Removal of manganese in batch and fluidized bed systems using beads of zeolite a as adsorbentBojana Obradovic
, Nataša Novak Tušar
, Iztok Arčon
, Janez Kovač
, Mina Jovanovic
, Nevenka Rajić
, 2016, izvirni znanstveni članek
Opis: In this study the uptake capacity of Mn(II) ions by zeolite A beads was investigated for different initial Mn concentration (100e400 mg Mn dm^-3) in batch mode at 25e55 C. The obtained adsorption capacity varying from 30 to 50 mg Mn g^-1 demonstrated a high affinity of zeolite A towards Mn(II) present in solutions. Kinetic studies indicated the intra-particle diffusion as the rate limiting step up to 45 C with apparent diffusivities in the range (1.2e2.0) x 10^-13 m2 s^-1 and the activation energy of 21.9 kJ mol^-1, which implies strong interactions between the zeolite A and Mn ions. At 55 C ion-exchange became the rate limiting step. The adsorption isotherms were studied at 25 C showing that the Mn adsorption is the best described by the Langmuir model suggesting a homogenous zeolite surface. XPS analysis of the Mnloaded beads showed that there is no surface accumulation of Mn but an almost uniform Mn distribution inside zeolite A, whereas XANES and EXAFS suggested that the adsorption of Mn(II) was followed by the Mn(II) oxidation and oxide formation. Regeneration of the spent zeolite was examined in 8 adsorption/desorption cycles by a chelating Na2EDTA in a fluidized column. It has been found that zeolite A beads could be reused for at least 4 cycles with satisfactory Mn(II) adsorption efficiencies of about 70%.
Najdeno v: ključnih besedah
Ključne besede: Zeolite A
Objavljeno: 01.04.2016; Ogledov: 3818; Prenosov: 0
Polno besedilo (1,27 MB)
KINETICS OF CELLULOSE DEGRADATION STUDIED USING SIZE EXCLUSION CHROMATOGRAPHYAneta Balažic Fabjan
, 2016, magistrsko delo
Opis: For more than five centuries, paper has been the predominant carrier of information and numerous medieval manuscripts bear witness of its durability. However, increasing demand for paper led to several changes in its production in the 19th century. High quality rag fibres were replaced by inferior wood-originating ones. Acid manufacturing technology was introduced which, due to its simplicity and low cost, continued to be used until the end of the 20th century. Inherently stable paper rapidly degrades in the presence of acids and its decay is further promoted by the poor storage conditions and environmental pollutants. As a result, the amount of degraded paper in libraries, archives and museums is reaching enormous proportions. In order to prolong the usable time of the vast quantities of original materials, paper collections may be deacidified and/or stored at lower temperatures. While preservation options are known, lack of the competent comparative studies leaves collection keepers hesitant of their use. The introductory part of the project is focused on development of analytical methodologies and model materials, representative of historical acid paper. As uniqueness and inherent value of cellulose-based cultural heritage limits the use of analytical methodologies to the non-destructive or micro-destructive ones. A new methodology for determination of the condition of paper was developed. The analytical technique-size exclusion chromatography for the first time allows us to reproducible determine the condition of paper which contains a significant amount of wood derived lignin. A few fibres suffice for the analysis, which renders the methodology suitable for characterisation of historical materials. The results of the research will represent the effect of deacidification processes with use of micro destructive analytical methodologies. As written word is all what we have for our legacy from generation to generation, evaluating preservation strategies for decaying collections, safekeeping and long term access to the endangered written cultural heritage is one of the most important facts.
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Ključne besede: paper, size exclusion chromatography, kinetics, deacidification process
Objavljeno: 02.09.2016; Ogledov: 4797; Prenosov: 237
Polno besedilo (1,33 MB)
Water reveals non-Arrhenius kinetics in protein folding experimentsArtem Badasyan
, 2020, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)
Opis: Statistical theories describe systems in equilibrium, and cannot be used to study kinetics. However, the theo-
ries are based on coarse-grained parameters, that include assumptions regarding the underlying kinetics. If
such assumptions are incorrect, the theoretical expressions, used to process the experimental data, will not
fit. I report on one such case we have met within the application of Zimm-Bragg  theory to process folding
experiments, and discuss the reasons and consequences.
