Zeolitic Rocks Research Articles

Mineralogical Characteristics and Cationic Exchange Properties of a Zeolite Mineral from Romana, NW Sardinia, Italy

AbstractAn investigation was conducted into the Tertiary ignimbrite formations in the Romana area in NW Sardinia. Scanning electron microscopy–energy‐dispersive spectrometry indicated the presence of clinoptilolite and subordinate smectite, quartz, mordenite and calcite. Laboratory analyses of representative samples collected from the deposit indicated a cation exchange capacity ranging from 85 to 135 mEq per 100 g. Ion exchange experiments conducted in flasks containing different initial cation concentrations and in columns supplied with solution having constant cation concentration, showed different selectivity towards the cations examined, in the order: NH4+> Pb2+> Cd2+> Cu2+> Zn2+> Mn2+> Ni2+. Compared to the untreated material, under the experimental conditions used and considering the eluate, and the Italian regulatory limits for discharge into surface waters, the zeolite treated with a 1‐N NaCl solution yielded a 1.3–5‐fold increase in the volume of treated water, depending on the cation examined. The experimental results obtained show that the cationic exchange properties of the zeolite rock from the Romana deposit are comparable with the average quality of zeolites currently imported into Italy from non‐European countries.

Phenol sorption on surfactant-modified Mexican zeolitic-rich tuff in batch and continuous systems

Surfactant modified clinoptilolite-rich tuff was used for the removal of phenol from aqueous solutions. The zeolitic rock from Oaxaca (Mexico) was treated with sodium chloride and then modified with hexadecyltrimethylammonium chloride or bencylcetildimethylammonium chloride in different experimental conditions. Phenol sorption isotherms and column experiments were performed; in both cases, phenol was determined in the aqueous solutions by UV–vis spectroscopy. The results showed that the sorption of phenol depends on the quantities of surfactant in the zeolitic rocks, the kind of surfactant, modification conditions and pH of the solutions. When the initial concentration of phenol increased, the adsorption of phenol in the surfactant-modified zeolite increased and the experimental data was best adjusted to the Langmuir model. The saturation of the columns rapidly reached high percentages.

EFFECTS OF PREPARATION AND EXPERIMENTAL CONDITIONS ON REMOVAL OF PHENOL BY SURFACTANT‐MODIFIED ZEOLITES

The removal of phenol from aqueous solutions using surfactant‐modified clinoptilolite‐rich tuffs (SMZ) prepared from two Mexican zeolitic tuffs (Chihuahua and Oaxaca) was investigated. Sodium homoionization of the zeolitic rocks was performed before they were modified with the surfactants: hexadecyltrimethylammonium chloride or bromide and bencylcetildimethylammonium chloride. The surfactants in the modified zeolitic materials were determined considering the total carbon in the samples. The phenol removal was determined in a batch system taking into consideration the different quantities of surfactants in the zeolitic tuffs, contact time, pH and initial phenol concentration. The phenol was determined in the aqueous solutions by UV/Vis spectroscopy. Results showed that the formation of a hemimicelle or admicelle on the zeolites depended on the initial surfactant concentration and they were responsible for the type of interactions between the phenol and the surfactant‐modified zeolites. Phenol adsorption by the surfactant‐modified zeolites was carried out in approximately three hours. Phenol adsorption data was best adjusted to the pseudo‐second order kinetic model. Both, surface properties of the surfactant‐modified zeolites and pH of solution play an important role in the removal of this pollutant from aqueous solutions and they are responsible for the type of mechanism involved.

Application of zeolitic volcanic rocks for arsenic removal from water

Natural zeolitic rocks consisting mainly of chabazite-phillipsite, clinoptilolite, and volcanic glass have been evaluated by means of batch methods to remove arsenic from waters with different mineralization degree (from deionized water to natural water with a specific conductivity of 1,600 μS cm − 1 ). Arsenic was previously spiked in the studied waters at concentrations of about 100 µg l − 1 to simulate actual cases. The compositional range of natural waters is representative of large hydrogeochemical regions around the world. The experiments were focussed on the application of natural common zeolitic rocks to water treatment for human consumption. The removal efficiency observed rises, in the better cases, 60–80% for chabazite-phillipsite raw materials whereas is 40–60% for clinoptilolite-bearing ones. The arsenic removal tends to increase with water mineralization degree, independently of the zeolitic rock type. A large zeolitic content in the chabazite-phillipsite raw materials increase the removal. Instead, the inverse situation is observed in the clinoptilolite-bearing rocks. The relevance of the quantitative mineralogical analysis, determining also the content of volcanic glass, as well as the use of natural waters in the removal tests has been demonstrated.

