Effects of acid neutralization on the morphology and properties of organoclay nanocomposites formed from K+ and Na+ poly(ethylene-co-methacrylic acid) ionomers

Nanocomposites were prepared by melt blending various sodium (Na⁺) and potassium (K⁺) ionomers formed from poly(ethylene-co-methacrylic acid) and the M₂(HT)₂ organoclay formed from montmorillonite (MMT). The effects of the neutralization level of the acid groups and the precursor melt index on the morphology and properties of the nanocomposites were evaluated using stress-strain analysis, wide angle X-ray scattering (WAXS), and transmission electron microscopy (TEM) coupled with particle analysis. The aspect ratio generally increases as the neutralization level increases, except for Na⁺ ionomer nanocomposites with neutralization levels >50%. It appears from both WAXS and TEM analyses that Na⁺ ionomer nanocomposites have higher levels of MMT exfoliation and particle orientation in the flow direction than K⁺ ionomer nanocomposites. DSC results indicate that the level of crystallinity in the Na⁺ ionomers generally increases slightly with MMT addition, while the crystallinity in the K⁺ ionomers decreases slightly with MMT addition. The relative modulus of K⁺ ionomer nanocomposites increases as the degree of neutralization increases. The relative moduli of Na⁺ ionomer nanocomposites are higher than the relative modulus of K⁺ ionomer nanocomposites, likely due to the increased crystallinity of the Na⁺ ionomers and the decreased crystallinity of the K⁺ ionomers upon addition of MMT, the higher exfoliation levels measured by the aspect ratios and the particle densities, and the higher particle orientation indicated by TEM and WAXS. The relative modulus generally increases as the aspect ratio increases. The elongation at break generally decreases as the MMT content increases and as the neutralization level increases for both ionomer types. The fracture energy of most of the ionomers increases with the addition of MMT, reaches a maximum between 2.5 and 5 wt% MMT, and then decreases upon further MMT addition.     

Effects of the cation valence on the mechanical properties of sulfonated polystyrene ionomers containing dicarboxylate salts

The dynamic mechanical properties of Ba(II)-neutralized poly(styrene-co-styrene sulfonate) ionomers-containing Ba salt of aliphatic diacid were investigated and compared with those of Na(I)-neutralized ionomers-containing Na diacid salt. It was found that the addition of diacid salts led to a negligible change in the matrix and cluster T _gs of the Ba and Na ionomers regardless of the chain length of the aliphatic diacid salts. The log E′ of Ba ionomers, however, increased linearly with increasing chain length of Ba diacid salt, which was different from that of Na ionomers. On increasing wt% of the salts in the ionomers, the matrix T _gs of Ba and Na ionomers did not change, but the cluster T _gs increased slightly for Ba and Na ionomers, except for the Na ionomer-containing C₁₆ diacid salt. In addition, the log E′ increased linearly with the wt% of diacid salts, but the increasing rate was higher for the Ba ionomers, compared to Na ionomers. Thus, it was suggested that the Ba diacid salts would face more difficulty in the formation of multiplet with the ionic groups of the ionomers, compared to Na ionomer system; thus, more Ba diacid salts were phase-separated, which showed a stronger filler effect. In addition, since the Ba ionomers did not flow easily above the cluster T _g of the ionomers, it was proposed that the multiplets of Ba ionomers acted still as effective physical cross-links above cluster T _g, to some extent. Finally, it was concluded that the difference in anionic groups, the increasing amount of Ba salts, and the divalent cation enhanced the filler effects strongly.     

Preparation,characterization, and some properties of ionomers from a sulfonated styrene–butadiene–styrene triblock copolymer without gelation

