Assessing and modifying China bentonites for aflatoxin adsorption
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Cation-exchange capacity
Saturation (graph theory)
Bentonite
This study was undertaken to determine the impact of the organic complex concentration on the adsorption of herbicide (acetochlor) at the surface of the organic modified montmorillonite. In this work, natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification. Cation-exchange capacity of this montmorillonite was determined using a methylene blue method (86 mmol/100 g of clay). Montmorillonite has been modified first with NaCl and then with hexadecyltrimethylammonium bromide (HDTMA-bromide) organic complex. Saturation of cation exchange capacity (CEC) was 50%, 100%, and 150%. Changes in the properties of the inorganic and organic montmorillonite have been examined using the X-ray diffraction, Fourier transform infrared spectroscopy, and batch equilibrium method. Montmorillonite modified with HDTMA-bromide demonstrated higher uptake of the herbicide, compared to the inorganic montmorillonite. Comparing the values Freundlich coefficients in batch equilibrium method, it can be seen that the adsorption of acetochlor decreased in the series: 0.5 CEC HM > 1 CEC HM > 1.5 CEC HM > NaM.
Cation-exchange capacity
Acetochlor
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Influences of introducing amount of Ca(OH)2 and CaCl2 on the swelling capacity and cation exchange capacity of montmorillonite are discussed.The microstructures of montmorillonite before and after modification were observed.Results show that both raw montmorillonite and Na-montmorillonite have lower swelling capacity after modified by Ca2+,but the reducing extent of modified raw montmorillonite is larger than that of the modified Na-montmorillonite.The swelling capacity decreases with the increase of Ca(OH)2 and CaCl2.The montmorillonite shows smaller swelling capacity,lower exchangeable calcium and compact microstructure when it was modified by 8%(wt) CaCl2.
Cation-exchange capacity
Swelling capacity
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Herein, a simple hydrothermal treatment method is proposed to separate high-purity montmorillonite from natural clay stone, bentonite, which contains various associated minerals. Specifically, a suspension of bentonite is placed in a closed vessel and heated to temperatures above approximately 100 °C. High-purity montmorillonite is collected by recovering the gel fabricated by heating. Evidently, the purity and collectability of montmorillonite is higher with higher temperatures and longer periods of treatment. High-purified montmorillonite aggregates and forms a gel in a dilute suspension of bentonite, after being heated at high temperatures over 110 °C, in a closed system. Using this property, we proposed a method for the separation of highly purified smectite from raw bentonite. The experimental result reveals that Ca-type smectite can be purified by the method.
Bentonite
Suspension
Hydrothermal reaction
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The mineral composition and chemical composition of bentonite from Sichuan and Xinjiang was analyzed.The attribute of bentonite are fingered out according to the results of XRD and XRF.The crystal chemical formula of purified montmorillonite was calculated on the base of 11(O).The type of samples was identified according to the original of layer charge.The results showed that the samples from Sichuan are Ca-bentonite and the samples from Xinjiang are Na-bentonite.The type of montmorillonite from Santai,Yanting,Qitai,Jimusaer is Cheto-Otay-type,Cheto-Chambers-type,Cheto-Tatatilla,Wyoming-type respectly.
Bentonite
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Cation-exchange capacity
Charge density
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Bentonite
Cation-exchange capacity
Swelling capacity
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A new method that can increase the exposure of siloxane surface was developed in this work.First the inorganic cations on bentonite were exchanged with Li+,and then a part of the Li+ were further exchanged with tetramethylammonium cation(TMA),i.e.,20% or 60% of the bentonite's cation exchange capacity.After that the samples were heated under 180℃ for 10h to make sure that most of the Li+ were transferred to bentonite sheets.By this way,the layer charge of bentonites can be effectively reduced while the layers of bentonite can be preserved by pre-exchanged TMA.The resulting organic bentonite showed larger specific surface areas and better adsorption capacity than those synthesized using traditional method(i.e.,first reducing the charge density and then exchanging TMA).For example,in the case of organic bentonite with 20% CEC TMA,the one synthesized using new method has almost twice the specific surface areas as the one synthesized using traditional method(236 vs 131m2/g),and the adsorption capacity of nitrobenzene also significantly increased.
Bentonite
Tetramethylammonium
Cation-exchange capacity
Nitrobenzene
Surface charge
Siloxane
Specific surface area
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This paper presents the results of laboratory work on mineralogy, physico-chemical characteristics the bentonite clay from two areas of Sabah, Malaysia, namely Andrassy and Mansuli. A standard Wyoming bentonite had been used as a potential comparison. This study included mineralogical, chemical composition, cation exchange composition, specific surface area and atterberg limit. The results from mineralogy investigation showed that Sabah bentonite less montmorillonite mineral content that Wyoming. Based on chemical composition, Sabah bentonite has ferrous iron content higher than Wyoming bentonite. Cation exchange capacity (CEC) and specific surface area values of Sabah bentonite is lower than Wyoming bentonite while from atterberg limit Sabah bentonite is closed to the Ca-montmorillonite.
Bentonite
Atterberg limits
Cation-exchange capacity
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In this study,10% Na2CO3 solution as modified to improve Ca-bentonite into Na-bentonite,and under different dosage and stirring time,the value of cation exchange capacity has been explored.The results show that,the value of cation exchange capacity of each soil sample reachs to maximum,when the 10% Na2CO3 solution dosage is 4% and stirring time is 20 min.The value of cation exchange capacity of Ca-bentonite which has been improved into Na-bentonite,is larger than the value of original Ca-bentonite.
Bentonite
Cation-exchange capacity
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The basic physical and chemical properties of bentonite from Xiazijie,Xinjiang;Siping,Jilin;Anji,Si'an and Changshan,Zhejiang were tested,and their montmorillonite structures were analyzed.Based on the above,the authors discussed the relation between the montmorillonite content,the exchangeable cationic type between layer and its amount,the montmorillonite structure and the swelling performance of bentonite.The results indicated that:(1) the better swelling performance the higher montmorillonite content;(2) the exchangeable cationic type between layer has a great influence on the swelling performance of Na-bentonite strongly,and the swelling performance of Na-bentonite is superior to the Ca-bentonite;(3) the better swelling performance the lower layer charge of Na-bentonite,however the Ca-bentonite is reversed;(4) As to Na-bentonite,the swelling performance decreasing with the montmorillonite structure ordering,but to Ca-bentonite,the relation between the two is not obvious.
Bentonite
Cationic polymerization
Swelling capacity
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