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.

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.

Poly [ (chloromethyl) styrene-co-divinylbenzene] Continuous Rod Column of Weak Cation Exchange Chromatography and its Applications in the Separation of Biopolymers

Macroporous poly [(chloromethyl) styrene-co-divinylbenzene] continuous rod was prepared by direct polymerization of the monomers in the presence of a porogenic diluent inside an empty chromatographic column. A new 'in-situ' technique was used to modify the synthesized polymer rod for a weak cation exchanger and it has been used successfully for the separation of biopolymers. It was found that the back pressure of the continuous rod column was much lower and its surface was proved to be modified well.

Synthesis of Monodisperse Poly(chloromethylstyrene divinylbenzene)Particle and Its Applications

Monodisperse poly (chloromethylstyrene divinylbenzene) particles were prepared by a two-step swelling method. It was demonstrated that the packings have comparative advantages for biopolymer separation with high column efficiency, low interstitial volume and low back pressure to the packings prepared with suspension polymerization method. Using size exclusionchromatography and weak ion exchange chromatography as examples, it was shown that these packings could be modified chemically more easily than poly (styrene divinylbenzene) packings.

Impacts of low-intensity prescribed fire on microbial and chemical soil properties in a Quercus frainetto forest

Prescribed fire is a common economical and effective forestry practice, and therefore it is important to understand the effects of fire on soil properties for better soil management. We investigated the impacts of low-intensity prescribed fire on the microbial and chemical properties of the top soil in a Hungarian oak(Quercus frainetto Ten.) forest. The research focused on microbial soil parameters(microbial soil respiration(RSM), soil microbial biomass carbon(Cmic) and metabolic quotient(qCO2) and chemical topsoil properties(soil acidity(pH),electrical conductivity(EC), carbon(C), nitrogen(N), C/N ratio and exchangeable cations). Mean annual comparisons show significant differences in four parameters(C/N ratio,soil pH, Cmic and qCO2) while monthly comparisons do not reveal any significant differences. Soil pH increased slightly in the burned plots and had a significantly positive correlation with exchangeable cations Mg, Ca, Mn and K.The mean annual C/N ratio was significantly higher in the burned plots(28.5:1) than in the control plots(27.0:1). The mean annual Cmic(0.6 mg g-1) was significantly lower although qCO2(2.5 lg CO2–C mg Cmic h-1) was significantly higher, likely resulting from the microbial response to fire-induced environmental stress. Low-intensity prescribed fire caused very short-lived changes. The annual mean values of C/N ratio, pH, Cmic and qCO2showed significant differences.

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.

Modelling thermo-hydro-mechano-chemical interactions for nuclear waste disposal

A fully coupled thermo-hydro-mechano-chemical（THMC） formulation is described in this paper.Special attention is paid to phenomena likely to be encountered in clay barriers used as engineered barriers in the disposal of nuclear radioactive waste.The types of processes considered in the chemical formulation include hydrolysis,complex formation,oxidation/reduction reactions,acid/base reactions,precipitation/dissolution of minerals and cation exchange.Both kinetics-and equilibrium-controlled reactions are incorporated.The formulation is implemented in a numerical code.An application is presented concerning the performance of a large-scale in-situ heating test simulating high-level radioactive waste repository conditions.

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.

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.

Fe-doped CoP core–shell structure with open cages as efficient electrocatalyst for oxygen evolution

Developing a facile approach based on transition metal-based Prussian blue(PB)and its analogues(PBAs)with core-shell nanostructure is a very promising choice for constructing cost-effective electrocatalysts for oxygen evolution reaction(OER).Herein,a bimetallic core-shell structure with open cages of Fe-doped CoP(Fe-CoP cage)has been synthesized using CoFe-PBA cage-4 as precursor through a facile hydrothermal method and following phosphating process.Interestingly,there is an open hole in each face center of Fe-CoP cage,which suggests the more exposure of active sites for OER.Electrochemical measurements show that Fe-CoP cage can afford a current density of 10 mA cm-2 at a low overpotential(300 mV),which is better than that of RuO2.The excellent performance can be attributed to Fe doping composition and unique open-cage core-shell structure.The synergistic effect derived from bimetallic active for OER has been discussed.And its great catalytic stability has been evaluated via 1000 cycles of CV and chronoamperometry measurement.This work provides a potential method to design multiple transitional metal-doping electrocatalysts with complex framework derived from PBAs for water splitting.

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.

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.

