scholarly journals Adsorption of uranyl ion on acid-modified zeolitic mineral clinoptilolite

2009 ◽  
Vol 63 (5) ◽  
pp. 407-414 ◽  
Author(s):  
Srdjan Matijasevic ◽  
Aleksandra Dakovic ◽  
Deana Iles ◽  
Sonja Milicevic
Keyword(s):  
Solid Phase ◽  
Exchange Capacity ◽  
Uranyl Ion ◽  
Ion Adsorption ◽  
Fluorometric Method ◽  
Kinetics Of Adsorption ◽  
Ph Values ◽  
Modified Clinoptilolite ◽  
Kinetics Of

In this paper, the results of adsorption of uranyl ion on acid-modified zeolitic mineral clinoptilolite are presented. Adsorption was investigated at different amounts of solid phase in suspension, as well as at different pH values. The modified clinoptilolite samples were obtained by treatment of clinoptilolite with acids: hydrochloric, oxalyc and citric. Starting and modified clinoptilolites were characterized by chemical analysis, thermal (DT/TG) analysis and by determination of cation exchange capacity, while starting and nonadsorbed amounts of uranyl ion were determined by fluorometric method. Uranyl ion adsorption experiments on natural unmodified zeolitic mineral showed that uranyl ion adsorption was low (29.2%) and that treatment of clinoptilolite with acids significantly increases the adsorption of uranyl ion (>90%). In the case of acid treated clinoptilolites, the highest adsorption of uranyl ion was achieved on clinoptilolite modified with hydrochloric acid. Kinetics of adsorption showed that adsorption of uranyl ion begins very fast and that the most of uranyl ion was adsorbed in first 30 min. Practically, there were no changes in uranyl ion adsorption within next 72 h.

Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarah B. Duckworth ◽  
Xavier Gaona ◽  
Alexander Baumann ◽  
Kathy Dardenne ◽  
Jörg Rothe ◽  
...  
Keyword(s):  
Solid Phase ◽  
Correction Factors ◽  
Mixed Salt ◽  
Ph Values ◽  
Reducing Conditions ◽  
Upper Limits ◽  
Salt Systems ◽  
Amorphous Character ◽  
Good Agreement

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m  ≤ 12 (with pH m  = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m  = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m  > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

Study on the Kinetics of Adsorption of Cadmium by Chitosan

2010 ◽  
Vol 160-162 ◽  
pp. 1804-1809
Author(s):  
Qiang Bi ◽  
Juan Qin Xue ◽  
Ying Juan Guo ◽  
Yu Jie Wang ◽  
Yun Feng Xue
Keyword(s):  
Kinetic Equations ◽  
Adsorption Kinetic ◽  
Maximum Adsorption Capacity ◽  
Kinetics Of Adsorption ◽  
Ph Values ◽  
Optimum Ph ◽  
Pseudo Second Order ◽  
Simulated Wastewater ◽  
Isotherm Equations ◽  
Kinetics Of

The adsorption of cadmium in simulated wastewater by chitosan was investigated. The influence of temperature, contact time and pH on adsorption efficiency of cadmium was examined. Some related mathematical models were used in the fitting of experimental data. The results showed that at room temperature, the optimum pH of adsorption is between 4 and 7. At lower pH values, a strong competition existed between cadmium ions and protons for sorption sites and the sorption efficiency was decreased. After 60 minutes the adsorption equilibrium can be achieved. Chitosan is very effective at removing cadmium with the maximum adsorption capacity is 112.05mg•g-1. The adsorption kinetic curves agree with the pseudo-second-order adsorption kinetic equations and the adsorption isotherms could be well described by Langmuir isotherm equations.

Reactive Diffusion upon Planar Dissolving Copper in Solder Melts

2011 ◽  
Vol 309-310 ◽  
pp. 127-134 ◽  
Author(s):  
Jaromír Drápala ◽  
Pavel Jopek ◽  
Daniel Petlák ◽  
Petr Harcuba ◽  
Petr Kubíček
Keyword(s):  
Interphase Boundary ◽  
Time Course ◽  
Solid Phase ◽  
Accurate Determination ◽  
Theoretical Description ◽  
Reactive Diffusion ◽  
Boundary Movement ◽  
Original Metal ◽  
Kinetics Of

Problems of reactive diffusion at a solid phase - melt contact were studied theoretically. The main intention was to calculate the time course of the solid phase dissolving in the case of planar dissolving. In our work we give heed especially to the dominating process, which is the solid metal A dissolving in solder melt B. During the dissolving, melt B saturates with metal A, and the process is influenced by convections which are characteristic for a given experimental configuration. A theoretical description of the kinetics of solid phase dissolving in the melt will be presented for the case of planar dissolving. The aim is to derive a relation for the interphase boundary movement (t) depending on time and a time course of growth of the element A concentration in the melt B. There are difficulties in accurate determination of the interphase boundary movement after heating of specimens for certain time intervals. It should be performed experimentally, since intermetallic phases are formed in original metal A both via diffusion and upon cooling and some phases segregate upon cooling of the solidifying melt. The main intention was to study experimentally the copper dissolving in melts of various solder alloys and the related reactive diffusion. We used pure Sn and Sn-Cu, Sn-Ag-Cu, Sn-Sb, Sn-Zn alloys as solder materials. Experiments aimed at the study of a Cu plate dissolving in the solder melt were carried out at various selected temperatures and times. The problems of reactive diffusion were studied both theoretically and experimentally and the problems that have to be solved preferably were emphasized. Concentration profiles of elements and thickness of layers of phases can be determined with SEM and X-ray microanalyses (WDX, EDX) of specimens after their diffusion heating.

