The sorption of lead, cadmium and strontium from aqueous solutions on sepiolite

The results of the characterization and the sorption properties of sepiolite from the locality Slovici are presented in this paper. X-Ray diffraction analysis, infrared spectroscopy and differential thermal analysis revealed sepiolite as the main phase and small amounts of magnesite as an impurity. The specific surface area of sepiolite, determined by nitrogen adsorption and by applying the BET equation was found to be 339 m2/g. The point of zero charge was determined by the batch equilibration method, under different conditions, and the shift in the point of zero charge, in the presence of Pb2+, Cd2+ and Sr2+ ions, was investigated. It was determined that the point of zero charge changed with modification of the solid/liquid ratio and by washing the powder, which indicated that under the investigated conditions some dissolution of the sepiolite and impurities took place also influencing the position of the point of zero charge. In the presence of Pb2+, Cd2+ and Sr2"1" ions, the point of zero charge was shifted toward lower pH values denoting specific ion sorption. The greatest shift and, therefore the largest specific sorption, appeared in the case of Pb2+ ions, somewhat less with Cd2+, and the least with Sr2"1" ions. The adsorption isotherms were determined for the Pb2+, Cd2+ and Sr2+ ions, as well as the amounts of these ions that were removed from aqueous media by the ion exchange of Mg2+ ions from the sepiolite structure, depending on the equilibrium ion concentrations. In the case of ion exchange, as in the case of specific sorption, the affinity of sepiolite for the investigated ions can be presented in the following order Pb2+ > Cd2+ > Sr2"1". For the removal of Sr2"1" ions from aqueous media by sepiolite, a third mechanism is important probably, the ion exchange of exchangeable ions from the sepiolite structure channels. As the result of the action of all the sorption mechanisms sepiolite is removes mostly Pb2+ ions, then Cd2+ and least of all Sr2"1" ions from the aqueous media.

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Preparation and Characterization: The Effect of Incorporation by Ion Exchange of Pt, Ni and Ru on a H-ZSM5 Zeolite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.727-728.32 ◽

2012 ◽

Vol 727-728 ◽

pp. 32-37 ◽

Cited By ~ 2

Author(s):

Antusia dos S. Barbosa ◽

A. Santos Barbosa ◽

Meiry Glaúcia Freire Rodrigues ◽

J. M. Grau

Keyword(s):

Ion Exchange ◽

Chemical Analysis ◽

Surface Area ◽

Platinum Complexes ◽

Nitrogen Adsorption ◽

Bifunctional Catalysts ◽

X Ray Diffraction ◽

X Ray ◽

Zsm5 Zeolite ◽

Bet Method

The objective of this work was based on catalysts Pt, Ni and Ru supported on zeolite NH4ZSM-5 and characterize them. In this work monometallic bifunctional catalysts were prepared (Pt/NH4ZSM-5; Ni/NH4ZSM-5; Ru/NH4ZSM-5), all containing the same concentration of each metal supported by competitive ion exchange, using solutions of platinum complexes [Pt (NH3)4] Cl2, Nickel [Ni (NH3)6] Cl2and chloride Ruthenium III (RuCl3). The samples were characterized by chemical analysis by X-ray Spectroscopy Energy dispersive (EDS), X-Ray Diffraction (XRD), nitrogen adsorption (BET method). Through the analysis of X-ray diffraction, its possible to identify the preservation of the structure of zeolite ZSM-5 after the competitive ion Exchange with metals (Ni, Pt, Ru) and calcination. The dispersion of platinum and ruthenium in zeolite ZSM-5, didnt modify the textural characteristics of the zeolite, but the dispersion of nickel caused a change in values of surface area of catalysts.

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Influence of organic cations sorption on the point of zero charge of natural zeolite

Hemijska industrija ◽

10.2298/hemind0904325k ◽

2009 ◽

Vol 63 (4) ◽

pp. 325-330 ◽

Cited By ~ 3

Author(s):

Milan Kragovic ◽

Aleksandra Dakovic ◽

Sonja Milicevic ◽

Zivko Sekulic ◽

Slobodan Milonjic

Keyword(s):

