Cation Exchange
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2021 ◽  
Vol 570 ◽  
pp. 151134
D. Amaranatha Reddy ◽  
K. Arun Joshi Reddy ◽  
Madhusudana Gopannagari ◽  
Yujin Kim ◽  
A. Putta Rangappa ◽  

2021 ◽  
Fatemeh Amir Aslanzadeh Mamaghani ◽  
Amin Salem ◽  
Shiva Salem

Abstract The efficient management of solid waste deposited in the landfill of used motor oil recovery units is an important environmental challenge which is originated from the regeneration by bentonite as an effective adsorbent. The current study was attempted to convert the black waste into zeolite based compounds through fusion technique. The collected waste powder were mixed with sodium hydroxide, and boehmite followed by treatment at different temperatures, 600-800 °C. Then, the obtained precursors were hydrothermally converted to zeolite A or hydroxysodalite. The effect of parameters like alkalinity, boehmite, and sodium aluminate ratios, fusion temperature, and aging time on structural characteristics, and cation exchange capacity (CEC) were studied in details. The potential of solid waste in the production of zeolite A is significantly affected by mentioned factors which govern on purity, crystallinity, morphology, and CEC. The cation exchange capacity about 190 mg g-1 can be achieved by alkali, and boehmite ratios of 2.00, and 0.53, respectively. The microstructural analyses showed the morphological evolution from rounded shape to sharp edges by fusion at 800 °C due to appropriate recrystallization. Besides, hydrosodalite powder with extended surface area, 77 m2 g-1, could be produced by limited content of boehmite in the presence of NaAlO2.

2021 ◽  
Maria Isabel Garcia Rosa ◽  
Gabriella Andrade Boga ◽  
Suellen Silva Vieira Cruz ◽  
Fabio Ramos Dias Andrade ◽  
Sheila Aparecida Correia Furquim ◽  

Abstract Mechanisms of Cr(VI) reduction by Fe(II) modified zeolite and vermiculite were evaluated. Adsorbents were treated with Fe(SO4).7H2O to saturate their exchange sites with Fe(II). Vermiculite (V-Fe) adsorbed more Fe(II) (21.8 mg g−1) than zeolite (Z-Fe) (15.1 mg g−1). Z-Fe and V-Fe were used to remove Cr(VI) from the solution by batch test to evaluate the effect of contact time and Cr(VI) initial concentration. Cr(VI) was 100% reduced to Cr(III) by Z-Fe and V-Fe from solution with 18 mg L−1 Cr(VI) in 1 minute. Considering that 3 moles Fe(II) are required to reduce 1 mole Cr(VI) (3Fe+2 + Cr+6 → 3Fe3+ + Cr+3), the iron content released from Z-Fe and V-Fe were sufficient to reduce 100% of Cr(VI) in solution by up to 46.8 mg L−1 Cr(VI), and about 90% (V-Fe) and 95% (Z-Fe) in solution with 95.3 mg L−1 Cr(VI). The assess of the Fe(II), Cr(III), Cr(VI), and K+ contents of the adsorbents and solutions after batch tests indicated that K+ ions from K₂Cr₂O₇ solution were the main cation adsorbed by Z-Fe, while vermiculite did not absorb any of these cations. The H+ of the acidic solution (pH around 5) may have been adsorbed by V-Fe. Therefore, the release of Fe(II) from Z-Fe and V-Fe involved cation exchange between, respectively, K+ and H+ ions from solution. The reduction of Cr(VI) by Fe(II) caused the precipitation of Cr(III) and Fe(III), and the decrease of pH of the solution to < 5. As acidity limits the precipitation of Cr(III) ions, they remained in solution and were not adsorbed by both adsorbents (since they prefer to adsorb K+ and H+). To avoid oxidation, Cr(III) can be removed by precipitation or adsorption by untreated minerals.

