Determination Of Cation Exchange Capacity Research Articles

Cation Exchange Capacity and Composition of Soluble Soil Organic Matter Fractions

The cation exchange capacity (CEC) of soils depends on the amount and composition not only of clay minerals but also of soil organic matter (SOM). While the CEC of soil clay minerals has been intensively studied, little is known about the CEC of organic matter (OM) fractions, in particular those obtained with newly developed SOM extraction techniques. The objective of this study was to develop and test a method to quantitatively determine the CEC of extracted OM fractions and to relate CEC(OM) to OM functional groups possibly responsible for sorption of cations. Water‐ and pyrophosphate‐soluble OM fractions were sequentially extracted from differently managed arable soils of two well‐known long‐term field experiments. The CEC of a freeze‐dried pyrophosphate‐soluble OM fraction [OM(PY)] (0.03 g) mixed with quartz sand (4.97 g) was determined by applying the standard percolation method. The chemical composition of OM(PY) was analyzed by Fourier‐transform infrared (FTIR) spectroscopy. For all plots except those fertilized with farmyard manure, the sorption properties of the OM(PY) fraction were found to be site specific and to reflect soil and crop rotation effects. The relative contribution of the CEC of OM(PY) to the CEC of the soil (0.8–11.6%) is dependent on soil C content and extractability. For all plots, however, the relative contents of carboxylic functional groups in OM(PY) determined with FTIR spectroscopy was found to be linearly related to the CEC of the OM(PY), similar to pure organic substances. This relationship indicates the usefulness of CEC determination on OM(PY) fractions. The results suggest that the relative contents of carboxylic functional groups in OM(PY) reflect long‐term effects of fertilization and crop rotation on the sorption properties of the SOM.

Comportamento de expansão de argilas bentoníticas organofílicas do estado da Paraíba

Argilas organofílicas apresentam uma vasta gama de aplicações industriais, desde a indústria do petróleo à farmacêutica e de cosméticos, passando pela retenção de resíduos e produção de nanocompósitos argila-polímeros. Este trabalho tem por objetivo analisar a influência do teor de sais quaternários de amônio na organofilização de argilas bentoníticas. As argilas utilizadas foram caracterizadas através da determinação de sua composição química, distribuição do tamanho de partículas e capacidade de troca de cátions. As argilas organofílicas foram preparadas utilizando dois sais quaternários de amônio: cloreto de alquil benzil amônio (Dodigen) e brometo de cetil trimetil amônio (Cetremide). As argilas organofilizadas foram caracterizadas por difração de raios X e espectroscopia de infravermelho. Os resultados mostraram que o espaçamento basal aumenta com o aumento na quantidade de sal utilizado para a organofilização e que o comportamento desse aumento depende do sal e da argila utilizados, sendo, linear quando da utilização do sal Dodigen e dependente do tipo da argila quando da utilização do sal Cetremide.

Measurement of Cation Exchange Capacity of Organic‐Matter Fractions from Soils using a Modified Compulsive Exchange Method

This article describes a modified compulsive exchange method suitable for the determination of cation exchange capacity (CEC) over a pH range on solid, separated organic‐matter fractions. The method is demonstrated to be a reproducible and relatively simple means of measuring CEC on fractions separated by physical means in conjunction with hydrofluoric acid (HF) treatment. By including a modification for measuring the residual magnesium (Mg2+) content by dilution and conductivity, the method is simplified to measure CEC versus pH using a single sample; the only laboratory instruments required are pH and conductivity meters and a balance. The lack of agreement between this method and the silver thiourea (AgTU) method for some fractions at low pH is attributed to the uncontrolled variation in solution ionic strength when acid is introduced to effect solution pH changes in the AgTU method.

Ion exchange and ion exchange voltammetry with functionalized mesoporous silica materials

Ordered mesoporous silicas prepared by the surfactant template route can be readily used as effective ion exchangers when they are functionalized with organic groups bearing either positive or negative charges. This is illustrated here on the basis of sulfonic acid- and/or quaternary ammonium-functionalized silica spheres obtained by the sol–gel process in the presence of cetyltrimethylammonium as a template. Various materials have been synthesized at several functionalization levels and their physico-chemical characteristics (especially their porosity) have been discussed with respect to the amount of functional groups in the porous solids. Their ion exchange behavior was then studied from batch experiments (determination of cation and anion exchange capacities) and by electrochemistry at carbon paste electrodes (CPE) modified with these solids (ion exchange voltammetry). The preconcentration efficiency was discussed on the basis of the organic group content in the materials as well as their structure and porosity. The series of materials containing both sulfonic acid and quaternary ammonium moieties displayed zwitterionic surfaces and thus both cation and anion exchange properties.

