Clinoptilolite Content Research Articles

Properties of cement mortars containing clinoptilolite as a supplementary cementitious material

This paper presents a study of the properties and behavior of cement mortar with clinoptilolite which is one of the most common zeolite minerals found in nature. Six mortar mixtures were prepared by replacing the Portland cement with 0%, 5%, 10%, 15%, 20% and 30% clinoptilolite by weight. Test results showed that water demand, soundness and setting times of the cement pastes increased with the increase of clinoptilolite content. Compressive and flexural strength of the mortars containing clinoptilolite were higher than the control mixture. Dry unit weight of the mortars with clinoptilolite was lower than the control mortar. Clinoptilolite replacement decreased water absorption and porosity of the mortars. The control mortar showed less durability to carbonation compared to the mortars made with clinoptilolite at the end of carbonation tests. Freeze–thaw resistance of the mortars containing 5% clinoptilolite was higher than control mortar. The effect of clinoptilolite incorporation on high-temperature resistance seemed to be dependent on amount of clinoptilolite, temperature level, and the cooling method.

Clinoptilolite Adsorption Capability of Ammonia in Pig Farm

In this paper, clinoptilolite, as an adsorbing material, which adsorption capability of ammonia was studied. Clinoptilolite is a porous crystal material, which adsorption properties of clinotiolite are strongly related to the framework structure, which has performance for the physical adsorption and ion exchange. China is in rich of nature clinoptilolite, which is cheap and suitable for extensive application in pig house. The experiment indicated that clinoptilolite had a characteristic of “rapid adsorption, slow equilibrium”, it took 3hours to reach adsorption equilibrium, clinoptilolite's particle size, moisture content and dosage had important effects on saturation adsorption time and ammonia adsorption capacity. With decreasing the particle size, clinoptilolite adsorption capacity increased, and the higher ammonia concentration, the better adsorption effect in the “rapid adsorption” phase. Different clinoptilolite's moistures also played an important role for adsorption effect, in the “rapid adsorption” phase, the effect was the best when moisture content of clinoptilolite was 40%; in the phase of “slow equilibrium”, wet clinoptilolite adsorption would be better than the natural, the rank was: 40%>50%>30%>20%>60%>the natural. By regression analyze, when moisture content was 42%, adsorption capability could be the best. Besides, clinoptilolite adsorption capacity was studied, per unit saturation adsorption capacity of 10g nature clinoptilolite was 0.09mg/g, 20g nature clinoptilolite's was 0.13mg/g. Therefore, it could be seen that increasing the amount of clinoptilolite would improve the total and units clinoptilolite adsorption capacity. Considering the significant sorption for ammonia, the method of clinoptilolite adsorption could be simple and economic, it should be foreseeable that clinoptilolite adsorption would have a good prospect for air purification in pig farm.

Preparation, characterization and anticorrosive properties of a novel polyaniline/clinoptilolite nanocomposite

Nanocomposite of polyaniline (PANI) with natural clinoptilolite (Clino) was prepared. Formation of nanocomposite and incorporation of polyaniline in the clinoptilolite channels was confirmed and characterized using FTIR spectroscopy studies, X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and cyclic voltammetry techniques. The anticorrosive properties of a 20 μm thickness coating of PANI/Clino nanocomposite with various weight ratios (1, 3 and 5%, w/w) of clinoptilolite content on iron coupons was evaluated and compared with pure polyaniline coating. According to the results in acidic environments PANI/Clino nanocomposite has enhanced corrosion protection effect in comparison to pure polyaniline coating. Comparative experiments revealed that PANI/Clino nanocomposite with 3% (w/w) clinoptilolite content has the best protective properties. Further experiments showed that the PANI/Clino nanocomposite has considerably different corrosion protection efficiencies in various corrosive environments.

