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Tytuł:
Adsorption of lanthanum(III) and yttrium(III) on kaolinite: kinetics and adsorption isotherms
Autorzy:
Zhou, Fang
Feng, Jian
Xie, Xiong
Wu, Baihong
Liu, Qi
Wu, Xiaoyan
Chi, Ruan
Tematy:
adsorption
kaolinite
rare earth
kinetics
Pokaż więcej
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:
https://bibliotekanauki.pl/articles/109951.pdf  Link otwiera się w nowym oknie
Opis:
Experimental investigations were carried out using kaolinite to adsorb two rare earth ions, lanthanum ion (La3+) and yttrium ion (Y3+), which will provide some useful information and new insights on the mineralization process and fractionation phenomenon of weathered crust elution-deposited rare earth ores. The results showed that the equilibrium adsorption capacity of Y3+ is greater than La3+ under the same experimental conditions. The adsorption of rare earth ions presents strongly temperature dependent indicating an endothermic adsorption process. The pseudo-first-order kinetic model and the pseudo-second-order kinetic model were applied to discuss the adsorption kinetics. It was found that the adsorption rate of rare earth follows the pseudo-second-order kinetic model among the adsorption temperature range. Furthermore, the adsorption process of rare earth ions on kaolinite followed the Langmuir isotherm model confirmed by the correlation of experimental equilibrium data to standard isotherm model, Langmuir and Freundlich isotherms. The activation energies for the adsorption of La3+ and Y3+ on kaolinite are 28.1903 kJ/mol and 25.4190 kJ/mol, respectively. All kaolinite before and after adsorption were characterized by XRD and SEM-EDX to understand the adsorption mechanism. The obtained results suggested that the adsorption of La3+ and Y3+ on kaolinite is an endothermic and chemisorption process.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mineralogical, geochemical and stable isotope studies of kaolin deposits in north-west Gonabad district (eastern Iran)
Autorzy:
Zirjanizadeh, S.
Rocha, F.
Samiee, S.
Tematy:
kaolinite
Iran
REE
O isotope composition
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Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/2059765.pdf  Link otwiera się w nowym oknie
Opis:
Kaolin deposits, situated ~10 km north-west of Gonabad (eastern Iran), formed by the intrusion of hydrothermal fluids from a granite dyke in the western part of the study area, and the alteration of rhyolite, dacite and rhyodacite related to Eocene volcanism. There are four major kaolin quarries. The rocks in the investigated area are mainly slate, dacite, rhyolite, andesite-trachyandesite, and lithic and felsic tuffs. The mineralogical compositions of the kaolin deposits are dominated by quartz, kaolinite, dickite and illite with minor chlorite, montmorillonite, albite, hematite, pyrite and gypsum. Sanidine and plagioclase crystals in rhyolite-rhyodacite are sericitized and kaolinized. Whole rock chemistry of the kaolin deposits shows high contents of SiO2 and Al2O3. Enrichments of Sr in some samples demonstrate retention of Sr and depletion of Rb, Ba, Ca and K during hydrothermal alteration of sanidine and plagioclase within the volcanic units. The chondrite-normalized rare earth element patterns of the clay deposits show LREE enrichments (La/Lu)cn = 6.75 to 57.74, pointing to kaolinization in low-pH waters. The isotope composition of the kaolin (δ18O ~+5‰) is consistent with formation at isotopic equilibrium with water of hydrothermal/magmatic origin. The mineralogical composition, REE contents and elemental ratios in these deposits suggest provenance of the kaolin deposits mainly from felsic rocks and hydrothermal fluids. The O isotopic character also supports these results.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Selective adsorption of anionic polyacrylamide onto ultra-low ash coal and kaolinite
Autorzy:
Zou, W.
Yu, C.
Sun, C.
Cao, Y.
Tematy:
coal
kaolinite
anionic polyacrylamide
adsorption
flotation
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Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:
https://bibliotekanauki.pl/articles/109333.pdf  Link otwiera się w nowym oknie
Opis:
To study the selectivity of polyacrylamide in the selective floc flotation of fine coal, adsorption of anionic polyacrylamide (PAM A401) onto ultra-low ash coal and kaolinite was studied, including the adsorption thermodynamics, floc size distribution and wettability changes. The thermodynamics of the adsorption process at the low concentration of 0-16 mg/dm3 of PAM A401 were studied at different contact times, doses, temperatures and pH values. Thermodynamic parameters of ΔGo, ΔHo, ΔSo and Ea were evaluated to understand the nature of the adsorption process. The results indicated that PAM A401 was selectively adsorbed onto ultra-low ash coal rather than kaolinite. Physical adsorption was the predominant mechanism, and the adsorption of PAM A401 at 12 mg•dm-3 onto coal was 2.15-fold larger than the adsorption on kaolinite. After the adsorption of PAM A401, the lipophilic hydrophilic ratio (LHR) of coal decreased from 9.23 to 7.28, indicating that the coal became less hydrophobic than before. In contrast, the LHR of kaolinite increased from 1.44 to 1.65. Floc size measurements showed that the d10, d50 and d90 of coal flocculated by PAM A401 (at 12 mg/dm3, pH 6.5) were 3.18, 2.76 and 2.59-fold greater than the corresponding levels of these parameters for kaolinite flocs, respectively.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adsorption of hydrated Fe(OH)2+ on the kaolinite surface: A density functional theory study
Autorzy:
Wu, Hongqiang
Miao, Yuqi
Long, Qibang
Yan, Huashan
Li, Yong
Qiu, Sen
Wu, Hao
Zhao, Guanfei
Qiu, Tingsheng
Tematy:
kaolinite
adsorption
Fe
density functional theory
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Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:
https://bibliotekanauki.pl/articles/27323639.pdf  Link otwiera się w nowym oknie
Opis:
The present study employed density functional theory (DFT) to analyze the adsorption configuration and mechanism of Fe(OH)2+ on the kaolinite (001) surface. The findings demonstrated that Fe(OH)2(H2O)4+ is the main type in which hydrated Fe(OH)2+ can be found in aqueous solution. On the surface of kaolinite, Fe(OH)2(H2O)4+ will be adsorbed. There are two forms of adsorption: outer-sphere and inner-sphere coordination (monodentate/bidentate) adsorption. Fe(OH)2(H2O)4+ has a moderate propensity to adsorb on the alumina octahedral sheet of kaolinite when the outer-sphere coordination adsorption takes place. In cases of inner-sphere coordination adsorption, Fe exhibits a tendency to form monodentate adsorption compounds in conjunction with Ou atoms. Additionally, it prefers to create bidentate adsorption compounds through coordination with both Ot and Ou atoms. The adsorption mechanism analysis results show that the ionic property of Fe atom decreases after outer-sphere coordination adsorption. After inner-sphere coordination adsorption, some electrons of Fe atom are transferred to the surface O atom. The presence of electrons between the Fe and O atoms enhances the formation of bonds, hence enhancing the covalent nature of the Fe-O bond. Theoretical FT-IR (Fourier transform infrared spectroscopy) calculations show that the formation of Fe-O chemical bonds. Because of the lower adsorption energy and more chemical bonds, hydrate Fe(OH)2+ is more likely to be bidentate adsorbed on the kaolinite surface.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Potassium response in some Malawi soils
Autorzy:
Lakudzala, D. D.
