Hauptanwendung: Aquakultur
Neben den zahlreichen Anwendungen in der Gasphase werden Zeolithe auch „versenkt“ – also komplett unter Wasser angewendet. Bei Naturzeolithen ist das sogar die häufigere Anwendungsart, weil diese Materialien neben der Verwendung als Betonzuschlagstoff am häufigsten zur Wasserfilterung eingesetzt werden. Insbesondere die durch den wachsenden Fischverbrauch der Welt zunehmende Aquakultur ist ein großes Anwendungsgebiet.
In der Literaturliste zu diesem Beitrag zeigt sich daher auch, dass die Ammoniumadsorption an unmodifizierten Klinoptilolithen der häufigste Anwendungsfall zu sein scheint. Zwar gibt es auch viel Literatur zur Schwermetallbeseitigung – Schwermetallbelastung von Ab- und Sickerwässern ist ebenfalls ein Überbevölkerungsproblem – aber die Ammoniumadsorption ist mit Sicherheit die am besten untersuchte Anwendung.
Uneinheitliche Versuchsbedingungen
Bei der Durchsicht der Literatur fällt auf, dass es kein einheitliches Setting für Versuche gibt, so dass jede Publikation für sich steht und nicht mit anderen verglichen werden kann. Natürlich existieren DIN-Normen zur Bestimmung der Ionenaustauschkapazität etc., aber insbesondere bei Publikationen, die Behandlungsversuche von lokalen Abwässern mit lokalen Zeolithen beschreiben, wird frei experimentierend nach den idealen Bedingungen gesucht. Einflussgrößen werden oft nicht systematisch variiert oder auch nur beschrieben. Das ist insbesondere bei „echten“ Medien wie Gülle ein Problem.
Fazit?
Ein Fazit lässt sich daher nicht ziehen, es sei denn dies: Jede Kombination von Zeolith und Abwasser/Substrat muss einzeln geprüft werden.
Verwendet werden entweder gröber bzw. feiner vermahlene Naturzeolithe oder pulverförmige synthetische Zeolithe. Die gebundenen, pelletierten synthetischen Zeolithe für die Gasphase sind im Wasser zwar zunächst stabil, wird der Zeolith jedoch thermisch regeneriert, hält die Bindung nicht stand und die Körner zerfallen oder verbacken.
Die folgende Liste führt einige Literatur der letzten fünf Jahre zu den jeweiligen Anwendungen auf.
Modifikationen
Komposite mit anderen Mineralien
Hydroxylapatit und Tenside
Zhan, Y., et al. (2013). „Preparation and characterization of surfactant-modified hydroxyapatite/zeolite composite and its adsorption behavior toward humic acid and copper(II).“ Environ Sci Pollut Res Int 20(4): 2512-2526.
A novel composite material, i.e., surfactant-modified hydroxyapatite/zeolite composite, was used as an adsorbent to remove humic acid (HA) and copper(II) from aqueous solution. Hydroxyapatite/zeolite composite (HZC) and surfactant-modified HZC (SMHZC) were prepared and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscope. The adsorption of HA and copper(II) on SMHZC was investigated. For comparison purposes, HA adsorption onto HZC was also investigated. SMHZC exhibited much higher HA adsorption capacity than HZC. The HA adsorption capacity for SMHZC decreased slightly with increasing pH from 3 to 8 but decreased significantly with increasing pH from 8 to 12. The copper(II) adsorption capacity for SMHZC increased with increasing pH from 3 to 6.5. The adsorption kinetic data of HA and copper(II) on SMHZC obeyed a pseudo-second-order kinetic model. The adsorption of HA and copper(II) on SMHZC took place in three different stages: fast external surface adsorption, gradual adsorption controlled by both film and intra-particle diffusions, and final equilibrium stage. The equilibrium adsorption data of HA on SMHZC better fitted to the Langmuir isotherm model than the Freundlich isotherm model. The equilibrium adsorption data of copper(II) on SMHZC could be described by the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The presence of copper(II) in solution enhanced HA adsorption onto SMHZC. The presence of HA in solution enhanced copper(II) adsorption onto SMHZC. The mechanisms for the adsorption of HA on SMHZC at pH 7 may include electrostatic attraction, organic partitioning, hydrogen bonding, and Lewis acid-base interaction. The mechanisms for the adsorption of copper(II) on SMHZC at pH 6 may include surface complexation, ion exchange, and dissolution-precipitation. The obtained results indicate that SMHZC can be used as an effective adsorbent to simultaneously remove HA and copper(II) from water.
Bentonit/Vermiculit/Bimsstein (für Cu(II), Zn(II))
Turan, N. G., et al. (2013). „Prediction of heavy metal removal by different liner materials from landfill leachate: modeling of experimental results using artificial intelligence technique.“ ScientificWorldJournal 2013: 240158.