Modification of montmorillonite with cationic surfactants. Thermal and chemical analysis including CEC determination

The thermal stability of synthesized and commercial organically modified montmorillonites has been investigated using thermogravimetric analysis (TGA). Four organo-montmorillonites have been prepared by replacing the inorganic cations of a commercial montmorillonite with aliphatic and aromatic ammonium bromide or chloride salts. The modification has been carried out by cation exchange to obtain a high level of intercalation in the montmorillonite. Conformations of the intercalated surfactants have been characterized using Fourier transform infrared spectroscopy (FTIR). Besides fixed organic surfactant, some surfactant in excess still remained in the montmorillonite after repeated washing with water or ethanol/water. The use of a suitable eluent for the surfactants in the washing step was the key issue as shown by the changes of the first degradation peak of Cloisite-Na +-hexadecyl benzyl dimethylammonium (CLO-BDHA), Cloisite-Na +-benzyl triethylammonium (CLO-BTA) and Cloisite-Na +-hexadecyl trimethylammonium (CLO-HTA). Hexadecyl trimethylammonium (HTA) was more sensitive to water and ethanol/water as eluents. Sonication and the use of a polar activator during the modification of montmorillonite increased the amount of surfactant adsorbed by cation exchange. Ammonium acetate method has been revealed as an adequate chemical method to measure the cation exchange capacity (CEC) of inorganic and organic montmorillonites. This method has the advantage with respect to TGA that it does not measure the unfixed surfactant.

Nanometer-scale chemical modification of nano-ball allophane

AbstractNano-ball allophane is a hydrous Al silicate with a hollow-sphere morphology that contains some defects or pores along the spherule walls. Enlargement of the pore openings by dilute alkali treatment was confirmed by cation exchange capacity determinations using various alkylammonium cations as replacement cations. An allophane sample with a low Si/Al ratio (0.67) was equilibrated with 10 mM CaCl2 (pH = 6.0) and the Ca2+ retained was extracted using aqueous 1 M NH4C1 or alkylammonium chloride salts. The Ca2+ extracted by NH4+ was 15.1 cmolc kg−1, but CH3NH3+${\rm{C}}{{\rm{H}}_3}{\rm{NH}}_3^ + $ (mean diameter = 0.38 nm) only extracted 7.9 cmolc kg−1 of Ca2+. After 10 mM NaOH treatment (0.25 g:100 mL) of the allophane, the Ca2+ extracted by NH4+${\rm{NH}}_4^ + $ was 29.7 cmolc kg−1, 29.6 cmolc kg−1 by CH3NH3+${\rm{C}}{{\rm{H}}_3}{\rm{NH}}_3^ + $, and 29.4 cmolc kg−1 by (CH3)2NH2+${{\rm{(C}}{{\rm{H}}_3}{\rm{)}}_2}{\rm{NH}}_2^ + $. The extraction of Ca2+ by the large C2H5NH3+${{\rm{C}}_2}{{\rm{H}}_5}{\rm{NH}}_3^ + $ cation (mean diameter = 0.46 nm) only decreased to 26.1 cmolc kg−1, indicating that pore diameters were enlarged from ∼0.35 to 0.45 nm. The significant increase in Ca2+ retention after NaOH treatment was attributed to the dissociation of increased numbers of newly exposed silanol groups in the enlarged pores. The low Si/Al ratio of the NaOH-dissolved material (0.35) and the decreased intensity of the 348 cm−1 IR band also suggested selective dissolution of the pore region. For allophane with a high Si/Al ratio (0.99) and much accessory polymeric Si, dissolution of polymeric Si and of the pore region occurred simultaneously. Alkali treatment produced a smaller increase in pore size and Ca2+ retention for allophanes with large Si/Al ratios than for allophanes with small Si/Al ratios. It was concluded that by altering the dilute alkali treatment conditions and varying the Si/Al ratio of allophane, the extent of structural modification or pore enlargement of the hollow spheres might be controlled.