Ion-exchange-induced Bi and K dual-doping of TiOx in molten salts for high-performance electrochemical nitrogen reduction

Electrocatalytic nitrogen reduction reaction (e NRR) at the ambient conditions is attractive for ammonia(NH_(3)) synthesis due to its energy-efficient and eco-friendly features. However, the extremely strong N≡N triple-bonds in nitrogen molecules and the competitive hydrogen evolution reaction lead to the unsatisfactory NH_(3) yield and the Faradaic efficiency (FE) of e NRR, making the development of high-performance catalysts with adequate active sites and high selectivity essential for further development of e NRR.Addressing this, we herein report a Bi and K dual-doped titanium oxide (BTO@KTO) material, which is prepared by a cation exchange reaction between K_(2)Ti_(4)O_(5) and molten BiCl_(2), for high-performance e NRR catalysts. Benefiting from the controllable molten-salt cation exchange process, a highly active surface containing Bi/K sites and rich oxygen vacancies has been obtained on titanium oxide. Under the synergy of these two merits, an efficient e NRR catalysis, with the NH_(3) yield rate of 32.02 μg h^(-1)mg_(cat)^(-1) and the FE of 12.71%, has been achieved, much superior to that of pristine K_(2)Ti_(4)O_(9). This work thus offers a highperformance electrocatalyst for e NRR, and more importantly, a versatile cation-exchange strategy for efficiently manipulating materials’ functionalities.

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.

Geotechnical Characterization of Termite Mound Soils of Congo

This study is to determine the activities and correlations in the fundamental properties of the termite mounds soils Cubitermes spp and Macrotermes sp. The Intrinsic properties depend on the mineralogy, organic composition and texture of soil. Grain size, Atterberg limits and soil blue values are geotechnical properties that were used to characterize the two soils. On the basis of the geotechnical properties, specific surface area, cation exchange capacity, relative activity, surface activity and soil activity were determined. The correlations obtained in the intrinsic soil properties are linear and polynomial fits. Indeed, the relationship between the plasticity index and the blue value of a soil on the one hand and between the specific surface area and the cation exchange capacity on the other hand, is a linear fit for all soils in general. The relationship between plasticity index and specific surface area is a linear fit for the soils (C, M). Correlations in intrinsic soil properties that have a coefficient of determination close to 1 can be used in geotechnical engineering to predict one of the two desired parameters.

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.

The Cation Exchange Capacity of Fibrous Feedstuff and Its Nutritive Characteristics

Current researches on the nutritive characteristics of fibrous feedstuff through determining the feedstuff cation exchange capacity (CEC) to evaluate its nutritive value at home and abroad were comprehensively discribed. and the methods of determining CEC value and the correlation between CEC value and chemical compositions, pH value, and the effect of CEC value on the digestion kinetics in ruminants were also emphatically introduced. The results of research showed that the CEC values of different feedstuff are different, closely correlated with nitrogen and acid detergent fibre (ADF) and lignin (LIG) content of the feedstuff. At the same time, there are markedly effect of CEC value in diet on the nutrients flow of digesta in the digestive tract of ruminants, the degradation rate and digestibility of nutrients in the rumen.

Effects of Functionalized Silica Nanoparticles on Characteristics of Nanocomposites PES Cation Exchange Membranes

Nanocomposite cation exchange membranes（CEMs） were prepared by adding various loadings of functionalized silica nanoparticles to the sulfonated polyethersulfone（s PES） polymeric matrix. The silica nanoparticles were functionalized by mercaptopropyl（F1, IEC=0）, propylsulfonic acid（F2, IEC= 2.71）, and sulfonic acid（F3, IEC=2.84）. The properties of prepared membranes were investigated by varying the loadings of functionalized silica nanoparticles. Applying functionalized nanoparticles provides additional ion exchange groups and enhances water contents as well as conductivities and permselectivities of the membranes. The maximum IEC of 1.9 meq.g^-1 was obtained for the membrane having 3 wt% F3 nanoparticles and the maximum conductivity of 0.237 S·cm^-1 was achieved for the membrane having 2 wt% F3 nanoparticles, which were 19.6% and 64% higher than the corresponding values for s PES membrane, respectively. The excellent properties of the nanocomposite cation-exchange membranes make them appropriate candidates for electrodialysis and desalination processes.

Elements, Structure and Electrochemical Property of Carbon Derived from La^(3+) Adulterating Polystyrene Cation Exchange Resin

The polystyrene cation exchange resin was exchanged by La 3+ and then were carbonized to make resin carbon material. The electrochemical properties of the resin carbon material as the electrode of the lithium ion cell were investigated. The test results show that comparing with the polystyrene cation exchange resin without adulterating, the contents of hydrogen, oxygen and sulfur are changed obviously for the resin carbon material derived from the La 3+ adulterating polystyrene cation exchange resin. The contents of hydrogen and oxygen are increased, and the one of sulfur is decreased. The test results also indicate that it is more easily to form the stratum graphite minicrystal structure with bigger diameter for the La 3+ adulterating resin. According to the electrochemical test results, the electrode derived from La 3+ adulterating polystyrene cation exchange resin has much better electrochemical property, and the capacity of charge and discharge of the electrode is increased about 30 mAh·g -1 in average.