Zeolitic rocks used as pigment for ceiling paints. Activation of the rock

The performance of a zeolitic rock, mainly clinoptilolite, was evaluated in ceiling paints, due to its adsorption properties. Natural and heated at 350 and at 800 °C materials were tested. The mineralogical and petrographical composition of the zeolitic rock as well as the chemical composition and thermal behavior were studied. Ceiling paints, with a PVC of 75% and 11.3% (by volume) of zeolitic rock were formulated. The behavior of the paints was assessed by humidity and ammonium adsorption tests and by adsorption–desorption cycles. A paint formulated without zeolitic rock was used as a blank. Higher adsorption values were obtained when using heated zeolitic rock in the formulation. The cyclic essays performed showed that the adsorption properties of the paints were half recovered within three hours.

Removal of Cadmium By Natural and Surfactant-Modified Mexican Zeolitic Rocks in Fixed Bed Columns

The dynamic removal of cadmium from aqueous solutions by natural and surfactant-modified Mexican zeolitic rocks (clinoptilolite–heulandite type) in fixed bed column systems was investigated. The performances of fixed bed columns were described through the breakthrough curves obtained from column experiments and the values of column parameters predicted as a function of bed height. The column adsorption data were evaluated in terms of the bed adsorption capacity and the efficiency of the process. The experimental results fitted well the bed depth service time model (BDST) for both adsorbents, and the empty bed residence time model (EBRT) was used to optimize column operating conditions. The surface modification of the zeolitic rock with surfactant affected the removal of cadmium in fixed bed systems. Moreover, a column experiment with surfactant modified zeolitic rock previously saturated with 4-chlorophenol was carried out and the results showed that this saturation had a negative effect on the performance of the column.

Sorption and Desorption of Dye Remazol Yellow onto a Mexican Surfactant-modified Clinoptilolite-rich Tuff and a Carbonaceous Material from Pyrolysis of Sewage Sludge

The sorption behavior of dye remazol yellow using surfactant modified zeolitic rock and a carbonaceous material obtained by pyrolysis of sewage sludge and treated with HCl (1.0%) solution was determined. The kinetic and sorption isotherms experimental results were best adjusted to the pseudo-second order model and to the Langmuir-Freundlich isotherm model which indicate that the sorption process is chemisorption on heterogeneous materials. Remazol yellow could be removed from the saturated modified zeolitic material by different processes, unfortunately, the surfactant was removed together with the dye, the best results were found using Fenton's reagent. Thermal treatment was the best method found to remove the dye from the carbonaceous material.

Characteristics of lightweight aggregates from primary and recycled raw materials

In the following, a brief survey of mineral lightweight granules manufactured on the basis of a wide variety of constituents is given. After that, research projects conducted at the Tomsk Polytechnic University (Russian Federation) and Bauhaus University Weimar (Germany) are introduced that focus on the development of lightweight aggregates from new raw materials sources. In Tomsk, zeolitic rocks were used, while the investigations in Weimar concentrated on the sand fraction of masonry rubble mixed with autoclaved aerated concrete.

A new pigment for smart anticorrosive coatings

The purpose of this paper was to evaluate the performance of a modified zeolite as an anticorrosive pigment for paints. A procedure to prepare the pigment was outlined and its anticorrosive properties assessed following the electrochemical behavior of a steel electrode in pigment suspension. In a second stage, alkyd paints were formulated employing different anticorrosive pigments: (1) 30% by volume (v/v) of the modified zeolitic rock, (2) 10% (v/v) of zinc phosphate, and (3) a mixture of 10% (v/v) zinc phosphate plus 20% (v/v) of the modified zeolitic rock. In every case, percentages were referred to the total pigment content. Titanium dioxide, zinc oxide, and barium sulfate were incorporated to complete the pigment formula. The pigment volume concentration/critical pigment volume concentration (PVC/CPVC) ratio was 0.8. The performance of the resulting anticorrosive paints was assessed by accelerated (salt spray and humidity chambers) tests and electrochemical (corrosion potential, ionic resistance, and polarization resistance) essays. It was demonstrated that the modified zeolite is effective in protecting steel from corrosion when it is used in combination with zinc phosphate. There exists a synergism between the modified zeolite and zinc phosphate that allows the zinc phosphate content in anticorrosive paints to be reduced.