Studies of relaxation phenomena in glass-forming liquids by default account for the shift in temperature by
some value, corresponding to the glass formation temperature, .In particular, temperature
appears in hydrated proteins because of the presence of partially glassy states giving rise to
Arrhenius relaxation times log τ ~ .
A phenomenological approach was suggested
by Adam and Gibbs as early as in 1965 to describe
the sudden increase of viscosity and the slowing down of the collective modes in super-cooled liquids as the
temperature is approaching. The key idea of Adam-Gibbs theory was to consider the supercooled liquid
as a set of clusters (cooperatively rearranging regions) of different sizes that change with temperature,
giving rise to the shift in re-
laxation time. The temperature shift factor is present in many theories
describing properties of water.
Thus, Truskett and Dill had to include the Adamm-Gibbs temperature
shift into their simple analytical model of water to achieve the agreement with experimental data on the tem-
perature dependence of self-diffusion coefficient . Later, Schiro and Weik have summarised recent in vitro
and in silico experimental results regarding the role of hydration water in the onset of protein structural dy-
namics, and have reported the presence of super-Arrhenius relaxation region above the ”protein dynamic
transition” temperature . Recently, Mallamace et al have used the Adam-Gibbs theory in their NMR meas-
urements of protein folding-unfolding in water  and to rationalise the complicated pressure-temperature
diagrams in these glass-forming systems.
Motivated by the considerations above, and taking into account the
relationship between the
unimolecular rate of folding in water and the relaxation time 45 , we
perature shift into the formulas used to fit experimental data on hydrated polypeptides.
By doing so we resolve the paradox and complete the new method of processing the Circular Dichroism ex-
perimental data on protein folding
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Ključne besede: water, protein folding, non-Arrhenius kinetics
Objavljeno: 20.07.2020; Ogledov: 1337; Prenosov: 64
Polno besedilo (2,35 MB)
Preparation of porous [alpha]-Fe[sub]2O[sub]3 thin films for efficient photoelectrocatalytic degradation of basic blue 41 dyeSaim Emin
, Lorena Butinar
, Branka Mozetič Vodopivec
, Mitja Martelanc
, Manel Machreki
, Takwa Chouki
, 2021, izvirni znanstveni članek
Opis: A novel method was developed for the preparation of porous hematite (α-Fe2O3) thin films. First, a solution containing iron precursor was spin-coated on fluorine-doped tin oxide substrate and later short heat-treated at 750 °C. The prepared α-Fe2O3 thin films were applied as dual-function catalyst in photoelectrochemical (PEC) water oxidation and textile dye degradation studies. For the first time, α-Fe2O3 thin films were used in efficient PEC degradation of a textile dye (Basic Blue 41 – B41) using in-situ generated reactive chlorine species. In comparison with photocatalytic and electrocatalytic approaches, the PEC technique allows faster degradation of B41 dye at an applied bias potential of 1.5 V versus reversible hydrogen electrode and under visible light illumination. In the presence of Cl− using the PEC approach the degradation of B41 reaches 99.8%. High-performance liquid chromatography coupled with UV–VIS system confirmed the degradation of B41 dye using PEC. Gas-chromatography coupled to mass spectrometry was used to study the by-products obtained during PEC degradation. Chemical oxygen demand analyses confirmed that the mineralization level of B41 is in the order of 68%. The α-Fe2O3 films developed in this study give a higher level of PEC degradation efficiency compared to other iron oxide-based systems.
Najdeno v: ključnih besedah
Povzetek najdenega: ...thin films, photoelectrocatalysis, kinetics, visible light, degradation, textile dye...
Ključne besede: thin films, photoelectrocatalysis, kinetics, visible light, degradation, textile dye
Objavljeno: 10.05.2021; Ogledov: 833; Prenosov: 4
Polno besedilo (0,00 KB)
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