Soil exchangeable base cations along a chronosequence of Caragana microphylla plantation in a semi-arid sandy land,China

As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla planta- tions modify organic carbon （SOC）, nitrogen （N） and phosphorus dynamics, bulk density and water-holding capacity and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil ex- changeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0-10, 10-20, and 20-30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium （Ca）, magnesium （Mg）, and potassium （K）, and cation exchange capacity （CEC） were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium （Na） neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0-10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly （P〈0.001） and positively correlated with SOC, total N, pH and electrical conductivity （EC）. Soil pH and SOC are regarded as the main factors influencing the variation in ex- changeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.

Effect of Simulated N Deposition on Soil Exchangeable Cations in Three Forest Types of Subtropical China

The effects of simulated nitrogen(N)deposition on soil exchangeable cations were studied in three forest types of subtropical China.Four N treatments with three replications were designed for the monsoon evergreen broadleaf forest (mature forest):control(0 kg N ha-1 year-1),low N(50 kg N ha-1 year-1),medium N(100 kg N ha-1 year-1)and high N(150 kg N ha-1 year-1),and only three treatments(i.e.,control,low N,medium N)were established for the pine and mixed forests.Nitrogen had been applied continuously for 26 months before the measurement.The mature forest responded more rapidly and intensively to N additions than the pine and mixed forests,and exhibited some significant negative symptoms,e.g.,soil acidification,Al mobilization and leaching of base cations from soil.The pine and mixed forests responded slowly to N additions and exhibited no significant response of soil cations.Response of soil exchangeable cations to N deposition varied in the forests of subtropical China,depending on soil N status and land-use history.

Influence of Types and Charges of Exchangeable Cations on Ciprofloxacin Sorption by Montmorillonite

As one of the most important soil components, montmorillonite plays a vital role in transport and retention of organic pollutants in soils. Ciprofloxacin （CIP）, an antibiotic of fluoroquiolones, has been frequently detected in water and soil environments due to its wide use in human and veterinary medicine. In this study, the adsorption of CIP onto different homoionic montmorillonite such as Na-, Ca- and Al-MMT was investigated, and the influence of types and charges of exchangeable cations in the interlayer of montmorillonite on CIP adsorption was evaluated. The results showed that different homoionic montmorillonite exhibited different sorption capacity of CIP. At pH 3, the sorption capacity of CIP decreased in the order Na-MMT Ca-MMT Al-MMT, following the lyotropic series. When solution pH increased to 11, the sorption capacity of CIP followed the order Ca-MMT Al-MMT Na-MMT. Accompanying CIP adsorption on Ca-MMT, a certain amount of Ca2＋ was released into solution. Compared to pH 3, the lower Ca concentration in solution at pH 11 indicated that the adsorption of CIP on Ca-MMT at strong alkaline pH was no longer via cation exchange, and surface complexation or cation bridging might contribute to CIP adsorption. The adsorption of CIP on Na- and Ca-MMT at pH 3 and 11 resulted in the expansion of d-spacing, indicative of intercalation of CIP into the interlayer space of the montmorillonite. However, a decrease of d-spacing was observed when CIP adsorbed on Al-MMT at pH 11, which might be attributed to the dissolution of Al-CIP complex formed between CIP and Al3＋ in the interlayer of montmorillonite. The results suggest that the types and charges of exchangeable cations in the interlayer of montmorillonite play an important role in CIP adsorption on montmorillonite.

Changes of Soil Water, Organic Matter, and Exchangeable Cations Along a Forest Successional Gradient in Southern China

Information on the distribution patterns of soil water content （SWC）, soil organic matter （SOM）, and soil exchangeable cations （SEC） is important for managing forest ecosystems in a sustainable manner. This study investigated how SWC, SOM, and SEC were influenced in forests along a successional gradient, including a regional climax （monsoon evergreen broad-leaved forest, or MEBF）, a transitional forest （coniferous and broad-leaved mixed forest, or MF）, and a pioneer forest （coniferous Masson pine （Pinus rnassoniana） forest, or MPF） of the Dinghushan Biosphere Reserve in the subtropical region of southern China. SWC, SOM, and SEC excluding Ca^2＋ were found to increase in the soil during forest succession, being highest in the top soil layer （0 to 15 cm depth） except for Na^＋. The differences between soil layers were largest in MF. This finding also suggested that the nutrients were enriched in the topsoil when they became increasingly scarce in the soil. There were no significant differences （P = 0.05） among SWC, SOM, and SEC. A linear, positive correlation was found between SWC and SOM. The correlation between SOM and cation exchange capacity （CEC） was statistically significant, which agreed with the theory that the most important factor determining SEC is SOM. The ratio of K^＋ to Na^＋ in the topsoil was about a half of that in the plants of each forest. MF had the lowest exchangeable Ca^2＋ concentration among the three forests and Ca^2＋：K^＋ in MPF was two times higher than that in MF. Understanding the changes of SWC, SOM, and CEC during forest succession would be of great help in protecting all three forests in southern China.