Granulated foam glass–ceramic material from zeolitic rocks

The objective of this research work was to investigate the production of granulated foam glass–ceramic material from zeolitic rocks. The investigations have shown that grinding raw materials to particle size less than 0.5 mm and adding 13.8% of alkali content provide production of material with the following properties: particle density – 340 kg/m 3, strength – 1.6 MPa and water adsorption – 13% at firing temperature of 850 °C. Expanded zeolite with alkali content is a material of glass–ceramic composition with amorphous part of 38.6% and crystalline part of 61.4% that gives higher strength in comparison with sponge glass.

Sorption Behavior of 4-Chlorophenol from Aqueous Solutions By a Surfactant-modified Mexican Zeolitic Rock in Batch and Fixed Bed Systems

The removal of 4-chlorophenol from aqueous solutions by both a Mexican clinoptilolite-heulandite zeolitic rock and the modified zeolitic material with the surfactant hexadecyltrimethylammonium bromide (HDTMABr), using batch and packed-bed (column) configurations, was investigated. The unmodified zeolitic rock did not show any adsorption of 4-chlorophenol. The effects of pH, contact time and concentration of 4-chlorophenol on the adsorption process by the surfactant modified material were examined. The sorption of 4-chlorophenol was not affected by the pH range from 4 to 9.5. 4-chlorophenol retention reached equilibrium in about 18 h and the rate of 4-chorophenol adsorption by the modified material was faster in the first 10 h than later. The experimental data were treated with the models: pseudo-first order, pseudo-second order, fractional power and Elovich models. Although, the last three gave correlation coefficients higher than 0.96, the pseudo-second order model was the best to describe the reaction rate. The experimental data follow a linear isotherm which is characteristic for sorption of organic solutes by the partition mechanism. The Bed Depth-Service Time Model was applied to the sorption results in order to model the column operation. The results showed that the surfactant modified zeolitic rock could be considered as a potential adsorbent for 4-chlorophenol removal from aqueous solutions.

THE CATION EXCHANGE CAPACITY OF THE GREEK ZEOLITIC ROCKS

Forty two zeolitic rock samples, from the Prefectures ofEvros, Rhodope, Samos and Cyclades, have been investigated for their cation exchange capacity (CEC, in meq/100g) and the mineralogical composition (wt.%), using the Ammonium Acetate Saturation method and Powder X-ray Diffraction method, respectively. HEU-type zeolite (heulandite-clinoptilolite) was found in Ρ etrota area (43-89 wt.%, CEC 101- 217), Samos island (34-91 wt.%, CEC 93-217), Pentalofos area (68-74 wt.%, CEC 124-202), Metaxades area (47-64 wt.%, CEC 119-140) and Thira island (33 wt.%, CEC 118). Mordenite was found in Samos island (64 wt.%, CEC 150), Polyegos island (61 wt.%, CEC 136), Thira island (56 wt.%, CEC 130), Milos island (45 wt.%, CEC 97), Kimolos island (30 wt.%, CEC 96) and Feres area (5 wt.%, CEC 22). Analcime was found in Samos island (27-71 wt.%, CEC 104-285) and Darmeni area (16 wt.%, CEC 62). Chabazite was found in Samos island (66 wt.%, CEC 243). HEU-type zeolite+mordenite were found in Feres area (45-74 wt.%, CEC 132-209), Samos island (81 wt.%, CEC 184), Thira island (72 wt.%, CEC 177), Polyegos island (66 wt.%, CEC 153) and Skaloma area (51-60 wt.%, CEC 126-143). HEUtype zeolite+phillipsite were found in Samos island (47 wt.%, CEC 170) and HEUtype zeolite+analcime were found in Samos island (55 wt.%, CEC 129). The CEC of the zeolitic rocks show positive correlations with the type of zeolite and the microporous minerals (zeolites+micas+clay minerals) content, mainly affected by the zeolites and to lesser extent by micas and clay minerals.