The conditions for the sulfonation of a highly unsaturated styrene–butadiene–styrene triblock copolymer (SBS) in cyclohexane containing a small amount of acetone with acetyl sulfate made by sulfuric acid and acetic anhydride without gelation were studied. After neutralization with metallic ions, the ionomers were characterized with IR spectrophotometry, dynamic mechanical analysis, and transmission electron microscopy. The melt flow, solution properties, and mechanical properties of the ionomers were studied. The results showed that gelation occurred during the sulfonation of SBS in cyclohexane at a 5–10% concentration without acetone, whereas in the presence of 5–10 vol % acetone, sulfonation proceeded smoothly without gelation. Transmission electron microphotographs of the lead ionomer indicated the presence of ionic domains. A dynamic mechanical spectrum showed the presence of three transition temperatures: ?82.9, 68, and 96.5°C. The melt viscosity of the ionomer increased with the sulfonate content. The melt viscosity of the different ionomers neutralized with different cations seemed to decrease with decreasing ionic potential for both monovalent cations and divalent cations The solution viscosity of the sodium‐sulfonated ionomer increased with increasing sulfonate content. The ionomer still behaved as a thermoplastic elastomer and showed better mechanical properties than the original SBS. The tensile strength of the different ionomers decreased as follows. For the monovalent cations, it decreased with decreasing ionic potentials: Li⁺ > Na⁺ > K⁺. For the divalent cations, it decreased with increasing ionic potentials: Pb²⁺ > Zn²⁺ > Mg²⁺. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1398–1404, 2005     

Ionomers made from terpolymers with uniform poly(methyl methacrylate) grafts

Terpolymers with uniform poly(methyl methacrylate) (PMMA) grafts were prepared by terpolymerization of PMMA macromonomer, butyl acrylate, and acrylic acid in benzene using AIBN as initiator. During terpolymerization the macromonomer polymerizes faster than the monomers at the beginning but slower at the latter stage. The terpolymers were purified by solvent extraction and fractional precipitation. The average grafting number per chain of the terpolymers was determined to be 3–8. Ionomers were obtained by neutralization of the terpolymers with alkali hydroxide or metallic acetate. Dynamic mechanical spectrum of the ionomer shows the existence of two T_g's, which implies the occurence of microphase separation. The ionomer exhibits high damping over a temperature range from ?25 to 100°C. Both PMMA grafts and metallic carboxylate content raise the tensile strength of the ionomer and lower the ultimate elongation. The tensile strength of ionomers neutralized with different metallic ions decreases in the following order: Pb²⁺ > Zn²⁺ > Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. The ionomers with uniform PMMA grafts show much better mechanical properties than the terpolymer without neutralization or the ionomer without PMMA grafts.     

Fracture mechanics investigation on the PP/EPDM/ionomer ternary blends using j-integral by locus method

The fracture mechanics investigation of the polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM)/ionomer ternary blends was performed in terms of the J-integral by measuring fracture energy via the locus method. Blends were prepared in a laboratory internal mixer. The composition of PP and EPDM was fixed at a 50/50 ratio by weight. Two kinds of Poly(ethylene-co-methacrylic acid) (EMA) ionomers were used. The J-integral value at crack initiation, Jc, of the PP/EPDM/EMA ionomer ternary blends were affected by the cation types (Na⁺ or Zn²⁺) and contents (5–20 wt %) of the added EMA ionomers. The ternary blend having 5 wt % of Na-neutralized ionomer showed a higher Jc value than that of any other ternary blends. The results were discussed with regard to the fracture topology by a scanning electron microscope (SEM). © 1994 John Wiley & Sons, Inc.     

Poly(styrene-b-isobutylene-b-styrene) block copolymer ionomers (BCPI) and BCPI/silicate nanocomposites. 2. NaBCPI sol-gel polymerization templates

Polystyrene (PS) blocks in poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers were partially sulfonated and the acid groups converted to Na⁺SO₃⁻ groups to create ionomers. Then, dimethylacetamide was used to selectively swell the ionic PS domains and the swollen films were exposed to sol-gel reactive tetraethylorthosilicate solutions. (EtO)_4−xSi(OH)_x monomers then permeated films so that sol-gel reactions occurred within/around the ionic PS domains. Environmental scanning electron microscopy/energy dispersive X-ray spectroscopy investigations showed that silicate structures can be incorporated within the interior of the ionomer films. Differential scanning calorimetry studies indicated that there is no variance in the PIB block T_g with respect to ionomer formation, or with respect to silicate loading of the ionomer at low levels, which suggests that the silicate component does not reside in the PIB phase. ²³Na solid state NMR spectroscopy detected isolated Na⁺SO₃⁻ groups as well as aggregated SO₃⁻Na⁺ ion pairs for ‘as cast’ and ‘dry’ non-silicate containing ionomer samples. In a hydrated sample, almost all Na⁺ ions were solvent-separated. AFM analysis showed that phase separation exists, but that the degree of order is significantly less than that for hybrids based on the corresponding benzyltrimethylammonium ionomer. This frustrated morphology was also seen in the results of small angle X-ray scattering experiments. Given the scale of organic/inorganic heterogeneity, these hybrids are properly classified as nanocomposites.     

