sorption characteristics
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Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 239
Author(s):  
Eduard Tokar ◽  
Mikhail Tutov ◽  
Pavel Kozlov ◽  
Arseni Slobodyuk ◽  
Andrei Egorin

A series of resorcinol–formaldehyde resins (RFR) samples for Cs-137 removal from liquid alkaline media have been synthesized. It has been demonstrated that the chemical stability as well as sorption characteristics are determined by the resorcinol/formaldehyde molar ratio and the solidification temperature. It has been also demonstrated that the sample synthesized at the resorcinol/formaldehyde molar ratio of 1.8/2.2 and solidified at 210 °C is characterized by the best sorption-selective characteristics and chemical stability. Under dynamic conditions, at feeding >1000 bed volumes of a model solution with pH > 13, the RFR 3-1 goes through six sorption cycles without noticeable changes in the sorption characteristics. The results are presented that demonstrate the possibility of RFR application in the decontamination of real LRW from Cs-137.


2021 ◽  
Vol 10 (4) ◽  
pp. 65-71
Author(s):  
A. V. Bondarev ◽  
E. T. Zhilyakova ◽  
N. B. Demina ◽  
K. K. Razmakhnin

Introduction. The mineral resource base of Russia has effective sorption substances that meet pharmaceutical requirements. Promising mineral raw materials are Zeolites, which combine the properties of an adsorbent and a "molecular sieve" due to the porous structure. In addition to the enterosorption direction, natural Zeolites are a source of macro-and microelements, which determines their use as biologically active food additives.Aim. Study of the physical and chemical characteristics of the Zeolites of the Kholinsky deposit.Materials and methods. The zeolite mineral raw materials of the Kholinsky deposit were used as objects of research. Optical microscopy was performed using a Leica DM direct microscope (Microsystems, Germany). Energy dispersion analysis was performed using an electron scanning microscope JSM-5300 (Jeol Ltd, Japan). The sorption characteristics were studied using the ASAP 2400 device (Micromeritics, USA) according to the method. The construction of a virtual three-dimensional molecular model of the Zeolite was carried out using the program Java Applet Jmol.Results and discussion. The physicochemical properties of Zeolites are investigated. It is established that morphologically the particles of the zeolite phase have a size of 5-30 microns, they are evenly distributed over the entire area of the site and represent the first structural level. Particles of the zeolite phase with a size of 5-6 microns form the second structural level due to Clinoptilolite crystals, microcracks and microgeodes. Based on the energy-dispersion spectral analysis, an increased content of the elements K, Na was revealed, which indicates the alkaline composition of the cation exchange complex. The studied Zeolite samples have micropores (volume 0.0031 cm3/g), mesopores (volume 0.0675 cm3/g), and a specific surface area of 29.1840 m2/g. A virtual three-dimensional molecular model of the Zeolite of the Kholinsky deposit has been developed. According to the molecular model, the sorption characteristics of the Kholinsky deposit Zeolite were: specific surface area - 1096.31 m2/g (1916.34 m2/cm3), the average diameter of the spherical molecule for adsorption in the pores is 5.97 A.Conclusion. The analysis of the sorption characteristics of the Zeolite revealed the following features: the pores occupy half the volume of the entire Zeolite, which are available for the sorption of water and low-molecular substances. Each pore in three mutually perpendicular directions communicates with the neighboring ones through "windows". A system of intracrystalline pores and cavities is formed, in which the occlusion and adsorption of molecules of the appropriate size easily occurs.


