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1
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Adsorption of mercury species on river sediments - effects of selected abiotic parameters

100%
Pelcová P., Margetínová J., Vaculovič T., Komárek J., Kubáň V.
Open Chemistry
|
2010
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vol. 8
|
issue 1
116-125
EN
Abiotic parameters (pH, temperature, current velocity, mercury species concentration, and sediment and aqueous media composition) influence mercury species (MeHg+, EtHg+, PhHg+ and inorganic Hg2+) adsorption on river sediments. The highest amount of adsorbed MeHg+ and EtHg+ (82–93% and 85–91% for static and agitated system, respectively) occurred at pH 3–4. For PhHg+ the maximum adsorption (90% and 95% for static and agitated systems) was located over the broad 3–10 pH range, while for Hg2+ (94% and 97% for static and agitated systems) it was at pH ∼ 3. Temperature (4.5–60°C) influenced the adsorption rate but not the quantity. Both rate and quantity increased in the order: static 2+ adsorption about 67%. Cations at pH 5.2 reduced either the adsorption rate (Ca2+, Al3+) or the total adsorption (Zn2+, Fe3+). Positive correlations were found between sediment C, N, S content as well as cation exchange capacity (CEC) with mercury adsorption (R = 0.45–0.66, 0.56–0.89, 0.45–0.61 and 0.55–0.73, respectively) while negative correlations were observed with Fe and Al (R = −0.63 to −0.90 and −0.65 to −0.86, respectively). [...]
2
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The effect of alloying on the H-atom adsorption on the (100) surfaces of Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag, and Pt-Au. A theoretical study

100%
Matczak P., Romanowski S.
Open Chemistry
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2011
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vol. 9
|
issue 3
474-480
EN
The effect of alloying on the adsorption of atomic hydrogen was studied using density functional theory (DFT). In the study the (100) surfaces of Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag, and Pt-Au alloys were considered by means of a cluster model. The structural and energetic properties of the H atom adsorbed on the Pd4Me (Me = Ag, Pt, Au) and Pt4Me (Me = Pd, Ag, Au) clusters were calculated and compared with the H-atom adsorption on monometallic clusters. The effect of alloying on the H-atom adsorption is evident for all the investigated bimetallic systems. However, it strongly depends on the second metal atom, Me, is placed in the surface layer or in the subsurface one. In general, the H atom adsorbed in a site containing the second metal exhibits different properties from those characteristic of its adsorption on Pd(100) and Pt(100). Hence, the modified interaction between atomic hydrogen and the alloyed surfaces may increase the selectivity of the catalytic hydrogenation reactions on such surfaces.
3
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Kinetic, Equilibrium and Thermodynamic studies on the removal of Cr(VI) by activated carbon prepared from Cajanus Cajan(L) Milsp seed shell

100%
Thamilarasu P., Kumar G., Tamilarasan R., Sivakumar V., Karunakaran K.
Polish Journal of Chemical Technology
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2011
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vol. 13
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issue 4
1-7
EN
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 500°C. 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 fitted well to the Freundlich isotherm. The thermodynamic parameters such as ΔH°, ΔS°, and ΔG° 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.
4
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A GREEN METHOD FOR THE REMOVAL OF ZINC(II) IONS FROM WASTEWATER USING MODIFED BIOPOLYMERS

100%
Jeyaseelan C., Jain A., Jugade R.
Progress on Chemistry and Application of Chitin and its Derivatives
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2021
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vol. 26
101-111
EN
Zinc pollution in wastewater is a global problem because it is highly toxic. Zinc is commonly used in industries that transfer the water containing zinc directly into water sources, leading to pollution. Exposure to a high level of zinc causes major health problems. This study evaluated the adsorption of zinc ions from aqueous system using modified biopolymers of chitosan by crosslinking with sulphates using the batch adsorption method; the concentration was determined using atomic absorption spectrophotometry. The sulphate cross-linked chitosan (SCC) was characterised by several method. The effects of various experimental parameters such as pH, contact time, concentration, adsorbent dosage and temperature were investigated. Under the optimised conditions, the percentage efficiency for the removal of zinc(II) was up to 85%. Freundlich and Langmuir isotherms were used to analyse the equilibrium adsorption data along with kinetic studies. Various thermodynamic parameters have also been reported.
5
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Excess interfacial energy change of solid/aqueous salt solution system with increasing salt concentration at a constant charge-determining ion activity based on the Gibbs equation and ionic components of charge