Investigation of the structure and properties of polyisobutylene-based telechelic ionomers of narrow molecular weight distribution. I.

The solid state morphology of recently developed sulfonated polyisobutylene (PIB) telechelic ionomers with narrow molecular weight distribution (MWD) (M¯_w/M¯_n ≈ 1.15) was investigated. A small angle X-ray scattering (SAXS) peak often associated with the aggregation of the ionic species in the bulk, as well as a secondary peak, have been observed in the narrow distribution sulfonated PIB telechelic ionomers for the first time. Ionomers of difunctional and tri-arm architecture at several number average molecular weights (M¯_n) with one of several counterions were investigated and the preparation method was also considered in terms of observed SAXS behavior. Compression-molded films made from these narrow MWD telechelics were examined in detail using SAXS. Primary and secondary peaks were observed in the slit-smeared SAXS profiles up to an M¯_n of 27 kg/mol. The ratio of the interdomain spacings derived from these peaks (ca. 2 : 1) suggests cylindrical or lamellar ordering in the morphology in both difunctional and tri-arm ionomers. Pinhole SAXS images showed no azimuthal dependence in the scattering pattern and thus, this ordering is on a local scale. It was found that the counterion has an inconsistent effect on the smeared interdomain spacing associated with the SAXS peak. The smeared interdomain spacings were systematic with respect to architecture and M¯_n for solution cast Cs⁺ ionomers. The difunctional telechelics exhibited higher smeared interdomain spacings than tri-arms of comparable M¯_n and unlike the compression-molded films, the smeared interdomain spacings of the solution cast Cs⁺ telechelic ionomers increased systematically with increasing M¯_n. Even a broad MWD (M¯_n/M¯_n ≈ 1.8) tri-arm telechelic ionomer M¯_n of 20.6 kg/mol exhibited a diffuse primary peak in SAXS when solution-cast. However, it exhibited no peak when compression-molded. © 1997 John Wiley & Sons, Inc.     

CO2 Separation Using Facilitated Transport Ion Exchange Membranes

Abstract

The use of ion-exchange membranes as supports for facilitated transport of C0₂ is demonstrated. Two different ionomer films were evaluated. The ionomers were a perfluorosul-fonic acid film and a sulfonated polybenzimida-zole film. Sodium (Na⁺) was exchanged into the membrane for diffusion experiments and ethylene-diamine (EDA) was exchanged for facilitated transport experiments. The results indicate that thin perfluorosulfonic acid membranes provide the best CO₂ flux and can also provide exceptionally high selectivity.     

Effects of compositional inhomogeneity on the mechanical properties and morphology of styrene-co-methacrylate random ionomer mixtures

A series of poly(styrene-sodium methacrylate) SMANa ionomers of varying ion contents was synthesized, and mixtures of the ionomers were made to artificially broaden the compositional inhomogeneity of the SMANa ionomers at a constant ion content of 7.3 mol%. The mechanical properties of the unblended SMANa ionomer containing 7.3 mol% of ions and the ionomer mixtures were compared. It was found that the ionic moduli of the unblended ionomer and ionomer mixtures were very similar to each other, indicating that the mixing process did not change the degree of clustering. However, the slope of ionic plateau became steeper as the difference in the ion contents of two ionomers in the ionomer mixture increased, suggesting that the inhomogeneity of the matrix and cluster phases increased. It was also observed that the difference between the matrix and cluster T_gs increased as the divergence of the ion contents of two ionomers in the ionomer mixture became wider. In addition, it was found that when the difference of the two ion contents exceeded over 6 mol%, the ionomer mixture started to show a trace of phase-separation. At ca. 9 mol% of ion content difference, the ionomer mixture exhibited a third loss tangent peak, possibly due to the presence of the phase-separated matrix regions. The SAXS study showed that, even though the three-dimensional arrangement of multiplets in an ionomer matrix was not changed upon mixing two ionomers, the matrix phase became inhomogeneous.     