Sorption of cobalt by two Mexican clinoptilolite rich tuffs zeolitic rocks and kaolinite

The sorption of cobalt from aqueous solutions was studied for two Mexican clinoptilolite rich tuffs zeolitic rocks and kaolinite clay. The effects of pH and contact time on the sorption were examined. Cobalt was determined by neutron activation analysis of the exchanged aluminosilicates. The sorption of cobalt by the aluminosilicates was similar in the pH range from 4 to 7. Kinetic studies showed a rapid sorption in the first 5 hours and equilibrium in about 24 hours. Sorption kinetics was best described by the second-order Ritchie modified model. The experimental results obtained at different concentrations and room temperature for both zeolites were fitted to Freundlich, Langmuir and Freundlich-Langmuir isotherms. The sorption pattern was found to follow the Freundlich model.

Characterization and pozzolanicity of zeolitic rocks from two Cuban deposits

A chemical, mineralogical and microstructural study was conducted on zeolitic rocks from two different formations in Cuba (Carolinas and Los Congos) to assess their value as pozzolanic components for cement. The samples were characterized using XRD, FTIR, BSE/EDX, optical microscopy 29Si and 27Al MAS NMR and BET-specific surface techniques. The studies showed the Carolinas rock to be hypocrystalline (predominantly glass) and contain subautomorphic and automorphic heulandite and/or clinoptilolite crystals, allotriomorphic calcite crystals–also present around the edges of the vacuoles–, and small, unevenly distributed masses of Fe and Ti oxide. Los Congos sample was found to be a vitreous (holohyaline), perlitic rock whose constituents included albite, small amounts of quartz, tiny veins and unevenly distributed specks of calcite, and Fe and Ti oxide appearing around the edges of cracks, as a cover over the veins and isolated masses, in addition to faujasite. Finally, both rocks were found to have pozzolanic properties. Both rocks exhibited pozzolanic properties, although the reaction rate with portlandite was much higher in the Carolinas than in the Los Congos samples. This result was related not to the particle size distribution of the materials, but to their soluble SiO 2 content and mineralogy.

Thermal behaviour of a zeolitic tuff

Natural zeolites undergo structural changes after heating which open their possible use in different fields, related to their chemical and physical properties, such as building stone, lightweight aggregate, ceramic foam, concrete bricks, tiles, porcelain stoneware and additive in puzzolonic cements. In this study, thermal behavior of zeolitic tuff quarried from Gördes-Manisa, region of Turkey was investigated. Zeolitic rocks were first reduced to 2 μm and pellets were prepared by dry-pressing. The pellets were heated for 30 min in the temperature range of 200–1200 °C. Heating the tuff up to 600 °C did not cause any structural change detectable by X-Ray powder diffraction (X-Ray), Fourier Transform Infrared Spectroscopy (FTIR) and thermal characterization methods with regard to the original sample, while further increase in the temperature caused structural breakdown of zeolitic tuff. The appearance of the broad low intensity peaks in X-Ray diffraction diagrams indicated most probably a partial transformation of crystal structure into an amorphous structure. The Scanning Electron Microscopy (SEM) micrographs showed that the crystals seen in the original rock sample were broken during grinding and pressing processes. The crystal structure disappeared above 1000 °C and the spherical pores was observed at 1200 °C. Chemical composition of the zeolitic tuff did not change significantly with respect to temperature. The highest density (2.28 g/cm 3) and hardness (387 Hv) were obtained by sintering the pellets at 1000 °C for 30 min.

Sorption of Cadmium from Aqueous Solutions at Different Temperatures by Mexican HEU-type Zeolite Rich Tuff

Many factors may affect the heavy metals sorption on natural zeolites among them the temperature, for this reason in this paper the cadmium retention behavior on Mexican zeolitic rich tuff as a function of temperature is considered. The kinetic and the isotherms were determined at 303, 318, and 333 K, the remaining cadmium in the solution samples was analyzed by atomic absorption spectrometry. The pseudo-second order rate constant, k, as well as the apparent diffusion coefficients were calculated from the cadmium uptake by the zeolitic rock as a function of the contact time and temperature, the highest amounts were found for the experiments done at 333 K. The maximum cadmium adsorption capacity by the zeolitic material was 12.2 mg Cd2+/g at 318 K corresponding to 20% of the effective ion exchange capacity of the Chihuahua zeolitic rock. In order to explain the cadmium sorption behavior different kinetics and isotherm models were considered.

