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

Abstract

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.     

Removal of Cesium Ions from Aqueous Solution by Polyaniline: A Radiotracer Study

The present work deals with the study of uptake behavior of cesium ions by polyaniline applying a radiotracer technique. The parametric study reveals that the increase of adsorbate concentration (10⁻⁸ to 10⁻³ mol dm⁻³) and temperature (303 to 333 K) enhances the removal of the ions and from thermal and kinetic data it is inferred that the adsorption of cesium ions follows first order rate law, obeys Freundlich isotherm and is endothermic in nature. The radiation stability of polyaniline was also investigated by exposing it to a 11.1 GBq (Ra-Be) source associated with gamma dose of 1.72 Gyh⁻¹.     

Hydraulic Testing of Ion Exchange Resins for Cesium Removal from Hanford Tank Waste

Abstract

The granular ion exchange resin SuperLig^® 644 is the ion exchange resin of choice for ¹³⁷Cs separation from Hanford tank wastes. Current testing activities are evaluating both ground gel and spherical resorcinol‐formaldehyde (RF) resins as alternatives to the sole‐source supplied SL‐644 while achieving comparable loading and elution performance. The purpose of this testing was then to compare the bed forces, resin particle breakage, and differential pressure across the resin bed during multiple load‐elute cycles. These tests were conducted in a small‐scale column with high flow rates to simulate the hydraulic conditions that would be experienced in a full‐scale column.     

Combined Extraction of Cesium and Strontium from Alkaline Nitrate Solutions

Abstract

The combined extraction of cesium and strontium from caustic wastes can be achieved by adding a crown ether and a carboxylic acid to the Caustic‐Side Solvent Extraction (CSSX) solvent. The ligand 4,4′(5′)‐di(tert‐butyl)cyclohexano‐18‐crown‐6 and one of four different carboxylic acids were combined with the components of the CSSX solvent optimized for the extraction of cesium, allowing for the simultaneous extraction of cesium and strontium from alkaline nitrate media simulating alkaline high level wastes present at the U.S. Department of Energy Savannah River Site. Extraction and stripping experiments were conducted independently and exhibited adequate results for mimicking waste simulant processing through batch contacts. The promising results of these batch tests showed that the system could reasonably be tested on actual waste.     

Preparation and Evaluation of Fullers Earth Beads for Removal of Cesium from Waste Streams

Abstract

Fullers earth beads and cylinders were prepared using chitosan and sodium silicate as binders, respectively, for removal of cesium ion from aqueous solutions. The cost of the adsorbent is expected to be significantly lower as the raw materials are low cost materials and readily available. The adsorbents were characterized by SEM, EDS, and x‐ray microanalysis. Adsorption capacity of the beads was evaluated under both batch and dynamic conditions. The adsorption capacity for Fullers earth beads was found to be 26.3 mg/g of adsorbent at 293 K when the liquid phase concentration of cesium was 1000 mg/L. The adsorption capacity of Fullers earth cylinder was found to be higher than that of beads, however, it was concluded that the alkaline nature of the cylinder precipitated out cesium increasing its capacity. The capacity of Fullers earth beads decreased by almost 62% when 1 mol/L NaCl and 2.25 mmol/L of strontium were present in the solution. The Freundlich, the Langmuir isotherm equations, and a modified Polanyi's equation were used to correlate the data. The isosteric heats of adsorption suggested the heterogeneity of the surface and multilayer coverage. The first order reversible kinetic model adequately described the dynamic system during the adsorption process. The adsorption (k₁) and desorption (k₂) rate constants were evaluated from the dynamic model.     

Removal of Suspended Solids and Petroleum Products from Aqueous Media

Theoretical Foundations of Chemical Engineering - Helical filter elements and a fibrous material based on basalt wool have been studied as potential filtering materials for removing solid...     

Modeling Ion-Exchange Processing with Spherical Resins for Cesium Removal

The spherical Resorcinol-Formaldehyde and hypothetical spherical SuperLig® 644 ion-exchange resins are evaluated for cesium removal from radioactive waste solutions. Modeling results show that spherical SuperLig® 644 reduces column cycling by 50% for high-potassium solutions. Spherical Resorcinol Formaldehyde performs equally well for the lowest-potassium wastes. Less cycling reduces nitric acid usage during resin elution and sodium addition during resin regeneration, thereby significantly decreasing life-cycle operational costs. A model assessment of the mechanism behind “cesium bleed” is also conducted. When a resin bed is eluted, a relatively small amount of cesium remains within resin particles. Cesium can bleed into an otherwise decontaminated product in the next loading cycle. The bleed mechanism is shown to be fully isotherm-controlled vs. mass transfer controlled. Knowledge of residual post-elution cesium level and resin isotherm can be utilized to predict rate of cesium bleed in a mostly non-loaded column. Overall, this work demonstrates the versatility of the ion-exchange modeling to study the effects of resin characteristics on processing cycles, rates, and cold chemical consumption. This evaluation justifies further development of a spherical form of the SuperLig® 644 resin.     