2021 ◽  
Author(s):  
◽  
Mathew James Cairns

<p>Nanostructured calcium silicate (NCS) is an X-ray amorphous silicate material consisting of randomly arranged platelets several tens of nanometres in size, forming agglomerates a few micrometres in size. This affords the material a high, readily accessible surface area of up to 600 m2 g -1 with chemically active surface-bound calcium and silanol groups being integral parts of the silicate structure. As such, it makes an ideal material for the sorption of many potential pollutant materials. However, NCS is highly thixotropic. This reduces its applicability for use as a sorbent material on a large scale, the thixotropic nature of NCS precluding its efficient separation from suspension. NCS, in contact with water, will ion-exchange surface-bound calcium with hydrogen ions, releasing calcium into solution, and leading to an increase in the pH value of the solution. The process may be exploited by using the material as a sorbent for cationic metal species forming insoluble hydroxides. This thesis demonstrates the use of NCS as a sorbent material for Cu2+, with the material exhibiting a sorption capacity for this ion of up to 10 mmol g -1. When the sorption capacity of the material is reached, all the calcium initially present in the NCS material (31-38 wt % CaO) is leached into solution. The copper is initially sorbed as an X-ray amorphous phase (most likely Cu(OH)2) but in the presence of excess copper, the more thermodynamically stable crystalline phase Cu2X(OH)3, X being chloride or nitrate, is formed. It was shown that the presence of calcium is necessary for this sorption to occur. When calcium was leached from the material prior to sorption studies, the sorption capacity of the material was significantly decreased. To aid the separation process of NCS from solution, bulk magnetite powder (Fe3O4), or superparamagnetic magnetite or maghemite (g-Fe2O3) were incorporated into the NCS structure during its synthesis. The addition of these additives to the NCS material reduced characteristics such as specific surface area or sorption capacity insofar as extra mass had been added to the system. The structure of the NCS was not degraded. The NCS material containing bulk magnetite powder was shown to be applicable to the sorption of phosphate in a continuous fluidised bed system, utilising the magnetic properties of the material to aid separation. Phosphate was chosen, as the sorption characteristics of NCS with respect to this ion were previously known. Attempts to use magnetic techniques to separate the superparamagnetic composites subsequent to copper sorption were unsuccessful. Although the composite materials exhibited similar sorption capacity for copper to the unmodified one, the acidic conditions of the copper solution degraded the composite, precluding the use of magnetic separation. Finally, composite materials of NCS and a conducting polymer, polyaniline, were prepared which provided potential redox-activity to a high surface area substrate. The sorption characteristics of this material were  demonstrated with its use as a sorbent for the perrhenate ion. This rhenium ion was chosen due to its chemical similarity to pertechnetate, a component of many radioactive wastewaters. It was demonstrated that the sorption process proceeded via an electrochemical mechanism in which the polyaniline caused the perrhenate ion to be reduced to a rhenium oxide species.</p>