Preparation and characterization of novel composites based on chitosan and clinoptilolite with enhanced adsorption properties for Cu 2+

Novel ionic composites based on chitosan (CS) and clinoptilolite (CPL), a widespread natural zeolite, were prepared in this work as microspheres by a “tandem” ionic/covalent cross-linking. The mass ratio between CPL and CS was varied in the range 1:10–1:2. The ionic gelation of CS was performed with sodium tripolyphosphate and epichlorohydrin was used as covalent cross-linker. An abrupt increase of the adsorption capacity for Cu 2+ with the increase of the CPL content loaded in the composite compared with cross-linked CS was observed, up to 20 wt.% of CPL. The external stimuli which control the adsorption of Cu 2+ were solution pH and temperature. The optimum adsorption pH was 5.0 and the adsorption process was well described by the pseudo-second-order kinetics. The maximum adsorption capacity of metal ions was observed after the 2nd cycle of adsorption, for all composites.

The zeolite–lime pozzolanic reaction: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

The early pozzolanic reaction in pastes of lime and natural zeolites was studied with time-resolved in situ synchrotron X-ray powder diffraction. For chabazite and Na-, K-, and Ca-exchanged clinoptilolite tuffs, which were mixed with lime and water, the evolution of the quantitative contents of crystalline phases was followed during the early pozzolanic reaction in the first hours and days. The dependence of the rate coefficient on temperature was examined by isothermal curing at 313, 323, and 333 K of lime–chabazite tuff pastes. Kinetic analysis indicates that the reaction rapidly displays a deceleratory character. This is explained by the modified Jander equation as a result of the reaction rate control by diffusion processes through a condensing reaction product boundary layer. The exchangeable cation content of clinoptilolite influences the duration of the initial induction period, the diffusion characteristics of the boundary layer of reaction products, and the structural evolution of the C–S–H reaction product. Alkali-exchanged clinoptilolites show a higher pozzolanic reactivity, a more permeable reaction product layer, and longer silicate chains in the C–S–H phase compared to their Ca-exchanged counterpart. The temperature dependence of the reaction rate coefficients in the lime–chabazite tuff pastes obeys the Arrhenius equation.

Mineralogy, Geochemistry, and Diagenesis of Clinoptilolite Tuffs (Miocene) in the Central Simav Graben, Western Turkey

AbstractMiocene rifting and associated rhyolitic (K-rich) volcanism resulted in the deposition of pyroclastic material in the central Simav graben, near Karacaderbent, Turkey. The pyroclastics were deposited in a lacustrine environment, altered to clinoptilolite-rich tuffs and cross-cut by several transform faults along which hydrothermal fluids circulated. Petrography and quantitative phase analysis by X-ray diffraction show that the Karacaderbent tuff consists mainly of the diagenetic products clinoptilolite, opal CT, smectite, and celadonite. Electron microprobe analyses and cation exchange capacity (CEC) measurements confirm the predominance of K-rich clinoptilolite. Near fault zones, clinoptilolite was replaced by authigenic opal CT and alkali feldspar, and the remaining clinoptilolite was enriched in Na. Silicification around fault zones was confirmed by X-ray fluorescence. Zeolitization of K-rich rhyolitic starting materials took place under mildly alkaline, low-salinity conditions, probably in a closed hydrologic system. The subsequent hydrothermal alteration along faults had only a minor impact. The homogeneous nature, large (74–87 wt.%) clinoptilolite content, large CEC, and K-rich composition of the deposit favor exploitation of this material for applications in agriculture, horticulture, and waste-water purification; as feed additives; and as pozzolans for cement production.