An intensive study has been made to see the performance of the different liner materials with bentonite on the removal efficiency of Cu(II) and Zn(II) from industrial leachate. An artificial neural network (ANN) was used to display the significant levels of the analyzed liner materials on the removal efficiency. The statistical analysis proves that the effect of natural zeolite was significant by a cubic spline model with a 99.93% removal efficiency. Optimization of liner materials was achieved by minimizing bentonite mixtures, which were costly, and maximizing Cu(II) and Zn(II) removal efficiency. The removal efficiencies were calculated as 45.07% and 48.19% for Cu(II) and Zn(II), respectively, when only bentonite was used as liner material. However, 60% of natural zeolite with 40% of bentonite combination was found to be the best for Cu(II) removal (95%), and 80% of vermiculite and pumice with 20% of bentonite combination was found to be the best for Zn(II) removal (61.24% and 65.09%). Similarly, 60% of natural zeolite with 40% of bentonite combination was found to be the best for Zn(II) removal (89.19%), and 80% of vermiculite and pumice with 20% of bentonite combination was found to be the best for Zn(II) removal (82.76% and 74.89%).
Zellulose (für Phenol)
Bizerea Spiridon, O., et al. (2013). „Phenol removal from wastewater by adsorption on zeolitic composite.“ Environ Sci Pollut Res Int 20(9): 6367-6381.
It is well known that adsorption is an efficient method of removal of various pollutants from wastewater. The present study examines the phenol removal from water by adsorption on a new material, based on zeolitic volcanic tuff. This compound contains zeolitic tuff and cellulose, another known adsorbent, in a mass ratio of 4 to 1. The performances of the new adsorbent composite were compared with those of a widely used adsorbent material, zeolitic volcanic tuff. The adsorbent properties were tested on batch synthetic solutions containing 1-10 mg L(-1) (1-10 ppm) phenol, at room temperature without pH adjustment. The influence of the adsorbent dose, pH and contact time on the removal degree of phenol from water was investigated. The experimental data were modeled using the Langmuir, Freundlich, and Temkin adsorption isotherms. The Langmuir model was found to best represent our data revealing a monolayer adsorption with a maximum adsorption capacity between 0.12 and 0.53 mg g(-1) at 25 degrees C, for 2.00 g of adsorbent, depending on the initial phenol concentration. The adsorption kinetic study was performed using a pseudo-first- and pseudo-second-order kinetic models illustrating that phenol adsorption on zeolite composite is well described by pseudo-first kinetic equations. Our results indicated that phenol adsorption on the new adsorbent composite is superior to that on the classic zeolite.
Flugasche aus Zementbrennöfen/Bentonit für Pb(II)
Salem, A., et al. (2012). „Removal of lead by using Raschig rings manufactured with mixture of cement kiln dust, zeolite and bentonite.“ J Hazard Mater 223-224: 13-23.
The present investigation is a follow-up of study on manufacturing Raschig ring for removal of lead from aqueous solution. The mixtures were formulated using cement kiln dust, zeolite, and bentonite, normally used as natural adsorbents in the industrial scale, according to mixture design algorithm and response surface method. The pastes were prepared by addition of 28.0wt.% de-ionized water, containing 0.1wt.% carboxymethyl cellulose, with mixed powders. The adsorbents were fabricated by extrusion of the pastes in Raschig ring form and calcination at 500 degrees C after drying in oven. The effects of starting materials on the mechanical behavior of rings were studied from view point of mixture design algorithm to optimize the adsorbent composition. This method demonstrated to yield valuable information on the effects of used materials on mechanical characteristics. The study concluded that the strength, reliability and sorption capacity of ring can be simultaneously optimized by the addition of 47.5wt.% cement kiln dust, 32.5wt.% zeolite, and 20.0wt.% bentonite. In the next part of work, the sorption kinetics was investigated. The kinetic study indicated that the modified model can successfully correlate the sorption data. The equilibrium result showed the possibility of lead immobilization by fabricated rings.
Polypropylen (für Pb(II)
Motsa, M. M., et al. (2011). „Preparation, characterization, and application of polypropylene-clinoptilolite composites for the selective adsorption of lead from aqueous media.“ J Colloid Interface Sci 359(1): 210-219.
A polymer composite of polypropylene (PP) and clinoptilolite (CLI) for the adsorption of lead has been prepared using the melt-mixing compounding technique in a rheomixer. Characterization of the composite was performed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), Brunuer-Emmett-Teller (BET), and Fourier transform infrared spectroscopy (FTIR). The influence of contact time, pH, initial metal-ion concentration, temperature, and pretreatment on the adsorption of lead (Pb) by the PP-CLI composite was investigated. Optimum pH was found to be between pH 6 and pH 8 while the maximum sorption of lead at optimal pH was 95%. No difference was observed between the adsorption behavior of composites functionalized with 20% and 30% clinoptilolite, respectively, while the pretreatment with HCl and NaCl made a slight difference to the adsorption capacity of composites. The findings from this study on the lead adsorption behavior of CLI-PP composite may have potential applications in wastewater and water purification works.
