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Title:Določevanje koncentracij in testiranje baktericidnega delovanja koloidnega srebra v vodi
Authors:Jerkič, Andrej (Author)
Korte, Dorota (Mentor) More about this mentor... New window
Files:.pdf Andrej_Jerkic.pdf (2,42 MB)
 
Language:Slovenian
Work type:Bachelor thesis/paper (mb11)
Tipology:2.11 - Undergraduate Thesis
Organization:FZO - Faculty of Environmental Sciences
Abstract:Koloidno srebro (Ag0) je vodna suspenzija delcev srebra v velikosti od 1 nm do 100 nm. Zaradi svojih edinstvenih lastnosti, kot so antibakterijsko in antivirusno delovanje, se pogosto uporablja predvsem v medicini in pri postopkih, povezanih z obdelavo vode. Koloidno srebro uvrščamo med težke kovine, ki jih človeško telo ni sposobno presnoviti, zaradi česar pride do nalaganja v ledvicah, koži, jetrih in nevronih, kar lahko vodi do negativnih zdravstvenih posledic. Nalaganje srebra v telesu lahko povzroči pljučni edem, krvavitve, nekrozo kostnega mozga, jeter in ledvic, argirijo, vrtoglavico ter nevrološke motnje. Prav zaradi morebitnih negativnih vplivov na živa bitja je pomembna natančna določitev koncentracije koloidnega srebra v vodi, ki je potrebna za ustrezno baktericidno delovanje in za zagotavljanje ustrezne kakovosti pitne vode, a hkrati ni nevarna zdravju. V diplomski nalogi smo določevali koncentracije koloidnega srebra v vodi iz 3 različnih virov z uporabo UV-Vis spektrofotometrije (SPEC) in spektroskopije s toplotnimi lečami (TLS). Z izračunom spodnje meje določevanja (LOD) za SPEC in TLS metodo smo pokazali, da je zaradi nižje LOD vrednosti TLS metoda primernejša za detekcijo Ag0 v vodi. Vrednosti koncentracije srebra so lahko nižje od LOD, katero lahko dosežemo s SPEC, zato ta metoda ni primerna za merjenje zelo nizkih koncentracij. S preučevanjem baktericidnega delovanja koloidnega srebra smo dokazali, da njegova prisotnost v koncentracijah, ki so enake maksimalnim dovoljenim koncentracijam (MCL), ni dovolj visoka za uničenje bakterij. Slednja koncentracija je ustrezna le za zaviranje oziroma onemogočanje razmnoževanja bakterij. Dokazali smo tudi, da imajo koncentracije Ag0, ki 300-krat presegajo vrednost MCL v vodi, visoko baktericidno učinkovitost (znižanje logaritemske vrednosti > 3). Baktericidno delovanje koloidnega srebra smo povezali z velikostjo in obliko nanodelcev. To smo določili z metodo, ki temelji na dinamičnem sipanju svetlobe (DLS), in z uporabo vrstičnega elektronskega mikroskopa (SEM). Ugotovili smo, da se povprečna velikost delcev srebra povečuje z višanjem koncentracije Ag0. Največje spremembe smo zaznali med vzorcema s koncentracijo 50 ppb in 1 ppm ter med vzorcema z koncentracijo 1 ppm in 5 ppm. Pri primerjavi povprečne velikosti delcev med koncentracijama 5 in 15 ppm nismo zaznali velikih razlik. Sklepamo lahko, da se pri koncentracijah, višjih od 5 ppm, velikosti nanodelcev srebra ne spreminjajo več značilno s povečevanjem koncentracije Ag0. Z višanjem koncentracije srebra so se tvorili aglomerati, katerih velikost se je z višanjem koncentracije povečevala.
Keywords:koloidno srebro, spektrofotometrija, TLS, bakterije, absorbanca, SEM, aglomerati
Year of publishing:2016
Source:Nova Gorica
COBISS_ID:4366075  Link is opened in a new window
URN:URN:SI:UNG:REP:EBS18UUA
Views:3648
Downloads:205
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Secondary language

Language:English
Title:Determination of colloidal silver in water and testing its bactericidal activity
Abstract:Colloidal silver (Ag0) is an aqueous suspension of particles with the size between 1 nm to 100 nm. As a result of its unique properties, colloidal silver is commonly used in medicine and in the water treatment processes, since it provides high bactericidal, antifungal and antiviral efficiency. On the other hand, silver belongs to the group of heavy metals, which cannot be metabolized. It is accumulated in liver, skin, kidneys and neurons and causes different disease, such as pulmonary edema, haemorrhaging, necrosis of the bone marrow, liver and kidneys, argyria, nausea, and different neurological disorders. Because of these harmful side effects of using colloidal silver it is very important to determine very precisely the concentration of Ag0 in water, to determine its optimal amount to ensure its bactericidal efficiency without any harm to living organisms. In the thesis we determined the concentration of colloidal silver in river water from 3 different sources with UV-vis spectrophotometry (SPEC) and thermal lens spectrometry (TLS). By calculating the limit of detection (LOD) of the SPEC and TLS methods, it was shown that TLS is a more suitable method for detecting colloidal silver in water, because its concentrations in the river water may be lower than the LOD of the SPEC method. By studying the bactericidal effects of colloidal silver, we found that the MCL (maximum contamination level) of colloidal silver is not high enough to kill the present bacteria, but is only efficient for inhibiting the bacterial reproduction. Furthermore, we found that the Ag0 concentration of 300 times above the MCL value has high bactericidal efficiency (log. red > 3). We also studied the bactericidal efficiency of colloidal silver in correlation to its size and shape. Thus, the DLS (dinamic light scattering) analysis and SEM (Scanning Electron Microscope) measurement were performed. It was found that the size of the silver nanoparticles increases drastically between the sample of concentration 50 ppb compared to 1 ppm and 1 ppm compared to 5 ppm. For the silver nanoparticles concentration between 5 ppm and 15 ppm only little differences in average particles size were observed. We can conclude that in case of samples with concentrations higher than 5 ppm, the particle size does not increase significantly with the increase of Ag0 concentration as it does for samples of silver nanoparticles concentration lower than 5 ppm. Furthermore, silver nanoparticles form agglomerates, which become larger in samples with higher silver concentrations.
Keywords:Colloidal silver, spectrophototermy, TLS, bacteria, absorbance, SEM, agglomerates


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