Clinoptilolite as a new proxy of enhanced biogenic silica productivity in lower Miocene carbonate sediments of the Bahamas platform: Isotopic and thermodynamic evidence

Massive clinoptilolite authigenesis was observed at about 1105 meters below sea floor (mbsf) in lower Miocene well-compacted carbonate periplatform sediments from the Great Bahama Bank [Ocean Drilling Program, ODP Leg 166, Site 1007]. The diagenetic assemblage comprises abundant zeolite crystallized within foraminifer tests and sedimentary matrix, as well as Mg smectites. In carbonate-rich deposits, the formation of the zeolite requires a supply of silica. Thus, the objective of the study is to determine the origin of the silica supply, its diagenetic evolution, and consequently the related implications on interpretation of the sedimentary record, in terms of local or global paleoceanographic change. For lack of evidence for any volcaniclastic input or traces of Si-enriched deep fluids circulation, an in situ biogenic source of silica is validated by isotopic data and chemical modeling for the formation of such secondary minerals in shallow-water carbonate sequences. Geochemical and strontium isotopic data clearly establish the marine signature of the diagenetic zeolite, as well as its contemporaneous formation with the carbonate deposition (Sr model ages of 19.6–23.2 Ma). The test of saturation for the pore fluids specifies the equilibrium state of the present mineralogical assemblage. Seawater–rock modeling specifies that clinoptilolite precipitates from the dissolution of biogenic silica, which reacts with clay minerals. The amount of silica (opal-A) involved in the reaction has to be significant enough, at least 10 wt.%, to account for the observed content of clinoptilolite occurring at the most zeolite-rich level. Modeling also shows that the observed amount of clinoptilolite (∼ 19%) reflects an in situ and short-term reaction due to the high reactivity of primary biogenic silica (opal-A) until its complete depletion. The episodic occurrence of these well-lithified zeolite-rich levels is consistent with the occurrence of seismic reflectors, particularly the P2 seismic sequence boundary located at 1115 mbsf depth and dated as 23.2 Ma. The age range of most zeolitic sedimentary levels (biostratigraphic ages of 21.5–22 Ma) correlates well with that of the early Miocene glaciation Mi-1 and Mi-1a global events. Thus, the clinoptilolite occurrence in the shallow carbonate platform environment far from volcanogenic supply, or in other sensitive marine areas, is potentially a significant new proxy for paleoproductivity and oceanic global events, such as the Miocene events, which are usually recognized in deep-sea pelagic sediments and high latitude deposits.

GEOLOGICAL AND MINERALOGICAL CHARACTERIZATION OF SOME ZEOLITIZED TUFFS FROM NWRN TRANSYLVANIA, ROMANIA

Zeolites are the most common products of transformation of silicic volcanic glass in the NW-rn part of Transylvania (Romania). Representative samples of volcanic tuffs from Mäcicas (Cluj county) were investigated by using optical (polarized light) microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and wet chemical analyses. The volcanic tuffare vitreous with an acid composition. Vitreous matrix and glass shards are replaced by zeolite minerals, mainly clinoptilolite and trace amounts ofopal-CT and mordenite. X-ray diffraction semiquantitative analysis indicated that clinoptilolite represent between 60 % and 70 % of the crystalline fraction of the tuff. The clinoptilolite content of the Mäcicas tuff deposits is one of the richest in Romania. According to the present status in the zeolite market in Europe, this deposit could have industrial potential in the construction industry and in environmental applications.

Zeolites and zeolitization of acid pyroclastic rocks from paroxysmal Paleogene volcanism, Eastern Rhodopes, Bulgaria

