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Diffusion models of gentamicin released in poly(vinyl alcohol)/chitosan hydrogel
No full textThis study presents comparison of our recently formulated two compartmental model with General fractional derivative (GFD) and Korsmeyer-Peppas, Makoid-Banakar and Kopcha diffusion models. We have used our GFD
model to study the release of gentamicin in poly (vinylalcohol)/chitosan/gentamicin (PVA/CHI/Gent) hydrogel aimed for wound dressing in medical treatment of deep chronical wounds. The PVA/CHI/Gent hydrogel was prepared by physical cross linking of poly(vinyl alcohol)/chitosan dispersion using freezing-thawing method, and then was swollen for 48 h in gentamicin solution, at 37 °C. Different physico-chemical (FTIR, SEM), mechanical and biological (cytotoxicity, antibacterial activity) properties have been determined. The concentration of released gentamicin was determined
using a high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS). The ratio between concentration of released gentamicin and initial concentration of gentamicin in the hydrogel was monitored for the
prolonged time period in order to obtain gentamicin release profile. It was proven that our novel diffusion GFD model better fitted with experimental data, and enabled the determination of diffusion coefficient precisely for the entire time period
Electrochemically synthesized biomaterials
No full textINTRODUCTION: Electrochemical methods were employed for synthesizing composites intended for applications in
medicine as antibacterial coatings on titanium bone implants or as highly efficient antibacterial hydrogels for
accelerated wound healing.
EXPERIMENTAL: Hydroxyapatite-based coatings were single-step electrophoretically deposited from fourcomponent
aqueous suspension containing 1 wt% hydroxyapatite powder (HAP, particles < 200 nm particle size, Sigma-
Aldrich), 0.1 wt% poly(vinyl alcohol) (PVA, medium molecular weight, Sigma-Aldrich), 0.05 wt% chitosan powder (CS,
medium molecular weight, Sigma-Aldrich), and aqueous gentamicin sulfate solution (Gent, concentration 50 mg/ml,
Sigma-Aldrich) on titanium plates (Sigma-Aldrich). Antibacterial activity of HAP/PVA/CS/Gent coating was evaluated
against Staphylococcus aureus TL (culture collection-FTM, University of Belgrade, Serbia) and Escherichia coli ATCC
25922. For poly(vinyl alcohol)/chitosan (PVA/CHI) hydrogel synthesis poly(vinyl alcohol) powder (PVA, Sigma Aldrich,
USA), chitosan powder (CHI, Sigma Aldrich, USA), graphene (Graphene Supermarket, USA), glacial acetic acid (Beta
Hem), silver nitrate (MP Hemija), potassium nitrate (Centrohem, Serbia) were used. For antibacterial properties
evaluation, monobasic and dibasic (Sigma Aldrich, USA) potassium phosphates were used. Cell culture suspensions for
cytotoxicity tests were prepared using MTT tetrazolium salt, EDTA, fetal calf serum and antibiotic-antimycotic solution
(Sigma Aldrich, USA).
RESULTS AND DISCUSSION: Surface modification of titanium with innovative bioactive coatings enhances
biomineralization and reduces post-operation pain and infection risk. Using powerful single-step electrophoretic
deposition (EPD) at a constant voltage we have produced various hydroxyapatite-based composite bioceramic coatings
in combination with polymers (lignin, chitosan), graphene, and antibacterial agents (silver, gentamicin).
Electrochemical methods enable in situ synthesis of AgNPs inside polymer matrices, with the main advantage being
the complete absence of any chemical reducing agents that are often toxic and difficult to remove from the material.
The electrochemical reduction of Ag+ ions is achieved only using electrical current or pure hydrogen gas that is generated
at the cathode in aqueous electrolytes, which allows for obtaining completely green and non-toxic product.
Modifications in the synthesis process also enable the control of AgNPs properties, such as size and concentration.
