching and mercerization. In a previous paper we presented the data for structural characteristics (density, crystallinity index, molecular orientation, void volume, diameter and the specific inner surface of void, etc.) of untreated regenerated cellulose fibers (viscose, modal and lyocell) [41]. We now compare the influence of different pre-treatment processes on fiber structure and the accessibility of the chemical groups of these fibers. In order to improve the accessibility, two pre-treatment processes were used: chemical bleaching of fibers and tensionless alkali treatment. The influence of these pre-treatment processes on the structure parameters was evaluated using viscosity measurements (determination of polymerization degree (DIN 54 270)) and iodine sorption ability measurements according to the Schwertassek method (determination of crystallinity index) [13, 16]. The reactivity and accessibility in a polar environment was determined using tensiometry. Contact angles between the fibers and liquids of different polarities were determined using the powder contact angle method and calculated from a modified Washburn equation [26, 28]. The surface free (Helmholtz) energy of differently treated fibers was determined from the contact angle data using the Owens-Wendt-Raeble-Kaelble approximation [30, 33, 35]. The differences in the accessibility of raw and pre-treated regenerated cellulose fibers obtained using tensiometry are compared with the results of the conventional method used to determine moisture adsorption (DIN 54 351, DIN 53 802). In regard to raw fibers, viscose shows the most hydrophilic characteristic: adsorbs the highest amount of moisture, has the fastest penetration velocities (Fig. 6), the smallest contact angle, and the highest SFE (Fig. 8). Modal fibers have the largest contact angle, the lowest SFE, and they adsorb the smallest amount of water vapor. Pre-treatments increase the sorption ability and the surface free (Helmholtz) energy while they decrease the contact angle. This makes the material more accessible to water and chemicals used in the finishing processes although the crystallinity index increases. The main modification in polymer properties caused by the treatments is an increase in the fiber SFE caused by an increase of the fiber surfaces because of swelling in the alkaline medium (washing, slack-mercerization), and due to an increase of accessible OH- and COOH-groups (bleaching). This enables the formation of an increased number of hydrogen bridges between the water molecules and the OH- and COOH-groups. Our investigations confirm the results published earlier thatthe main property necessary for the proper sorption behavior of cellulose materials are the accessible, less ordered regions and not the degree of crystallinity.
Ključne besede: regenerated cellulose fibers, fiber pre-treatment, iodine sorption, cristallinity, tensiometry, contact angle, Helmholtz surface energy, water adsorption
Objavljeno: 01.06.2012; Ogledov: 1555; Prenosov: 19
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Influence of magnetic field on the aragonite precipitation
Lucija Črepinšek-Lipuš, Danijela Urbancl, 2007, izvirni znanstveni članek

Opis: Many laboratory investigations of magnetic water treatment (MWT) for scale control explained the formation of less compact scales by raised portion of aragonite, which is needle-like and less adhesive than rhombohedral calcite crystals, while our experiment was conducted with tap water, which contains Mg+2 and Fe+2 ions in concentrations exceeding thresholds for calcite inhibition, common for major tap waters. MWT efficiency was evaluated by amounts of scale precipitated in boilers and pipes during three-weeks run of two parallel experimental lines-one with and another without magnetic treatment. All scales were identified by X-ray diffractometer to be aragonite,but in the case of magnetic treatment, scales occurred in much smaller amounts: the scale on heating copper-pipe spiral was 2.5-times thinnerdue to MWT and in zinc-coated steel pipe occurred as very thin powder-like coating, while in the line without the treatment abundant hard lining was formed. The scalesć morphology was observed by scanning electron microscope: the husks from both lines consisted of parallel distributed needles, but these crystals were about four times thinner in the case of MWT. The present work demonstrates that hard scale deposits can form even under conditions where aragonite precipitates predominantly, and that MWT can also affect the crystallization of this polymorph in a manner conducive to scaling control.
Ključne besede: water, magnetic water treatment, scale, aragonite, cristallization, water supply pipes
Objavljeno: 01.06.2012; Ogledov: 1079; Prenosov: 31
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Water pre-treatment process in food industry
Marjana Simonič, 2009, izvirni znanstveni članek

Ključne besede: drinking water, food industry, pre-treatment, membrane
Objavljeno: 10.07.2015; Ogledov: 510; Prenosov: 7
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The influence of physico-chemical parameters on water scale precipitation on washing machines' heaters
Danijela Urbancl, Darko Goričanec, Jurij Krope, 2007, strokovni članek

Opis: The paper presents the results of analysis of physico - chemical parameters influence on the intensity of water scale precipitation on washing machines heaters. Washing machines of the same producer were, to this end, modified to an endless cycle of washing with the same amount of cotton fabric at the same conditions. On the basis of various experiments it was determined that water hardness, the amount of exceeded carbon dioxide, water turbulence around the heater, the amount of cotton fibres in water exceeded from fabrics, and heater specific heat strength have the key role in water scale building up in washing machines heaters.
Ključne besede: magnetic water treatment, magnetic hydrodynamics, water scale, calcium carbonate, scale prevention, washing machine, electrical heater
Objavljeno: 21.12.2015; Ogledov: 495; Prenosov: 22
.pdf Celotno besedilo (544,97 KB)
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The influence of electrogalvanic device on scaling
Marjana Simonič, Irena Ban, 2013, izvirni znanstveni članek

