Ion Exchange for Product Recovery in Lactic Acid Fermentation

Abstract

Lactic acid fermentation is a product-inhibited fermentation, and product recovery costs in downstream processing are considerable. In this paper the feasibility of ion exchange as a technique for product separation is investigated. In initial experiments an indigenously manufactured weak-base resin was found to show promise, and detailed equilibrium and kinetic data required for design and scale-up of the separation process have been obtained for this resin under conditions of relevance to the fermentation. The equilibria show Langmuir-type characteristics. The equilibria have also been established with HCl, which is a possible eluent. Kinetic studies show that the uptake can be described by a shrinking-core mechanism, with diffusion through the particle controlling. The effect of important medium components such as glucose and phosphate on the uptake of lactic acid has been established. Studies of the uptake of these components from fermentation media have been carried out.     

Removal of Alkaline Catalysts from Polyols by Ion Exchange

Abstract

Resin regeneration is crucial in the feasibility of polyol purification by ion exchange. In order to get an economically viable commercial process, a new regeneration process, including initial and final methanol flushing steps and treating with a 4.5 M aqueous mineral acid solution, has been investigated. An important reduction in regeneration costs was reached by minimizing the amount of acid used and recycling one part of the regenerant solution to the process. The composition of regeneration effluents has been studied in order to recover their valuable components. This simple resin regeneration technique lends itself to a technically and economically viable commercial process for the treatment of polyol products.     

A MECHANISM FOR ENHANCING IONIC ACCESSIBILITY INTO SELECTIVE ION EXCHANGE RESINS

ABSTRACT

A bifunctional monophosphonic/sulfonic acid ion exchange resin with high capacity has been synthesized. Metal ion studies have been carried out with europium, americium, and ferric nitrate in solutions of varying acidity, with and without sodium nitrate added. The bifunctional resin complexes far higher levels of Eu(III) from 0.5 and 1 N nitric acid than the monofunctional phosphonic acid resin. It is postulated that the sulfonic acid ligand provides an access mechanism for the metal ions into the polymer matrix by hydrating the matrix and preventing its collapse in high ionic strength solutions thus allowing for rapid ionic complexation by the selective phosphonic acid ligands. The bifunctional monophosphonic/sulfonic acid resin has both ligands bound to a polystyrene support. It complexes higher levels of metal ions than a comparable resin differing only by having the monophosphonic acid ligand directly bound to the C-C backbone. Results are compared to a diphosphonic / sulfonic acid resin.     

SOLVENT EXTRACTION CHEMISTRY: A FEW THOUGHTS ABOUT ITS INTERDISCIPLINARY NATURE,CHALLENGES AND OPPORTUNITIES

Abstract

In this article, the results of the application of a boron removal treatment based on a process of chemosorption on liquid waste of urban, agricultural, or industrial origin is presented. The isotherms of the process have been established and a study of the influence of the different variables in the tests in columns has been carried out. The results obtained indicate that the process of chemosorption shows strongly favorable isotherms, and moreover it is notably influenced by the variable “flow rate,” making the breakthrough point appear earlier and the curves move towards the left. However, important differences in the curves for the variable “dimensions of the bed” have not been observed. Furthermore, a pH‐dependent mechanism for the treatment process of boronated effluents by means of chemosorption with the specific Amberlite IRA-743 resin was developed. According to breakthrough point data, experimentally achieved in elution tests for the maximum value allowed by environmental legislation, of 3 mg B L^?1, a double mechanism is proposed. It can be suggested that for basic pH the mechanism corresponds to stereospecific reactivity between the borate ion and hydroxide groups of the N‐methylglucamine active site of the resin in cis‐position, a maximum appearing between pH 8.5 and 9.5, corresponding to borate ion predominance. On the other hand, a mechanism based on the hydrogen bridge bond formation reaction between the ionized amino group of the resin and boric acid is suggested for neutral and slightly acid pH. This last reaction differentiates this resin from the other absorbents used for boron removal in industrial wastes, such as metallic oxides, clays, humic acids, and so on.     

KINETICS OF URANIUM EXTRACTION BY MACROPOROUS BIFUNCTIONAL PHOSPHINIC ACID RESIN

ABSTRACT

The rate of extraction of uranium by macroporous bifunctional phosphinic acid (MPBPA) resin from nitric acid medium has been studied under particle diffusion controlled conditions. The internal diffusion coefficient was found to increase with increase in temperature and decrease with increase in particle size. The activation energies and entropies suggest that the extraction of uranium essentially follows ion exchange mechanism at low concentration of nitric acid while it is through linkage of >P=0 group of the resin at high concentrations.     