Ion Exchange ◽

Natural Zeolite ◽

Point Of Zero Charge ◽

Organic Cations ◽

Ammonium Ions ◽

Inorganic Cations ◽

Ph Values ◽

Zero Charge ◽

Basic Characteristics

In this paper, the results of the surface modification of natural zeolite with different amounts (2, 5 and 10 mmol M+/100g) of octadecyldimethylbenzyl ammonium ions (ODMBA) are presented. The obtained organozeolites were denoted as OZ-2, OZ-5 and OZ-10. The degree of ion exchange was followed by determination of amounts of inorganic cations released from zeolite. Results confirmed that reaction between ODMBA and starting zeolite has occurred via ion exchange mechanism. The obtained value for point of zero charge, pHpzc, of natural zeolite was 6.8?0.1, while for OZ-2, OZ-5 and OZ-10 pHpzc was 7.0?0.1. Below the pHpzc, the surfaces of materials are positive while at pH values higher than pHpzc their surfaces are negative. Compared to the pHpzc of natural zeolite, no significant differences in pHpzc was observed for all three organozeolites indicating that obtained products have similar functional groups with similar acid and basic characteristics as starting zeolite. The pHpzc was not dependent on the amount of ODMBA ions at the zeolitic surface and the value of pHpzc for all investigated sorbents is the same for all three electrolyte concentrations indicating that the pHpzc of each material is independent of the ionic strength of KNO3.

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Functionalization of thermo-acid activated sepiolite by amine-silane and mercapto-silane for chromium(VI) adsorption from aqueous solutions

Hemijska industrija ◽

10.2298/hemind121026117m ◽

2013 ◽

Vol 67 (5) ◽

pp. 715-728 ◽

Cited By ~ 2

Author(s):

Vesna Marjanovic ◽

Slavica Lazarevic ◽

Ivona Jankovic-Castvan ◽

Bojan Jokic ◽

Andjelika Bjelajac ◽

...

Keyword(s):

Aqueous Solutions ◽

Nitrogen Adsorption ◽

Parent Material ◽

Point Of Zero Charge ◽

X Ray Diffraction ◽

Ph Values ◽

Chromium Vi ◽

Initial Ph ◽

Adsorption Desorption ◽

Trimethoxy Silane

Chromium(VI) adsorption from aqueous solutions onto thermo-acid activated sepiolite functionalized with (3-mercaptopropyl)trimethoxy-silane and [3-(2-aminoethylamino)pro-pyl]trimethoxy-silane, was investigated. Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption-desorption, and determination of the point of zero charge were used to characterize the obtained adsorbents. It has been established that the silanes were successfully grafted on the thermo-acid activated sepiolite surfaces and that the structure of parent material was preserved during the functionalization. The adsorption of Cr(VI) onto functionalized thermo-acid activated sepiolite was tested as a function of initial pH values at 298 K. The amine functionalized thermo-acid activated sepiolite showed a higher adsorption capacity than the mercapto functionalized thermo-acid activated sepiolite at all studied initial pH values, especially at the initial pH = 2.

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Tetracycline Adsorption from Aqueous Media by Magnetically Separable Fe3O4@Methylcellulose/APTMS (Isotherm, Kinetic and Thermodynamic Studies)

10.21203/rs.3.rs-1115245/v1 ◽

2021 ◽

Author(s):

Sobhan Maleky ◽

Ali Asadipour ◽

Alireza Nasiri ◽

Rafael Luque ◽

Maryam Faraji

Keyword(s):

Aqueous Solutions ◽

Aqueous Media ◽

Point Of Zero Charge ◽

Gravimetric Analysis ◽

Order Kinetic ◽

X Ray Diffraction ◽

Solution Ph ◽

Enthalpy Changes ◽

Isotherm Equations ◽

Kinetic And Thermodynamic Studies

Abstract This study aimed to synthesize Fe3O4@Methylcellulose/3-Aminopropyltrimethoxysilane (Fe3O4@MC/APTMS) as a new magnetic nano-biocomposite by a facile, fast, and new microwave-assisted method and to be utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. Fe3O4@MC/APTMS was characterized by Fourier transform-infrared (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), Mapping, X-ray diffraction (XRD), Thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) and vibrating sample magnetometer (VSM). The point of zero charge (pHzpc) value of the nano-biocomposite was estimated to be 6.8 by the solid addition method. Optimum conditions were obtained in TC concentration: 10 mg L−1, adsorbent dosage: 80 mg L−1, contact time: 90 min, and solution pH: 6 with the maximum TC removal of 90% and 65.41% in synthetic and actual samples, respectively. The kinetic and isotherm equations pointed to a pseudo-second order kinetic and Langmuir isotherm optimum fitting models. Based on the values of entropy changes (ΔS) (50.04 J/mol k), the enthalpy changes (ΔH) (9.26 kJ/mol), and the negative Gibbs free energy changes (ΔG), the adsorption process was endothermic, random, and spontaneous. The synthesized adsorbent exhibited outstanding properties, including proper removal efficiency of TC, excellent reusability, and simple separation from aqueous media by a magnet. Consequently, it is highly desirable that Fe3O4@MC/APTMS magnetic nano-biocomposite could be used as a promising adsorbent for TC adsorption from aqueous solutions.

