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Wyszukujesz frazę "chromium" wg kryterium: Temat

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    Wyświetlanie 1-10 z 10
    Tytuł:
    Sorption and reduction of chromiumion ions by the chelating ion exchanger Diaion CR20
    Autorzy:
    Wójcik, Grzegorz
    Powiązania:
    https://bibliotekanauki.pl/articles/109632.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    chromium(III)
    chromium(VI)
    reduction
    ion exchange
    speciation
    chelating resin
    Opis:
    The chelating ion exchanger Diaion CR20 was applied for removal of chromium(VI) ions in the pH range from 1.5 to 10 and in the presence of 1 M H2SO4. The speciation analysis was used to predict the reduction process. Reduction of chromium(VI) to chromium (III) was observed during the chromium(VI) ions sorption. The kinetic parameters for the pseudo-first-order and pseudo-second-order, Elovich and intraparticle diffusion models were calculated. The most common three isotherm models: Freundlich, Langmuir and Dubinin-Radushkevich were used to describe chromium(VI) uptake. It was proved that the polyamine groups present in selected ion exchanger are able to sorb both chromium(VI) and (III) ions. The maximal sorption capacity towards chromium(VI) ions was estimated at pH 1.5 – 169.49 mg Cr(VI)/g and 159.31 mg Cr(VI)/g in 1 M H2SO4. Both static and column methods were used in the investigations.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2019, 55, 6; 1382-1393
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Quick and simple speciation analysis of chromium in cements
    Autorzy:
    Grabarczyk, Malgorzata
    Wardak, Cecylia
    Powiązania:
    https://bibliotekanauki.pl/articles/2146952.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    cement
    extraction
    chromium speciation
    voltammetric determination
    Opis:
    The extraction of total Cr(VI) from commercially available cements, based on DTPA + 0.2 mol dm-3 (NH4)2SO4/NH4OH mixture solution and subsequent selective determination of Cr(VI) has been proposed. The determination was carried out using the adsorptive voltammetric stripping method. The study was conducted using three different commercially available cement samples. It has been checked that the proposed extraction procedure guaranteed no changes of chromium speciation during cement analysis. For comparison extraction was also carried out with the use of recommended by United States Environmental Protection Agency (EPA) Method 3060A, based on 0.28 mol dm-3 Na2CO3 + 0.5 mol dm-3 NaOH). Additionally, the extraction process was carried out using only distilled water as an extraction mixture which allows to evaluate concentration of only soluble Cr(VI) forms contained in cement. In all three cements, the content of soluble Cr(VI) was below 2 ppm, i.e. the limit value by European Union Directive 2003/53/EC.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 2; art. no. 144445
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Use of dead and living fungal biomass for removal of hexavalent chromium
    Autorzy:
    Holda, A.
    Mlynarczykowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/109742.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    hexavalent chromium
    Aspergillus niger
    biosorption
    bioaccumulation
    Opis:
    The removal of hexavalent chromium from aqueous solution was carried out in batch experiments using dead and living biomass of Aspergillus niger. The effects of the operating parameters such as influent Cr(VI) concentration, influent pH and biomass concentration on the Cr(VI) reduction were investigated. The results indicates that the removal rate of Cr(VI) increased with a decrease in pH or with increase of Cr(VI) and biomass concentrations. For chromium bioaccumulation along with nutrients the process is the most intensive within the first 5 days of mycelium formation. For biosorption, the greatest binding of this metal is achieved within the first 4 days of the process.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2016, 52, 2; 551-563
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Efficient chromium removal from aqueous solutions by precipitate flotation using rhamnolipid biosurfactants
    Autorzy:
    Shojaei, V.