88%
Ratajczak T., Drzymala J.
Open Chemistry
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2012
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vol. 10
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issue 6
1927-1932
EN
A thermodynamic equation relating the change of interfacial excess (Gibbs) energy in the solid/aqueous salt solution system, caused by a variation of concentration of inorganic salt at a constant charge-determining ion activity, temperature and pressure, is derived. The equation is based on the Gibbs equation and ionic components of charge parameters. On the basis of literature experimental data for the AgI/aqueous KNO3 and TiO2/aqueous NaCl systems it was shown that the interfacial excess energy decreases with increasing salt concentration due to variation of the ionic components of charge of the interface. [...]
6
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Uptake of phenol from aqueous solution by burned water hyacinth

88%
Uddin M., Islam M., Islam M., Abedin M.
Polish Journal of Chemical Technology
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2008
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vol. 10
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issue 2
43-49
EN
The potential of burned water hyacinth (BWH) for phenol adsorption from aqueous solution was studied. Batch kinetic and isotherm studies were carried out under varying experimental conditions of contact time, phenol concentration, adsorbent dosage and pH. The pH at the point of zero charge (pHPZC) of the adsorbent was determined by the titration method and the value of 8.8 ± 0.2 was obtained. The FTIR of the adsorbent was carried out in order to find the potential adsorption sites for the interaction with phenol molecules. The Freundlich and Langmuir adsorption models were used for the mathematical description of adsorption equilibrium and it was found that the experimental data fitted very well to the Langmuir model. Maximum adsorption capacity of the adsorbent was found to be 30.49 mg/g. Batch adsorption models, based on the assumption of the pseudo-first-order and pseudo-second-order models, were applied to examine the kinetics of the adsorption. The results showed that kinetic data closely followed the pseudo-second-order model.
7
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Quinine sulfate: a pharmaceutical product as effective corrosion inhibitor for carbon steel in hydrochloric acid solution

88%
Samide A., Tutunaru B.
Open Chemistry
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2014
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vol. 12
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issue 9
901-908
EN
Quinine sulfate dihydrate (QNS), IUPAC name: (8S,9R)-6-methoxy-4-quinolenyl-5-vinyl-2-quinuclidinyl methanol sulfate dihydrate, was tested as corrosion inhibitor for carbon steel in 1.5 mol L−1 HCl solution using the potentiodynamic polarization and the electrochemical impedance spectroscopy (EIS) associated with UV-Vis spectrophotometry. The electrochemical results showed that, the inhibition efficiency (IE) increased with the increase in QNS concentration, reaching a maximum value of 93.35±0.25%. The polarization resistance (R p) followed the same trend, obtaining the highest value of 659.7 Ω cm2, while the corrosion current density (i corr) reached the lowest level of 195 µA cm−2. The action mechanism of QNS was proposed considering the ability of quinine (QN) to be adsorbed on the metal surface via the lone pairs of electrons from hydroxyl oxygen atom, and/or from quinoline and quinuclidinic nitrogens. The occurrence of the complexes between inhibitor and iron ions was considered an additional process, which may contribute to protective layer formation. The Temkin adsorption isotherm was found as the best fitting for the degree of surface coverage (θ) values. In order to elucidate the mechanism of protective layer formation, the free energy of adsorption (ΔG o ads) value was calculated. This indicates that the inhibitor acts by chemical adsorption on the steel surface.
8
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Nanosized centers for mercury(II) ions adsorption on a surface of modified silica

88%
Belyakova L., Shvets O., Lyashenko D.
Open Chemistry
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2008
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vol. 6
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issue 4
581-591
EN
The present work investigates the adsorptive interactions of Hg(II) ions in aqueous medium with hydroxylated silica, aminopropylsilica and silica chemically modified by β-cyclodextrin. Batch adsorption studies were carried out with various agitation times and mercury(II) concentrations. The maximum adsorption was observed within 15–30 min of agitation. The kinetics of the interactions, tested with the model of Lagergren for pseudo-first and pseudo-second order equations, showed better agreement with first order kinetics (k1 = 3.4 ± 0.2 to 5.9 ± 0.3 min−1). The adsorption data gave good fits with Langmuir isotherms. The results have shown that β-cyclodextrin-containing adsorbent has the largest adsorption specificity to Hg(II): K L = 4125 ± 205 mmol−1. “β-cyclodextrin-NO3-” inclusion complexes with ratio 1: 1 and super molecules with composition C42H70O35 ⊎ 3 Hg(NO3)2 are formed on the surface of β-cyclodextrin-containing silica. [...]
9
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Synthesis and characterization of silica gel microspheres encapsulated by salicyclic acid functionalized polystyrene and its adsorption of transition metal ions from aqueous solutions