An extensive bimodal volcanic suite developed in the Late Paleogene in the Eastern Rhodopes Mountains, Southern Bulgaria. Most of the widespread and thick rhyolitic tuffs and ignimbrites, erupted during two major Early Oligocene acid phases, were emplaced in a shallow marine environment and subsequently altered. K-rich Ca-clinoptilolite (in some places K-clinoptilolite, mordenite or analcime), clay minerals (celadonite or/and smectite), adularia (or albite) and opal-CT replace the volcanic glass. The zeolitized pyroclastic rocks are strongly depleted in MnO, Na2O, K2O, and enriched in CaO, Fe2O3, TiO2 and MgO. Regional zoning in distribution of the major glass-replacing minerals has been established: quartz + adularia (or albite) ± zeolites in the proximal to the vent area; zeolites in the medial and clay minerals in the distal area. Vertical zoning has been also recognized because only the basal pyroclastic layer is transformed into adularia + quartz whereas clinoptilolite, accompanied by opal-CT and clay minerals, prevails in the rest of the section. The zeolitized glass shards are characteristically zoned: (1) a thin rim (<5μm thick) of celadonite coats the shard surface retaining their original shape; (2) a 30–50μm-thick zone, made of contiguous platy zeolite crystals, oriented perpendicular to the rim and (3) a central zone of large euhedral crystals, surrounding a central hollow area. Phenocrysts are not affected by the zeolitization and some relict glass is found in the top of the pyroclastic section. According to the semiquantitative X-ray analysis and heat of immersion test of Culfaz et al. (1973) the clinoptilolite content in the zeolitized pyroclastic rocks varies from 38 to 72 wt.%. The cation exchange capacity values range between 40 and 153 meq/100 g and show a significant positive correlation with clinoptilolite content obtained by the heat of immersion test (r = 0.71). The lateral zoning and presence of typical hydrothermal minerals such as celadotite indicate that zeolitization of the thick Eastern Rhodopes pyroclastic series results from the operation of a large low temperature hydrothermal system. The hydrothermal solutions consist of marine water heated by the anomalous geothermal gradient of the active volcanic areas or/and by the hot pyroclastic deposits.

The effect of electron irradiation on the optical properties of the natural armenian zeolite-clinoptilolite

Abstract Infrared (IR) absorption and luminescence in chemically and radiation-modified natural Armenian Zeolite (clinoptilolite) samples have been studied. The luminescence was studied in 390–450 nm and 620–710 nm wavelength bands, and the IR measurements were carried out in the 400–5400 cm−1 range. It is shown that the luminescence intensity depends on the content of pure clinoptilolite in the samples and, probably on the distribution of “passive” luminescence centers over Si and Al sites that became “active” under radiation or chemical treatment. The samples of electron irradiated clinoptilolite have higher luminescence intensity than the chemically and thermally treated ones. A decrease in the intensity of IR absorption bands at 3550 cm−1 and 3650 cm−1 was found after irradiation.

Mathematical modeling of the ion exchange processes of sodium clinoptilolite with heavy metal ions from residual waters

The ion-exchange capacity of volcanic tuff in the Na+ form (70% clinoptilolite content), used for removing heavy metals in residual waters, was investigated under different conditions (temperature, time and exchange solution concentration). These parameters are necessary and sufficient for the mathematical modeling of the ion-exchange process. The corresponding mathematical models show common characteristics due to the good arrangement of the experimental points on the response surfaces and correlation coefficients close to unity. Differences appear with respect to the shape of the response surface and model equations. .

Calculation of chemical composition of zeolites in mordenite-clinoptilolite rocks

Individual chemical composition of mordenite and clinoptilolite, which are both found in zeolite rocks and acid modification effect on them have been calculated. For the purpose of this study, samples of rocks of the same deposit (village Lypcha, Transcarpatia) with different content of mordenite and clinoptilolite have been used.

Zeolites in biomedical application: Zn-exchanged clinoptilolite-rich rock as active carrier for antibiotics in anti-acne topical therapy

