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    Wyświetlanie 1-9 z 9
    Tytuł:
    Reduction and Biosorption of Cr(VI) from Aqueous Solutions by Acid- -Modifi ed Guava Seeds: Kinetic and Equilibrium Studies
    Autorzy:
    Ortíz-Gutiérrez, Marel
    Alfaro-Cuevas-Villanueva, Ruth
    Martínez-Miranda, Verónica
    Hernández-Cristóbal, Orlando
    Cortés-Martínez, Raúl
    Powiązania:
    https://bibliotekanauki.pl/articles/778567.pdf
    Data publikacji:
    2020
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    Guava seeds
    chromium reduction
    biosorption
    isotherms
    Opis:
    The use of guava seeds (GS) and acid-modified guava seeds (MGS) for the removal of Cr(VI) from aqueous solutions was investigated. Batch-type experiments were performed with Cr(VI) aqueous solutions and biosorbents to determine the kinetic and equilibrium sorption parameters. Results indicated that GS and MGS were capable of reducing and remove Cr(VI) from solutions, but the reduction was only observed at some experimental conditions. Infrared analysis showed that several functional groups were involved in the reduction, and biosorption of Cr(VI), particularly alcohol, phenolic, carboxylic, and methoxymethyl structures. The mechanisms of reduction and biosorption depended upon the type of biosorbent, pH, and temperature of the system. The pseudo-second-order kinetic model describes the kinetic sorption data, and the Langmuir-Freundlich (L-F) model describes the isotherm data in most cases. Significantly high total chromium biosorption capacities were obtained. Acid modification of guava seeds improves chromium biosorption performance.
    Źródło:
    Polish Journal of Chemical Technology; 2020, 22, 4; 36-47
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Novel lignocellulosic wastes for comparative adsorption of Cr(VI): equilibrium kinetics and thermodynamic studies
    Autorzy:
    Haroon, H.
    Gardazi, S. M. H.
    Butt, T. A.
    Pervez, A.
    Mahmood, Q.
    Bilal, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/778473.pdf
    Data publikacji:
    2017
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    chromium VI
    equilibrium kinetics
    lignocellulosic waste adsorbents
    thermodynamics
    Opis:
    Cr(VI) adsorption was studied for abundantly available low-cost lignocellulosic adsorbents in Pakistan namely, tobacco stalks (TS), white cedar stem (WCS) and eucalyptus bark (EB). Several process variables like contact time, adsorbent dose, pH, metal concentration, particle size and temperature were optimized in batch mode. EB showed high Cr(VI) adsorption of 63.66% followed by WCS 62% and TS 57% at pH 2, which is higher than most of the reported literature. Langmuir isotherm (R2  = 0.999) was well fitted into the equilibrium Cr(VI) data of EB, suggesting homogeneous active sites and monolayer coverage of Cr(VI) onto the EB surface. Freundlich (R2  = 0.9982) isotherm was better fitted to the equilibrium data of TS and WCS, revealing the adsorption sites with heterogeneous energy distribution and multilayer Cr(VI) adsorption. Moreover, the Cr(VI) adsorption of studied adsorbents followed the pseudo-second order kinetic model. Thermodynamic properties were investigated in two temperature ranges, i.e., T1  (303–313 K) and T2  (313–323 K). TS and EB showed the exothermic at T1 and endothermic reactions at T2 with entropy controlled adsorption at the solid-liquid interface, and WCS exhibited an opposite thermal trend with decreasing disorderness at solid-liquid interface as temperature rises. Gibbs free energy (ΔG>0) confirmed the non-spontaneous adsorption process for all studied adsorbents.
    Źródło:
    Polish Journal of Chemical Technology; 2017, 19, 2; 6-15
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Equilibrium and kinetic studies of Cr (VI) removal from synthetic wastewater by Acroptilon repense flower powder
    Autorzy:
    Ghaneian, M. T.
    Ehrampoush, M. H.
    Arany, A. M.
    Jamshidi, B.
    Dehvari, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/778278.pdf
    Data publikacji:
    2013
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    Acroptilon repens
    biosorbent
    Hexavalent Chromium
    adsorption kinetic and isotherm
    Opis:
    In this study the removal of Cr (VI) from synthetic wastewater was investigated using Acroptilon repens (Russian Knapweed) flower powder under various conditions (pH, contact time and initial concentration of Cr). The capacity of chromium adsorption at equilibrium conditions by this biosorbent was increased by adsorbate concentration. The results also showed that the removal efficiency of Cr (VI) was increased by increasing the contact time. By increasing the initial concentration of Cr (VI) solution, chromium removal was reduced. The suitability of adsorbents and their constants was tested or evaluated with the Langmuir, Freundlich and Temkin isotherms models. The results indicated that the Freundlich and Langmuir models (R2 > 0.99) gave a better concordance to the adsorption data in comparison with the Temkin equation (R2 = 0.97). The adsorption of Cr (VI) followed the pseudo-second-order kinetics (R2 = 0.991). The study showed that Acroptilon repens flower powder can be used as an effective lignocellulosic biomaterial and biosorbent for the removal of Cr (VI) from wastewater.