Comparison and Evaluation of Two Analytical Methods for Cation Exchange Capacity and Exchangeable Sodium Percentage of Five Soil Types in Central Sudan

Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was carried out for different horizons. All samples were analyzed using two different methods to determine Cation Exchange Capacity (CEC) and exchangeable sodium percentage (ESP). Statistical analysis (T-test) was used in order to investigate the differences between soil samples for the studied locations. Significant differences appeared when compared the two methods for CEC determination at Gedaref area, Wad Medani and Nile flood plain and that appeared in evaluation of ESP at Nile flood plain and Shambat area. The results also revealed that, the developed method used in this study was more practical, simple and reliable for determination of CEC and ESP as the currently used in most soil laboratories. In addition, it will be safer than the other methods in some problematic soils. The adoption of this developed method is advisable because it is less time consuming as it omits the washing step. In contrast, the old method cannot be a good substitute in laboratories which have no possibility to determine sodium by using flame photometer. We conclude that when the developed method is used to determine CEC and ESP time will be saved, that fewer amounts of chemicals will be used and that accurate results will be achieved.

Atomically Adjustable Rhodium Catalyst Synthesis with Outstanding Mass Activity via Surface-Li mi ted Cation Exchange

Rh has been widely studied as a catalyst for the promising hydrazine oxidation reaction that can replace oxygen evolution reactions for boosting hydrogen production from hydrazine-containing wastewater.Despite Rh being expensive,only a few studies have examined its electrocatalytic mass activity.Herein,surface-limited cation exchange and electrochemical activation processes are designed to remarkably enhance the mass activity of Rh.Rh atoms were readily replaced at the Ni sites on the surface of NiOOH electrodes by cation exchange,and the resulting RhOOH compounds were activated by the electrochemical reduction process.The cation exchange-derived Rh catalysts exhibited particle sizes not exceeding 2 nm without agglomeration,indicating a decrease in the number of inactive inner Rh atoms.Consequently,an improved mass activity of 30 A mg_(Rh)^(-1)was achieved at 0.4 V versus reversible hydrogen electrode.Furthermore,the two-electrode system employing the same CE-derived Rh electrodes achieved overall hydrazine splitting over 36 h at a stable low voltage.The proposed surface-limited CE process is an effective method for reducing inactive atoms of expensive noble metal catalysts.

Study on Exchangeable Cation Determining Base Saturation Percentage of Soil in South China

Base saturation percentage (BSP) is an important soil chemical index in soil fertility and soil taxonomy. However, it is still unclear what exchangeable cation dominates BSP of soil in south China. Therefore, in this study, the data of BSPs and exchangeable H+, Al3+, Ca2+, Mg2+, K+ and Na+ of 109 and 45 horizon samples of 50 and 28 soil species in red soil and yellow soil groups in the Database of Chinese Soil Species were used to explore further the characteristics of BSPs and exchangeable cations as well as the correlation between BSPs and exchangeable cations. The results showed that the concentrations of exchangeable cations in both red soil and yellow soil groups were in an order of Al3+ (4.55 ± 1.47 and 4.22 ± 1.2 cmol(+)/kg) > Ca2+ (0.32 ± 0.21 and 0.36 ± 0.24 cmol(+)/kg) > H+ (0.23 ± 0.13 and 0.19 ± 0.10 cmol(+)/kg) > K+ (0.16 ± 0.09 and 0.16 ± 0.11 cmol(+)/kg) > Mg2+ (0.13 ± 0.09 and 0.11 ± 0.08 cmol(+)/kg) > Na+ (0.08 ± 0.06 and 0.11 ± 0.06 cmol(+)/kg). For red soil group, Al3+ concentration was significantly higher than those of other exchangeable cations, Ca2+ and H+ concentrations were significantly higher than those of K+, Mg2+ and Na+;while for yellow soil group, Ca2+, H+ and K+ concentrations were significantly higher than those of Mg2+ and K+. BSP of red soil group was codetermined by Ca2+, Al3+, Mg2+ and Na+, with the contributions of 33.81%, 19.82% and 14.49%, respectively;while BSP of yellow soil group was codetermined by Al3+, Ca2+, Mg2+, K+ and Na+, with the contributions of 24.91%, 21.55%, 19.91% and 14.21%, respectively. A higher concentration of exchangeable cation does not mean the higher importance of the cation to soil BSP.