scholarly journals Adsorption of nicotine from aqueous solutions on montmorillonite and acid-modified montmorillonite

2019 ◽  
Vol 51 (1) ◽  
pp. 93-100
Author(s):  
Irena Ilic ◽  
Natasa Jovic-Jovicic ◽  
Predrag Bankovic ◽  
Zorica Mojovic ◽  
Davor Loncarevic ◽  
...  
Keyword(s):  
Isotherm Model ◽  
Kinetics Of Adsorption ◽  
Nicotine Concentration ◽  
Ph Values ◽  
Modified Montmorillonite ◽  
Langmuir Isotherm Model ◽  
Pseudo Second Order ◽  
Ft Ir ◽  
Kinetics Of ◽  
Ft Ir Spectroscopy

Montmorillonite (Mt) and acid modified montmorillonite (MtA) were tested as nicotine adsorbents. The samples were characterized using FT-IR spectroscopy and low temperature nitrogen physisorption. Nicotine adsorption was performed with respect to contact time, pH and initial nicotine concentration. The kinetics of adsorption obeyed the pseudo-second-order kinetics. The optimal pH values for nicotine adsorption were 6 and 9 for Mt and MtA, respectively. The isotherms related to adsorption on Mt at pH = 6 and 9 as well as for MtA at pH=6 were best fitted with Sips isotherm model, while adsorption onto MtA at pH=9 obeyed Langmuir isotherm model.

scholarly journals Aflatoxin B1 adsorption by the natural aluminosilicates - concentrate of montmorillonite and zeolite

2016 ◽  
Vol 70 (5) ◽  
pp. 519-524 ◽  
Author(s):  
Marija Markovic ◽  
Aleksandra Dakovic ◽  
George Rottinghaus ◽  
Mirjana Stojanovic ◽  
Vera Dondur ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Aflatoxin B1 ◽  
Natural Zeolite ◽  
Cation Exchange Capacity ◽  
Active Sites ◽  
Solid Phase ◽  
Bentonite Clay ◽  
Exchange Capacity ◽  
Composition Determination

Aflatoxin B1 adsorption by the concentrate of bentonite clay - montmorillonite and the natural zeolite - clinoptilolite and was investigated at the initial toxin concentration 4 ppm, with different amonunts of solid phase in suspension (10, 5, 2 and 1 mg/10 mL) and different pH values - 3, 7 and 9. Results indicated that for both minerals, decreasing the amount of solid phase in suspension, decrease the amount of active sites relevant for adsorption of aflatoxin B1. Thus, for concentrate of montnorillonite, at the lowest level of solid phase in suspension (1 mg/10 mL), aflatoxin B1 adsorption indexes were 97% at pH 3, 88% at pH 7 and 82% at pH 9, while for the natural zeolite, adsorption of toxin was 9% at pH 3 and 7% at pH 7 and 9. Since inorganic cations in minerals are mainly responsible for aflatoxin B1 adsorption, even the natural zeolite - clinoptilite has much higher cation exchange capacity (the content of inorganic exchangeable cations) compared to the concentrate of montmorillonite, adsorption of aflatoxin B1 by this mineral is much lower. Comparing the molecular dimensions of aflatoxin B1 molecule with the dimension of channels of clinoptilolite and interlamellar space of montmorillonite it is obvious that this toxin is adsorbed only at the external surface of clinoptilolite while in the montmorillonite all active sites are equally available for its adsorption. Thus, the concentrate of montmorillonite posess by higher adsorption capacity for aflatoxin B1. Results presented in this paper confirmed the fact the differences in the structure of minerals led to their different efficiency for adsorption of aflatoxin B1. Mineralogical and chemical composition, determination of cation exchange capacity, etc., are very important parameters influencing the effectiveness of minerals as aflatoxin B1 adsorbents. [Projekat Ministarstva nauke Republike Srbije, br. 451-03-2802-IP Tip1/142, br. 172018 i br. 34013] <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/HEMIND170208003E">10.2298/HEMIND170208003E</a><u></b></font>

scholarly journals Effect of the Exchanged Cation in an Algerian Montmorillonite Used as a Heterogeneous Catalyst for Biginelli Reaction

2021 ◽  
Vol 68 (2) ◽  
pp. 355-362
Author(s):  
Fatiha Belferdi ◽  
Farida Bouremmad ◽  
Shalima Shawuti ◽  
Mehmet Ali Gulgun
Keyword(s):  
Heterogeneous Catalyst ◽  
Catalytic Properties ◽  
Biginelli Reaction ◽  
Reaction Medium ◽  
Exchange Capacity ◽  
Basal Spacing ◽  
Exchange Operation ◽  
Kinetics Of

In this work, an Algerian montmorillonite (Mt) is exchanged by different cations from the transition metals family, namely: Cu2+, Ni2+, Cr3+, Co2+, Fe2+ and Fe3+, it is used as a heterogeneous catalyst for Biginelli reaction. The exchanged cations are known for their catalytic properties in homogeneous catalysis. The main purpose is to study the effect of the exchanged cations on the yield and the kinetics of the reaction. The characterization of montmorillonite was carried out by XRD, which allows us to follow the evolution of the basal spacing d001 as a function of the exchanged cation and to show that the exchange operation has not altered the montmorillonite structure. The cation exchange capacity (CEC) is determined by the titration of the exchanged cation by atomic absorption. The product of the reaction is characterized by NMR, IR and by the determination of the melting point. In addition, the importance of the introduction order of the reagents into the reaction medium has been demonstrated on the yield and the kinetics. Finally, the obtained results show that the exchanged montmorillonite is competitive with other costly heterogeneous and homogeneous catalysts.

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