    Źródło:
    Polish Journal of Chemical Technology; 2013, 15, 2; 40-47
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Removal of Cr(III) ions from salt solution by nanofiltration: experimental and modelling analysis
    Autorzy:
    Kowalik-Klimczak, A.
    Zalewski, M.
    Gierycz, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/779045.pdf
    Data publikacji:
    2016
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    nanofiltration
    chromium(III)
    DSP model
    extended Nernst-Planck equation
    Opis:
    The aim of this study was experimental and modelling analysis of the nanofiltration process used for the removal of chromium(III) ions from salt solution characterized by low pH. The experimental results were interpreted with Donnan and Steric Partitioning Pore (DSP) model based on the extended Nernst-Planck equation. In this model, one of the main parameters, describing retention of ions by the membrane, is pore dielectric constant. In this work, it was identified for various process pressures and feed compositions. The obtained results showed the satisfactory agreement between the experimental and modelling data. It means that the DSP model may be helpful for the monitoring of nanofiltration process applied for treatment of chromium tannery wastewater.
    Źródło:
    Polish Journal of Chemical Technology; 2016, 18, 3; 10-16
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Removal of Hexavalent Chromium from Aqueous Solution by the Pod of Acacia gerrardii
    Autorzy:
    Abdulaziz, Mohammed A.
    Bakri, Abdulrahman A.
    Al-Zahrani, Saleh A.
    Al-Zahrani, Majed S.
    Al-Lehebi, Abdulrahman N.
    Banjar, Fadil M.
    Nabag, Mohand I.
    Powiązania:
    https://bibliotekanauki.pl/articles/779613.pdf
    Data publikacji:
    2019
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    Biosorption
    chromium
    Acacia gerrardii
    isotherm models
    Park kinetic models
    Opis:
    This study aims at investigating the potential of Acacia gerrardii pod for the removal of Cr(VI) in batch system. Effect of solution pH, biosorbent dosage, initial concentration of Cr(VI), contact time on the removal process was examined. Complete removal of hexavalent chromium was achieved at pH values 1.0 and 2.0 whereas maximum removal of total chromium was obtained at pH of 3.0. The study showed that the biosorption and bioreduction mechanisms were involved in the removal process. The time required for complete removal of Cr(VI) using the pod of Acacia gerrardii was shortened with an increase in biomaterial dosage and decrease in Cr(VI) concentration. Kinetic data was well described using Park kinetic model. Freundlich isotherm model adequately fitted the equilibrium data indication multilayer adsorption of total chromium on the surface of biomaterial. The pod of Acacia gerrardii could be used efficiently for the removal of hexavalent chromium from aqueous solutions.
    Źródło:
    Polish Journal of Chemical Technology; 2019, 21, 2; 14-19
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of temperature on o-cresol methylation in a fluidized bed of commercial iron-chromium catalyst TZC-3/1
    Autorzy:
    Berkowicz, G.
    Żukowski, W.
    Baron, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/778096.pdf
    Data publikacji:
    2013
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    2,6-dimethylphenol
    o-cresol methylation
    iron-chromium catalyst TZC-3/1
    fluidized bed
    Opis:
    The paper presents the results of the synthesis of 2,6-dimetyhlphenol (26DMP) from o-cresol. The target compound is an important substrate for polymer chemistry. Due to a large amount of o-cresol which is generated as a by-product, during the synthesis of 2,6-dimethylphenol from phenol, the methylation of o-cresol to 2,6-dimethylphenol should be examined as a separate process. The alkylation of o-cresol was carried out in a fluidized bed of commercial iron-chromium catalyst TZC-3/1. Undesirable decomposition of methyl alcohol on the catalyst generates a number of environmentally dangerous by-products such as methane, carbon dioxide, carbon monoxide. The effect of temperature on the yield of the synthesis was investigated. The synthesis process was monitored on-line in the temperature range 310-380°C, completely covering the maximum efficiency of the process. Online analysis of the process by FTIR spectroscopy gave information about products of both methylation of o-cresol and pyrolysis of methanol. The maximum 85% yield of desired 2,6-dimethylphenol with more than 85% conversion of o-cresol was achieved at 340°C, at 1:6 molar ratio of o-cresol:methanol.