(Hier wurde allerdings auffallend nicht auf die Transporteigenschaften des Kompositmaterials geachtet!)
Oberflächenmodifikation
Immobilisierte Gerbsäure, für Phenol
Leone, V., et al. (2013). „A novel organo-zeolite adduct for environmental applications: Sorption of phenol.“ Chemosphere.
A novel organo-zeolite adduct has been synthesized by sorbing humic acids (HA) onto zeolitic tuff and then heating the resulting complex at 330 degrees C for 1.5h. Desorption tests showed that this procedure effectively immobilized HA on the tuff. The crystal structure of the zeolitic tuff and the chemical structure of HA were not altered during the preparation. Phenol sorption analysis demonstrated that the HA-zeolite adduct had good sorbing properties; moreover, the sorbed amount markedly decreased with increased ionic strength. These results point to prospective application of the HA-zeolite adduct as a low-cost and environmentally friendly sorbent for water purification from phenol and possibly other neutral organic pollutants.
Cetylpyridiniumbromid, für Gerbsäure
Zhan, Y., et al. (2010). „Removal of humic acid from aqueous solution by cetylpyridinium bromide modified zeolite.“ J Environ Sci (China) 22(9): 1327-1334.
Natural zeolite was modified by loading cetylpyridinium bromide (CPB) to create more efficient sites for humic acid (HA) adsorption. The natural and CPB modified zeolites were characterized with X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. The effects of various experimental parameters such as contact time, initial HA concentration, solution pH and coexistent Ca2+, upon HA adsorption onto CPB modified zeolites were evaluated. The results showed that natural zeolite had negligible affinity for HA in aqueous solutions, but CPB modified zeolites exhibited high adsorption efficiency for HA. A higher CPB loading on natural zeolites exhibited a larger HA adsorption capacity. Acidic pH and coexistent Ca2+ were proved to be favorable for HA adsorption onto CPB modified zeolite. The kinetic process was well described by pseudo second-order model. The experimental isotherm data fitted well to Langmuir and Sips models. The maximum monolayer adsorption capacity of CPB modified zeolite with surfactant bilayer coverage was found to be 92.0 mg/g.
Cyclodextran für p-Nitrophenol
Li, X., et al. (2009). „Surface modification of zeolite with beta-cyclodextrin for removal of p-nitrophenol from aqueous solution.“ Water Sci Technol 60(2): 329-337.
The surface of zeolite was modified by cationic beta-cyclodextrin (CCD), which was synthesized with 2, 3-epoxypropyltrimethylammonium chloride (ETMAC) and beta-cyclodextrin (beta-CD), to prepare a novel and effective sorbent for removal of p-nitrophenol (p-NP) from aqueous solution. FTIR, SEM and EDS were used to characterize the surface modification. It was found that CCD, which was synthesized at different conditions such as the mole ratio of ETMAC against beta-CD and pH, made an impact on sorption capacity of p-NP on CCD-modified zeolite (CCDMZ). Given ETMAC: beta-CD = 7:1 and pH = 13, the cationic process of beta-CD might be optimum for CCD to bond to zeolite surfaces. In addition, CCD concentration and modification time affected sorption capacity of p-NP on CCDMZ too. The sorption of p-NP on CCDMZ, activated zeolite (AZ) and natural zeolite (NZ) was investigated by contact time, initial p-NP concentration and sorption isotherms with the batch sorption experiments. The results showed that the sorption of p-NP on CCDMZ satisfactorily fitted the known Langmuir model and the sorption capacity of CCDMZ was higher than that of AZ and NZ although the contact time of CCDMZ appeared to be shorter than other two.
Ionenaustausch
K-Klinoptilolith für Schweinegülle
Penn, C. J., et al. (2010). „Maximizing ammonium nitrogen removal from solution using different zeolites.“ J Environ Qual 39(4): 1478-1485.
