Saturating Cation Research Articles

The effect of natural organic matter on the adsorption of microcystin-LR onto clay minerals

In this study, we examined the extent and time-dependence in the adsorption and desorption of microcystin-LR (MCLR) to kaolinite, illite and montmorillonite as a function of pH, electrolyte cation and Suwanee River fulvic acid (SRFA) concentration. Clay suspensions were pre-loaded with SRFA at concentrations ranging from 0 to 25 mg/L SRFA in either Na- or Ca-enriched conditions at pH 5 or 7. Kaolinite adsorbed the highest amount of SRFA that resulted in a reduction in MCLR adsorption at pH 5, but little effect at pH 7. Illite adsorbed little SRFA and its presence altered MCLR adsorption in a manner that differed with pH and saturating cation. This result we take to indicate the formation of solution-phase MCLR-SRFA complexes that had complex interactions with illite. Montmorillonite adsorbed the most MCLR and did so more rapidly than did the other clays. It also adsorbed a moderate amount of SRFA, which enhanced MCLR adsorption to Na-montmorillonite, but not to Ca-montmorillonite. Desorption of MCLR varied for the systems, but was more evident at pH 7 than pH 5. Overall, the results demonstrate clay type and electrolyte cation were more important factors for MCLR adsorption than was the presence or concentration of SRFA.

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.

Assessing factors influencing the release of hexazinone from clay-based formulations

New designs of pesticide formulations based on organoclays are receiving increasing attention in reducing offsite movement of pesticides in the environment and in prolonging the efficacy of soil-applied pesticides. In the present article, we report the results of laboratory and field experiments conducted to evaluate the influence of the saturating cation, the sorbent : herbicide ratio, and the type of preparation on the controlled release properties of organoclay-based formulations of the herbicide hexazinone. Two organoclays with different affinities for hexazinone (hexadecyltrimethylammonium-exchanged Arizona montmorillonite, HDTMA-SA, and phenyltrimethylammonium-exchanged Arizona montmorillonite, PTMA-SA), two herbicide loadings (10% and 20% AI), and three types of preparation were assayed. Laboratory experiments showed that hexazinone formulations based on HDTMA-SA displayed slow-release properties in water, retarded herbicide leaching through soil columns, and maintained a herbicidal efficacy similar to that of the currently available commercial hexazinone formulation (wettable powder). In contrast, PTMA-SA formulations released the herbicide instantaneously and did not display slow-release properties. High organoclay-herbicide ratios and the use of organic solvent made the interaction between HDTMA-SA and the herbicide more intimate and reduced the release rate of hexazinone, suggesting that a range of release and leaching behaviours can be achieved by selecting the type of preparation and the herbicide loading in the formulations. A field experiment confirmed the usefulness of HDTMA-SA formulations of hexazinone to reduce herbicide leaching while maintaining weed-control efficacy.

Interaction of Iron Chelating Agents with Clay Minerals

Organic ligands play an important role in metal transport and availability in soils. However, their interaction with the solid phase of soils has not been sufficiently investigated. Two efficient Fe chelators were investigated in this study, as free ligands as well as Fe complexes: (i) the microbial siderophore ferrioxamine B (desferrioxamine B [DFOB] and ferrioxamine B [FOB], respectively); (ii) the synthetic chelating agent ethylenediamine di‐o‐hydroxyphenylacetic acid (EDDHA and FeEDDHA, respectively). Batch experiments were conducted to characterize their adsorption to Ca‐ and Na‐montmorillonite as well as to Fe‐montmorillonite (for EDDHA and FeEDDHA) and Ca‐kaolinite. Kinetics of adsorption, equilibrium adsorption isotherms, and effects of pH on adsorption were measured. Adsorption of DFOB and FOB to montmorillonite was rapid and adsorption isotherms indicated high affinity. The type of saturating cation affected the adsorption of DFOB but not that of FOB. Significant hysteresis between adsorption and desorption was exhibited. The effect of Ca2+ in solution on desorption compared with that of Na+, was found to vary with their solution concentrations. Ethylenediamine di‐o‐hydroxyphenylacetic acid adsorption to montmorillonite exhibited a linear adsorption isotherm and significantly higher affinity than that of FeEDDHA. The adsorption decreased significantly with the following order of saturating cation: Ca2+ > Fe3+ > Na+ Adsorption of all examined substances to kaolinite was extremely low. Adsorption mechanisms of DFOB and EDDHA and their Fe complexes to clays and the environmental implications are discussed.