Opis: The use of an electrogalvanic device for scale neutralisation is descibed in this paper. Physico-chemical analyses were performed before and after the treatment. The results were compared with those obtained by using magnetic water treatment device. By measuring some individual parameters and the implementation of chemical analysis, the satisfactory functioning of the electrogalvanic device was demonstrated. The quality of drinking water did notchange much after the water treatment method. The results of determination of calcium carbonate saturating index showed that the raw drinking water is incarbonate equlibrium as well as both treated water samples. The calcite/aragonite ratio was studied by means of microscopy and X-ray powder diffraction. Inspection of crystals formed during the experiments with microscopy indicated that aragonite crystal structure of the precipitates prevailed over the calcite stucture. The diffractograms showed that the share of aragonite increased after using the electrogalvanic device compared with raw drinking water samples where the share of calcite was higher.
Ključne besede: water treatment, electrogalvanic device, calcite, aragonite
Objavljeno: 03.04.2017; Ogledov: 364; Prenosov: 76
.pdf Celotno besedilo (1,40 MB)
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Kinetic studies of catalytic ozonation of atrazine
Brigita Tepuš, Marjana Simonič, 2008, izvirni znanstveni članek

Opis: The aim of our work was to degrade atrazine by the ozone treatment of both a model and the original drinking water samples, using Pt-catalyst, and to evaluate the performance of this catalyst. The rate constant for the reaction of atrazine with ozone was determined in the model water sample. The activation energies and the reaction orders of ozone decomposition were determined in both the model and the drinking water samples. Ozone treatment using Pt-catalyst has some influence on the loss of atrazine in the sources of drinking water. The concentration of some metabolites in the model and drinking water was observed during ozone treatment. The toxicity of atrazine to crustacean Daphnia magna in the original drinking water and in the ozone treated water samples was also assessed.
Ključne besede: ozone, Pt-catalyst, atrazine, water treatment, waste water, kinetics
Objavljeno: 05.07.2017; Ogledov: 183; Prenosov: 42
.pdf Celotno besedilo (185,82 KB)
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Magnetic field effects on redox potential of reduction and oxidation agents
Mojca Božič, Lucija Črepinšek-Lipuš, Vanja Kokol, 2008, izvirni znanstveni članek

Opis: Redox potentials of two reducing (sodium dithionite and glucose) and two oxidizing (hydrogen peroxide and sodium hypochlorite) agents were monitored at various concentrations and at different temperatures for 30-75 minutes after the exposure of their water solutions (glucose and hypochlorite solutions once; sodium dithionite and hydrogen peroxide solutions one, two and/or three-times) to the static magnetic field of flux density of 0.9 V s M-2 . The aim of the investigation was to suggest improvements, i.e., intensification and stability, of the reduction-oxidation ability of selected agents applicable in textile fibre processing, primarily bleaching and vat dyeing. Results of the experiments show that magnetic treatment (of solutions) raises both the reducing ability of glucose and the oxidation ability of hydrogen peroxide and sodium hypochlorite, promising some technological and economical benefits for the textile industry as well as forother fields of chemistry.
Ključne besede: magnetic water treatment, sodium dithionite, glucose, hydrogen peroxide, sodium hypochlorite, redox potential, textile vat processing
Objavljeno: 05.07.2017; Ogledov: 202; Prenosov: 37
.pdf Celotno besedilo (206,88 KB)
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Reduction of sludge volume in waste waters at the end of the drinking water treatment process
Rebeka Fakin, 2018, magistrsko delo

Opis: Water treatment at Seierstad drinking water treatment plant is done by chemical coagulation using aluminum-based coagulant. The quality of the drinking water source – Lake Farris, has decreased throughout the years, that is why more and more particles, organic matter and dissolved minerals must be removed. That contributes to the volume of sludge being produced at the end of the process. The main objective of the assignment is to reduce sludge volume by coagulation and flocculation in the sedimentation basins using a coagulant/flocculent. In order to choose the right coagulant tests have been performed in the laboratory and on the actual process. The laboratory analyses showed great potential and one of the coagulants has been chosen and tested on the actual process. The testing was followed up for the entire summer of 2016 and then compared to the year before. We have been following the pH and Al3+ content in the water being released back to the environment and visibility in the top water layer in the sedimentation basin. Cost analysis, including the cost of chemicals and electricity usage, has been done. The sludge reduction was successful, and it was approximately 49% less than the year before.
Ključne besede: Water treatment, lake Farris, sludge treatment using coagulation and flocculation, effects of aluminum on the environment.
Objavljeno: 09.03.2018; Ogledov: 230; Prenosov: 42
.pdf Celotno besedilo (2,97 MB)

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