Rizkiy Amaliyah Barakwan ◽  
Yulinah Trihadiningrum ◽  
Arseto Yekti Bagastyo ◽  
Ellina Sitepu Pandebesie

Toxics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 268
Andrea Vannini ◽  
Elisabetta Bianchi ◽  
Diego Avi ◽  
Nicole Damaggio ◽  
Luigi Di Lella ◽  

The aim of this study was to investigate the ability of biochar amendment to reduce the availability of Pb in the soil and its uptake in lettuce (Lactuca sativa L. var. adela). Seedlings of lettuce were cultivated in Pb-contaminated soils, both with and without 5% biochar (w/w), as well as in a simplified soilless system (hydroponics) at the ecologically relevant Pb concentration of 100 µM, both with and without 1% biochar. Soils amended with biochar resulted in a ca. 50% reduction of the extractable (bioavailable) fraction of Pb, limiting the accumulation of this toxic element in the leaves of lettuce by ca. 50%. A similar behavior was observed for lettuce plants grown hydroponically, even with a much higher reduction of Pb uptake (ca. 80%). Increased cation exchange capacity and pH were likely the main factors limiting the bioavailability of Pb in the soil. Complexation with functional groups and precipitation/co-precipitation both on the biochar surface and in soil aggregates were likely the main mechanisms immobilizing this element.

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6223
Katarzyna Karaś ◽  
Anetta Zioła-Frankowska ◽  
Marcin Frankowski

This paper presents a new method for the simultaneous speciation analysis of arsenic (As(III)-arsenite, As(V)-arsenate, DMA-dimethylarsinic acid, MMA-methylarsonic acid, and AsB-arsenobetaine) and selenium (Se(IV)-selenite, Se(VI)-selenate, Se-Methionine, and Se-Cystine), which was applied to a variety of seafood and onion samples. The determination of the forms of arsenic and selenium was undertaken using the High-Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC–ICP–MS) analytical technique. The separation of both organic and inorganic forms of arsenic and selenium was performed using two analytical columns: an anion exchange column, Dionex IonPac AS22, containing an alkanol quaternary ammonium ion, and a double bed cation–anion exchange guard column, Dionex Ion Pac CG5A, containing, as a first layer, fully sulfonated latex for cation exchange and a fully aminated layer for anion exchange as the second layer. The ammonium nitrate, at pH = 9.0, was used as a mobile phase. The method presented here allowed us to separate the As and Se species within 10 min with a suitable resolution. The applicability was presented with different sample matrix types: seafood and onion.

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Chadha Mejri ◽  
Walid Oueslati ◽  
Abdesslem Ben Haj Amara

The performance of a clay mineral geomembrane used in the context of a geological barrier for industrial and radioactive waste confinement must pass through the understanding of its hydrous response as well as the limits of the cation exchange process which are closely related to the solid/liquid ratio constraint. The Na-rich montmorillonite is used, as starting material, to evaluate the link between the applied external constraint (variable solid/liquid ratio) and the structural response of the material. The geochemical constraint is realized at the laboratory scale, and the possible effects are investigated in the cases of Ba2+ and Ni2+ heavy metal cations. The structural analysis is achieved using the XRD profile modeling approach to quantify the interlayer space (IS) deformation. The quantitative XRD analysis, which consists of the comparison of experimental 001 reflections with the calculated ones deduced from structural models, allowed us to determine the optimal structural parameters describing IS configuration along the c ∗ axis. The obtained result showed an interstratified hydration character, for both studied exchangeable cations, regardless of the solid/liquid ratio being described probably by a partial cation exchange process. The theoretical mixed layer structure (MLS) suggests the coexistence of more one cristallite species saturated by more than one exchangeable cations, indicating a partial saturation of all exchangeable sites. The optimum structural parameter values, from the theoretical model, allowed us to follow the evolution of several intrinsic properties versus the applied constraint strength. The variable solid/liquid ratio effect on the material porosity is examined by the BET-specific surface area and BJH pore size distribution (PSD) analyses. The adsorption measurement outcomes confirm XRD results concerning mainly the link between several intrinsic clay properties and the constraint strength.

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