2021 ◽  
Author(s):  
◽  
Mathew James Cairns

<p>Nanostructured calcium silicate (NCS) is an X-ray amorphous silicate material consisting of randomly arranged platelets several tens of nanometres in size, forming agglomerates a few micrometres in size. This affords the material a high, readily accessible surface area of up to 600 m2 g -1 with chemically active surface-bound calcium and silanol groups being integral parts of the silicate structure. As such, it makes an ideal material for the sorption of many potential pollutant materials. However, NCS is highly thixotropic. This reduces its applicability for use as a sorbent material on a large scale, the thixotropic nature of NCS precluding its efficient separation from suspension. NCS, in contact with water, will ion-exchange surface-bound calcium with hydrogen ions, releasing calcium into solution, and leading to an increase in the pH value of the solution. The process may be exploited by using the material as a sorbent for cationic metal species forming insoluble hydroxides. This thesis demonstrates the use of NCS as a sorbent material for Cu2+, with the material exhibiting a sorption capacity for this ion of up to 10 mmol g -1. When the sorption capacity of the material is reached, all the calcium initially present in the NCS material (31-38 wt % CaO) is leached into solution. The copper is initially sorbed as an X-ray amorphous phase (most likely Cu(OH)2) but in the presence of excess copper, the more thermodynamically stable crystalline phase Cu2X(OH)3, X being chloride or nitrate, is formed. It was shown that the presence of calcium is necessary for this sorption to occur. When calcium was leached from the material prior to sorption studies, the sorption capacity of the material was significantly decreased. To aid the separation process of NCS from solution, bulk magnetite powder (Fe3O4), or superparamagnetic magnetite or maghemite (g-Fe2O3) were incorporated into the NCS structure during its synthesis. The addition of these additives to the NCS material reduced characteristics such as specific surface area or sorption capacity insofar as extra mass had been added to the system. The structure of the NCS was not degraded. The NCS material containing bulk magnetite powder was shown to be applicable to the sorption of phosphate in a continuous fluidised bed system, utilising the magnetic properties of the material to aid separation. Phosphate was chosen, as the sorption characteristics of NCS with respect to this ion were previously known. Attempts to use magnetic techniques to separate the superparamagnetic composites subsequent to copper sorption were unsuccessful. Although the composite materials exhibited similar sorption capacity for copper to the unmodified one, the acidic conditions of the copper solution degraded the composite, precluding the use of magnetic separation. Finally, composite materials of NCS and a conducting polymer, polyaniline, were prepared which provided potential redox-activity to a high surface area substrate. The sorption characteristics of this material were  demonstrated with its use as a sorbent for the perrhenate ion. This rhenium ion was chosen due to its chemical similarity to pertechnetate, a component of many radioactive wastewaters. It was demonstrated that the sorption process proceeded via an electrochemical mechanism in which the polyaniline caused the perrhenate ion to be reduced to a rhenium oxide species.</p>


Author(s):  
Jie Xu ◽  
Yucen Xie ◽  
Narayan Paul ◽  
M.S. Roopesh ◽  
Devendra H. Shah ◽  
...  

2021 ◽  
Vol 251 ◽  
pp. 723-729
Author(s):  
Denis Lutskiy ◽  
Aleksander Ignatovich

Over the past decade, there has been a steady growth in demand for rare metals, with rhenium being one of the most highly demanded, but  also one of the most expensive and difficult to obtain. The  high demand for rhenium is  due to its use as a key component of metallurgical alloys or as a component of catalysts used in the oil refining industry. The aggregate of facts causes profitability of processing of the rhenium-containing mineral resources, which also are the copper substandard concentrates obtained at processing of the Zhezkazgan sandstones. The study focuses on the processes of extraction of copper and sorption recovery of rhenium from solutions of ammonia leaching of copper substandard concentrates.  Model solutions similar in the elemental composition to solutions of ammonia leaching solutions of copper substandard concentrates obtained during the processing of Zhezkazgan sandstones were used as an object of the study. The paper estimates extraction characteristics of copper recovery using LIX 84-I solution in kerosene, as well as sorption characteristics of the rhenium recovery process using the Purolite PPA100 anion exchanger. Based on the obtained characteristics the possibility of hydrometallurgical processing of ammonia leaching solutions of substandard copper-sulfide concentrates, and recovery of the obtained commercial products is shown.


Capillarity ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 1-11
Author(s):  
Xiangjie Qin ◽  
Harpreet Singh ◽  
Jianchao Cai

2021 ◽  
Vol 12 (4) ◽  
pp. 4518-4528

The paper summarized the literature data on using ground peels, outer leaves, and garlic roots (Allium sativum L.) as sorption materials to remove various metal ions, dyes, and antibiotics from aqueous media. This paper provides brief information on the amount of waste generated from processing garlic, its chemical composition, and ways of reuse. It gives the adsorption processes parameters and the values of sorption parameters for the studied pollutants. It was shown that garlic residue sorption characteristics for various pollutants could be increased by chemical modification with various chemical reagents. It was determined that the Langmuir model more accurately describes the pollutant’s adsorption isotherms in most cases, and the kinetics of the process more accurately describes the pseudo-second-order model. It was shown that garlic peels and steam are good precursors for activated carbons production.


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