A clinoptilolite-rich rock was evaluated as inorganic Zn 2+ releasing carrier for antibiotic erythromycin. The perspective is its use in the topical treatment of acne, a diffused skin pathology, given the efficacy of zinc-erythromycin combination against resistant Propionibacterium strains. The tested rock is an ash-rich epiclastite collected in Northern–Central part of Sardinia island (Italy). ICP chemical analyses of the bulk rock evidenced a composition compatible with topical applications. A 66 wt.% of clinoptilolite content was determined by means of XRD analysis (reference intensity ratio [RIR] technique). EDS chemical analyses of zeolite crystals were performed on polished thin section. The CEC of the rock is 1.45±0.08 meq/g. Using a specific exchange method, the material was previously Na-conditioned then Zn-conditioned. A substantially complete Zn-form was obtained, as demonstrated by AAS analyses. A back-exchange reaction toward Na-form was performed in the same conditions (65 °C in 1 M NaCl solution): zinc release was fast and almost complete (94%). Zn-conditioned powder was then micronized to achieve a volume/surface ratio suitable for a topical therapy. After micronization, the specific surface area, determined by BET gas adsorption, was 30.2 m 2/g, and 92% of the powdered rock was lower than 30 μm in size (measured by a Coulter Counter apparatus); the so-called “volume-surface diameter” was 6.48 μm, compatible with the intended topical application. Zn 2+ release was measured on micronized rock at 37 °C both in physiologic solution as in 0.05 M KH 2PO 4/Na 2HPO 4 buffer. Also in these conditions, a prompt and significant zinc release was recorded: after 30 min, 68% and 60%, respectively. Erythromycin was charged onto the micronized material using a solvent evaporation method. HPLC determinations showed that 85% of the drug contacted with the carrier was loaded. The simultaneous release of zinc and erythromycin were evaluated in phosphate buffer. Eighty-two percent of the loaded antibiotic was released after 30 min. Zinc exchange is substantially unaffected by the contemporary drug release. The request to file an international patent for this pharmaceutical application has been accepted by the European International Preliminary Examination Office.

Effects of Mineralogy, Exchange Capacity, Surface Area and Grain Size on Lithium Sorption to Zeolitic Alluvium near Yucca Mountain, Nevada

AbstractThe Li+ ion is used frequently as an environmentally acceptable surrogate for sorbing radionuclides in field tracer tests, and experiments using Li are an important part of assessing the potential transport of radionuclides in saturated alluvium south of Yucca Mountain, Nevada, the site of a proposed nuclear waste repository. Equilibrium partition constants (Li+ Kds) were measured using batch studies incorporating a wide range of Li+ concentrations and two different grain-size fractions of alluvium samples from multiple depth intervals in two wells. Cation exchange capacity, surface area, bulk mineralogy from quantitative X-ray powder diffraction, and trace Mn- and Fe-oxyhydroxide mineralogy from extractive studies were evaluated as predictors for linearized Li+ Kd values (K1in) in the alluvium. Many of the predictor variables are correlated with each other and this was considered in the analysis. Linearized Kd values were consistently higher for fine particle-size fractions than for coarse fractions. Single and multivariate linear regression analyses indicated that the clinoptilolite + smectite content, taken together as a combined variable, was the best predictor for Li+ sorption in the alluvium, although clinoptilolite content was clearly a better predictor when the two variables were considered separately in simple linear regressions. Even so, Li+ Klin predictions based on clinoptilolite and smectite abundance were accurate only to within about ±100%. This uncertainty suggests that there is either a high inherent variability in Li+ Klin values or that additional alluvium characteristics not measured or evaluated here may play an important role in simple Li+ cation exchange in the alluvium.

Barium-rich authigenic clinoptilolite in sediments from the Japan Sea—a sink for dissolved barium?

Exceptional barium-rich clinoptilolite, a heulandite-group zeolite, with Ba contents of up to 1.83 wt.% BaO occurs in Miocene sediments from the Yamato Basin of the Japan Sea (ODP Site 797). The clinoptilolites with highest Ba-concentrations occur directly below the base of the sulfate reduction zone, where pore water Ba concentrations are high due to the dissolution of biogenic barite. Downcore variations of the Ba content in clinoptilolites and pore water show that the formation of Ba-rich crystals at 299 m depth coincides with a decrease of the pore water Ba concentration. Thus, formation of Ba-rich zeolites seems to provide a sink for dissolved Ba, although the occurrence of authigenic barite near the base of sulfate reduction might also contribute to the depletion of pore water Ba. These findings show that the intrachannel cation content of authigenic clinoptilolite is not directly controlled by a mineralogical precursor, but seems to reflect the geochemical conditions of the surrounding pore fluids. The formation of Ba-rich clinoptilolites in a sulfate-depleted environment with elevated pore water Ba concentrations and the concurrent decrease of dissolved Ba in the pore fluids documents the mutual influence of pore water composition and mineral chemistry during diagenetic processes in marine sediments.