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Ion-Exchanged ZIF-67 Synthesized by One-Step Method for Enhancement of CO2 Adsorption

Journal of Nanomaterials ◽

10.1155/2020/1508574 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Fujiao Song ◽

Yan Cao ◽

Yunxia Zhao ◽

Ruiyu Jiang ◽

Qi Xu ◽

...

Keyword(s):

Ion Exchange ◽

Physical Adsorption ◽

Point Of Zero Charge ◽

X Ray Diffraction ◽

Step Method ◽

Adsorption Performance ◽

Particle Size Analyzer ◽

One Step ◽

The One ◽

Electronic Microscope

Li+- and Na+-exchanged ZIF-67 was synthesized by a new one-step method of ion as-exchange technique and tested as CO2 adsorbents. As a comparison, the standard ion-exchange procedure was also carried out. The powder X-ray diffraction (XRD), scanning electronic microscope (SEM), particle size analyzer (PSD), and thermal gravimetry analysis (TGA) were used to investigate the effect of ion-exchange techniques on the structure of the materials. CO2 uptake of ZIF-67 ion exchanged by one-step method is much higher than that by the standard ion-exchange procedure. All of the adsorption isotherms show linear patterns with stable adsorption rate from 0 bar to 1 bar, which reveals the materials could get excellent adsorption performance at higher pressure range (>1 bar). Elemental analysis, N2 physical adsorption, and the point of zero charge (PZC) were carried out to confirm the adsorption mechanism. van der Waals interaction determined by the surface area and coordination interaction resulting from electrostatic interaction work in synergy to enhance CO2 adsorption performance of ZIF-67 ion exchanged by the one-step method.

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Relations Between Structure and Texture in Nano-Sized Aluminas

MRS Proceedings ◽

10.1557/proc-351-157 ◽

1994 ◽

Vol 351 ◽

Cited By ~ 2

Author(s):

Dominique J. Coster ◽

Pierre Levitz ◽

Jose J. Fripiat

Keyword(s):

Heat Treatment ◽

Aluminum Content ◽

High Surface ◽

Aqueous Media ◽

High Surface Area ◽

Nitrogen Adsorption ◽

X Ray Diffraction ◽

X Ray ◽

Degree Of Condensation ◽

High Surface Area Materials

ABSTRACTAlumina xerogels were prepared by a two step hydrolysis in non-aqueous media. This synthesis produced high surface area materials with controlled amount of pentacoordinated aluminum. The effect of heat treatment and of the preparation procedure on the physical characteristics of the powder was determined by nitrogen adsorption and X-Ray diffraction, whereas the aluminum coordination was studied by 27Al MAS NMR. The pore size distribution and the pentahedral aluminum content (up to 700°C) are closely related to the degree of condensation of the prehydrolysed oligomer species.

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The Influence of the Solid/Liquid Ratio on the Point of Zero Charge of Alumina

Materials Science Forum ◽

10.4028/www.scientific.net/msf.453-454.361 ◽

2004 ◽

Vol 453-454 ◽

pp. 361-366 ◽

Cited By ~ 5

Author(s):

Ž.N. Todorović ◽

S.K. Milonjić ◽

V. Dondur

Keyword(s):

Point Of Zero Charge ◽

Liquid Ratio ◽

Zero Charge ◽

Solid Liquid

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Mechanisms of halosulfuron methyl pesticide biosorption onto neem seeds powder

Scientific Reports ◽

10.1038/s41598-021-88929-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Atta ul Haq ◽

Muhammad Saeed ◽

Muhammad Usman ◽

Ameer Fawad Zahoor ◽

Muhammad Naveed Anjum ◽

...