    Khoshdast, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/110347.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    kinetics
    wastewater
    chromium
    rhamnolipid biosurfactant
    precipitate flotation
    Opis:
    In the present research study, the efficient removal of hexavalent chromium from aqueous solutions by precipitate flotation method was investigated. The experiments were carried out with the use of ferrous sulfate as a precipitating agent for chromium and rhamnolipid bio surfactant (RL) as a precipitate collector. The effects of rhamnolipid and co-precipitate concentrations, aeration rate, solution pH, and salt addition on the chromium removal were studied using a full factorial design. The chromium removal and water recovery to foam products were analyzed as process responses. Statistical analyses showed that the effects of all factors on the chromium removal followed a non-linear trend with a peak at the middle level. After the process optimization, the maximum chromium removal of 96.75±0.3% was obtained at pH value of 8, RL/Cr ratio of 0.01, Fe/Cr ratio of 3, and aeration rate of 50 cm3/min. Addition of salt with different cationic and anionic groups negatively influenced the removal efficiency. Kinetic studies suggested that the process of chromium removal by the precipitate flotation followed the first-order process with a rate constant of about 0.018 sec-1. Given the good removal capacity and kinetics, rhamnolipid biosurfactants can be a promising environmental-friendly bio collector for the removal of chromium ions from aqueous solutions.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 3; 1014-1025
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Selective solvent extraction of some heavy metal ions from aqueous solutions by octafunctionalized resorcin[4]arenes
    Autorzy:
    Kończyk, Joanna
    Dlugosz, Jan
    Powiązania:
    https://bibliotekanauki.pl/articles/110830.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    solvent extraction
    lead
    chromium
    calixresorcinarene
    metal removal
    Opis:
    This paper presents the results of the study on the extraction capacity of 1,8,15,22-tetra(1- heptyl)resorcin[4]arene and its octasubstituted derivatives containing thiophosphoryl, ester and amide groups in the presence of Pb(II), Zn(II), Cd(II) and Cr(III) in solvent extraction process. Effects of the structure and concentration of the resorcinarene extractant and the composition of the aqueous phase as well as its acidity on the efficiency and selectivity of removal of the examined metal ions from model aqueous solutions were determined. The 1:1 stoichiometry for complexes formed between Pb(II) and Cr(III) and the octasubstituted resorcin[4]arenes was determined by classical slope analysis and loading test.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 2; 271-285
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Biological removal of Cr(VI) ions from aqueous solutions by trichoderma viride
    Autorzy:
    Holda, A.
    Kisielowska, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/109693.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    bioaccumulation
    chromium
    Cr(VI)
    microscopic fungi
    Trichoderma viride
    Opis:
    The paper presents biological removing of Cr(VI) ions from aqueous solution by applying autochtonic fungi seedling of Trichoderma viride originated from chromium mud samples. The growth of organism and removing of chromium(VI) was performed in aqueous solution of various chromium(VI) contents and at optimal value of pH. During 14 days of incubation, samples of 5 cm3 each were collected every day for determination of chromium(VI) in solution and the efficiency of biological removal was specified. Since removal of chromium(VI) from aqueous solution may occur because of reduction, biosorption or bioaccumulation processes, to determine which one occurred, the Cr(III) contents were determined in samples of the medium as well in ooze after mycelium irrigating and in mycelium.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2013, 49, 1; 47-60
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kinetic modeling of chromium(III) extraction with aliquat 336 from alkaline aqueous solutions containing chlorides
    Autorzy:
    Wionczyk, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/110327.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    extraction
    chromium(III) chloride
    Aliquat 33
    kinetic analysis
    Opis:
    The effects of time, composition and history of preparation of the aqueous phase on the liquidliquid extraction of chromium(III) with Aliquat 336 from the aqueous alkaline solutions containing chlorides were studied. At time far from the equilibrium the yield and initial rate of the chromium(III) extraction depend on NaOH concentration, ionic strength of the aqueous phase and the way of its preparation. At the constant composition of the feed solution, rate of the Cr(III) extraction in approach to the equilibrium is higher when chromium(III) is extracted from the alkaline aqueous phase freshly prepared by direct dissolution of a weighted sample of CrCl3 than from that obtained by dilution of aged stock solution of CrCl3. Kinetic analysis by the mathematical models showed that within the whole period of time needed to reach the equilibrium, the rate of the Cr(III) extraction is limited by the second-, and third-order chemical reaction towards Cr(III), irrespective of composition and preparation history of the aqueous phase. The three-dimensional diffusion and chemical reaction at phase boundary substrateproduct (the contracting volume) models have a significant effect on the chromium(III) extraction within the initial extent of the process.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2013, 49, 2; 587-605
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Utility of Chromobacterium violaceum SUK1a, an indigenous bacterial isolate for the bioremediation of Cr(VI)
    Autorzy:
    Prabhakaran, D. C.
    Krishnan, S.
    Ramamurthy, P. C.