Redeposited zeolitic rocks from the NE Rhodopes, Bulgaria

The redeposited zeolitic rocks of Early Oligocene age in the NE Rhodopes, Bulgaria, are composed of zeolitic rock fragments. Material for the study was collected from four sections situated to the north of the Arda river, Haskovo district. These rocks occurred in a rhythmic series of sediments, occupying the interval between the products of two episodes of acidic volcanism (Lower Oligocene). They consist predominantly of subangular to subrounded clinoptilolitic rock fragments in which are preserved the specific relict textures of earlier zeolitized volcanic glass shards. The clinoptilolite content, which has been determined both under the microscope and by X-ray diffraction, varies between 10% and 80% but is usually about 50% by volume. Implications for the paleogeographic and tectonic regime of the area are considered.

The properties of the NH 4-clinoptilolite. Part 1

A clinoptilolite sample from the Zlatokop deposit (Vranje, Yugoslavia) was transformed into the mono-ionic ammonia form. Changes in the behavior of thermally treated NH 4 -clinoptilolite at T ⩾ 473 K were followed by thermal analysis (d.t.a., d.t.g., t.g.), X-ray analysis, chemical and i.r. analysis. On the basis of the results of X-ray analysis and ion exchange data, the content of clinoptilolite (about 85% w/w) and ingredients quartz and feldspars (about 15% w/w) were determined in the original sample from the deposit. Ion exchange did not affect significantly parameters of the unit cell of clinoptilolite. The prepared mono-ionic ammonia form of clinoptilolite was calcined in the temperature range 473–773 K under isothermal conditions. The structural changes in these samples were followed by X-ray analysis, which showed that the crystallinity of the calcined samples was preserved. Thermal analysis showed that the process of dehydration was developing at temperatures from 378 to 416 K, and the exothermal process of oxidation of ammonia to oxides of nitrogen at temperatures from 784 to 810 K. At T ⩾ 673 K the process of dealumination of clinoptilolite framework occurred too, when cationic aluminum formed different forms, depending on the temperature of calcination. By analyzing i.r. spectra of the calcined samples it was established that the degree of dealumination was the same for all samples treated at T ⩾ 673 K.

Hydrogeologic control on zeolitic diagenesis of the White River sequence

Smectite, opal-CT, and clinoptilolite are common alteration products in the White River sequence, a mid-Tertiary unit in the Great Plains and northern Rocky Mountains. The White River sequence is largely made up of fine-grained tuffaceous material that is rich in unaltered rhyolitic glass. Smectite is ubiquitous, and it or a precursor phase was present during White River soil formation but also formed after burial. Smectite Fe (from 5% to 7% Fe 2 O 3 ) and Ti (from 0.4% to 0.8% TiO 2 ) concentrations in mud rocks suggest formation from dacitic to latitic glass. Rhyotitic glass, however, was the primary source for opal-CT and clinoptilolite. Opal-CT and clinoptilolite have a highly variable distribution over macroscopic to regional scales of observation. Stable isotopic compositions of smectite (δ 18 O (SMOW) = 11.8‰ to 13.3‰), opal-CT (δ 18 O (SMOW) = 19.9‰ to 24.3‰), and late diagenetic calcite (δ 18 O (SMOW) = 10.3 ± 2.0‰) suggest that burial diagenetic reactions took place at temperatures ranging from 27 to 55 °C. Clinoptilolite apparently formed in areas with high contact times between paleoground water and vitroclastic material. In White River rocks of Wyoming, clinoptilolite occurs only in localities that are interpreted as lying within paleo-ground-water discharge zones. In the Great Plains, clinoptilolite is rare in eastern Colorado and southern Nebraska but progressively increases in abundance to the north, reflecting a northward decrease in permeability. Zeolitic alteration near Douglas, Wyoming, changed the hydrologic role of tuffs from aquifers to aquitards. Tuffs were originally aquifers because of their high Permeability (>30 md) relative to interbedded mud rocks (10 -4 to 1 md), Signigicant thicknesses (0.5 to 2 m presentday), and lateral continuity. Tuff alteration, however, decreased permeability by ∼4 orders of magnitude relative to glass-rich portions. Similar diagenetic effects on mud-rock permeabilities are likely. Mass flux into altered tuffs at Douglas is indicated by an increase in bulk rock density from ∼1.3 g/cm 3 for glass-rich tuff to ∼1.7 and ∼2.0 g/cm 3 , respectively, for zeolitic and siliceous counterparts. Local silica redistribution accouts for the bulk of the density increases. A systematic increase in Ba content of clinoptilolite over a 150-m vertical section (from 0.1 to 6.6 mol% of the exchangeable cations) suggests that it was derived from underlying units.