Implications of Weak Donnan Potential in Ion-Exchange Reactions. An Alternate Strategy for Modeling Sorption Processes

ABSTRACT

Donnan potential generated during an ion-exchange process is conventionally believed to play an important role in partitioning co-ions in the resin and solution phases; most earlier studies implied near total exclusion of co-ions from the resin pores. The present work attempts to investigate implications of weak Donnan potential with specific reference to the sorption of acids on weak base resins. An alternate mathematical treatment has been proposed to describe the sorption behavior of any type of acid by assuming diffusion and sorption of single species, the composite acid molecule, in the resin pores. Fick's law is then used to characterize the diffusion process. The proposed model is validated using data reported in the literature for the sorption of a strong monobasic acid (HCl) and also for a weak monobasic acid (HCOOH). The fit of the model is excellent, and the regressed values of the effective diffusion coefficient are shown to be reasonable and correct to the order of magnitude. The model is expected to offer a simpler and unified approach for modeling sorption behavior of different types of acids and will be more useful in problems of acid separation from mixtures.     

OXIDATIVE TREATMENT FOR THE PREVENTION OF CHROMIUM ACCUMULATION IN A POLYMERIC MATRIX

ABSTRACT

Chromium (III) species tend to accumulate in the organic matrix with carboxylic groups like weak acid ion exchanger resins. Using conventional acidic solutions, chromium (III) can be partially eluted in some circumstances, while an oxidative stripping using hydrogen peroxide in alkaline media seems to be useful. Previously, Cr(III)–H₂O₂ reaction has been studied in aqueous solutions (homogeneous system) at 20°C, testing for 0.5, 1.0 and 2.0?mM of Cr(III) as total metal concentration. The effect of hydroxide ion on the rate of oxidation was also examined. Chromate was continuously monitored using an FIA system. The general mechanism of the homogeneous reactions has been postulated and the main kinetic parameters of the reactions have been calculated. Ageing of chromium (III) solutions has an important effect on the experimental results. Metal elution from cationic resin is usually carried out by strong acids, but here chromium loaded onto a cation-exchange resin is completely stripped after oxidation to chromate ion. The reaction rate is mainly controlled by intraparticular diffusion of the anionic species through the cationic resin. Surprisingly, these are not rejected from the resin phase by the Donnan exclusion. This apparently anomalous behaviour has been explained in terms of the reaction mechanism.     

Novel Bifunctional Resins in Metal Ion Separations: Ion Exchange/Coordination Resins and Ion Exchange/Precipitation Resins

Abstract

Dual mechanism bifunctional polymers (DMBP's) as metal ion extractants are described within the context of two new examples. The carboxylic acid/pseudocrown resin is a new example of the DMBP class of resins described as ion exchange/ coordination resins. The polyethylene glycol ligand within the resin functions as a coordinating site for metal ions which are brought into the resin via ion exchange with the acid ligand. Initial studies with alkali metal ions are presented. The third general class of DMBP's is also presented. In this case, precipitation is the reaction occurring along with ion exchange thus yielding the ion exchange/precipitation resins. Barium recovery from aqueous solution via barium sulfate precipitation is described.     

Absence of Donnan Exclusion at High‐Concentration Ion Exchange for Macroporous Anionic Resin

Abstract

High‐concentration ion exchange has been studied for an anionic macroporous resin. The mechanism of interaction of Lewatit MP‐500 (strong base resin) with several high‐concentration inorganic salts was analyzed in order to determine the effect of the Donnan potential in the process.

The systems under study were Cl^?, SO₄ ^2? as counter‐ions and K⁺, Na⁺ as co‐ions in different combinations as single electrolytes. These salts were chosen because of their interest as raw materials in the fertilizer industry. The study focuses mainly on the behavior of high‐concentration (over 1 M) counter‐ and co‐ions in the anionic resin. The results showed that Donnan exclusion does not take place completely and that electrolyte penetration inside the resin is observed. Furthermore, a certain amount of ion exchange was observed for the co‐ions (K⁺ and Na⁺) when the resin was presaturated with sulphate and chlorides that were present in the solution. Equilibrium and kinetics data were obtained under these special experimental conditions. Equilibrium constants were obtained for counter‐ions and adsorption constants for co‐ions using a constant separation factor isotherm, while diffusion coefficients were obtained using a pore diffusion model.     

Investigation of Selectivity and Kinetic Behavior of Strong‐Base Ion Exchange Resin Purolite A 520E for Nitrate Removal from Aqueous Solution

Abstract

The aim of this work is to present experimental results on the removal of nitrate by nitrate selective ion exchange resin, Purolite A 520E. The resin particle size, nitrate concentration, temperature, and stirring speed were investigated as experimental parameters and the optimum conditions for nitrate removal were determined. Nitrate removal by strong base anion exchange resin Purolite A 520E was carried out with the batch method in the presence of chloride and sulfate ions. The existence of a high concentration of competing ions in a solution resulted in a reduction of nitrate removal. Nitrate removal ratios decreased from 98% to 85% and 88%, respectively, in the presence of chloride and sulfate ions when the chloride and sulfate ratios were increased in solution. The process kinetics were predicted by using Homogenous Diffusion Models. It was seen that about 98% of nitrate in the aqueous solution could be removed using optimum conditions.     