Measurement of Cation Exchange Capacity (CEC) of Plant Cell Walls by X-Ray Microanalysis (EDX) in the Transmission Electron Microscope

Cation exchange capacity (CEC) characterizes the number of fixed negative charges of plant cell walls and is an important parameter in studies dealing with the uptake of ions into plant tissues, especially in roots. Conventional methods of CEC determination use bulk tissue, the results are the mean of many cells, and differences in the CEC of different tissue types are masked. Energy-dispersive microanalysis (EDX) in the transmission electron microscope allows CEC determinations on much finer scales. Shoot and fine root tissue of Picea abies was acid washed to remove exchangeable cations. Tissue blocks or semithin tissue sections were loaded with 0.2 mM CaCl2, AlCl3, or Pb(NO3)2 at pH 4.0. The amount of Ca, Al, or Pb adsorbed to the exchange sites of cell walls was determined by EDX. The CEC of cell walls of different tissue types was highly different, ranging in shoot tissues from 0 to 856 mM Ca and 5.8 to 1463 mM Al (block loading) or 4.3 to 1116 mM Ca and 0 to 2830 mM Al (section loading). In root tissue, Pb adsorption to semithin sections yielded CEC values between 29.1 and 954 mM Pb. In most P. abies shoot tissues, the binding capacity was clearly higher for Al than for Ca.

Prediction of cation exchange capacity from soil index properties

AbstractIn many areas of geotechnical engineering it is necessary to have an estimate of the cation exchange capacity (CEC) of a soil in order to allow preliminary design estimates. Standard methods of CEC determination are time-consuming and involve several steps (e.g. displacement of the saturating cation requires several washings with alcohol). Therefore, a rapid method of CEC estimation would be very useful. During preliminary site investigations, the soil engineering parameters can be estimated from the considerable number of correlations available in the literature. In this study, relationships between CEC and various other soil engineering properties have been investigated, resulting in a quick method for estimating CEC.Simple correlations were developed between CEC and specific surface area (SSA), soil organic matter (OM), clay fraction (CF), activity (A), Atterberg limits (liquid (LL), plastic (PL), and shrinkage (SL)), and modified free swell index (MFSI) of the soils. Strong correlations are observed between the CEC values and those for ethylene glycol monoethyl ether (EGME) uptake and methylene blue (MB) titration. However, no significant correlation was found between CEC and N2_SSA. No unique relationship was seen between CEC and CF (r2 <0.5). No relationship was observed between CEC and OM in this study. The best correlation coefficient between the CEC and Atterberg limits exists between CEC and LL (r2 = 0.61). No significant relationship was seen between CEC and PL or SL. The correlation coefficient between CEC and MFSI was 0.65. Multiple linear regression analyses were developed to investigate the contributions of different soil parameters to CEC. These analyses show that EGME_SSA, in combination with LL, accounted for 91% of the variation in CEC. Correlations between CEC and EGME_SSA, MB_SSA and LL appear to be sufficiently good to enable an indication of CEC to be estimated from these parameters.

Cation exchange capacity methodology III: Correct exchangeable calcium determination of calcareous clays using a new silver–thiourea method

Cation exchange capacity (CEC) is a fundamental property of clays and soils. Determination of CEC for samples that contain Ca-carbonate minerals, such as calcite and dolomite, is problematic because Ca 2+ released by dissolution of carbonates during CEC determinations interferes with the accuracy of CEC values. This paper describes a new method for the determination of correct exchangeable Ca 2+ values of calcareous clays and soils. For the method, a silver–thiourea exchange solution is saturated with Ca 2+ by treatment with fine-grained calcite prior to the start of the exchange procedure. Using this exchange solution, calcite in the sample can no longer be dissolved but exchangeable Ca 2+ is desorbed quantitatively. The case for dolomite is similar, because dissolution of dolomite is minimised. However, the determination of reasonable exchangeable Ca 2+ values for samples containing gypsum is not possible because gypsum is soluble in the exchange solution.