Spherical Resorcinol‐Formaldehyde Resin Testing for Cesium Removal from Hanford Tank Waste Simulant

Abstract

A new spherical form of resorcinol‐formaldehyde (RF) resin was tested for efficacy of cesium removal from Hanford tank waste. Two spherical RF formulations, prepared by varying curing temperature, were tested. Both resins had a tight particle size distribution and a high degree of sphericity. Small‐scale column testing (on ～20‐mL resin beds) was conducted evaluating the cesium load profile with AZ‐102 simulated tank waste and the cesium elution profile using 0.5 M HNO₃ eluant. The load and elution profiles were compared in side‐by‐side testing with ground‐gel RF resin and SuperLig® 644, the Waste Treatment Plant baseline ion exchanger. Although breakthrough capacity was not as high as the other resins tested, the spherical RF resin met plant cesium loading requirements with the AZ‐102 simulant matrix. Excellent reproducibility of cesium load and elution was demonstrated over three process cycles with no evidence of degraded performance. Residual cesium on the resin beds after elution was nearly a factor of 10 lower than that of the ground‐gel RF and SuperLig^® 644.     

The Effectiveness in the Removal of PAHs from Aqueous Solutions in Physical and Chemical Processes: A Review

Polycyclic aromatic hydrocarbons (PAHs) are relatively well-known organic pollutants and due to their carcinogenic and mutagenic properties, their presence in the aqueous environment still attracts a lot of attention. This article presents a critical review of the literature on the application of physical and chemical processes for removal of PAHs from aqueous solution, including water and wastewater. The effectiveness of coagulation, chemical oxidation, photodegradation, sorption, and membrane processes in the degradation or removal of these micropollutants is described. The PAHs removal efficiency (coagulation ～ 99%, chemical oxidation ～ 87%, photodegradation ～ 93%, sorption ～ 100%, and membrane ～ 100%) during the above processes is difficult to compare due to the works conducted under different conditions and using various mediums, e.g., water, wastewater, PAHs model aqueous solutions.     

Application of Comparative Method for Estimating Microporosity of Porous Solids in Adsorption from Solutions

The concept of a comparative method in terms of the liquid adsorption on solids is presented. This method is based on comparison of the excess adsorption isotherm on a porous solid with that measured on a reference nonporous adsorbent. It is proved that proposed approach gives the possibility for separating a total excess adsorption isotherm into partial isotherms, proper for micro- and mesopores. Several experimental systems are analyzed to illustrate the usefulness of the comparative method for evaluating the surface phase capacity, which presents an important quantity in the study of adsorption from solution in the whole concentration region. The comparative method examined for adsorption systems of microporous active carbons seems to be useful for investigating other porous materials as silica gels, zeolites or metal oxides.     

Experimental Studies on Electrodeionization for the Removal of Copper Ions from Dilute Solutions

Abstract

The purpose of this study is to investigate the ability of electrodeionization to remove copper ions from dilute solutions without chemical regenerations. Experiments were carried out in a bench‐scale stack using a feed solution containing about 50 mg/L of copper. It was demonstrated that electrodeionization operated in either the “enhanced transfer” or the “electroregeneration” regime. In the “electroregeneration” regime, the process was able to produce a pure water product containing non‐detectable concentrations of copper, while CuO scale was found on the surface of anion exchange membranes. With optimal conditions, a steady and continuous process can be achieved.     

Selective Cesium Removal from a Sodium Nitrate Aqueous Medium by Nanofiltration—Complexation

Abstract

In aqueous medium, selective complexation increases the ionic separation by nanofiltration. Within the context of the nuclear effluent treatment, the nanofiltration-complexation association is applied to sodium/cesium separation. Resorcinarene, a water-soluble ligand of cesium, is associated to the FILMTEC NF 70 membrane. Effects of pH, transmembrane pressure, ligand concentration, and ionic strength on salts retention and filtration fluxes are described. Finally, cesium complexation constants with resorcinarene are determined by using the nanofiltration-complexation process.     

Removal of Detergents from Aqueous Solutions by Foaming

Abstract

The anionic (sodium tetrapropylenebenzenesulfonate, Nansa HS-55) and nonionic (polyethoxylated alkylphenol, Alfenol) detergents were removed by the foaming method. It was found that there is a possibility of improving the foaming effect of a nonionic detergent by the introduction of a feeding solution into the foam phase. As far as an anionic detergent is concerned, the influence of the kind of feeding was minor in the case of aqueous solutions as well as with those containing sodium chloride. A simple graphic method is presented for the determination of the number of the foaming processes or the number of columns which are to be used in order to obtain the required detergent removal effect.     