Interaction of Iron Chelating Agents with Clay Minerals

Organic ligands play an important role in metal transport and availability in soils. However, their interaction with the solid phase of soils has not been sufficiently investigated. Two efficient Fe chelators were investigated in this study, as free ligands as well as Fe complexes: (i) the microbial siderophore ferrioxamine B (desferrioxamine B [DFOB] and ferrioxamine B [FOB], respectively); (ii) the synthetic chelating agent ethylenediamine di-o-hydroxyphenylacetic acid (EDDHA and FeEDDHA, respectively). Batch experiments were conducted to characterize their adsorption to Ca- and Na-montmorillonite as well as to Fe-montmorillonite (for EDDHA and FeEDDHA) and Ca-kaolinite. Kinetics of adsorption, equilibrium adsorption isotherms, and effects of pH on adsorption were measured. Adsorption of DFOB and FOB to montmorillonite was rapid and adsorption isotherms indicated high affinity. The type of saturating cation affected the adsorption of DFOB but not that of FOB. Significant hysteresis between adsorption and desorption was exhibited. The effect of Ca2+ in solution on desorption compared with that of Na+, was found to vary with their solution concentrations. Ethylenediamine di-o-hydroxyphenylacetic acid adsorption to montmorillonite exhibited a linear adsorption isotherm and significantly higher affinity than that of FeEDDHA. The adsorption decreased significantly with the following order of saturating cation: Ca2+ > Fe3+ > Na+ Adsorption of all examined substances to kaolinite was extremely low. Adsorption mechanisms of DFOB and EDDHA and their Fe complexes to clays and the environmental implications are discussed.

Role of Iron Oxides in the Phosphate Adsorption Properties of Kaolinites From the Ivory Coast

AbstractThe phosphate adsorption properties of three clay samples, with kaolinite as the dominant mineral, from different deposits in the Ivory Coast have been investigated. The clays contain varying amounts of crystalline Fe oxides and kaolinite with structural Fe. All measurements were made in dilute suspension under controlled conditions of temperature, pH, ionic strength and saturating cation. Data have been fitted to Langmuir adsorption isotherms. Both P adsorption and surface area measurements have been made on samples before and after chemical removal of Fe oxides. The samples have large P adsorption capacities, which are not entirely explained by their large specific surface areas. The presence of Fe oxides makes a strong contribution to the surface area and enhances the adsorption capacities. There is little evidence that structural Fe makes a strong contribution to the enhanced P adsorption capacity.

Adsorption Mechanism and Structure of the Montmorillonite Complexes with (CH3)2XO (X=C, and S), (CH3O)3PO, and CH3–CN Molecules

The formation of complexes with different ligands in the interlayer space of montmorillonite saturated in Na+, Mg2+, Ca2+, Co2+, Cu2+, Ni2+, Fe3+, and Cr3+ was studied. Acetone, acetonitrile, dimethyl sulfoxide, and trimethylphosphate were used as ligands. The nature of the complexes was studied by means of X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, microcalorimetry, and ab initio quantum mechanical methods. In all cases, the organic ligands penetrate into the interlayer space at room temperature, forming complexes stable in vacuum with the interlayer cations. The ligand–cation ratio depends on the valence of the saturating cation. The cation–ligand interaction in these complexes has an ion–dipole electrostatic nature. The complexes are formed by the direct interaction of the oxygen or nitrogen atom of ligand and the interlayer cation. Using the quantum mechanical approach, allow us to determine the disposition of the ligand in these complexes. In all cases, only one layer of ligands is present in the stable complexes.

Natural soil colloids To retard simazine and 2,4-D leaching in soil.

Natural or synthetic sorbents for pesticides can be used to reduce contamination of soils and natural waters. The sorption of simazine and 2,4-D on montmorillonite minerals has been studied and their potential use to retard pesticide leaching in soil evaluated. Simazine and 2,4-D did not sorb on high-layer charge montmorillonite, whereas sorption on the lower layer charge montmorillonite SWy varied depending on the saturating cation. Simazine sorption increased in the order Ca(2+)SWy << K(+)SWy < Fe(3+)SWy. Simazine molecules sorb on hydrophobic microsites of the montmorillonite. Once protonated, further sorption through cation exchange takes place in the interlamellar space of the montmorillonite, as corroborated by X-ray diffraction and FT-IR studies. 2,4-D does not sorb on K(+)SWy or Ca(2+)SWy, but does sorb on Fe(3+)SWy, because the acidic character of this sorbent allows the molecular form of 2, 4-D to sorb by hydrogen bonding and/or by hydrophobic interactions. Leaching experiments in hand-packed soil columns indicate that simazine and 2,4-D application as a complex with FeSWy renders later breakthrough and lower maximum concentration peaks, and the total herbicide leached is lower than when applied as the pure analytical grade compound. These results suggest the possible use of natural soil colloids as sorbents for herbicides such as simazine and 2,4-D to retard pesticide leaching in soil, thus reducing their ground water contamination potential.

