Pretreatment of natural clinoptilolite in a laboratory-scale ion exchange packed bed (original) (raw)
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PRETREATMENT OF CLINOPTILOLITE IN ION EXCHANGE PACKED BEDS
The impact of the operational and chemical conditions of pretreatment upon the effective capacity of clinoptilolite has been investigated. Pretreatment tests have been performed in an ion exchange packed bed. The parameters examined were the volumetric flow rate, the concentration, the total volume, and the pH of the pretreatment solution. Furthermore, the effect of flow mode was investigated (upflow and downflow conditions). An optimal flow rate and a minimum concentration were determined, for downflow mode, for a pretreatment that leads to a high effective capacity of the material. Lower pH value and upflow operation resulted to higher effective capacity.
Aim of this study was to evaluate the feasibility of the use of clinoptilolite as a barrier material to eliminate heavy metals from roof runoff. The effect of chemical conditioning with 1 M NaCl solution upon the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite has been investigated. According to the batch experiments the modified clinoptilolite has up to 100% higher sorption capacity, regarding Zn than the natural material. The pre-treatment of clinoptilolite results in an acceleration of the ion exchange process up to 40% regarding zinc. In order to define the reasons of this behaviour, both materials, modified and natural, were analysed for: (i) chemical composition, (ii) density, (iii) pore size distribution and (iv) zeta potential. The clogging of the pores, the charge of the grain surface, the pH of the initial metal solution and the ion metal concentration are the factors which are mainly affecting the ion exchange capacity and the rate of zinc uptake by clinoptilolite. r
In the present work, the effect of acid treatments on the structure of a natural and sodium exchanged clinoptilolite was evaluated using experimental and theoretical methods. The results demonstrated the good stability of the samples submitted to HCl treatments, although it was proven that aluminum was extracted from the framework. It was verified that the sodium clinoptilolite (AZ) is more resistant than its natural form (NZ) to the acid treatment since the aluminum extraction is smaller and the percent of estimated crystallinity is higher in AZ. An increase in the micropore volume, as well as the creation of new narrow micropores, was also verified. The simulation results indicated that the aluminum at T2 position is the easiest to remove during the dealumination process, and it was also noted that, during dealumination, different slabs are formed in the structure, creating a framework like a clay. Calculations suggested that the stability of the dealuminated frameworks was related to attractive and repulsive interactions, which take place between the species involved in the dealumination process. Our work demonstrates that sodium modification is an essential step to obtain a structurally stable acidic natural clinoptilolite.
Basic Treatment in Natural Clinoptilolite for Improvement of Physicochemical Properties
Minerals
Natural zeolites are low in cost and exhibit interesting properties for applications in adsorption and catalysis. However, the fact that they are natural materials, not obtained in pure form, and can incorporate various compensating ions can compromise their properties and restrict their use. As their textural and chemical properties are of great relevance for adsorption and catalysis applications, this work aims to study the modification of the natural zeolite clinoptilolite to obtain materials with better physicochemical properties. Clinoptilolite was treated with NaOH under various conditions. The treated material was characterized by X-ray diffraction, X-ray fluorescence, N2 adsorption and desorption at 77 K, CO2 adsorption at 273 K, and pyridine adsorption. The treatment allowed the removal of silicon from the material, improving the textural properties and preserving the structural Al. With the removal of Si, the Si/Al ratio decreased, and consequently, the number of acid and ...
Sustainable Water Resources Management, 2016
Hard water causes many problems in domestic and industrial usage, which has to be removed using costeffective technologies. To achieve this, the main goal of this study is to assess and optimize the factors controlling water softening applications. The research approach included a combined use of batch and column experiments performed in laboratory conditions through the ion exchange process, evaluating the effectiveness of natural and homoionic clinoptilolite on the removal characteristics of divalent cations. The equilibrium data could be fitted by both the Langmuir and the Freundlich models, even though it was fitted better by the Langmuir model with a maximum adsorption capacity of 10.5 mg g-1 for homoionic clinoptilolite (HC) and 9.68 mg g-1 for the natural clinoptilolite (NC). The adsorption kinetics can be successfully fitted to pseudo-second order kinetic model and the results of the intraparticle diffusion model suggest intraparticle diffusion was not the only rate-controlling step. It was also observed that the statistics indices of agreements from non-linear Thomas model were higher than that linear Thomas model. Nevertheless, the slope of the breakthrough curve for the linearized method decreased with increasing time as compared to non-linear method, thereby resulting in a slightly steeper slope for the nonlinear method and reducing the adsorption capacity. The study also concludes that the non-linear method is slightly more effective in predicting the performance of the selective removal efficiency of hardness ions. Results illustrate that clinoptilolite may be used as an alternative to more costly materials, due to its low cost and high abundance.