CONCLUSIONS: Composite antibacterial coatings were obtained on titanium plates using EPD. Strong antibacterial
activity against E. coli and S. aureus was found. Biocompatibility was confirmed using in vitro MTT testing since a noncytotoxic
effect was shown towards healthy human peripheral blood mononuclear cells PBMC, fibroblast cell lines MRC-5
and L929, suggesting high potential for bone tissue engineering and medical applications. Hydrogels composed of physically
cross-linked poly(vinyl alcohol)/chitosan with embedded AgNPs were successfully developed for applications as antibacterial
wound dressings due to their highly favorable properties of silver release, antibacterial activity, and non-toxicity
The preliminary study on the natural zeolite as a potential carrier of tetracycline
No full textThe purpose of this study is to investigate adsorption of the antibiotic tetracycline on the natural zeolite - clinoptilolite. The adsorption was followed at the different initial concentrations of the drug in buffer solution at pH 3.4. Characterization of adsorbent before and after adsorption of tetracycline was done by the determination of zeta potential and by FTIR spectroscopy. Results showed that adsorption of the drug increased with increasing of its initial concentration and maximum adsorbed amount of the tetracycline was 27.5 mg/g. Characterization results confirmed presence of tetracycline at the zeolitic surface
Removal of methyl orange using layered double hydroxide originated from spent acid liquor
No full textProduction of organic dyes has been constantly increasing in the last decades, hence their us-age leaves a huge environmental impact usually on aquatic biota. Wastewaters carrying dissolved dyes are toxic to all organisms existing in water, therefore such wastewater streams have to be ap-propriately treated before they can be released into the environment. Development of effective ad-sorbents, which can be used in wastewater treatment, is mandatory. Another concern in the produc-tion of sorbing materials is the formation of spent acids or bases since they are commonly used for the activation of adsorbents. Spent acid liquor produced during the activation of expanded vermicu-lite (EVer) is utilized as the start material for the preparation of layered double hydroxide (LDH-EVer) by the method of co-precipitation process at low supersaturation. The prepared adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-EDS). Fabricated material is utilized as an adsor-bent of methyl orange dye from aqueous solutions. During the experiments, contact time were varied and thus the rate of adsorption is determined. The obtained results show a high adsorption capacity of 63 mg g-1
Acute toxicological profiles of the selected modified natural clays in rats
No full textSince natural clays have their toxicological profiles and their modification can change this property, acute toxicological evaluation on the two modified natural clays by chitosan, signed as modified bentonite (MBNT) and modified halloysite (MHAL) was performed in this study
Photocatalytic degradation of fungicide using composite catalysts based on titanium(IV) oxide with ecotoxicology monitoring of degradation products
No full textГлавна тема ове докторске дисертације била је ефикасна фотокатализована разградња
фунгицида помоћу новосинтетисаних катализатора на бази титан(IV)-оксида под дејством
симулираног сунчевог зрачења. Површина почетног материјала модификована је оксидима
сребра (Аg-P25) и церијума (Cе-P25), ванадатима железа (FeVO4/r-TiO2) и ванадијум
супституисаним оксихидроксидима гетита (Fe1-xVxOOH/r-TiO2). Припремљени материјали
су подвргнути исцрпним структурно-морфолошким испитивањима.
Фотокатализатори су потом примењени у процесима фотокаталитичке деградације
тиофанат- метила (Тф-Ме) уз праћење деградационих путева и еколошког притиска овог
процеса. Током оптимизације процеса разградње, испитани су различити утицаји
процесних параметара. Ефикасност процеса уклањања пестицида одређена је праћењем
кинетике путем ултраљубичасте/видљиве спектроскопије и течне хроматографије.
Употребом 0,07 g/l FeVO4/r-TiO2 и Fe1-xVxOOH/r-TiO2 при концентрацији пестицида од 5
mg/l потпуно разлагање Тф-Ме је детектовано након 180 и 150 min, редом.