Sorption and Redox Activity of Cobalt Corrinoids on Hectorite

AbstractHalogenated synthetic organic compounds are widespread contaminants of the environment; however, little is known concerning their potential dehalogenation by extracellular corrinoids. Our primary objective was to determine if corrinoids sorbed to soil colloids are redox active and thus viable electron transfer mediators of contaminant dehalogenation in reduced soils and sediments. Dicyanocobínamide, cyanocobalamin (vitamin B12), and aquocobalamin were sorbed onto Ca2+‐, K+‐, and Na+‐hectorite and sorption isotherms determined. Additional assessment of sorption reactions was performed using x‐ray diffraction (XRD) and infrared (IR) spectroscopy. Redox states of the sorbed corrinoids in hectorite suspensions were monitored using ultraviolet and visible (UV‐VIS) spectrophotometry. Corrinoid molecular size and charge, as well as the saturating cation, controlled corrinoid sorption. The XRD results indicated that Co corrinoids intercalated hectorite, expanding the basal spacing from 1.45 to 2.21 nm for Ca2+‐, 1.17 to 2.70 nm for K+‐, and 1.31 to 2.81 nm for Na+‐hectorite. The IR spectra of bound corrinoids yielded little information on binding mechanisms, but indicated that axial ligands remained intact. The central metal of bound corrinoids was reduced to Co(I) by Ti(III) and reoxidized to Co(III) by introduction of O2, thus demonstrating that redox activity of sorbed corrinoids was maintained and reversible. Microbially produced extracellular corrinoids may act as potential electron transfer mediators when in association with clays, possibly participating in the reductive dehalogenation of organic contaminants.

BONDING BETWEEN POLYACRYLAMIDE AND CLAY MINERAL SURFACES

The objectives of this research were to determine the effects of clay mineralogy on the efficacy of cationic and anionic polyacrylamides (PAM) as flocculents for dispersed clays and to evaluate bonding mechanisms between clay mineral surfaces and both cationic and anionic PAM. A relative flocculation index was used to quantify the interaction between PAM and the Ca- and Na-forms of kaolinite, illite, and quartz. The cationic PAM was highly effective for flocculating all three minerals regardless of the electrolyte concentration or saturating cation. Under basic (pH = 10.9) conditions, the cationic PAM was slightly less effective than under neutral (pH = 5.9-8.2) or acidic (pH = 3.4) conditions. Positive charge functional groups on the cationic PAM are believed to bond directly with negative charge sites on the mineral surfaces. The efficacy of anionic PAM as a flocculent varied with saturating cation (Ca ≫ Na), mineralogy (kaolinite > illite ≫ quartz), and treatment (acid > salt > H2O > base). The results suggest that cation bridging (PAM-Ca-clay) is the major bonding mechanisms between anionic PAM and clay mineral surfaces. However, hydrogen bonding between electronegative moieties on the PAM and protonated nonbridging aluminol groups on lateral edges of kaolinite and illite and hydrophobic bonding between the carbon chain of the anionic PAM and basal surfaces of kaolinite were also suggested by the flocculation data.

Interaction of Rimsulfuron with Smectites

AbstractThe adsorption of the sulfonylurea herbicide rimsulfuron, [N-((4,6-dimethoxypyrimidin-2-yl)aminocarbonyl)-3-(ethylsulfonyl)-2-pyridinesulfonamide], on clay minerals with different saturating cations was studied. Three smectites with different lattice charge distribution (hectorite, montmorillonite and nontronite) were selected and made homoionic to Ca2+, Cu2+ and Al3+. Because of the instability of rimsulfuron in water, the experiments were carried out in chloroform solution. The interaction mechanism depends on the nature of the saturating cation and the tetrahedral layer charge of the silicate. Among the exchangeable ions studied, only Al3+ is able to produce degradation of the herbicide to N-(4,6-dimethoxypyrimidin-2-yl)-N-[(3-(ethylsulfonyl)-2-pyridinyl]urea. In this case, the lower the tetrahedral charge, the more active the degradation. The Ca2+-saturated clays are ineffective in the degradation. In contrast, the formation of a stable chelate complex with the saturating ion permits rimsulfuron to be adsorbed to a rather high extent into Cu(II)-clays and to be stable against degradation.