Zeolite minerals are ideal for removing ammonium nitrogen (NH4(+)-N) from animal wastes, leachates, and industrial effluents. The objectives of this study were to compare NH4+ removal and kinetics among several commercially available zeolites under various conditions and determine if calorimetry could provide information regarding kinetics of NH4+ removal. Ammonium sorption onto potassium (K) saturated zeolites was compared using synthetic vs. natural swine effluent and with either traditional batch-shaken system or a „tea bag“ approach in which zeolites were contained in a mesh sack and suspended in a solution of swine effluent. Ammonium sorption was measured at four retention times using a flow-through system, and the resulting heat response was measured using isothermal calorimetry. Ammonium removal was not significantly different in synthetic vs. natural swine effluent. Ammonium removal was lower in batch-stirred compared to batch-shaken systems, suggesting that diffusion between particles was rate-limiting in the former system. Flow-through cells possessing contact times > 100 s displayed greater NH4+ sorption than batch systems, suggesting that maintaining high NH4+ concentration in solution, removal of exchange products, and sufficient reaction time are critical to maximizing NH4+ removal by zeolites. Within 100 s after NH4+ addition, endothermic heat responses indicated that NH4(+)-K+ exchange had peaked; this was followed by significant heat rate reduction for 50 min. This confirmed findings of an initial fast NH4(+)-K+ exchange followed by a slower one and suggests the 100-s period of rapid reaction is an indicator of the minimum flow through retention time required to optimize NH4+ sorption to zeolites used in this study.
Fe-getauschter Klinoptilolith für Cu(II)
Doula, M. K. and A. Dimirkou (2008). „Use of an iron-overexchanged clinoptilolite for the removal of Cu2+ ions from heavily contaminated drinking water samples.“ J Hazard Mater 151(2-3): 738-745.
Clinoptilolite, a natural zeolite, was used for the synthesis of a high surface area clinoptilolite-iron oxide system, in order to be used for the removal of Cu2+ ions from drinking water samples. The solid system was obtained by adding natural clinoptilolite in an iron nitrate solution under strongly basic conditions. The Clin-Fe system has specific surface area equal to 151 m2 g(-1) and is fully iron exchanged (Fe/Al=1.23). Batch adsorption experiments were carried out to determine the effectiveness of the Clin and the Clin-Fe system in removal of copper from drinking water. Adsorption experiments were conducted by mixing 1.00 g of each of the substrates with certain volume of water samples contaminated with 10 different Cu concentrations (from 3.15×10(-5) to 315×10(-2) M or from 2.00 to 2000 ppm Cu). For our experimental conditions, the maximum adsorbed Cu amount on Clin was 13.6 mg g(-1) whereas on the Clin-Fe system was 37.5 mg g(-1). The main factors that contribute to different adsorption capacities of the two solids are due to new surface species and negative charge of the Clin-Fe system. In addition, the release of counterbalanced ions (i.e. Ca2+, Mg2+, Na+ and K+) was examined, as well as the dissolution of framework Si and Al. It was found that for the most of the samples the Clin-Fe system releases lower concentrations of Ca, Mg and Na and higher concentrations of K than Clin, while the dissolution of Si/Al was limited. Changes in the composition of water samples, as well as in their pH and conductivities values were reported and explained.
Unmodifizierte Zeolithe
Klinoptilolith
Als Träger für einen Rieselfilter:
Bratkova, S., et al. (2013). „Biological treatment of mining wastewaters by fixed-bed bioreactors at high organic loading.“ Bioresour Technol 137: 409-413.
Acid wastewaters contaminated with Fe – 1000 mg L(-1) and Cu – 100 mg L(-1) were remediated by microbial sulfate-reduction at high organic loading (theoretical TOC/SO4(2-) ratio 1.1) in a laboratory installation. The installation design includes a fixed-bed anaerobic bioreactor for sulfate-reduction, a chemical reactor, a settler and a three-sectional bioreactor for residual organic compounds and hydrogen sulfide removal. Sulfate-reducing bacteria are immobilized on saturated zeolite in the fixed-bed bioreactor. The source of carbon and energy for bacteria was concentrated solution, containing ethanol, glycerol, lactate and citrate. Heavy metals removal was achieved by produced H2S at sulfate loading rate 88 mg L(-1)h(-1). The effluent of the anaerobic bioreactor was characterized with high concentrations of acetate and ethanol. The design of the second bioreactor (presence of two aerobic and an anoxic zones) makes possible the occurrence of nitrification and denitrification as well as the efficiently removal of residual organic compounds and H2S.
Für einen Regenwasserfilter:
Wium-Andersen, T., et al. (2012). „Sorption media for stormwater treatment–a laboratory evaluation of five low-cost media for their ability to remove metals and phosphorus from artificial stormwater.“ Water Environ Res 84(7): 605-616.
Five sorption materials were studied with a focus on polishing pretreated stormwater: crushed limestone, shell-sand, zeolite, and two granulates of olivine. These materials are commercially available at comparatively low cost and have been subjected to a minimum of modification from their natural states. The sorbents were tested for phosphorus, arsenic, cadmium, chromium, copper, nickel, lead, and zinc at concentration and conditions relevant for typical stormwater. The materials were tested for sorption capacity and kinetics. Desorption was tested under neutral and alkaline conditions and in the presence of chloride. For most sorbent/sorbate combinations, significant sorption occurred within the first minutes of contact between sorbent and sorbate. Treatment to the low microgram per liter range could be achieved by contact times of less than 1 hour. The study indicated that sorption filters can be designed for long life expectancy at comparatively low cost by applying the materials tested.