Decationization and dealumination of clinoptilolite tuff and ammonium exchange on acid-modified tuff
Journal of Colloid and Interface Science, 2005
The paper presents results of investigation of exchange of the clinoptilolite tuff cations with hydrogen ions from HCl solution of concentration 0.1 mmol cm −3 and ammonium ions solutions of concentrations 0.0071 to 2.6 mmol cm −3. Molal concentrations, x (mmol g −1) of cations exchanged in acid solution and in ammonium ions solutions were compared with molal concentrations of cations obtained by determination of the cation-exchange capacity of clinoptilolite tuff. The obtained results show that at ammonium ion concentrations lower than 0.1 mmol cm −3 , with regard to exchange capacity for particular ions, best exchanged are Na + ions, followed by Mg 2+ and Ca 2+ ions, while exchange of K + ions is the poorest (Na + > Mg 2+ > Ca 2+ > K +). At ammonium concentrations from 0.2 to 1 mmol cm −3 the order is Na + > Ca 2+ > Mg 2+ > K +. At concentrations higher than 1 mmol cm −3 the order is Na + > Ca 2+ > K + > Mg 2+. The results are a consequence of the uptake of hydrogen ions by zeolite samples in ammonium ions solutions at concentrations lower than 1 mmol cm −3 and indicate the importance of Mg 2+ (besides Na + ions) for the exchange between clinoptilolite cations and H + ions, in contrast to K + ions, whose participation in the reaction with H + ions is the lowest. During decationization of the clinoptilolite in acid solution, best exchanged are Na + , Mg 2+ , and Ca 2+ ions, while exchange of K + ions is the poorest. Due to poor exchange of K + and H + ions and good exchange of Na + , Mg 2+ , and Ca 2+ ions, it is to be assumed that preservation of stability of the clinoptilolite structure is caused by K + ions present in the channel C. Clinoptilolite is dissolved in the clinoptilolite A and B channels where Na + , Mg 2+ , and Ca 2+ ions are present. On the acidmodified clinoptilolite samples, exchange of ammonium ions is poorer than on natural zeolite. The longer the contact time of the zeolite and acid solution, the worse ammonium ions exchange. It can be assumed that H + ions exchanged with zeolite cations are consumed for solution of aluminum in the clinoptilolite structure; therefore the concentration of H + ions as exchangeable cations decreases. In the ammonium ion solution at a concentration of 0.0065 mmol cm −3 , from the acid-modified zeolite samples, Al 3+ ions are exchanged best, followed by Na + , Mg 2+ , Ca 2+ , and K + ions. Further to the results, it is to be assumed that exchangeable Al 3+ ions available from clinoptilolite dissolution are best exchanged with H + ions in acid solution.
Immobilisation of selected ions in natural clinoptilolite incorporated in cement pastes
Many industrial activities and disposal of wastes can cause environmental risk connected to the release of toxic elements both in anionic and cationic form (e.g. heavy metal cations or chromate, arsenate and phosphate ions). In many cases, the most effective method of removing the toxic ions is using the natural zeolites. However, after the treatment the zeolite can partly release sorbed ions and their immobilization should be solidified. The most commonly used matrices for solidification of the zeolite after sorption are different kinds of cements or alkali-activated slag binders The work presents results of research in which natural clinoptilolite originating from Polish deposit was used for heavy metal cations immobilisation (Pb2+, Cr3+, Cd2+ and Zn2+). It was obtained in the process of sedimentation and transformed into sodium form. Surface properties of the studied material have been modified by applying organic compound names hexadecyltrimethlammonium bromide (HDTMA-Br). (HDTM...
Aquaculture water treatment by ion exchange: Continuous ammonium ion removal with clinoptilolite
Aquacultural Engineering, 1989
The performance of Hector Clinoptilolite as an ion exclumge medium during uptake attd regeneration in small continuous fixed bed col, rams is examined. The model system used was the multi ion system Na+/ NH~ -K ~ -Mg -'+ -Ca -'+ in the presence of Cl-as the co-ion. The objective of the work was to examine the suitability of clinoptilolire as an exchange medium ]'or fish farm water treatment in ]}'esh water recycle systems. Ammonia uptake, the most important criteriott used to ussess performance, was strongly influenced by ammonium ion concentration in the feed attd in the concentration range studied (1-5 mg Nttu-.V litre -t) the exchange capacity Jor ammonittm varied linearly with feed cotwentration. The presettce oJcalcium ion appeared to depress the capacity of the clinoptilolite after the first uptake/regeneration cycle. 77w mtdti cycle use of clinoptilolite may be inhibited by this loss of capaci O" and the relatively inefficient rinsing characteristics which were exhibited.
Evaluation of groundwater hardness removal using activated clinoptilolite
Environmental Science and Pollution Research, 2019
Current study aimed to investigate modified natural clinoptilolite for removal of calcium and magnesium from the groundwater. Feasibility of clinoptilolite for groundwater hardness removal in production and operation was verified by static adsorption experiment and the experiment of fixed bed and degasification column. Subsequently, the main parameters for groundwater treatment using clinoptilolite were also explored. Results show that in the process of clinoptilolite in adsorption is dominant reaction process. The adsorption equilibrium time was unchanged when the hardness of raw water changes from 450 to 550 mg/ L. With respect to comparative analysis of price and performance, NaCl found to be the most suitable clinoptilolite regenerated agent. The adsorption efficiency was high when the residence time was 20-25 min in the pilot experiments. The reaction mechanism was mainly substitution reaction according to ion equilibrium, and the treatment capacity of the degasifier combined with the fixed bed was 20% higher than that of with only fixed bed.