Effects of matrix polarity and ambient aging on the morphology of sulfonated polyurethane ionomers

Summary Ethylene oxide units were incorporated into the backbone of Na⁺ sulfonated polyurethane ionomers in an attempt to induce aggregate dissociation at elevated, but observable, temperatures by reducing the incompatibility between ions and polymer. However, no dissociation could be observed by small-angle x-ray scattering (SAXS) before the onset of degradation, even when the polyol was pure EO. At 100°C and above, the SAXS patterns for all samples were quite similar, indicating morphological similarity. However, after annealing for several days at room temperature, two of the specimens appeared to develop a greater degree of microdomain order as evidenced by a narrowing of the main peak at q^* and the development of a shoulder at 2q^*x.     

Analysis of SAXS data from ionomer systems

A model was proposed earlier for the microstructure of ionomers which attributes the small-angle X-ray scattering (SAXS) peak observed in these materials to interparticle interference between small ionic domains arranged in the hydrocarbon matrix with a liquid-like degree of order. In this work, that model is used to interpret SAXS results obtained for a number of different ionomer systems. In addition, the effect of swelling of sulphonated polystyrene ionomers with water is investigated using this approach. Finally, the effect of temperature on the scattering was studied. The results reveal some interesting differences in domain size between different ionomer systems. The ethylene/methacrylic acid ionomers contain very small domains consistent with the concept of a multiplet, while the sulphonated EPDM rubbers have rather large domains. The results of the water absorption studies were inconsistent with the assumption that there is no change in the number of ionic domains upon swelling but if that assumption is not made, the data can be rationalized with the model. The elevated temperature measurements demonstrated the stability of the ionic domains even at temperatures well above those where the materials can be processed, leading to speculation regarding the mechanism of melt flow in ionomers.     

Novel polyimide ionomers: CO2 plasticization, morphology, and ion distribution

Aluminum crosslinked 6FDA-6FpDA:DABA 2:1 and 1:2 copolyimide membranes were synthesized and their CO₂-induced plasticization was investigated. The membranes are unstable against CO₂ plasticization in long-term permeation tests at 40 atm CO₂ feed pressure at 35 °C. To correlate the plasticization with the polymer morphology, scanning transmission electron microscopy (STEM) was used to image the ionomers. STEM shows Al-rich aggregates in both ionomers, but the aggregate size and shape distribution in the 1:2 film is much more heterogeneous than in the 2:1. The 1:2 ionomer contains spherical aggregates with diameters from ∼5 to 25 nm, chainlike assemblies of small spherical aggregates, vesicular aggregates, large distorted vesicular aggregates, and long band-like structures that extend up to 1000 nm in one dimension. The 2:1 ionomer only contains a few approximately spherical aggregates. Large fractions of both ionomers do not exhibit visible aggregates on the STEM length scale. IR spectroscopy reveals a neutralization level of the acid groups above 60% and transmission electron microscopy detects unreacted neutralizing agent in the polymer. Small angle and wide angle X-ray scattering patterns show scattering patterns that can be linked to the solid-state structure of the polymer backbone rather than the ionic aggregates.     

Synthesis and properties of random poly(lactic acid)-based ionomers

A random poly(lactic acid), PLA, based ionomer was synthesized by copolymerizing a methacrylate-terminated PLA macromonomer and methyl methacrylate. The copolymerization kinetics were studied using ¹H NMR spectroscopy and the copolymer composition was characterized by ¹³C NMR spectroscopy. Carboxylic acid groups were introduced into the copolymer by reacting the hydroxyl end groups of the PLA macromonomer with succinic anhydride, and the acid groups were neutralized with metal acetates to produce Na-, Ca-, and Y-PLA ionomers. Significant increases in T_g were observed for the ionomers and thermomechanical analysis indicated that the ionomers were more resistant to penetration by a weighted probe and an apparent rubbery plateau was observed above T_g. The ionomers were more hydrophilic than PLA, but relatively low water absorption could be achieved for the Ca²⁺-salt ionomer.     