Determination of the cation exchange capacity of clays with copper complexes revisited

AbstractThe determination of the cation exchange capacity (CEC) of clays by exchange with the cationic copper complexes [Cu(en)2]2+ and [Cu(trien)]2+ is revisited. The procedures reported by Bergaya & Vayer (1997) and Meier & Kahr (1999) are modified slightly. The concentration of the copper complexes in the equilibrium solutions is measured by spectral photometry. Correct CEC values of the [Cu(en)2]2+ exchange are only obtained when a buffer (‘tris’, tris (hydroxymethyl) aminomethane, pH = 8) is added to the equilibrium solution after separation of the clay, because the molar extinction coefficient of this complex depends on the pH of the solution. A standard procedure is recommended as a reference method. In most cases, tris addition is not needed for the determination with [Cu(trien)]2+ cations. Nevertheless, tris addition is recommended in the standard procedure. Determination of CEC for 40 samples (kaolins, ‘common clays’, bentonites, montmorillonites and beidellite) shows a good agreement between measurements using [Cu(en)2]2+ and [Cu(trien)]2+ cations and with results by the ammonium acetate method.

Determination of Cation Exchange Capacity on Low to Highly Calcareous Soils

Four different methods were evaluated for determining the soil cation exchange capacities (CEC) of calcareous soils with calcium carbonate contents ranging from less than 100 g kg−1 to over 900 g kg−1, and for acid soils with 100 to 600 g kg−1 of added CaCO3. The results showed that for calcareous soils, linear correlations existed between measurements obtained by any two of the four methods, either with or without CaCO3 removal. CEC values were decreased by the removal of carbonate from calcareous soils when the calculation was based on soil sample actual weight (i.e., weight adjusted for either the removal or the addition of CaCO3). The removal of CaCO3 from calcareous soils caused the CEC to decrease by 13.4% to 22.4%, while the addition of CaCO3 to acid soils caused the CEC to increase by 2.8% to 16.9%. The results indicate that with existing methods, the interference of CaCO3 on CEC was unavoidable, even though the solution pH for all four methods was 8.0 or 8.2. The modified LiEDTA and lithium (Li) formate methods produced low CEC values because of the low affinity of Li to the soil colloids. The double saturating solution method (CaCl2‐CaCl2) seemed to produce fairly accurate measurements, but the overestimation with too many complex procedures made this method impractical. The method using NaOAc‐NaCl in 60% ethanol as the saturating solution (method 4) proved to be sufficiently accurate and simple for application to calcareous soils with a wide range of CaCO3 contents. Soils with such a wide range of CaCO3 in south Florida (10–90%) can be calculated from the following equation established to describe and predict CEC by method 4:

Use of Diffusion to Determine Soil Cation-Exchange Capacity by Ammonium Saturation

Soil cation-exchange capacity (CEC) is often determined by NH4 saturation, using a 1 M solution of NH4C2H3O2 at pH 7. A study was conducted to ascertain whether this determination can be performed by employing a simple diffusion technique previously developed for direct inorganic-N analysis of soils. Values obtained for 10 diverse Illinois surface soils following overnight NH4 saturation were correlated very highly with CEC data collected for the same samples on the basis of NH4 analyses by steam distillation (r = 0.999, P < 0.001) or colorimetry (r = 0.999, P < 0.001), and also with data obtained by summing atomic absorption measurements of calcium (Ca), magnesium (Mg), and potassium (K) displaced during NH4 saturation (r = 0.811, P < 0.01). As a much more rapid and convenient alternative to existing methods for preparation of NH4-saturated soil, a simple saturation technique was developed whereby 0.500 g of soil was leached under vacuum with 15 mL of 1 M NH4C2H3O2 (pH 7) in a 10-mL disposable syringe containing a stainless-steel frit, and then with 30 mL of 2-propanol. After drying for a few minutes, the soil sample was transferred to a 473-mL (1-pint) wide-mouth Mason jar, treated with 10 mL of 2 M KCl, and analyzed for exchangeable NH4 by diffusion with MgO for 1.75 h at 45–50°C on a hot plate. Except for a calcareous soil, CEC measurements by the rapid saturation-diffusion approach did not differ significantly (P < 0.05) from diffusion data involving overnight NH4 saturation. This approach allows CEC determinations to be accomplished in a few hours instead of days, and will be especially useful for routine soil characterization and testing.