88%
Xu Q., Yin P., Zhao G., Yin G., Qu R.
Open Chemistry
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2010
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vol. 8
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issue 1
214-222
EN
The present study was undertaken to develop a novel adsorbent for heavy metal ions, and this paper presents the synthesis and characterization of a composite material-silica gel microspheres encapsulated by salicyclic acid functionalized polystyrene (SG-PS-azo-SA) with a core-shell structure. SG-PS-azo-SA was used to investigate the adsorption of Mn(II), Co(II), Ni(II), Fe(III), Hg(II), Zn(II), Cd(II), Cr(VI), Pd(II), Cu(II), Ag(I), and Au(III) from aqueous solutions. The results revealed that SG-PS-azo-SA has better adsorption capacity for Cu(II), Ag(I) and Au(III). Langmuir and Freundlich isotherm models were applied to analyze the experimental data, the best interpretation for the experimental data was given by the Langmuir isotherm equation with the maximum adsorption capacity for Cu(II), Ag(I), and Au(III) at 1.288 mmol g−1, 1.850 mmol g−1 and 1.613 mmol gt-1, respectively. Thus, silica gel encapsulated by salicyclic acid functionalized polystyrene (SG-PS-azo-SA) is favorable and useful for the removal of Cu(II), Ag(I) and Au(III) metal ions. [...]
10
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Content available

Packed-Bed Column Adsorption of Metanil Yellow (MY) from Simulated Wastewater using Granular NaOH-Activated Carbon from Cassava (Manihot esculenta) Peels

88%
Isiuku B. O., Horsfall Jr. M.
World News of Natural Sciences
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2017
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vol. 14
11-35
EN
The ability of NaOH-activated carbon derived from cassava peels waste to remove MY from aqueous solution was carried out in a fixed-bed column adsorber. The parameters studied included initial solution concentration, Co, carbon bed height and volume flow rate. The temperature of operation and initial solution pH were 29 °C and 5.32, respectively. The optimum adsorption capacity, qe 4.12 mg/g was obtained at Co 10mg/L, bed height 10cm and flow rate, 13.3ml/min. Experimental data were analyzed with Langmuir, Freundlich and Temkin isotherm, as well as the Thomas, Yoon-Nelson and Clark kinetic models. All the models were good fits for experimental data based on correlation coefficient, R2 values. The ΔGads and Freundlich n (1.587) show that the biosorption was spontaneous, good and physical. Results show that NaOH-activated carbon from cassava peels has low capacity to remove MY from aqueous solutions.
11
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Catalytic degradation of methylene blue in aqueous solutions over Ni- and Co- oxide systems

88%
Stoyanova M., Christoskova S.
Open Chemistry
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2011
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vol. 9
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issue 6
1000-1007
EN
The oxidative catalytic degradation of the cationic dye methylene blue (MB) with NaOCl in aqueous solutions was studied using individual and iron modified Ni- and Co-oxide systems as catalysts. The adsorption extent and the contribution of the uncatalyzed oxidation on the overall degree of MB were determined. The results indicate that methylene blue-a representative of a class of dyestuffs resistant to biodegradation-could be successfully decolorized and degraded using nickel and cobalt oxide catalysts at room temperature. The highest catalytic activity manifests in the Co-oxide system which is consistent with the adsorption data. The oxidative degradation reaction proceeds via first-order kinetics. Temperature has a relatively small effect on the methylene blue degradation kinetics. The results obtained reveal that the catalysts investigated are suitable for oxidative destruction of methytlene blue dye in wastewaters. [...]
12
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A promising absorbent of acrylic acid/poly(ethylene glycol) hydrogel prepared by glow-discharge electrolysis plasma