Mechanism and kinetics study on removal of Iron from phosphoric acid by cation exchange resin

Iron element is one of the main impurities in wet-process phosphoric acid and it has a significant impact on the subsequent phosphorus chemical products. This paper studied the feasibility of using Sinco-430 cation exchange resin for iron removal from phosphoric acid. The specific surface area and the total exchange capacity of resin were 8.91 m2·g-1 and 5.18 mmol·g-1, respectively. The sorption mechanism was determined by FTIR and XPS and the results indicated that iron was combined with-SO3 H in resin. The removal process was studied as a function of temperature, H3 PO4 content and mass ratio between resin and solution. The unit mass of resin to remove iron was 0.058 g·g-1 resin when the operating parameters were T = 50 ℃, H3 PO4 content = 27.61 wt%and S/L = 0.1, respectively. Kinetics study demonstrated that pseudo-second-order reaction model fits this study best and the calculated activation energy of overall reaction is 29.10 kJ·mol-1. The overall reaction process was mainly controlled by pore diffusion.

Spatial Variability of Soil Cation Exchange Capacity in Hilly Tea Plantation Soils Under Different Sampling Scales

Studies on the spatial variability of the soil cation exchange capacity （CEC） were made to provide a theoretical basis for an ecological tea plantation and management of soil fertilizer in the tea plantation. Geostatistics were used to analyze the spatial variability of soil CEC in the tea plantation site on Mengding Mountain in Sichuan Province of China on two sampling scales. It was found that, （1） on the small scale, the soil CEC was intensively spatially correlative, the rate of nugget to sill was 18.84% and the spatially dependent range was 1 818 m, and structural factors were the main factors that affected the spatial variability of the soil CEC; （2） on the microscale, the soil CEC was also consumingly spatially dependent, and the rate of nugget to sill was 16.52%, the spatially dependent range was 311 m, and the main factors affecting the spatial variability were just the same as mentioned earlier. On the small scale, soil CEC had a stronger anisotropic structure on the slope aspect, and a weaker one on the lateral side. According to the ordinary Kriging method, the equivalence of soil CEC distributed along the lateral aspect of the slope from northeast to southwest, and the soil CEC reduced as the elevation went down. On the microscale, the anisotropic structure was different from that measured on the small scale. It had a stronger anisotropic structure on the aspect that was near the aspect of the slope, and a weaker one near the lateral aspect of the slope. The soil CEC distributed along the lateral aspect of the slope and some distributed in the form of plots. From the top to the bottom of the slope, the soil CEC increased initially, and then reduced, and finally increased.

Cokriging of Soil Cation Exchange Capacity Using the First Principal Component Derived from Soil Physico-Chemical Properties

As soil cation exchange capacity （CEC） is a vital indicator of soil quality and pollutant sequestration capacity,a study was conducted to evaluate cokriging of CEC with the principal components derived from soil physico-chemical properties.In Qingdao,China,107 soil samples were collected.Soil CEC was estimated by using 86 soil samples for prediction and 21 soil samples for test.The first two principal components （PC1 and PC2） together explained 60.2% of the total variance of soil physico-chemical properties.The PC1 was highly correlated with CEC （r=0.76,P0.01）,whereas there was no significant correlation between CEC and PC2 （r=0.03）.The PC1 was then used as an auxiliary variable for the prediction of soil CEC.Mean error （ME） and root mean square error （RMSE） of kriging for the test dataset were-1.76 and 3.67 cmolc kg-1,and ME and RMSE of cokriging for the test dataset were-1.47 and 2.95 cmolc kg-1,respectively.The cross-validation R2 for the prediction dataset was 0.24 for kriging and 0.39 for cokriging.The results show that cokriging with PC1 is more reliable than kriging for spatial interpolation.In addition,principal components have the highest potential for cokriging predictions when the principal components have good correlations with the primary variables.

