Performance Of Ion Exchange Columns Research Articles

MATHEMATICAL MODELING SINGULARLY PERTURBED PROCESSES OF WATER SOFTENING ON SODIUM-CATIONITE FILTERS

Mathematical model of the process of water softening using ion exchange pre-treatment of waters to desalination, with a view to removal of scale forming components, such as calcium and magnesium, are formed in the paper. In this process, no additional chemicals, except for brines formed during desalination, are required for regeneration of ion-exchanger in operation cycles. An asymptotic approximation of a solution of a corresponding model problem is constructed. Theoretical description and modelling assumptions included the set of differential equations of mass balance, initial, boundary and operational conditions. The paper deals with the development of a computer model for description and prediction of the performance of ion exchange columns.

Intensification of ammonia removal from waste water in biologically active zeolitic ion exchange columns

The use of nitrification filters for the removal of ammonium ion from waste-water is an established technology deployed extensively in municipal water treatment, in industrial water treatment and in applications such as fish farming. The process involves the development of immobilized bacterial films on a solid packing support, which is designed to provide a suitable host for the film, and allow supply of oxygen to promote aerobic action. Removal of ammonia and nitrite is increasingly necessary to meet drinking water and discharge standards being applied in the US, Europe and other places. Ion-exchange techniques are also effective for removal of ammonia (as the ammonium ion) from waste water and have the advantage of fast start-up times compared to biological filtration which in some cases may take several weeks to be fully operational. Here we explore the performance of ion exchange columns in which nitrifying bacteria are cultivated, with the goal of a “combined” process involving simultaneous ion-exchange and nitrification, intensified by in-situ aeration with a novel membrane module. There were three experimental goals. Firstly, ion exchange zeolites were characterized and prepared for comparative column breakthrough studies for ammonia removal. Secondly effective in-situ aeration for promotion of nitrifying bacterial growth was studied using a number of different membranes including polyethersulfone (PES), polypropylene (PP), nylon, and polytetra-fluoroethylene (PTFE). Thirdly the breakthrough performance of ion exchange columns filled with zeolite in the presence of aeration and in the presence of nitrifying bacteria was determined to establish the influence of biomass, and aeration upon breakthrough during ammonium ion uptake.The methodology adopted included screening of two types of the naturally occuring zeolite clinoptilolite for effective ammonia removal in continuous ion-exchange columns. Next, the performance of fixed beds of clinoptilolite in the presence of nitrifying bacteria is compared to that in columns in which only ion exchange is occurring. The aeration performance of each of the chosen membranes was compared experimentally using a newly developed membrane support module which is also described. Comparison of ammonia removal in columns equipped with in-situ aeration using each membrane was undertaken and the breakthrough characteristics determined. The results showed that ammonia removal in the presence of the nitrifiers was significantly intensified. Column operation with membrane aeration showed further enhancement of ammonia removal. The greatest enhancement was observed in the case of the polyethersulfone membrane (PES). It is concluded that combined nitrification and ion-exchange is significantly intensified in packed columns by in-situ aeration using a novel membrane module. There is significant potential for extending the ion-exchange cycle time and thus potential cost reduction.

Probing the kinetic performance limits for ion chromatography. I. Isocratic conditions for small ions

The first use of the kinetic plot method to characterise the performance of ion-exchange columns for separations of small inorganic anions is reported. The influence of analyte type (mono- and divalent), particle size (5 and 9 μm), temperature (30 and 60 °C) and maximum pressure drop upon theoretical extrapolations was investigated using data collected from anion-exchange polymeric particulate columns. The quality of extrapolations was found to depend upon the choice of analyte, but could be verified by coupling a series of columns to demonstrate some practical solutions for ion chromatography separations requiring relatively high efficiency. Separations of small anions yielding 25–40,000 theoretical plates using five serially connected columns (9 μm particles) were obtained and yielded deviations of <15% from the kinetic plot predictions. While this approach for achieving high efficiencies results in a very long analysis time ( t 0 = 21 min), separations yielding approximately 10,000 theoretical plates using two serially connected columns ( t 0 < 5 min) were shown to be more practically useful for isocratic separations when compared to use of a single column operated at optimum linear velocity ( t 0 > 10 min).

Modeling Ion-Exchange for Cesium Removal from Alkaline Radioactive Waste Solutions

The performance of spherical Resorcinol-Formaldehyde ion-exchange resin for treatment of radioactive waste solutions is investigated through computer modeling. Results show that ion-exchange is an efficient method for cesium removal from highly alkaline radioactive waste solutions. On average, two 1300 liter columns operating in series are able to treat 690,000 liters of waste with an initial cesium concentration of 0.09 mM in 11 days achieving a decontamination factor of over 50,000. The study investigated the sensitivity of ion-exchange column performance to variations in flow, temperature, and column dimensions. Modeling results can be used to optimize the design of the ion exchange system.