88%
Lu Q., Yu J., Gao J., Yang W., Li Y.
Open Chemistry
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2012
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vol. 10
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issue 4
1349-1359
EN
An acrylic acid/poly(ethylene glycol) (AAc/PEG) hydrogel was synthesized in aqueous solution by a simple one-step method using glow-discharge electrolysis plasma (GDEP) technique. The structure of AAc/PEG hydrogel was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Factors influencing the adsorption of heavy-metal ions such as solution pH, contact time, initial heavy-metal ion concentration were examined systematically by batch experiments. Results showed that both chemical complexation and ion exchange played an important role for heavy-metal ion adsorption onto AAc/PEG hydrogel. The adsorption isothermals followed the Langmuir isotherm and the adsorption kinetics fitted the pseudo-second-order model at 25°C with a pH 6. In addition, AAc/PEG hydrogel can be also regenerated and re-used. [...]
13
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Adsorption of cystine at mercury/ aqueous solution of chlorate (VII) interface in solutions of different water activity

88%
Nosal-Wiercińska A.
Open Chemistry
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2012
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vol. 10
|
issue 4
1290-1300
EN
[...]
14
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Content available

Adsorption behavior of pharmaceutically active dexketoprofen as sustainable corrosion Inhibitor for API X80 carbon steel in acidic medium

88%
Nkem B. I., Abosede O. J.
World News of Natural Sciences
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2019
|
vol. 27
22-37
EN
The inhibition of X80 carbon steel corrosion in 1 M HCl solution by dexketoprofen (DKP) was studied using weight loss (WL), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and scanning electron microscopy (SEM) techniques. The results indicated that DKP acts by way of adsorption as an effective protective inhibitor in the aggressive acid medium. The inhibition efficiency of DKP increased with concentration but was lower at higher temperature. The results of potentiodynamic polarization showed that DKP molecule behaved as a mixed type inhibitor by reducing both the anodic and the cathodic electrochemical reactions. Dexketoprofen was adsorbed on the X80 steel surface in accordance with Langmuir adsorption isotherm. SEM analyses supported formation of protective film on the X80 steel in the presence of DKP.
15
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Competitive adsorption of toxic metals on activated carbon

88%
Šváb M., Sukdolová K., Švábová M.
Open Chemistry
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2011
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vol. 9
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issue 3
437-445
EN
Competitive adsorption of zinc and copper on activated carbon is studied in this article. Main aim was to suggest an advanced model for competitive adsorption of both metals considering pH influence and precipitation. A surface-complexation approach was employed for the modeling. Two models were considered: simple adsorption and ion exchange. System “The Geochemists Workbench” was used for calculation of both static and dynamic adsorption tasks. From the batch experiments, concentration of four types of sorbing sites on the carbon surface and its protonation and sorption constants were deduced. Then, batch competitive adsorption experiments were compared with the models’ results. Finally, a column experiment (fixed bed adsorption) was carried out. It was observed that the model of ion exchange can satisfyingly predict both chromatographic effect and increase of zinc concentration in effluent over its initial value, although a quantitative agreement between the model and the experiment was not totally precise.
16
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Comparative studies on the removal of copper (II) by Ulva fasciata activated carbon and commercially activated carbon

88%
Suresh Jeyakumar R. P., Chandrasekaran V.
Polish Journal of Chemical Technology
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2012
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vol. 14
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issue 4
88-94
EN
In this work, the efficiency of Ulva fasciata sp. activated carbons (CCUC, SCUC and SSUC) and commercially activated carbon (CAC) were studied for the removal of Cu (II) ions from synthetic wastewater. Batch adsorption experiments were carried out as a function of pH, contact time, initial copper concentration and adsorbent dose. The percentage adsorption of copper by CCUC, SSUC, SCUC and CAC are 88.47%, 97.53%, 95.78% and 77.42% respectively. Adsorption data were fitted with the Langmuir, Freundlich and Temkin models. Two kinetic models pseudo first order and the pseudo second order were selected to interpret the adsorption data.
17
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Uranium (VI) adsorption equilibrium on purolite resin SGA 600 U/3472