Cation exchange capacity measurements on illite using the sodium and cesium isotope dilution technique: Effects of the index cation, electrolyte concentration and competition: Modeling

AbstractThe isotope dilution technique using Na and Cs as index cations was used to determine the cation exchange capacity (CEC) of illite du Puy as a function of background electrolyte composition. The work showed, in accord with previous studies, that the CEC values were in the order Cs-CEC &gt; Na-CEC. Sodium is commonly chosen as the index cation in CEC determinations using the isotope dilution method. The experimentally measured Na-CEC values for Na-illite increased from ∼75 to ∼200 meq kg−1 for NaClO4 concentrations in the range 5.6 × 10−4 to 1.25 × 10−2 M. Cesium CEC determinations showed a much less pronounced trend over a CsNO3 concentration range from 10−3 to 10−2 M. A reference Cs-CEC value of 225 meq kg−1 was chosen. Careful chemical analyses of the supernatant solutions revealed that Ca and Mg at the (sub)μmolar level were present in all the determinations, despite the extensive conditioning procedures used. Competition between (Ca + Mg) and Na for the exchange sites was put forward as an explanation for the variation of Na-CEC values. This hypothesis was confirmed in a series of single (45Ca) and double (45Ca plus 22Na) labeling experiments. Calcium-sodium selectivity coefficients ((NaCaKc)) were calculated from the experimental data for NaClO4 concentrations from 5.6 × 10−4 to 0.1 M and exhibited a variation from 1.6 to 14.3. A two-site cation exchange model was developed with site capacities and NaCaKc values for each site: planar site capacity =180 meq kg−1, NaCaKcPS=2; type II site capacity = 45 meq kg−1, NaCaKcII=80. The model was able to predict the Na and Ca occupancies in the Na-CEC experiments over the whole range of NaClO4 concentrations. It is recommended that Cs should be used instead of Na as the index cation for determining the CEC of illite.

Surfactant Templated Sulfonic Acid Functionalized Silica Microspheres as New Efficient Ion Exchangers and Electrode Modifiers

Porous sulfonic acid functionalized silica spheres have been prepared by oxidation ofthiol-functionalized mesoporous silica samples obtained by co-condensation of (mercaptopropyl)trimethoxysilane and tetraethoxysilane in the presence ofcetyltrimethylammonium as a template. The physicochemical characteristics of the resulting ion exchangers have been analyzed by various techniques and discussed with respect to the amount of functional groups in the materials. Their ion exchange behavior was then studied from batch experiments (determination of cation exchange capacities) and by electrochemistry at carbon paste electrodes modified with these solids. In particular, ion exchange voltammetry applied to two model electroactive cations, Cu2+ and Ru(NH3)6(3+), has pointed out the key role played by the content of organofunctional groups in the materials (which strongly affects their structure and porosity) on their performance as electrode modifiers for preconcentration of target analytes prior to electrochemical detection.

Bentonite deposits of Northern Patagonia

Some Argentine North Patagonia bentonite deposits have been characterised by chemical and differential thermal analysis (DTA), X-ray diffraction and Isoelectric Point (IEP), Cation Exchange capacity (CEC) and specific surface area ( S) determinations. Samples with high degree of tetrahedral isomorphic substitution, and consequently high interlayer cation charge compensation, would be used as organic pollutant adsorbent when the adsorption was a cation exchange mechanism.

A rapid method for the determination of cation exchange capacities of sandstones: preliminary data

Abstract A rapid and efficient single-extraction procedure for measuring cation exchange capacities in sandstones has been developed and tested. The method is based on the use of a SrCl 2 (0.25 mol l −1 ) solution to displace the exchangeable cations. The cation exchange capacities (CEC) of three types of natural building stones were analysed, both in freshly quarried material and in weathered samples. Large differences in the sorptive properties of these materials were observed. The measurement of profiles of CEC in weathered sandstones revealed a significant decrease of CEC in the weathered zone close to the exposed surface, most likely reflecting the partial dissolution of clay minerals due to acid attack. CEC measurements appear to be a very sensitive indicator of chemical weathering profiles.