Процесу фотокатализе је у одређеним експерименталним поставкама претходила
предконцентрација коришћењем шаржног или континуалног адсорптивног процеса. При
томе, употребљене су модификоване мембране на бази отпадне целулозе. Варирани су
различити процесни параметри ради оптимизације читавог система. Фотокатализатори Аg-
P25 и Ce-P25 показали су веома високу ефикасност. Наиме, најбољи резултати добијени су
при следећим оперативним условима: раствор Тф-Ме концентрације 5 mg/l у систему са
0,07 g/l изабраног катализатора, при pH = 5,5. Тотална деградација је регистрована након
120 min. Продукти деградације су праћени и одређивани током целог процеса.
Добијени раствори су касније подвргнути екотоксиколошком испитивању резидуалне
токсичности. Екотоксиколошки тестови додатно су објаснили утицај раствора пестицида
на коришћени модел организам.The main topic of this doctoral dissertation was the efficient photocatalyzed degradation of
fungicides using newly synthesized catalysts based on titanium(IV)-oxide under the influence of
simulated solar radiation. The surface of the initial material was modified with silver oxides (Ag-
P25) and cerium oxide (Ce-P25), iron vanadates (FeVO4/r-TiO2) and vanadium-substituted
goethite oxyhydroxides (Fe1-xVxOOH/r-TiO2). The prepared materials were subjected to
exhaustive structural and morphological tests.
The photocatalysts were then applied in the processes of photocatalytic degradation of
thiophanate- methyl while monitoring the degradation pathways and environmental pressure of
this process. During the optimization of the degradation process, various influences of the process
parameters were examined. The efficiency of the pesticide removal process was determined by
monitoring the kinetics through UV/Vis spectroscopy and liquid chromatography. Using 0.07 g/l
FeVO4/r-TiO2 and Fe1-xVxOOH/r-TiO2 at a pesticide concentration of 5 mg/l, complete
degradation was observed after 180 and 180 min, respectively.
In some experimental settings, the photocatalysis process was preceded by preconcentration using
a batch or continuous adsorptive process. For this purpose, modified membranes based on waste
cellulose were used. Various process parameters were varied in order to optimize the entire system.
Photocatalysts Ag-P25 and Ce-P25 showed very high efficiency. Namely, the best results were
obtained under the following operating conditions: a thiophanate-methyl solution with a
concentration of 5 mg/l in a system with 0.07 g/l of the selected catalyst, at pH = 5.5. Total
degradation was observed after 120 min. Degradation products were monitored and determined
throughout the process.
The obtained solutions were later subjected to ecotoxicologycal assessment of residual toxicity.
Ecotoxicological tests additionally explained the impact of pesticide solutions on the used model
organisms
Adsorption of lead ions from aqueous solution utilizing Fe/Mg-enriched hydrochar
No full textIn our research, we explored the potential use of waste grape pomace hydrochar as an adsorbent for lead ions from aqueous solution. For the production of hydrochar, grape pomace underwent hydrothermal carbonization in an aqueous medium at 220°C for 1 hour. To additionally enhance the adsorption capacity of the prepared hydrochar, the material was treated with magnesium and iron salts, and then was subjected to pyrolysis at 300°C. The resulting material named Fe/Mg-pyro-hydrochar (FeMg-PHC) was subjected to lead removal tests. Our findings indicated that the modified pyro-hydrochar has a significantly high affinity towards lead ions. Investigating the impact of the initial solution's pH, we found that the optimal removal takes place at a pH of 5.0. The isothermal study revealed that the adsorption equilibriums was determined by the Sips isotherm model, with a maximum theoretically achieved capacity of 157.24 mg/g. In conclusion, our study suggests that the one-step hydrothermal carbonization followed by pyrolysis is a promising method for producing effective adsorbents for lead removal
Chemical durability of glasses based on secondary raw materials