Pozzolanic reactivity of zeolitic rocks from two different Cuban deposits: Characterization of reaction products

Volcanic pozzolans are vitreous or poorly crystallized materials rich in SiO 2 and Al 2O 3 that react with the portlandite generated during cement hydration to yield hydrated calcium silicates and aluminates with low solubility and good cementitious properties (pozzolanic reaction). The purpose of the present study was to analyze the reaction between calcium hydroxide and two natural, partially crystalline pozzolans found in Cuba, characterize the C–S–H gels produced and determine the relationship between pozzolan composition and structure and its capacity to fix calcium. The findings of the XRD and FTIR analyses conducted with this aim included a gradual decline of the zeolite (heulandite and faujasite) peaks on the diffractograms with reaction time, and changes in the IR absorption bands attributed to the zeolites, along with the appearance of new bands indicative of the formation of the CSH gel. Although the amount of Ca fixed by the two pozzolans after 90 days was similar, the reaction rate was faster in the Los Congos material. The gel forming in the Carolinas sample had Al in its composition, with Q 3 (1Al) and Q 2 (1Al) units whose content increased with time. The presence of Fe in the Los Congos sample hampered the analysis of the gel formed, although the presence of Al in its composition could be inferred from the 27Al MAS NMR data. The thermodynamic data showed that C–S–H gel was formed in both cases.

The role of clinoptilolite in organo-zeolitic-soil systems used for phytoremediation

The present work is an extension of earlier research [Leggo, P. (2000) An investigation of plant growth in an organo-zeolitic substrate and its ecological significance. Plant and Soil, 219: 135–146.] in which zeolitic tuffaceous rock containing clinoptilolite, a commonly occurring natural zeolite mineral, was composted with organic waste to produce a very effective bio-fertilizer thought to be activated by a very large increase in the population of nitrifiers. This material has now been modified by the addition of extra untreated zeolitic tuff (i.e. un-ammoniated clinoptilolite). Comparing plant growth in a series of substrates containing increasing amounts of zeolitic tuff the limit of growth enhancement has been established. Aqueous leachate analysis has demonstrated a correlation between shoot growth and the mobilization of cations in the soil pore water. Measurement of soil water suction pressure has shown that soil moisture is directly related to the amount of the zeolitic tuff amendment. It has also been found that the zeolite component of the soil system supports biofilm formation and this behaviour is thought to account for the additional plant growth in substrates containing extra untreated tuff. Similar trends are found for plants growing in clean and metal polluted soils. It is now clear that organo-zeolitic-soil systems offer an opportunity to re-vegetate land made barren by metal pollution and as a consequence, erosion and dissemination of contaminants are reduced. By harvesting metal tolerant plants it would appear feasible to recover metals and clean the rhizosphere simultaneously.

Zeolitic rock as a new pigment for ceiling paints.: Influence of the pigment volume concentration

The performance of a zeolitic rock, mainly clinoptilolitic (heated at 350 °C) is studied as humidity and ammonia adsorber in ceiling paints. The paints were formulated with 39% and 75% of zeolitic rock by volume of the total pigment content and 75% and 85% pigment volume concentration (PVC). A blank, without zeolitic rock, was also formulated. The performance of the paints were assessed by gas (water and ammonia) adsorption and adsorption–desorption cycled tests. The results show that the paints containing zeolitic rock have better performance than the blank. Moreover, paints with 75% PVC behaved better than paints with PVC 85%. This behaviour may be due to the higher pigment content because the paints with PVC 85% retain more water during the curing period diminishing their adsorption capacity.

Characterization and Improvement of Ion Exchange Capacities of Mexican Clinoptilolite-rich Tuffs

Clinoptilolite-rich tuffs from the states of Chihuahua and Oaxaca in Mexico were modified with NaCl solutions to improve their ion exchange properties using different conditioning processes. First, the elemental and sodium compositions were identified by both induced coupled plasma atomic emission spectroscopy and neutron activation, respectively. The clinoptilolite-rich tuffs were characterized by scanning electron microscopy and X-ray diffraction and the surface areas were also determined in both tuffs. Effective, internal and external cation exchange capacities were determined. It was found that the elemental composition was different in both zeolitic rocks. A sodium treatment using a 0.1 M NaCl solution and reflux thus, improves effective cation exchange capacities of the Mexican clinoptilolite-rich tuffs. The external and internal cation exchange capacities depend on the size of the particle, as well as the source of the zeolitic rocks. The quaternary ammonium salt (HDTMABr or BCDMACl) considered is important in those determinations.