88%
Botez A., Dobre T., Panturu E., Filcenco-Olteanu A.
Open Chemistry
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2014
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vol. 12
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issue 7
769-773
EN
This paper characterizes uranium (VI) sorption from synthetic solutions using a fixed bed Purolite resin SGA 600 U/3472 system. The effect of the sulphate anion presence in the liquid phase on sorbtion dynamics and equilibrium is analysed. In the industrial processing of solutions obtained from leaching of uranium ore (alkaline/acid), in a continuous system, there are several compounds which strongly compete with uranium for ion exchange sites and consequently these substances depress the uranium adsorption. The influence of vanadate, molybdate, chloride, and nitrate is known, therefore, in this paper, the adsorption equilibrium isotherms for uranium (VI) are obtained for different sulphate ion concentrations in solution. The adsorption capacity variation of the Purolite resin SGA 600U/3472 with the number of adsorption/desorption cycles is also studied. The experimental results reveal the negative impact of high sulphate ion content in solution on the adsorption capacity of the resin Purolite SG 600 U / 3472 with uranium (VI) and therefore it is considered one of the compounds which strongly affect the uranium adsorption.
18
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Interaction of montmorillonite with phenothiazine dyes and pyronin in aqueous dispersions: A visible spectroscopy study

88%
Czímerová A., Čeklovský A., Bujdák J.
Open Chemistry
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2009
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vol. 7
|
issue 3
343-353
EN
Layer charge is one of the key parameters used for the characterisation of expandable clay minerals, smectites. It determines most significant properties of the material which are important from the industrial application point of view. This work is related to a novel method introduced to characterize the layer charge of smectites, based on using cationic organic dyes as molecular sensors. One xanthene and four phenothiazine cationic dyes were tested using reduced charge montmorillonites (RCMs) and compared with methylene blue, which has been used most frequently. The characterization of the charge was based on the formation of molecular assemblies (H- and J-aggregates) composed by dye cations, which were easily detectable using absorption spectroscopy in the UV/VIS spectrum. More detailed characterization of the spectra required calculations of second-derivative curves. For all of the reaction systems tested in this work, the molecular aggregation increased with the layer charge of RCMs. Slight to moderate differences in the formation of dye assemblies related to the differences in the molecular structures of the individual dye cations. For example, the molecular asymmetry of azure A brought about the formation of coexistent species of similar structures. The structure of the heteroaromatic skeleton affected the extent of the aggregation and spectral changes with time. The presence of reactive, non-substituted amino groups in thionine cations probably partially decomposed in the clay mineral colloids based on high-charge RCMs. Any of the tested dyes could be used as molecular sensors for empirical characterization of the layer charge of clays taking into account the differences mentioned above. [...]
19
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Application of NRTL activity coefficient model to describe the kinetics of gas adsorption

88%
Nieszporek K., Banach T., Podkościelny P.
Open Chemistry
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2014
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vol. 12
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issue 2
185-193
EN
The Non-Random Two-Liquid activity coefficient model is applied to describe the kinetics of pure gas adsorption on energetically heterogeneous solid surfaces. The surface energetic heterogeneity has been represented by the Gaussian-like function of the adsorption energy distribution. Two different kinetic isotherms have been presented. One of them, determined by using the statistical rate theory, has been critically discussed. The applicability of the presented approach has been demonstrated by a quantitative analysis of two sets of experimental data previously reported in the literature.
20
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Adsorption behavior of Pb(II) onto xanthated rubber (Hevea brasiliensis) leaf powder

88%
Khalir W., Hanafiah M., So'ad S., Ngah W.
Polish Journal of Chemical Technology
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2011
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vol. 13
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issue 4
84-88
EN
A plant waste, rubber (Hevea brasiliensis) leaf powder was modified with carbon disulfide (xanthation) for the purpose of introducing sulfur groups, and the adsorbent performance in removing Pb(II) ion was evaluated. Pb(II) adsorption was confirmed by spectroscopic analysis, which involved Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The amount of Pb(II) adsorbed increased with increasing pH, contact time and concentration but slightly decreased with increasing ionic strength. Adsorption equilibrium was achieved in less than 60 min and followed the pseudo-second order model. The isotherm data indicated that Pb(II) adsorption on xanthated rubber leaf (XRL) fitted well with Langmuir isotherm model. The maximum adsorption capacity computed from the Langmuir isotherm model was 166.7 mg/g. Pb(II) adsorption occurred via ion-exchange and complexation mechanisms.
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