No full textThe use of waste materials to obtain new products is in accordance with the principles of the circular economy and is gaining more and more importance, taking into account that it saves natural resources while simultaneously reducing the amount of waste that ends up in landfills. This paper presents the examination of the chemical durability of two glasses of different compositions based on fly ash with additives (glass cullet, sugar beet factory lime, CaCO3). The chemical composition of the obtained glasses was determined by atomic absorption spectroscopy. Structural characteristics were determined using infrared spectroscopic analysis. The chemical durability of glasses was determined at 95 °C in: distilled water, HCl solution with a concentration of 0.01 mol/dm3 and NaOH solution with a concentration of 0.01 mol/dm3. The results for the dissolved mass of the glasses, the concentration of the elements in the solution after dissolution and infrared spectroscopy were used to evaluate the chemical stability of the glasses. The results show that both glasses have the characteristic structure of aluminosilicate glasses. The chemical durability of the glasses is satisfactory, the mass change is less than 1%
Importance of material microstructure studies for the optimization of the roasting processes in nonferrous metallurgy
No full textRoasting processes in the pyrometallurgical production of non-ferrous metals are very complex,
taking into account the chemical and mineralogical composition of the raw materials, as well as
the complexity of the chemical reactions which take place in the roasting aggregate. Laboratoryscale
characterization of the initial materials, intermediates, and final products gives researchers
the possibility to propose the most likely possible reaction mechanism in order to guide the roasting
process towards the desired products. On the other hand, studying the microstructure of materials
helps to understand the reasons for the lack of the roasting process efficiency for a certain
application case. More recently, the development and application of advanced thermodynamic
software additionally helps to predict more accurately the phase distribution and overall dynamics
of the roasting process, prior to experimental laboratory tests, thus increasing the probability of
successful replication on a larger scale.
This paper presents the results of microstructural investigation of three different materials which
are used in non-ferrous metallurgy as primary or secondary raw materials: 1) copper-iron sulphide
flotation concentrate (Republic of Serbia), 2) lead and arsenic containing dust from copper smelter
(Republic of Kazakhstan), and 3) gold containing residues from gold winning plant (Republic of
Uzbekistan).
Samples of sulphide copper concentrate were roasted at 425°C, 675°C and 950°C in an air
atmosphere for 1 hour. The experimental characterization included chemical and quantitative
microstructural analysis of the initial sample, XRD and SEM/EDS analyses of the initial sample
and roasted products. Thermodynamic prediction of the equilibrium compositions and phase distribution at elevated temperatures was done using HSC Chemistry software (ver. 6.1) under the
incomplete and complete roasting conditions.
Samples of lead- and arsenic-containing dust from copper smelter were subjected to sulphatising
roasting in a pilot-scale fluidised bed furnace at temperatures of 400-550°C for 1 hour. The data
of the initial dust and calcine samples investigation by scanning electron microscopy and X-ray
spectral microanalysis (SEM and XRMS) allowed to detect and eliminate the cause of insufficient
efficiency of impurity removal into the gas phase. The samples were also studied by chemical
analysis and X-Ray diffraction analysis.
In the next example under consideration, the starting material and products of oxidative roasting
of sulphide- and carbonaceous-bearing gold plant residues at 500-700°C were investigated. In
addition to the methods of chemical analysis, optical studies, X-ray phase analysis and diagnostic
leach, the use of the scanning electron microscope study equipped with a dual-detector X-ray
microanalysis system provided the most complete information explaining the cause of incomplete
gold recovery at the downstream roasting stage of cyanidation.
Application of the scanning electron microscopy method with local X-ray spectral analysis allows
not only to establish the percentual content of minerals in the investigated sample, but also to
determine the elemental distribution within the mineral, the degree of mineral liberation in
individual particles of the sample, as well as to determine the association of the mineral/component
of interest with other minerals, the quality of its surface, size and shape. This information helps
the scientists and experts to optimise metallurgical processes, particularly, as the results have
shown, the roasting process