Keyword(s):

Aqueous Media ◽

Sorption Kinetics ◽

Point Of Zero Charge ◽

Neem Seed ◽

Solution Ph ◽

Chemical Surface ◽

Operation Conditions ◽

Zero Charge ◽

Pseudo Second Order ◽

Kinetics Of

AbstractThe current investigation was designed to remove halosulfuron methyl from aqueous media by means of neem seed powder (NSP) in batch modes. Characterizations of NSP were carried out by using EDX, SEM, FTIR, point of zero charge and surface analysis. Optimum operation conditions were scrutinized by studying the influence of different factors like solution pH, dose of NSP, contact time, initial halosulfuron methyl concentration and temperature. Result indicates the dependency of the removal of halosulfuron methyl on solution pH and maximal removal (54%) was achieved in acidic medium (i.e. pH 3.0). To identify the chemical surface of NSP, point of zero charge of NSP was determined and was found to be 6.5 which imply that the surface of NSP is positively charged below pH 6.6 and favored the anionic sorption. Kinetics of halosulfuron methyl were demonstrated well by pseudo second order due to highest R2 (0.99) owing to the nearness between experimental and calculated sorption capacities. Isotherm results imply that Langmuir was found to the principal model to explain the removal of halosulfuron methyl and maximum monolayer sorption capacity was determined to be 200 mg g−1. Thermodynamic parameters like ΔH°, ΔG° and ΔS° were calculated from van’t Hoff plot and were found negative which suggest that removal of halosulfuron methyl is exothermic and spontaneous at low temperature. These outcomes insinuate that neem seed power may be a valuable, inexpensive and ecofriendly biosorbent for the removal of pesticides.

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Self-Recognizing π-π Stacking Interactions Designed for the Generation of Ultrastable Mesoporous Hydrogen-Bonded Organic Frameworks

10.26434/chemrxiv.9729494 ◽

2019 ◽

Author(s):

KAIKAI MA ◽

Peng Li ◽

John Xin ◽

Yongwei Chen ◽

Zhijie Chen ◽

...

Keyword(s):

Pore Size ◽

Fiber Composite ◽

Aqueous Media ◽

Stacking Interactions ◽

Mustard Gas ◽

X Ray Diffraction ◽

X Ray ◽

Expansion Strategy ◽

Π Stacking ◽

Hydrogen Bonded

Creating crystalline porous materials with large pores is typically challenging due to undesired interpen-etration, staggered stacking, or weakened framework stability. Here, we report a pore size expansion strategy by self-recognizing π-π stacking interactions in a series of two-dimensional (2D) hydrogen–bonded organic frameworks (HOFs), HOF-10x (x=0,1,2), self-assembled from pyrene-based tectons with systematic elongation of π-conjugated molecular arms. This strategy successfully avoids interpene-tration or staggered stacking and expands the pore size of HOF materials to access mesoporous HOF-102, which features a surface area of ~ 2,500 m2/g and the largest pore volume (1.3 cm3/g) to date among all reported HOFs. More importantly, HOF-102 shows significantly enhanced thermal and chemical stability as evidenced by powder x-ray diffraction and N2 isotherms after treatments in chal-lenging conditions. Such stability enables the adsorption of dyes and cytochrome c from aqueous media by HOF-102 and affords a processible HOF-102/fiber composite for the efficient photochemical detox-ification of a mustard gas simulant.

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Action Time-Effect and Mechanism of Low-Calcium Fly Ash in Cement-Based Composites

Crystals ◽

10.3390/cryst11060681 ◽

2021 ◽

Vol 11 (6) ◽

pp. 681

Author(s):

Na Yan ◽

Qingqing Tang ◽

Ying Zhang ◽

Guowen Sun

Keyword(s):

Fly Ash ◽

Nitrogen Adsorption ◽

Chemical Effect ◽

Hydration Products ◽

X Ray Diffraction ◽

Degree Of Hydration ◽

Surface Areas ◽

Activity Effect ◽

Low Calcium ◽

Pore Size Distributions

This study was conducted in order to investigate when low-calcium fly ash plays a physical or chemical effect and what is the chemical effect proportion of low-calcium fly ash. Two types of low-calcium fly ash and quartz powder, with similar fineness as active and inert admixtures, were used as materials in this study. Under different water/binder ratios and hydration ages, the effects of the different types of admixtures and their dosages on the flexural and compressive strength of the composites were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption methods, in addition to an assessment of the degree of hydration of the fly ash, were employed to observe the hydration products at different ages, the microstructures of the hydration products, as well as their surface areas and pore size distributions. The results show that during the hydration period of 28 days, the low-calcium fly ash has a micro-aggregate filling physical effect. However, after 56 days, the hydration degree of fly ash begins to exceed 1%. This illustrates that the low-calcium fly ash has both the pozzolanic activity effect and micro-aggregate filling effect. In contrast, the low-calcium fly ash hydrated for 90 days is still dominated by the physical filling effect.

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