Cesium Absorption from Acidic Solutions Using Ammonium Molybdophosphate on a Polyacrylonitrile Support (AMP-PAN)

Abstract

Recent effort at the Idaho Chemical Processing Plant (ICPP) have included evaluation of cesium removal technologies as applied to ICPP acidic radioactive waste streams. Ammonium molybdophosphate (AMP) immobilized on a polyacrylonitrile support (AMP-PAN) has been studied as an ion exchange agent for cesium removal from acidic waste solutions. Capacities, distribution coefficients, elutability, and kinetics of cesium extraction have been evaluated. Exchange breakthrough curves using small columns have been determined from 1M HNO₃ and simulated waste solutions. The theoretical capacity of AMP is 213 g Cs/Kg AMP. The average experimental capacity in batch contacts with various acidic solutions was 150 g Cs/kg AMP. The measured cesium distribution coefficients from actual waste solutions were 3287 mL/g for dissolved zirconia calcines, and 2679 mL/g for sodium-bearing waste. The cesium in the dissolved alumina calcines was analyzed for; however, the concentration was below analytical detectable limits resulting in inconclusive results. The reaction kinetics are very rapid (2-10 minutes). Cesium absorption appears to be independent of acid concentration over the range tested (0.1 M to 5 M HNO₃).     

饮用水除砷工艺研究进展

介绍了饮用水中砷的毒性、卫生标准与我国饮用水砷污染现状。在国内外文献基础上,详细阐述现有各种处理工艺对饮用水中砷污染去除的原理、效果与优缺点,并作出简要评价。     

Separation of Organic Compounds from Surfactant Solutions: A Review

Abstract

This review summarizes the recent development in separation of emulsified organic compounds from surfactant solutions for surfactant reuse and/or surfactant‐contaminant disposal. Three major principles have been employed for separating organic compounds and/or surfactants from aqueous solutions, namely, organic compound inter‐phase mass transfer, surfactant micelle removal, and manipulation of surfactant solution phase behavior. Details of these principles and their applications are discussed, with the advantages and limitations of each separation method compared. Separation based on mass transfer of the organic compounds into a secondary phase is currently more practical than the others. Finally, two major issues requiring further research are identified.     

Sorption of Cesium and Strontium Radionuclides by Synthetic Ivanyukite from Model and Process Solutions

Theoretical Foundations of Chemical Engineering - The sorption of 137Cs and 90Sr radionuclides from model and real solutions of various salt compositions has been studied on a synthetic powder and...     

Cesium Removal Demonstration Using Selected Actual Waste Samples from the Hanford Reservation Tank Farm

Abstract

Approximately 40 million curies of Cs‐137 are currently contained in High Level Waste stored in 177 underground storage tanks at the Hanford Nuclear Reservation near Richland, Washington. A series of actual waste, small‐scale column tests were performed to evaluate the performance of a selected ion exchange resin for cesium removal from a range of planned feed streams. These tests demonstrated that the selected cationic resin–SuperLig 644^®‐has more than adequate resin capacity to treat each of three potential feed streams. Furthermore, tests indicate an acceptable mass transfer zone for each of the three types of feed material, and that the elution of the resin can be accommodated within the design criteria for the proposed Waste Treatment Plant.     

Flotation Using Microgas Dispersions for the Removal of Pentachlorophenol from Aqueous Solutions

ABSTRACT

Microgas dispersions called colloidal gas aphrons (CGAs) were generated using cationic, anionic, and nonionic surfactants, and were used in an adsorptive bubble flotation process in a semibatch mode to remove pentachlorophenol (PCP) from the aqueous phase. The aqueous solution was maintained at pH values by using buffers. CGAs generated with Tergitol, which is a nonionic surfactant, were found to be the most efficient for the removal of PCP; the efficiency remained nearly independent of pH. In the case of an anionic surfactant, sodium dodecylbenzene sulfonate (DDBS), the efficiency of removal improved from 15 to 36% with a change in pH from 10.1 to 3.0. For a cationic surfactant, hexadecyltrimethylammonium bromide (HTAB), the removal at pH 10.1 was 81%, which decreased to 68.1% at pH 3.0. The charges on the encapsulating film of CGAs may explain the higher percentage of adsorption of PCP on the CGAs generated using HTAB as compared to CGAs generated using DDBS. For all the surfactants, an increase in concentration improved the removal efficiency. These results were compared with the removal efficiencies using conventional flotation techniques used by other researchers. Solvent sublation appears to be effective in the removal of PCP, but even in the presence of a surfactant it required 300% more air volume per volume of liquid when compared with CGA flotation.     

Removal of Lead from Aqueous Solutions Using Rice Husk

ABSTRACT

Rice husk, an agricultural waste, was studied as a potential scavenger of lead from various aqueous solutions. Physicochemical parameters such as selection of appropriate electrolyte, shaking time, and the concentrations of adsorbent and adsor-bate were studied to optimize the conditions to be utilized on a commercial scale for the decontamination of effluents using a batch technique. Maximum adsorptionwas observed with 0.01 mol·dm?³ acid solutions (HNO₃, HC1, H₂SO₄ and HC1O₄) using 1000 mg of adsorbent for a 4.82 × 10?⁵ mol·dm?³ lead concentration in less than 10 minutes equilibration time. Studies show that the adsorption decreases with an increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the 9.65 × 10?⁵to4.83 × 10?³ mol·dm?³ range of lead concentration. The characteristic Freundlich constants, i.e.,l/n = 0.93 ± 0.04 and A = 19.86 ± 0.82 m·mol·g?¹, have been computed for the sorption system. Thermo- dynamic parameters, i.e.,ΔG°ΔSdeg;,and ΔHdeg; have also been calculated for the system.