    Sivry, Y.
    Quantin, C.
    Subramanian, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/109867.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    biosorption
    bioremediation
    chromium
    bioreduction
    Chromobacterium violaceum SUK1a
    Opis:
    The potential of an indigenous bacterial strain, Chromobacterium violaceum SUK1a, isolated from surface water samples collected from Sukinda Valley in Odisha, India, has been evaluated for the first time for the bioremediation of toxic hexavalent chromium (Cr(VI)) ions. The isolate was assessed for its Cr(VI) biosorption efficiency and the various parameters affecting the biosorption process were evaluated. A maximum Cr(VI) biosorption of about 50% was obtained, and the residual chromium was in the form of less toxic Cr(III). The Gibbs free energy of biosorption was determined to be -26.3 kJ/mol, suggestive of a chemisorption process. Additionally, the Cr(VI) biosorption by the isolate followed pseudo second order kinetics. FTIR spectral studies indicated that the surface functional groups present on the bacterial isolate such as, carboxyl, hydroxyl, amino, and phosphate groups were involved in the complexation of chromium ions with the bacterial cells. X-ray photoelectron spectroscopic studies on Cr(VI) interacted bacterial cells revealed an additional peak corresponding to Cr(III) in the Cr(2p) spectra. The surface charge of the bacterial cells subsequent to interaction with Cr(VI) were less negative compared to the pristine cells, which further substantiated the bioreduction of Cr(VI) to Cr(III). The bioremediation mechanism of Cr(VI) by the bacterial isolate is delineated to be governed by both biosorption and bioreduction processes under metabolism independent conditions. The results obtained indicate that the isolate can be a promising candidate for Cr(VI) bioremediation applications.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 4; 1266-1281
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kinetics of chromium(iii) transport through the double-carrier supported liquid membrane
    Autorzy:
    Religa, P.
    Rajewski, J.
    Lobodzin, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/109375.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    SLM
    chromium
    D2EHPA
    Cyanex27
    separation
    membrane
    Opis:
    The kinetics of chromium(III) transport through a supported liquid membrane containing both a di-(2-ethylhexyl) phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272) as an ions carrier was investigated. It was found that under a characteristic concentration of the carriers into the organic phase membrane provides much higher efficiency than the membrane containing only one of the extractants. In the studied system the optimal carrier concentration in the membrane is 0.16 mol/dm3 and 0.9 mol/dm3 for Cyanex272 and D2EHPA, respectively. Moreover, the authors indicate that only D2EHPA can act as an individual carrier in the membrane. In the case of Cyanex272 the stable structures with chromium(III) ions are formed in the membrane, which prevents effective re-extraction. Additionally, intensive stirring of an aqueous phase in another factor that has a positive influence on the transport kinetics in the double-carrier membrane. Increasing a stirring rate up to 1200 rpm shortens the process time and allows total re-extraction of chromium.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2016, 52, 1; 87-97
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Extraction properties of tetraheptylresorcin[4]arenes in relation to Cr(III) ions
    Autorzy:
    Konczyk, J.
    Miroshnychenko, S.
    Kozlowski, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/109751.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    solvent extraction
    resorcin[4]arenes
    chromium(III)
    cadmium(II)
    zinc ions
    Opis:
    Resorcin[4]arene-based ligand bearing four heptyl chains at the lower rim of the molecule was prepared and modified by four tetradietoxyphosphoryl groups in the upper rim. The compounds obtained were characterized by NMR spectroscopy and their extractability toward chromium(III) ions was studied. The influence of process parameters such as the pH of aqueous phase, agitation time and also extractant’s structure and concentration on efficiency of Cr(III) ions solvent extraction is presented. The highest yield of Cr(III) solvent extraction was obtained for two-hour agitation time of 5.010−4 M metal solution of pH 5.0 and 5.010−3 M chloroform solution of the tetradietoxyphosphorylated derivative of heptyl-resorcin[4]arene. Under optimal conditions, competitive solvent extraction of Cr(III), Zn(II), and Cd(II) ions was performed and separation factor values were established as 77.0 and 24.9 for Cr(III)/Cd(II) and Cr(III)/Zn(II) ions pairs, respectively. The stoichiometry of formed metal-ligand complexes 1:1 was found by classical slope analysis method.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2016, 52, 2; 835-844
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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