Deponiesickerwässer:
Shahriari, H., et al. (2008). „Investigation of organic, inorganic and synthetic adsorbents for the pretreatment of landfill leachate.“ Environ Technol 29(5): 543-552.
An investigation into the use of organic, inorganic and synthetic adsorbents for the pretreatment of landfill leachate, generated by the City of Ottawa Trail Road Landfill, was carried out. The purpose of this project was to reduce the concentration of contaminants in order to meet the local Sewer Use By-Laws, prior to transporting the leachate from the generating site to the local municipal sewage treatment plant, and thereby reducing the disposal fees. Peat moss, compost, clinoptilolite, basalt and two types of activated carbon (DSR-A and F400) were investigated to determine the adsorption capacity for contaminants from leachate. Kinetic studies were also performed. The results based on batch adsorption isotherms show that peat moss has the highest adsorption capacity for boron (B) and barium (Ba), compared with the other adsorbents. Also peat moss has good removals of Total Kjeldahl Nitrogen (TKN), Total Organic Carbon (TOC), and benzene, toluene, ethylbenzene and xylene (BTEX), but these are lower than the removals obtained with activated carbon. Because of its relatively low cost and higher adsorption of B and Ba, peat moss was selected as the filter media for the column studies. The treated leachate was tested for B, Ba, TKN, carbonaceous biological oxygen demand (CBOD5) and hydrogen sulfide (H2S). The breakthrough curves for B and Ba showed the effectiveness of peat moss in removing these contaminants.
Karadag, D., et al. (2008). „Ammonium removal from sanitary landfill leachate using natural Gordes clinoptilolite.“ J Hazard Mater 153(1-2): 60-66.
Removal of ammonium ion (NH(4)(+)) from leachate from Odayeri sanitary landfill, located in the European part of Istanbul, was examined using Gordes (Turkish) clinoptilolite. The effects of pH, flow rate, ammonium concentration and competitive cations on the removal efficiency were investigated in both batch and column studies. Thomas model were used to analyze the breakthrough data. Nonlinear least square method was applied for fitting the column data. The competitive effect was observed more effective in lower ammonium concentration and higher cation concentrations. Conditioning and regeneration using NaCl improved removal efficiency of ammonium from leachate.
Abwasser aus der Olivenölpressung:
Santi, C. A., et al. (2008). „Reduction of organic pollutants in Olive Mill Wastewater by using different mineral substrates as adsorbents.“ Bioresour Technol 99(6): 1945-1951.
Physico-chemical treatments of Olive Mill Wastewater (OMW) were carried out using different inorganic substrates such as soil, bentonite and zeolite, in order to assess their efficiency to remove the organic load from OMW, in particular polyphenols (Pp) and to reduce chemical oxygen demand (COD). The effect of repeated treatments of OMW with different minerals and the possibility of regenerating them by the Low Temperature Ashing (LTA) technique, an eco-friendly procedure, for the reutilization of treated OMW, has been investigated. Zeolite was found to be highly efficient in adsorbing Pp and COD from OMW and was easy to regenerate by means of the LTA technique.
Ammonium:
Tosun, I. (2012). „Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.“ Int J Environ Res Public Health 9(3): 970-984.
The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (G degrees ), enthalpy (H degrees ) and entropy (S degrees ) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.
Cyrus, J. S. and G. B. Reddy (2011). „Sorption and desorption of ammonium by zeolite: Batch and column studies.“ J Environ Sci Health A Tox Hazard Subst Environ Eng 46(4): 408-414.
The major objective of this research was to investigate the efficiency of zeolite in the removal of NH(4)-N from swine wastewater and desorption of the sorbed NH(4)-N from the zeolite saturated with N. Sorption experiments were conducted on the sorbents, zeolites I, II and III. Zeolites II and III which are natural and unmodified, showed better sorption (4400-4500 mg kg(-1) with 500 mg L(-1) feed concentration) compared to Zeolite I (3053 +/- 127 mg kg(-1) with 500 mg L(-1) feed concentration), which is a surfactant modified zeolite. Freundlich and Langmuir isotherms were plotted from the sorption experimental data. Column studies indicated that, columns with flow rates of 2 and 3 mL min(-1), reached the breakthrough point within about 100 h. The possibility of regeneration of the column material was investigated by flushing the column with 0.1 N HCl. The results from this experiment showed that even after desorption with DI water for more than 250 h, considerable amount of N was still available in the column that was available for desorption by 0.1 N HCl. This confirms that zeolite could be a good substrate for slow N release in soil. The application of Zeolite II for the NH(4)-N removal from swine wastewater supports this observation.
Siljeg, M., et al. (2010). „The ground water ammonium sorption onto Croatian and Serbian clinoptilolite.“ J Hazard Mater 178(1-3): 572-577.