The control of miscibility of PP/EPDM blends by adding lonomers and applying dynamic vulcanization

The control of miscibility for isotactic polypropylene (PP) and ethylene-propylene-diene terpolymer (EPDM) has been attempted by adding poly(ethylene-comethacrylic acid) (EMA) ionomers and by applying dynamic vulcanization. The rheological properties, crystallization behavior, and morphology of the dynamically vulcanized EPDM/PP/ionomer ternary blends were investigated with a Rheometrics dynamic spectrometer (RDS), a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Two kinds of EMA ionomers neutralized with different metal ions (Na⁺ and ZN⁺⁺) were investigated. Blends were prepared on a laboratory internal mixer at 190°C. Blending and curing were performed simultaneously, i.e., EPDM was vulcanized with dicumyl peroxide (DCP) in the presence of PP/ionomer. The composition of PP and EPDM was fixed at 50/50 by wt% and the contents of EMA ionomer were vaired from 5 to 20 parts based on the total amount of PP and EPDM. It was found that the addition of ionomers and the application of the dynamic vulcanization were effective in enhancing the miscibility of PP and EPDM. The structure of the blends was controlled by the following three component phases, i.e., the phase of the dynamially valcanized EPDM, PP, and Zn-neutralized ionomer. The ternary blends showed more miscibility than the PP/EPDM binary blend. This is due to the thermoplastic interpenetrating polymer network (IPN) of the ternary blends. The structure and properties of the ternary blends differed, depending on the types and contents of ionomer, i.e., the ternary blend containing Na-neutralized ionomer did not show a thermoplastic IPN structure clearly, even though the blend was prepared by dynamic vulcanization. The ternary blend containing Zn-neutralized ionomer clearly showed the behavior of a thermoplastic IPN when the contents of ionomer and DCP were 15 parts and 1.0 part, respectively.     

Rheological properties,tensile properties,and morphology of PP/EPDM/lonomer ternary blends

The rheological and tensile properties and the morphology of polypropylene (PP)/ethylenepropylene-diene terpolymer(EPDM)/ionomer ternary blends were investigated, using a rheometric dynamic spectrometer (RDS), a dynamic mechanical thermal analyzer (DMTA), a tensile tester, and a scanning electron microscope (SEM). Two kinds of poly(ethylene-co-methacrylic acid) (EMA) ionomers, neutralized with different metal ions (Na⁺ and Zn⁺⁺), were used. Blends were melt-mixed, using a laboratory internal mixer at 190°C. The composition of PP and EPDM was fixed at 50/50 by wt % and the EMA ionomer contents were varied from 5 to 20 wt %, based on the total amount of PP and EPDM. It was found that the ternary blends, containing Na-neutralized ionomer, showed considerably different rheological properties and morphology as compared to the PP/EPDM binary blends, due to the compatibilizing effect of the ionomer for PP and EPDM, while the ternary blends, containing the Zn-neutralized ionomer, did not. The compatibilizing effect was most prominent at 5 wt % ionomer concentration. © 1994 John Wiley & Sons, Inc.     

Evaluation of polymethacrylic ionomer as compatibilizers for MCPA6/clay composites

The compatibilization effects provided by polymethacrylic ionomer (PMMA ionomer) on monomer‐casting polyamide6 (MCPA6)/clay (pristine sodium montmorillonite) composites were studied in this work. The PMMA ionomer used in this study was sodium polymethacrylate ionomer (PMMA Na⁺‐ionomer), which is a copolymer of methyl methacrylate and sodium methacrylate, prepared using emulsion polymerization. MCPA6/clay/PMMA Na⁺‐ionomer composites were prepared by in situ anionic ring‐opening polymerization (AROP) of ε‐caprolactam (CLA). X‐ray diffraction (XRD) and transmission electron microscopy (TEM) plus rheological measurement were used to characterize those composites. The results indicated that PMMA Na⁺‐ionomer is a good compatibilizer for this system. With increasing PMMA Na⁺‐ionomer content, a better dispersion of clay layers was successfully achieved in the MCPA6 matrix. Furthermore, differential scanning calorimetry (DSC) and XRD results indicated that well dispersed silicate layers limit the mobility of the MCPA6 molecule chains to crystallize, reduce the degree crystalline, and favor the formation of the γ‐crystalline form of the MCPA6 matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Quantum chemical consideration of CO adsorption over cation exchanged faujasite

CNDO/2 calculation for atomic charges, Wiberg bond orders and adsorption energies of CO molecules on the cluster model whose Si/Al ratio varied were carried out. The data for the normal cluster and dealuminated cluster were compared. Decationization energies of the cations increased with the charge densities of cation and number of aluminum involved. Adsorption process of CO on the monovalent cations such as H⁺, Li⁺, Na⁺ and divalent cations, Be²⁺, Ca²⁺, and Mg²⁺ was supposed to be occurring by the donation of non-bonded electrons from CO. The decationization energies of cations obviously decreased by the dealumination process. Adsorption energies of CO on the cations generally decreased as the dealumination look place except the case of H⁺ and Na⁺.     