Determination of cation exchange capacity by one-step soil leaching column method

Many methods have been proposed for measuring exchangeable cations and cation exchange capacity (CEC) in soils. Most of these methods are multi-step operations, which are time-consuming and, therefore, not applicable for routine soil tests. Speed and simplicity of operations are necessary. The objective of this study was to develop a one-step soil column leaching method to determine CEC using 0.01 M SrCl2 solution [CEC(SrCl2)]. Measured CEC(SrCl2) values correlate to the conventional CEC [1 M NH4-acetate (NH4OAc, pH 7)] in slightly acidic, alkaline, and neutral pH soils. CEC(SrCl2) was also compared to the effective CEC (ECEC by 0.01 M SrCl2 and pH 7, 1 M NH4OAc solutions (soil column leaching method) in red soils. Here, ECEC(SrCl2) and ECEC(NH4OAc) are the sum of exchangeable K+, Na+, Ca2+, Mg2+, and Al3+ in soil column leachates. The correlation between CEC(SrCl2) versus ECEC(SrCl2), and CEC(SrCl2) versus ECEC(NH4OAc) of seven red soils showed a linear relationship (r2 values being 0.99 and 0.98, respectively). The correlation between CEC(SrCl2) and conventional CEC(NH4OAc) of five soils (i.e., slightly acidic, alkaline or neutral pH soils) was 0.99. However, a comparison of CEC(SrCl2) to conventional CEC(NH4OAc) shows significant differences (p< 0.01) for seven red soils, but not for five other soils (p>0.05). Thus, these results indicate that the advantage of the CEC(SrCl2) from one-step soil leaching column technique can consider it as ECEC of red soils and CEC of the other slightly acidic, alkaline and neutral pH soils. The one-step soil leaching column method is a rapid, simple technique for determining CEC of most soils and ECEC of red soils.

Infrared study of some synthetic saponites: Effect of NH4/Al and H2O/(Si+Al) ratios during the crystallization

Ammonium-saponite samples of (NH)MgSiCuO(OH) compositions were synthesized at 280°C during 74 h at autogenous water pressure. X-ray diffraction of the resulting saponites showed trace amounts of artefact corundum and amorphous material were present. Cation Exchange Capacity (CEC) determination, chemical analyses and 91 magic-angle solid-state nuclear magnetic resonance spectroscopy (MAS-NMR) showed that the interlayer contained only limited amounts of ammonium and mainly Al as the interlayer cation.

Effects of heavy metal contamination on macronutrient availability and acidification parameters in forest soil in the vicinity of the Harjavalta CuNi smelter, SW Finland

Four experiments were established (1992) in Scots pine stands at distances of 0.5, 2, 4 and 8 km along a line running to the SE of the CuNi smelter at Harjavalta, SW Finland, in order to investigate the effects of Cu and Ni emissions on macronutrient availability and estimates of cation exchange capacity (CEC) and base saturation (BS). The accumulation of Cu and Ni (total, exchangeable) in forest soil close to the smelter has resulted in a deficit of base cations (exchangeable Ca, Mg, K and BS) in the organic layer caused by inhibition of mineralisation and the displacement of base cations from cation exchange sites by Cu and Ni cations. No signs of soil acidification were found in the topmost layers of the soil measured as a change in pH, exchangeable acidity and Al. The determination of CEC by the summation method in heavy-metal polluted forest soils is not recommended unless heavy metal cations are also included in the calculations.

Al-pillared clays: from lab syntheses to pilot scale production characterisation and catalytic properties

The textural and structural characteristics, and the acid and catalytic properties of Al-pillared saponites prepared in kg amounts (pilot installation) have been compared with those of lab analogues (few grams, and 100 g batch quantities). The pillared clays have been examined by X-ray diffraction, and characterized by different techniques and methods including nitrogen sorption isotherms, determination of the residual cation exchange capacities and acid contents. The catalytic performances were evaluated by means of the bifunctional hydroconversion of heptane over Pt-impregnated samples. The important differences of the textural characteristics of the lab and pilot samples did not significantly affect the catalytic results. Al-pillared saponites were much more efficient hydroisomerisation catalysts than Al-pillared montmorillonites.