The removal of ammonium from the Valpovo region ground water (VGW) with the use of natural clinoptilolite samples from the Donje Jesenje deposit (Croatia) and the Zlatokop deposit in Vranjska Banja (Serbia) was studied. The natural Serbian (SZ) and Croatian zeolites (CZ) were transformed to the Na-form (Na-CZ and Na-SZ) in order to increase the exchange capacity of zeolite. The CZ and SZ theoretic ammonium sorption capacities were 24.24 mg NH(4)(+)/g CZ and 32.55 mg NH(4)(+)/g SZ, respectively. The application of natural and Na-form of clinoptilolite for efficient removal of ammonium ions from VGW was further investigated. For that purpose, the four „filter guard“ vessels filled with zeolite samples were set in parallel in the ground water purification pilot plant. The complete ammonium removal, with the use of SZ and Na-SZ was achieved during 20 h. After having observed saturation of clinoptilolite, the samples were regenerated with the use of 2 mol/L NaCl, and reused for determination of ammonium sorption efficiency. The regenerated samples showed to be still very efficient for NH(4)(+) removal and, in addition, the SZ was shown as superior for ammonium removal in comparison to the CZ.
Cu(II), Mn(II), Zn(II) und Pb(II)
Jovanovic, M., et al. (2012). „Novel kinetic model of the removal of divalent heavy metal ions from aqueous solutions by natural clinoptilolite.“ J Hazard Mater 233-234: 57-64.
Removal of heavy metal ions from aqueous solutions using zeolites is widely described by pseudo-second order kinetics although this model may not be valid under all conditions. In this work, we have extended approaches used for derivation of this model in order to develop a novel kinetic model that is related to the ion exchange mechanism underlying sorption of metal ions in zeolites. The novel model assumed two reversible steps, i.e. release of sodium ions from the zeolite lattice followed by bonding of the metal ion. The model was applied to experimental results of Cu(II) sorption by natural clinoptilolite-rich zeolitic tuff at different initial concentrations and temperatures and then validated by predictions of ion exchange kinetics of other divalent heavy metal ions (i.e. Mn(II), Zn(II) and Pb(II)). Model predictions were in excellent agreements with experimental data for all investigated systems. In regard to the proposed mechanism, modeling results implied that the sodium ion release rate was constant for all investigated metals while the overall rate was mainly determined by the rate of heavy metal ion bonding to the lattice. In addition, prediction capabilities of the novel model were demonstrated requiring one experimentally determined parameter, only.
Methylenblau und andere Farbstoffe:
Rafatullah, M., et al. (2010). „Adsorption of methylene blue on low-cost adsorbents: a review.“ J Hazard Mater 177(1-3): 70-80.
In this article, the use of low-cost adsorbents for the removal of methylene blue (MB) from solution has been reviewed. Adsorption techniques are widely used to remove certain classes of pollutants from waters, especially those which are not easily biodegradable. The removal of MB, as a pollutant, from waste waters of textile, paper, printing and other industries has been addressed by the researchers. Currently, a combination of biological treatment and adsorption on activated carbon is becoming more common for removal of dyes from wastewater. Although commercial activated carbon is a preferred adsorbent for color removal, its widespread use is restricted due to its relatively high cost which led to the researches on alternative non-conventional and low-cost adsorbents. The purpose of this review article is to organize the scattered available information on various aspects on a wide range of potentially low-cost adsorbents for MB removal. These include agricultural wastes, industrial solid wastes, biomass, clays minerals and zeolites. Agricultural waste materials being highly efficient, low cost and renewable source of biomass can be exploited for MB remediation. It is evident from a literature survey of about 185 recently published papers that low-cost adsorbents have demonstrated outstanding removal capabilities for MB.
Valdes, H., et al. (2009). „Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite.“ Water Sci Technol 60(6): 1419-1424.
This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.
Uran:
Camacho, L. M., et al. (2010). „Uranium removal from groundwater by natural clinoptilolite zeolite: effects of pH and initial feed concentration.“ J Hazard Mater 175(1-3): 393-398.
Adsorption of uranium (VI) on a natural clinoptilolite zeolite from Sweetwater County, Wyoming was investigated. Batch experiments were conducted to study the effects of pH and initial feed concentrations on uranium removal efficiency. It was found that the clinoptilolite can neutralize both acidic and low basic water solutions through its alkalinity and ion-exchange reactions with U within the solution, and adsorption of uranium (VI) species on clinoptilolite not only depends on the pH but also the initial feed concentration. The highest uranium removal efficiency (95.6%) was obtained at initial uranium concentration of 5mg/L and pH 6.0. The Langmuir adsorption isotherm model correlates well with the uranium adsorption equilibrium data for the concentration range of 0.1-500 mg/L. From the experimental data obtained in this work, it was found that the zeolite sample investigated in this work is a mixture of clinoptilolite-Na zeolite and mineral impurities with a relatively large specific surface area (BET of 18 m(2)/g) and promising adsorption properties for uranium removal from contaminated water.