[Poly(ethylene terephthalate) ionomer]/silicate hybrid materials via polymer–in situ sol‐gel reactions

A scheme was developed for producing poly(ethylene terephthalate (PET) ionomer)/silicate hybrid materials via polymer–in situ sol‐gel reactions for tetraethylorthosilicate (TEOS) using different solvents. Scanning electron microscopy/EDAX studies revealed that silicate structures existed deep within PET ionomer films that were melt pressed from silicate‐incorporated resin pellets. ²⁹Si solid‐state NMR spectroscopy revealed considerable Si—O—Si bond formation, but also a significant fraction of SiOH groups. ²³Na solid‐state NMR spectra suggested the presence of ionic aggregates within the unfilled PET ionomer, and that these aggregates do not suffer major structural rearrangements by silicate incorporation. For an ionomer treated with TEOS using MeCl₂, Na⁺ ions are less associated with each other than in the unfilled control, suggesting silicate intrusion between PET–SO Na⁺ ion pair associations. The ionomer treated with TEOS + tetrachloroethane had more poorly formed ionic aggregates, which illustrates the influence of solvent type on ionic aggregation. First‐scan DSC thermograms for the ionomers demonstrate an increase in crystallinity after the incorporation of silicates, but solvent‐induced crystallization also appears to be operative. Second‐scan DSC thermograms also suggest that the addition of silicate particles is not the only factor implicated in recrystallization, and that solvent type is important even in second‐scan behavior. Silicate incorporation does not profoundly affect the second scan T_g vs. solvent type, i.e., chain mobility in the amorphous regions is not severely restricted by silicate incorporation. Recrystallization and melting in these hybrids appears to be due to an interplay between a solvent‐induced crystallization that strongly depends on solvent type and interactions between PET chains and in situ‐grown, sol‐gel‐derived silicate particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1749–1761, 2002; DOI 10.1002/app.10586     

EQUILIBRIUM OF METALS WITH IMINODIACETIC RESIN IN BINARY AND TERNARY SYSTEMS

ABSTRACT

Experiments of binary and ternary ion exchange equilibrium of heavy metals and sodium were carried out in a complexing iminodiacetic resin Lewatit TP 207. First, binary equilibrium data were obtained at different temperatures and ionic strength and fixed to models considering two different ion exchange stoichiometrics. For ternary equilibrium data, two distinct simple models were applied. One to be applied to systems showing very different selectivity for the metals (for instance, Cu²⁺/Co²⁺/Na⁺) and the other for systems with similar selectivity for the metals (such as Zn²⁺/Co²⁺/Na⁺). The ternary equilibrium data obtained is presented in this work and fitted using the two above mentioned models. These models allow us to obtain the equilibrium parameters for binary and ternary system to be used in the design of equipment using this iminodiacetic resin.     

Treatment of industrial wastewater using zeolitite and sepiolite,natural microporous materials

This work investigates the ability of natural microporous materials, such as a zeolite-rich tuff (zeolitite) and a modulated phyllosilicate (sepiolite), to remove heavy-metal ions from simulated inorganic polluted industrial wastewater. Fixed beds of sepiolite and zeolitite were percolated by a solution of Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ (concentration of each cation, 2 ? 10^?3 N; total concentration, 10^?2 N) and were regenerated with a 2 ? 10^?3 N Na⁺ solution. The order of decreasing affinity was, for sepiolite: Cu²⁺ > Zn²⁺ > Cd²⁺ > Pb²⁺ ? Co²⁺, and, for zeolitite: Pb²⁺ “Cd²⁺ > Cu²⁺ > Zn²⁺ > Co²⁺. After regeneration with Na⁺ solution, a fraction of the retained heavy metals was quickly released by the beds as follows: sepiolite, Co²⁺ ? Pb²⁺ > Cd²⁺ > Zn²⁺ > Cu²⁺; zeolitite, Cd²⁺ > Cu²⁺ ? Zn²⁺ > Co²⁺ > Pb²⁺. XRD and DTA-TGA analyses examined structural changes in the natural and final materials.