Separation of Clay Minerals from Host Sediments Using Cation Exchange Resins

Classic physical and chemical treatments applied to separating clay minerals from the host sediments are often difficult or aggressive for clay minerals. A technique using cation exchange resins (amberlite IRC\|50H and amberlite IR\|120) is used to separate clay minerals from the host sediments. The technique is based on the exchange of cations in the minerals that may be associated clay minerals in sediments, such as Ca and Mg from dolomite; Ca from calcite, gypsum and francolite with cations carried by resin radicals. The associated minerals such as gypsum, calcite, dolomite and francolite are removed in descending order. Separation of clay minerals using cation exchange resins is less aggressive than that by other classic treatments. The efficiency of amberlite IRC\|50H in the removal of associated minerals is greater than that of amberlite IR\|120.

Acarbose Isolation with Gel Type Strong Acid Cation Exchange Resin： Equilibrium, Kinetic and Thermodynamic Studies

Acarbose, a potent α-glucosidase inhibitor, is widely used as an oral anti-diabetic drug for the treatment of the type 2, non-insulin-dependent diabetes. In this work, a gel type strong acid cation exchange resin 001×4 was applied to isolate acarbose from fermentation broth. It was demonstrated that cation exchanger 001×4 displayed a large adsorption capacity and quick exchange rate for acarbose. The static adsorption equilibrium data were well fitted to the Langmuir equation. Column adsorption experiments demonstrated that high dynamic adsorption capacity was reached at bed height of 104.4 mm, feed flow rate of 1.0 ml·min 1and acarbose concentration of 4.0 mg·ml 1.Under the optimized conditions, the column chromatography packed with cation exchanger 001×4 recovered 74.3%(by mass) of acarbose from Actinoplanes utahensis ZJB-08196 fermentation broth with purity of 80.1%(by mass),demonstrating great potential in the practical applications in acarbose separation.

Kinetic and thermodynamic studies of the esterification of acidified oil catalyzed by sulfonated cation exchange resin

This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins（SCER）. The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids（FFAs）. The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5：1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.

Protein retention in dextran-grafted cation exchange chromatography:The influence of pHs,counterions and polymer structure

Polymer-grafted ion exchange adsorbents were of great interest for the development of high-performance protein chromatography in biopharmaceutical and related fields.In this work,protein retention was systematically investigated in ion exchange chromatography packed respectively with dextran-grafted cation exchange adsorbents containing sulphopropyl(SP)ligand,SP Sepharose XL and Capto S,and non-grafted cation exchange adsorbent,SP Sepharose FF,using five proteins.With an increase of buffer p Hs,retention factors of proteins decreased among all the adsorbents,demonstrating the dominant role of electrostatic interaction for protein binding on cation exchange adsorbents.The evidences further revealed that the scattered positive charges on the surface of protein molecules,rather than net charge of protein molecule,determined protein retention on cation exchange adsorbent.Likely,counterions including NH4^+,K^+,Na^+and Mg^2+exhibited distinct influence on protein retention.It was well ascribed to solvent-mediated indirect ion-macromolecule interactions and direct ion-macromolecule interactions.Compared with SP Sepharose FF,polymer structure in dextran-grafted cation exchange adsorbents ultimately brought about different ligand distributions and smaller pore sizes,thereby regulating protein retention in cation exchange chromatography.By comparing the retention of myoglobin andβ-lactoglobulin B in SP Sepharose XL and Capto S,we reasonably speculated that the enhancement of nonelectrostatic interaction caused by reducing the space arm length was a major reason for an increasing retention factor of myoglobin in Capto S.The results in this research help us understand adsorption mechanism of protein in polymer-grafted adsorbents and give scientific guidance for the development of chromatographic materials.