Ni(II):
Argun, M. E. (2008). „Use of clinoptilolite for the removal of nickel ions from water: kinetics and thermodynamics.“ J Hazard Mater 150(3): 587-595.
This paper describes the removal of Ni(II) ions from aqueous solutions using clinoptilolite. The effect of clinoptilolite level, contact time, and pH were determined. Different isotherms were also obtained using concentrations of Ni(II) ions ranging from 0.1 to 100 mg L(-1). The ion-exchange process follows second-order reaction kinetics and follows the Langmuir isotherm. The paper discusses thermodynamic parameters, including changes in Gibbs free energy, entropy, and enthalpy, for the ion-exchange of Ni(II) on clinoptilolite, and revealed that the ion-exchange process was spontaneous and exothermic under natural conditions. The maximum removal efficiency obtained was 93.6% at pH 7 and with a 45 min contact time (for 25 mg L(-1) initial concentration and a 15 g L(-1) solid-to-liquid ratio).
Phillipsit-Faujasit-Mischgestein für Paraquat (ein Herbizid)
Ibrahim, K. M. and H. A. Jbara (2009). „Removal of paraquat from synthetic wastewater using phillipsite-faujasite tuff from Jordan.“ J Hazard Mater 163(1): 82-86.
A phillipsite-faujasite tuff (faujasite) from Jordan has been activated and characterized to evaluate its efficiency in removing paraquat from synthetic wastewater and to specify optimum conditions with maximum efficiency of the faujasite tuff. Noticed variation in CEC is indicated and explained by selectivity of the faujasite to K(+) and Na(+). Removal of paraquat by using faujasite directly gave average removal efficiency equal to 59%. Thermal activation of the samples enhances their performance. The higher is the temperature of activation the higher the efficiency. Treatment of paraquat effluent using faujasite is a good alternative. Na- or K-loading of the original sample give better results. Loading with Ca and Mg however is not recommended because they always exhibit lower efficiency, which might be related to their lower CEC value. Removal of paraquat from wastewater using charcoal and the non-activated faujasite increased efficiency to about 82%. Thermal activated faujasite at 200 degrees C and 300 degrees C increased the uptake up to about 93% and 99.5%, respectively. Therefore thermal activation of faujasite is necessary to improve its uptake performance.
Mordenit
Wang, Y., et al. (2007). „Removal of low-concentration ammonia in water by ion-exchange using Na-mordenite.“ Water Res 41(2): 269-276.
Removal of low-concentration ammonia (2-10ppm) in water by ion exchange with Na-form zeolites was investigated using a flow system at 278-333K. Results indicated that Na-mordenite was the most efficient cation-exchanger (compared with Na-ferrierite, Na-ZSM-5, Na-beta, and Na-Y, as well as the K- and H-form mordenite) for the removal of low-concentration ammonia. The ammonia uptake and the ion-exchange level achieved using mordenite with NH(4)(+) for removal of 10ppm ammonia at 333K were 1.21mmolg(-1) and 79.1%, respectively. The high efficiency of Na-mordenite for removal of low-concentration ammonia in water is due to the strong acidity of the corresponding H-form mordenite as demonstrated by ammonia temperature-programmed desorption. Ammonia uptake on the Na-mordenite was minimally influenced by operating temperature in the range of 278-333K. The coexistent K(+) and Na(+) in water had little influence on ammonia uptake of the Na-mordenite. In contrast, coexistent Ca(2+) and Mg(2+) significantly lowered the efficiency of the Na-mordenite for ammonia removal.
Eigens hergestellt
Aus Zuckerrohr-Flugasche (für Pb(II) und Cd(II)
Turan, N. G., et al. (2013). „Prediction of heavy metal removal by different liner materials from landfill leachate: modeling of experimental results using artificial intelligence technique.“ ScientificWorldJournal 2013: 240158.
An intensive study has been made to see the performance of the different liner materials with bentonite on the removal efficiency of Cu(II) and Zn(II) from industrial leachate. An artificial neural network (ANN) was used to display the significant levels of the analyzed liner materials on the removal efficiency. The statistical analysis proves that the effect of natural zeolite was significant by a cubic spline model with a 99.93% removal efficiency. Optimization of liner materials was achieved by minimizing bentonite mixtures, which were costly, and maximizing Cu(II) and Zn(II) removal efficiency. The removal efficiencies were calculated as 45.07% and 48.19% for Cu(II) and Zn(II), respectively, when only bentonite was used as liner material. However, 60% of natural zeolite with 40% of bentonite combination was found to be the best for Cu(II) removal (95%), and 80% of vermiculite and pumice with 20% of bentonite combination was found to be the best for Zn(II) removal (61.24% and 65.09%). Similarly, 60% of natural zeolite with 40% of bentonite combination was found to be the best for Zn(II) removal (89.19%), and 80% of vermiculite and pumice with 20% of bentonite combination was found to be the best for Zn(II) removal (82.76% and 74.89%).