Investigation of cyclic self-sustaining ion exchange process for softening water solutions on the basis of mathematical modeling

New possibilities of using ion exchange pretreatment of saline waters to desalination, with a view to removal of scale forming components, such as calcium and magnesium, are considered in the paper. A cyclic self-sustaining process driven by electro-selectivity effect is discussed. In this process, no additional chemicals, except for brines formed during desalination, are required for regeneration of ion-exchanger in operation cycles. The paper deals with the development of a computer model for description and prediction of the performance of ion exchange columns. Theoretical description and modeling assumptions included the set of differential equations of mass balance, initial, boundary and operational conditions. The impact of the phenomenon of isothermal supersaturation of solutions in ion exchange bed was taken into consideration. Correlations between observations and calculations were tested. The mathematical model was verified by experiments carried out with seawater and a model solution of brackish water and with modified zeolite of A-type which was used as a softening cation-exchanger. Experimental break-through curves (concentration histories) were fitted by calculation data with a good accuracy. Issues related to the choice of optimal parameters were addressed. The stability of the process was analysed in case of a leakage of solutions. The results of investigation demonstrate the possibility of maintaining the cyclic self-sustaining process in a wide range of compositions of raw solutions.

ION EXCHANGE OF SEVERAL RADIONUCLIDES ON THE HYDROUS CRYSTALLINE SILICOTITANATE, UOP IONSIV IE-911

ABSTRACT The crystalline silicotitanate, UOP IONSIV IE-911, is a proven material for removing radionuclides from a wide variety of waste streams. It is superior for removing several radionuclides from the highly alkaline solutions typical of DOE wastes. Our laboratory previously developed an equilibrium model applicable to complex solutions for IE-910 (the powder form of the granular IE-911), and more recently, we have developed several single component ion-exchange kinetic models for predicting column breakthrough curves and batch reactor concentration histories. In this paper, we model ion-exchange column performance using effective diffusivities determined from batch kinetic experiments. This technique is preferable because the batch experiments are easier, faster, and cheaper to perform than column experiments. We also extend these ideas to multicomponent systems. Finally, we evaluate the ability of our equilibrium model to predict data for IE-911.

ION EXCHANGE OF SEVERAL RADIONUCLIDES ON THE HYDROUS CRYSTALLINE SILICOTITANATE, UOP IONSIV IE-911

ABSTRACT The crystalline silicotitanate, UOP IONSIV IE-911, is a proven material for removing radionuclides from a wide variety of waste streams. It is superior for removing several radionuclides from the highly alkaline solutions typical of DOE wastes. Our laboratory previously developed an equilibrium model applicable to complex solutions for IE-910 (the powder form of the granular IE-911), and more recently, we have developed several single component ion-exchange kinetic models for predicting column breakthrough curves and batch reactor concentration histories. In this paper, we model ion-exchange column performance using effective diffusivities determined from batch kinetic experiments. This technique is preferable because the batch experiments are easier, faster, and cheaper to perform than column experiments. We also extend these ideas to multicomponent systems. Finally, we evaluate the ability of our equilibrium model to predict data for IE-911.

Aqualink ‐‐ Computer Prediction of Ion Exchange

This months column describes an easy‐to‐use computer program available in the public domain to aid water treatment engineers in the prediction of ion exchange column performance. This QuickBasic Macintosh program is well suited to predicting the breakthrough curves (effluent histories) of contaminant ions during multicomponent ion exchange.

Shale Oil Denitrogenation with Ion Exchange

Abstract The nitrogen-containing aromatics normally found in crude retorted shale oils have been shown to be involved in reactions leading to the deposition of insoluble gums and sediments. These nitrogen-containing compounds must be removed in order to permit the effective utilization of the shale oil product. A process is proposed in which the nitrogen-containing compounds found in raw shale oil are removed by mild hydrodenitrogenation followed by resin ion exchange. Ion exchange data from experimentation involving six jet fuel (15M-271°C) and diesel fuel (271–343°C) boiling point cuts are presented. Amberlyst A-15, a macroreticular, strongly acidic, cation exchange resin is used in this study. Three types of experiments were performed: batch sorption equilibrium experiments, batch sorption kinetics experiments, and dynamic ion-exchange column performance tests. The Langmuir isotherm was found to describe the equilibrium sorption behavior of the shale oil/ion-exchange resin system fairly Well. The sorpt...

Theory of ion-complexing effects in ion-exchange column performance

Theory of ion-complexing effects in ion-exchange column performance

Interpretation and correlation of ion exchange column performance under nonlinear equilibria

AbstractVarious methods are known for interpreting experimental data for linear‐equilibrium cases or constant‐pattern break‐through curves where either external or internal diffusion alone controls the rate in the ion exchange column. The present paper provides interpretive techniques for nonlinear equilibrium cases where the rate is controlled by a combined diffusion mechanism. The techniques can be applied whether or not the value of the equilibrium constant is known.A completely general correlational method is derived for adding the mass transfer resistances under conditions of nonlinear equilibrium. Published break‐through results from numerous sources and from new measurements, evaluated by the techniques described, are used to determine the numerical constants for the general correlation.