Effects of Mineralogy on the Sorption of Strontium and Cesium Onto Calico Hills Tuff

ABSTRACTSorption and desorption measurements were made of strontium and cesium onto clinoptilolite and Calico Hills tuff. The object was to see whether there was a correlation between sorption of strontium and cesium onto Calico Hills Tuff and the clinoptilolite based on the content of clinoptilolite in the Calico Hills Tuff. If sorption onto Calico Hills Tuff is solely due to the presence of clinoptilolite, then the ratios of the sorption ratios on tuff to those on clinoptilolite at similar conditions should be the weight fraction of the clinoptilolite in the tuff. Since the tuff contained about 50% clinoptilolite, the ratios would be expected to be about 0.5 if sorption was due solely to clinoptilolite. The experimental evidence showed that the ratios were generally near 0.5 for both cesium and strontium sorption and that ion-exchange processes were operative for both the clinoptilolite and the tuff. However, the ratios differed to a small extent for different conditions, and there were indications that other sorption processes were also involved.

化学処理による斜プチロルフッ石系凝灰岩の物理化学的特性の変化 ＩＩＩ 水酸化ナトリウム溶液処理による影響

The effect of alkali treatment on some physico-chemical properties of clinoptilolite tuff from Futatsui, Akita Pref., was investigated by means of powder X-ray diffraction, chemical analyses, measurement of CO2 adsorption and gaschromatography. The material was treated with 0.01-5N NaOH aqueous solution at 97-98°C in the water bath for 2 hrs. At the concentration of NaOH below 1N, only silica in the tuff was dissolved without changing of the clinoptilolite structure. The content of clinoptilolite relatively increased a little due to the removal of α-cristobalite in the concentration range of 0.25-1N and hence the ratio of silica to alumina decreased from 9.9 in the original tuff to 8.1-7.7. The chemical compositions such as silica, alumina, etc. were dissolved at the concentration of 2-5N and therefore the ratio of silica to alumina in the treated tuff decreased sharply. Intensity of X-ray diffraction peak 132 of clinoptilolite and the amount of CO2 adsorbed also decreased with the increasing of the concentration of NaOH above 2N. These decreases corresponded to the degree of clinoptilolite structure collapsed. By alkali treatment, Na+ ion exchanged H+ and a part of K+ in the clinoptilolite but not Ca++ and Mg++. In the concentration range of 0.25-1N, the ratio of Na to all cations in the samples increased from 29.6% in the original tuff to around 50%. Alkali treatment for clinoptilolite tuff contracted the pore size of clinoptilolite. Consequently the adsorption rate of CO2 became slowly with the increase of NaOH concentration. Also evil affections were observed for the gascrhomatographic separation.