    Źródło:
    Polish Journal of Chemical Technology; 2013, 15, 3; 100-102
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kinetic, Equilibrium and Thermodynamic studies on the removal of Cr(VI) by activated carbon prepared from Cajanus Cajan(L) Milsp seed shell
    Autorzy:
    Thamilarasu, P.
    Kumar Vijaya, G.
    Tamilarasan, R.
    Sivakumar, V.
    Karunakaran, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/779758.pdf
    Data publikacji:
    2011
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    adsorpcja
    izoterma
    węgiel
    chrom i nasiona powłoki
    adsorption
    isotherm
    activated carbon
    chromium and seed shell
    Opis:
    This paper presents the feasibility of the removal of hexavalent chromium ions from aqueous solutions by using activated carbon prepared from Cajanus Cajan(L) Milsp. It was carbonized and activated by treating it with concentrated sulfuric acid followed by heating for 5 h at 500oC. Batch adsorption experiments were carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data fi tted well to the Freundlich isotherm. The thermodynamic parameters such as ΔHo, ΔSo, and ΔGo were calculated, which indicated that the adsorption was spontaneous and endothermic in nature. The adsorbent used in this study was characterized by FT-IR and SEM before and after the adsorption of metal ions. The results indicate that Cajanus Cajan(L) Milsp can be employed as a low cost alternative and commercial adsorbents in the removal of chromium (VI) from water and waste water.
    Źródło:
    Polish Journal of Chemical Technology; 2011, 13, 4; 1-7
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Novel Calix[4]arene network resin for Cr(VI) ions Remediation : A Response Surface Approach
    Autorzy:
    Siyal, A. N.
    Memon, S. Q.
    Powiązania:
    https://bibliotekanauki.pl/articles/779157.pdf
    Data publikacji:
    2012
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    modified amberlite XAD-2
    calixarene
    cavities
    network
    optimization
    remediation
    removal
    chromium
    response surface methodology
    factorial design
    isotherms
    Opis:
    Novel Calix[4]arene Netwok (NCN) resin has been synthesized using Amberlite XAD-2 as the starting material. Hydroxyl groups have been introduced onto the para position of alkylated phenyl ring of Amberlite XAD-2 followed by the condensation to NCN by reacting it with formaldehyde. The NCN resin has been used for the remediation of Cr(VI) contaminated water using factorial design approach. A face-centered Draper-Lin composite design predicted ~100% removal effi ciency at optimum variables (the initial concentration of Cr(VI) ion 10 mg/l sorbent dose 200 mg, agitation time 136 min and pH 2). The accuracy and the fi tting of the model were evaluated by ANOVA and R2 (0.9992) values. The 99.5% removal effi ciency has been achieved experimentally at the optimum values of the variables. The Langmuir and D-R isotherm models were applicable to the sorption data with the value of RL and the sorption free energy 0.0057-0.1 and 7.93 kJ/mol respectively, suggesting favorable and physical/ion-exchange nature of the sorption. The calculated sorption capacity was 176.1š2.4 mg/g. The recycling studies of NCN resin showed that the multiple use of resin is feasible. Effect of concomitants has also been studies and proposed method was applied successfully for removal (98.7%) of Cr (VI) from electroplating wastewater.
    Źródło:
    Polish Journal of Chemical Technology; 2012, 14, 3; 21-28
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pigments precipitated from chromate post-galvanic solutions in emulsion systems
    Autorzy:
    Klapiszewska, B.
    Krysztafkiewicz, A.
    Jesionowski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/779987.pdf
    Data publikacji:
    2007
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    pigment zielony
    pigmenty
    krzemian chromu strącany
    układ emulsyjny
    odpady pogalwaniczne
    green pigments
    precipitated chromium(III) silicates
    emulsion system
    post-galvanic wastes
    Opis:
    Studies were conducted on the production of chromium(III) silicates, the green pro-ecological pigments. The pigments were precipitated from sodium silicate and chromium(III) sulphate solutions in the system of two emulsions prepared in hexane in the presence of a non-ionic surfactant as an emulsifier. The chromium(III) sulphate represented a reduction product of chromate(VI) compounds present in post-galvanic wastes. The reduction agent involved metanal in an acidic medium. The obtained products were subjected to a comprehensive physicochemical analysis, their dispersive and morphological properties were determined. The precipitated green products exhibiting intense colour, were uniform and their particles manifested a low tendency to form agglomerate structures.
    Źródło:
    Polish Journal of Chemical Technology; 2007, 9, 2; 27-29
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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