Interaction of metamitron and metolachlor with organic and inorganic smectites

To obtain useful data for the interpretation of the adsorption results in pesticide‐clay‐water systems a study of the interaction of the herbicides metamitron and metolachlor with montmorillonite saturated with inorganic cations and trimethylalkylammonium cations using x‐ray diffraction (XRD) and infrared spectroscopy (IR) was performed. XRD results indicated that both herbicides are adsorbed in the interlayer space of the inorganic montmorillonites forming definite and stable complexes, with d001 basal spacings of 14.72 A and 19.62 A in metamitron, and 16.85 A in metolachlor. The degree of interlayer expansion of the silicate was found to depend on the nature of the saturating cation and the structure and size of the herbicide molecule. IR results showed that the molecules of both herbicides interact with interlayer cations through the C = O groups. The herbicides also formed interlayer complexes with the organo clays, with d001 spacings ranging from 14.71 to 25.22 A for the metamitron complexes and from...

Flocculation and Coagulation of Ca- and Mg-Saturated Montmorillonite in the Presence of a Neutral Polysaccharide

AbstractThe objective of this study was to observe flocculation of montmorillonite in the presence of a glucose polymer (dextran) and to observe the effect of saturating cation and coagulant addition on the flocculation process. Flocculation of montmorillonite was dependent on polymer molecular weight, polymer/clay ratio (w/w), nature of exchangeable cation, and ionic strength of the suspension to which the polymer was added. The T500 dextran (molecular weight = 5 × 105) caused enhanced sedimentation of Ca-montmorillonite suspension at a polymer/clay ratio of ≤0.01. Increasing the polymer concentration above this level stabilized the suspension such that sedimentation was less than or equal to that of the control. The T2000 dextran (molecular weight = 2 × 106) caused a similar increase in the sedimentation of Ca-montmorillonite at polymer/clay ratios of &lt;0.1. The ability of the T2000 polymer to cause flocculation at greater polymer/clay ratios as compared to the T500 polymer was attributed to the lower osmotic pressure between clay particles for equal concentrations of the two polymers. Flocculation of Ca-montmorillonite by dextran was enhanced when the clay had initially been coagulated by the addition of salt. Reduction of the diffuse double layer upon addition of salt permitted the polymer to extend beyond the electrostatic barrier of the clays. Dextran was not able to flocculate Mg-montmorillonite suspensions with or without the presence of coagulant. The displacement of water molecules at the clay surface rather than within the hydration shell of the more highly polarizing Mg cations by polymer segments resulted in a greater polymer collapse on the clay surface leaving fewer and shorter polymer loops and tails available for contacting adjacent clay particles.

Preparation and characterization of smectite-model humic acid complexes

A humic acid analog was prepared by oxidative polymerisation of catechol in the presence of triglycine (PCT) and reacted in unbuffered medium with montmorillonite (M) homoionic to Na +, Ca 2+, Mn 2+, Cu 2+, Fe 3+ and Al 3+, and with two additional M samples treated with polynuclear hydroxyaluminium (Al-hydr) and manganese oxide (Mn-ox). PCT had an average molecular weight of 30 000 Da, a carboxylic acidity of 2.6 meq g −1 and a triglycine: catechol ratio of 0.65. Adsorption isotherms showed that the amounts of PCT adsorbed and bound to M increased according to the saturating cation, in the sequence: Ca 2+ < Na 2+ < Mn 2+ < Cu 2+ < Fe 3+ < La 3+ < Al-hydr. Electrophoretic mobility (EPM), bulk pH in water (pH b) and X-ray diffraction spectra were determined for the M-PCT complexes. The M-PCT bonds were not reversible at pH values lower than that of their formation. The surface acidity (as indicated by pH b) and the negative charge density (as indicated by EPM) of the complexes were higher than those of the respective homoionic M. This suggested that the binding of PCT involved complexation of surface clay cations by carboxyl groups and that the exchanged protons were held less strongly by the clay surface than they were by PCT. The expansion of M in M-PCT complexes was limited, and not related to the amounts of PCT bound, suggesting that interactions with external surfaces of M predominated in most cases.

Influence of pH, Sodium Adsorption Ratio, and Salt Concentration on Settling Kinetics of Suspended Solids in Coal‐Mine Ponds

AbstractColloidal particle‐settling experiments were conducted in the laboratory to test the influence of pH and dissolved solids on the kinetics of settling of suspended solids in a coal‐mine spoil sample obtained from western Kentucky. Potentiometric titrations suggested that the pH range of colloid coflocculation for the sample tested was around 4.2. Repulsive diffuse double layers at pH above 4.2 appeared to control‐suspended solid behavior. The rate of settling of suspended solids decreased as the pH of the suspension increased. This rate was highly influenced by the ionic strength, sodium adsorption ratio (SAR) and type of divalent cation (Ca or Mg). With Ca as the saturating cation and SAR values below 1, the suspended solids dropped below the required 35 mg/L limit within a 2–h period. At SAR values above 4 and pH near and/or above 7 suspended solids exceeded those required by law. When the divalent cation was Mg, the coal‐mine spoil solids appeared to be less dispersive. For sedimentation ponds neutralized with NaOH, this type of kinetic information is necessary to improve sediment trapping efficiency and design ponds with appropriate water detention times.