Boosting solar water oxidation activity of BiVO_(4) photoanode through an efficient in-situ selective surface cation exchange strategy

The sluggish kinetics for water oxidation is recognized as one of the major problems for the unsatisfied photoelectrochemical(PEC) performance. Herein, we developed a feasible strategy based on in-situ selective surface cation exchange, for activating surface water oxidation reactivity toward boosted PEC water oxidation of BiVO_(4) photoanodes with fundamentally improved surface charge transfer. The asconstructed Co/BiVO_(4) photoanodes exhibit 2.6 times increase in photocurrent density with superior stability, in comparison to those of pristine counterpart. Moreover, the faradaic efficiency of as-fabricated photoanode can be up to ~ 95% at 1.23 V(vs. RHE). The unique selective replacement of Bi by Co on the surface could modify the electronic structure of BiVO_(4) with reduced energy barrier of the deprotonation of OH^(+) to O, thus favoring the overall excellent PEC performance of Co/BiVO_(4) photoanode.

Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water

In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.

Assessment of Cation Exchange Membrane Method and Estimation of Potassium Critical Values

Soil and tissue analyses are usually used in identifying potassium(K) deficiencies and predicting K fertilizer requirements of crops.The critical levels of both soil and fresh leaf tissue at seventh leaf stage were developed and assessed for canola,chickpea and sunflower grown on two Saskatchewan,soils,with six rates of K fertilizer supply, in a growth chamber experiment.The available potassium in soils was determined by two methods:1)resin strip extraction, and 2) NH4OAC extraction. The potassium in fresh leaves was determined at seventh leaf stage by a simple procedure using a common garlic press and injector to extract the plant sap and testing the sap with a handheld ion selection electrode meter. The results shoWed significant relationships between the resin strip extractable K and NH4OAC extractable K, and between the plant uptake of total K and the supply of available K in the soils determined by the two methods. Good relationships were also found between the potassium in fresh leaves and the plant uptake of total K for canola, chickpea and sunflower.The resin strip extraction for K was calibrated using common NH4OAC extraction, and recommended for routine analyses because of its simplicity and sensitivity.

Use of Cation Exchange Membrane in Soil Potassium Release and Wheat Response to Potassinm

A pot experiment was conducted in the growth chamber on Saskatchewan soils with dfferent texture todeterniine the K release status and wheat K demand. The relationship between K uptake and soil availableK extracted by cation exchange membrane (CEM-K) and the effect of K fertilizer on wheat growth and soilavailable K was also evaluated. Theatments of 0, 60 and 120 mg K/kg were applied to sandy, low and highK loamy and clay soils. The highest yields were achieved with the application of 120 mg K/kg in sandysoil and 60 mg K/kg in other soils. On the whole, the clay soil contributed K more than other soils fromslowly available fraction. Regression revealed a linear relationship between the soil available K extractedby NH_4OAc(Ka) and CEM-K in suspensions (r=0.93). Results also showed that CEM-K in burial and insuspensions were different not only in the amount but also in correlation with Ka or K uptake.

Adsorption behavior and mechanism of cadmium on strong-acid cation exchange resin

The adsorption behavior of Cd2+ on 001×7 strong-acid cation exchange resin was studied with the static adsorption method. The adsorption process was analyzed from thermodynamics and kinetics aspects. The influences of experimental parameters such as pH, temperature, initial concentration and adsorption rate were investigated. The experimental results show that in the studied concentration range, 001×7 resin has a good sorption ability for Cd2+, and the equilibrium adsorption data fit to Freundlich isotherms. The adsorption is an exothermic process which runs spontaneously. Kinetic analysis shows that the adsorption rate is mainly governed by liquid film diffusion. The best adsorption condition is pH 4-5. The saturated resin can be regenerated by 3 mol/L nitric acid, and the desorption efficiency is over 98%. The maximal static saturated adsorption capacity is 355 mg/g (wet resin) at 293 K. The adsorption mechanism of Cd2+ on 001×7 resin was discussed based on IR spectra.

A statistical reappraisal of the relationship between liquid limit and specific surface area, cation exchange capacity and activity of clays

More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2 values ranging between 0.71 and 0.92.Independent data were also used to validate the correlations.Estimated SSA values slightly overestimate the measured SSA up to 100 m^2/g.Regarding the estimated CEC values,they overestimated the measured CEC values up to 20 meq/(100 g).A probabilistic approach was performed for the correlations of SSA,CEC and activity versus LL.The analysis shows that the relations of SSA,CEC and activity with LL are robust.Using the LL values,it is possible to assess other basic engineering properties of clays.