Tematy:
potassium (K)
kaolinite
Malawi soils
minerals
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Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Powiązania:
https://bibliotekanauki.pl/articles/412437.pdf  Link otwiera się w nowym oknie
Opis:
Potassium (K) response curves were generated for some Malawi soils using four different rates of potassium fertilizer, with grass being used to estimate plant availability. The study was conducted to find the point of maximum response for potassium. The soils were characterized, limed and fertilized with equal amounts of nitrogen. Potassium was applied at four rates: 0.0, 0.1, 0.2 and 0.4 me K/100 cm3 soil. The K treated soils were put in pots and cropped with grass. The grass was harvested six weeks after planting, dried and weighed. In general, addition of potassium resulted in increased growth of grass in all soils, with some soils showing better response than others. For montmorillonitic soils and soils with mixed mineralogy response was linear up to the highest rate of 0.4 me K/100 cm3. Apparently the 0.4 me K/100 cm3 soil was not enough to give maximum yield for these potassium depleted soils. For the kaolinitic soils 0.4 me K/100 cm3 soil was beyond point of maximum response. The variation of response to added potassium in the different soils calls for soil specific fertilizer additions. Smallholder farmers should move from blanket (crop specific) fertilizer recommendations currently being used to crop and soil specific fertilizer recommendations. Basal fertilizer dressings (starter packs) should always contain potassium. Correlation and calibration studies should be conducted to establish a potassium low optimum level for Malawi soils.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Paleogene marginal marine sedimentation in central-western Poland
Autorzy:
Widera, M.
Kita, A.
Tematy:
Paleogene
lithostratigraphy
palaeogeography
kaolinite sands
deposit extent
Pokaż więcej
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/2059473.pdf  Link otwiera się w nowym oknie
Opis:
The Paleogene deposits of central-western Poland area have been studied in more than 300 bore holes and several out crops with lithological, mineralogical and sedimentological methods. Grain-size analyses, heavy mineral analyses, XRD analyses and pebble analyses were mainly used to characterize these deposits. From the Late Eocene until the Late Oligocene central-western Poland area was a marginal part of the NW European Tertiary Basin. For this time interval five informal lithostratigraphical units have been determined: the Pomorze, Lower Mosina, Czempiń, Upper Mosina and Leszno "formations" and addi tionally the Kaolinite Sand Unit. Their correlation is based on lithological features obtained from archival descriptions of borehole profiles. Deposits from boreholes and newly discovered exposures are mainly marine while only the Czempiń "Formation", with lignite intercalations, represent a non-marine environment. These findings help reconstruct the structural and palaeogeographic evolution of the eastern, marginal fragment of the NW European Tertiary Basin. The succession shows evidence of at least four interregional transgressive-regressive cycles. More over, the pres ent-day extent of the Paleogene deposits has been determined much more precisely. The southern limit of marine sedimentation in Paleogene times should be pushed at least a few tens of kilometres south in the vicinity of Konin and Turek, central-western Poland.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study on electrokinetic of kaolinite particles in aqueous suspensions
Autorzy:
Min, F.
Zhao, Q.
Liu, L.
Tematy:
kaolinite
zeta potential
pH
immersion time
electrophoresis
Pokaż więcej
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:
https://bibliotekanauki.pl/articles/110918.pdf  Link otwiera się w nowym oknie
Opis:
Influence of aqueous phase properties and process parameters on kaolinite particle zeta potential was quantified by electrophoresis experiments. The results indicated that pH strongly altered the zeta potential of kaolinite and it decreases at the beginning and then increases in the range of pH = 2–13. The activity of different cations changes the zeta potential and has the following tendency of Al3+ > Ca2+ > Mg2+ > Na+ and the zeta potential increases due to heterocoagulation of different mineral particles in suspension. It was found that the zeta potential of kaolinite particles increases after the suspension was stirred and decreases at the beginning, and then increases with soaking time. The FTIR results showed that the zeta potential takes into account ion adsorption and the change of Si–O, Al–O and Al–OH groups on the surface of the kaolinite particles.
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-10 z 40

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