H-Y für Simazin (ein Herbizid)
Sannino, F., et al. (2012). „Cyclic process of simazine removal from waters by adsorption on zeolite H-Y and its regeneration by thermal treatment.“ J Hazard Mater 229-230: 354-360.
Removal of the agrochemical simazine from polluted waters through adsorption by zeolite Y in its protonic form was studied. The investigated parameters were: pH, time, initial simazine concentration and solid/liquid ratio. An iterative process of simazine removal from waters is proposed, featuring: (i) final agrochemical concentration well below 0.05 mg/dm(3), the maximum concentration allowed by Italian laws in wastewaters; (ii) regeneration of the adsorbent by a few minutes thermal treatment in air at about 500 degrees C, which results in the combustion of simazine without damage of the adsorbent; (iii) destruction of the agrochemical compound by combustion.
Na-P und K-P
Yusof, A. M., et al. (2010). „Removal of Ca2+ and Zn2+ from aqueous solutions by zeolites NaP and KP.“ Environ Technol 31(1): 41-46.
Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca2+) and zinc (Zn2+) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K+ with Na+ which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K+ on zeolite NaP was determined through the Freundlich isotherm equilibrium study. Characterization of zeolite KP was determined using infrared spectroscopy and X-ray diffraction (XRD) techniques. From the characterization, the structure of zeolite KP was found to remain stable after the ion exchange process. Zeolites KP and NaP were used for the removal of Ca and Zn from solution. The amount of Ca2+ and Zn2+ in aqueous solution before and after the adsorption by zeolites was analysed using the flame atomic absorption spectroscopy method. The removal of Ca2+ and Zn2+ followed the Freundlich isotherm rather than the Langmuir isotherm model. This result also revealed that zeolite KP adsorbs Ca2+ and Zn2+ more than zeolite NaP and proved that modification of zeolite NaP with potassium leads to an increase in the adsorption efficiency of the zeolite. Therefore, the zeolites NaP and KP can be used for water softening (Ca removal) and reducing water pollution/toxicity (Zn removal).
(Zeolith P ist ein synthetischer fluoridhaltiger, großporiger Zeolith mit linearen Kanälen.)
Aus Flugasche, für Schwermetalle
Wang, C., et al. (2009). „Evaluation of zeolites synthesized from fly ash as potential adsorbents for wastewater containing heavy metals.“ J Environ Sci (China) 21(1): 127-136.
The pure-form zeolites (A and X) were synthesized by applying a two-stage method during hydrothermal treatment of fly ash prepared initial Cu and Zn gel. The difference of adsorption capacity of both synthesized zeolites was assessed using Cu and Zn as target heavy metal ions. It was found that adsorption capacity of zeolite A showed much higher value than that of zeolite X. Thus, attention was focused on investigating the removal performance of heavy metal ions in aqueous solution on zeolite A, comparing with zeolite HS (hydroxyl-solidate) prepared from the residual fly ash (after synthesis of pure-form zeolite A from fly ash) and a commercial grade zeolite A. Batch method was used to study the influential parameters of the adsorption process. The equilibrium data were well fitted by the Langmuir model. The removal mechanism of metal ions followed adsorption and ion exchange processes. Attempts were also made to recover heavy metal ions and regenerate adsorbents.
Zeolith A für Cs(+) und Sr(++)
El-Kamash, A. M. (2008). „Evaluation of zeolite A for the sorptive removal of Cs+ and Sr2+ ions from aqueous solutions using batch and fixed bed column operations.“ J Hazard Mater 151(2-3): 432-445.
Zeolite A was chemically synthesized and evaluated, as inorganic ion exchange material, for the removal of cesium and strontium ions from aqueous solutions in both batch and fixed bed column operations. Batch experiments were carried out as a function of pH, initial ion concentration and temperature. Simple kinetic and thermodynamic models have been applied to the rate and isotherm sorption data and the relevant kinetic and thermodynamic parameters were determined from the graphical presentation of these models. Breakthrough data were determined in a fixed bed column at room temperature (298 K) under the effect of various process parameters like bed depth, flow rate and initial ion concentration. The results showed that the total metal ion uptake and the overall bed capacity decreased with increasing flow rate and increased with increasing initial ion concentrations and bed depth. The dynamics of the ion exchange process was modeled by bed depth service time (BDST) model. The sorption rate constants (K) were found to increase with increase in flow rate indicating that the overall system kinetics was dominated by external mass transfer in the initial part of the sorption process in the column
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