Adsorption du chlorfenvinphos et du methidathion sur argiles saturees par differents cations

Summary Adsorption of chlorfenvinphos and methidathion from dissolutions on H+, Ca++, Na+ and K+ are studied. In all cases the saturating cation distinctly influenced the Freundlich‐type adsorption, with adsorption decreasing in the following sequence: H+> Ca++> Na+ > K+. Chlorfenvinphos adsorption was slightly greater than methidathion in two clays, and the adsorption extent for them in kaolinite is slower that bentonite.

Effect of saturating cation on tactoid size distribution in bentonite suspensions

AbstractCentrifugal photosedimentation was used to determine the size distribution of dilute bentonite suspensions as a function of saturating cation. This method is shown to give a better estimate of the effect of saturating cation on tactoid size than the techniques that are currently used. The results indicate that tactoids may occur in preferred size ranges.

Critical Coagulation Concentrations of Sodium and Potassium Illite as Affected by pH

AbstractThe effects of saturating cation (Na or K) and pH on the critical coagulation concentrations (CCCs) of illite were measured. Flocculation series tests showed that between pH 6 and 11, the time‐invariant CCCs of Na illite increased from 6 to 58 mol Na m−3; release of interlayer K was controlled by adding 0.1 mol K m−3 to Na‐illite suspensions. The CCCs of K illite increased from 3 to 14 mol K m−3 over the pH range 6 to 10. The lower CCCs of K illite relative to Na illite were consistent with a higher surface affinity for K. Increasing CCC with increasing pH was explained by charge alterations on the edge surfaces due to surface‐specific proton interactions. A comparison of our Na‐illite CCCs to published Na‐kaolinite and Na‐montmorillonite CCCs revealed a greater pH dependence for Na‐illite and Na‐kaolinite CCCs.

Cation exchange in synthetic manganates: I. Alkylammonium exchange in a synthetic phyllomanganate

AbstractOn treatment with dodecylammonium chloride, a synthetic Na-saturated phyllomanganate undergoes a cation-exchange reaction in which the structure expands from a collapsed basal spacing of 7 Å or a hydrated one of 10 Å to ∼ 25·5 Å. The exchange reaction is strongly influenced by the saturating cation in the original manganate and by the degree of hydration of the interlayer zone in which the exchangeable cations are located. Of the 12 cations tested, from Groups IA, IIA and IIB of the Periodic Table, only Co-manganate undergoes alkylammonium exchange when fully-dehydrated by evacuation. The results are discussed in the context of existing knowledge of the synthetic phyllomanganate and, by extrapolation, the potential value of the technique in the characterization of natural manganates has been assessed.

Ion Exchange, Thermal Transformations, and Oxidizing Properties of Birnessite

AbstractSynthetic sodium bimessite, having a cation-exchange capacity (CEC) of 240 meq/100 g (cmol/kg) was transformed into Li, K, Mg, Ca, Sr, Ni, and Mn2+ cationic forms by ion exchange in an aqueous medium. Competitive adsorption studies of Ni and Ba vs. Mg showed a strong preference for Ni and Ba by bimessite. The product of Mg2+-exchange was buserite, which showed a basal spacing of 9.6 Å (22°C, relative humidity (RH) = 54%), which on drying at 105°C under vacuum collapsed to 7 Å. Of the cation- saturated bimessites with 7-Å basal spacing, only Li-, Na-, Mg-, and Ca-bimessites showed cation exchange.Heating bimessite saturated with cations other than K produced a disordered phase between 200° and 400°C, which transformed to well-crystallized phases at 600°C. K-exchanged bimessite did not transform to a disordered phase; rather a topotactic transformation to cryptomelane was observed. Generally the larger cations, K, Ba, and Sr, gave rise to hollandite-type structures. Mn- and Ni-bimessite transformed to bixbyite-type products, and Mg-bimessite (buserite) transformed to a hausmannite-type product. Li-bimessite transformed to cryptomelane and at higher temperature converted to hausmannite. The hollandite-type products retained the morphology of the parent bimessite. The mineralogy of final products were controlled by the saturating cation. Products obtained by heating natural bimessite were similar to those obtained by heating bimessite saturated with transition elements.