Evaluation of Elution Parameters for Cesium Ion Exchange Resins

Abstract

Cesium ion exchange is one of the planned processes for treating and disposing of waste at the U.S. Department of Energy Hanford Site. Radioactive supernatant liquids from the waste tanks will undergo ultrafiltration, followed by cesium ion exchange using a regenerable organic ion exchange resin. Two resins, SuperLig^®644 and a resorcinol‐formaldehyde resin, are being evaluated for cesium removal and cesium elution characteristics. The main purpose of this study is to optimize the cesium elution to provide a resin that, after undergoing elution, would meet the U.S. Department of Energy/Office of River Protection Project‐Waste Treatment Plant processing and resin disposal criteria. Columns of each resin type were loaded to greater or equal to 90% breakthrough with a Hanford waste stimulant and eluted with nitric acid. The temperature, flow rate, and nitric acid concentration were varied to determine the optimal elution conditions. Temperature and eluant flow rate were the most important elution parameters. As would be predicted based upon kinetic consideration alone, decreasing the eluant flow rate and increasing the temperature provided the optimal elution conditions. Varying the nitric acid concentration did not have a significant effect on the elution completion; however, elutions performed using both high acid concentration (1 M) and elevated temperature (45°C) resulted in resin degradation, causing gas generation and resin bed disruption.     

Removal of inorganic mercury from mine waste water by ion exchange

The present study has been undertaken to investigate a process that might remove inorganic mercury from mine waste water streams by use an ion exchange resin system. A number of commercial resins have been evaluated as ion exchangers and the mercury content of the waste water, ranging from 70 to 90 ppm, is reduced to a permitted level of 34 ppb. Dowex XZS‐1, a strong cationic ion exchanger in a gel Form, has the most pronounced selectivity for mercury. The loaded resin was regenerated efficiently using HCl solutions, due to increased competition between Hg and hydronium ions and formation of an HgCl ₄ ²⁻ ionic complex. © 2000 Society of Chemical Industry     

Preparation of silica supported 1-nitroso-2-naphthol-grafted- poly(p-hydroxystyrene) resin for the removal of trace cobalt from acidic solution

ABSTRACT

Trace cobalt ion in the zinc sulfate electrolyte is the most difficult to be removed among all metallic impurities and has the most detrimental effect on zinc electrowinning. In this study, poly(p-hydroxystyrene) resin was first prepared from polystyrene, and then 1-nitroso-2-naphthol was grafted onto poly(p-hydroxystyrene) resin through -O- group by a series of reactions to obtain the 1-nitroso-2-naphthol-grafted-poly(p-hydroxystyrene) resin. Finally, the grafted resin was supported on SiO₂. The supported resin could removal trace cobalt ions with good selectivity and reusability in the zinc sulfate leachate, which can meet the requirements of the industrial electrolytic zinc process.     

UPTAKE OF METAL IONS BY A NEW CHELATING ION EXCHANGE RESIN. PART 3: PROTONATION CONSTANTS VIA POTENTIOMETRIC TITRATION AND SOLID STATE 31P NMR SPECTROSCOPY

Abstract

A new chelating ion exchange resin which incorporates methylenediphosphonate, carboxylate, and sulfonate functional groups in a polystyrene-divinylbenzene matrix has been prepared. This resin exhibits exceptionally high affinity for polyvalent cations even from moderately acidic aqueous media. Metal ion coordination occurs primarily at the diphosphonate group with the secondary binding sites contributing to charge neutralization when necessary and possible, and to increasing hydrophilicity of the resin pores. In the present investigation, the protonation equilibria of the phosphonate groups in the resin are investigated via potentiometric titration and solid-state ³¹P NMR spectroscopy of the resin. Intrinsic equilibrium constants for the first two diphosphonate protonation reactions are pk₄7equal; 10.47 and pK₃ = 7.24. The last two protons added to the diphosphonate group are acidic having pK_a values less than 2.5. These protonation constants are consistent with those reported previously for monomer analog 1,1-diphosphonic acids. This result implies that thermodynamic data available in the literature can be used to predict the relative affinity of the resin for polyvalent cations.     

Bifunctional Phosphinic Acid Resins for the Complexation of Lanthanides and Actinides

Abstract

Phosphinic acid ion exchange/redox resins are synthesized by the reaction between polystyrene beads and phosphorus trichloride followed by base hydrolysis. The reaction requires a temperature of 73°C for full functionalization to occur. The effect of lower functionalization temperatures on resin acid capacity was determined and the concomitant effect on ion exchange investigated. The acid capacity was found to vary from 1.68 mequiv/g to 4.79 mequiv/g in the functionalization temperature range studied (15°C to 73°C). The percent resin sites loaded with zinc ions is independent of the actual capacity. The extracting ability of the phosphinic acid resin for europium, thorium, uranium, americium, and plutontutn was examined as a function of acid concentration from acid nitrate solutions both at varying and constant ionic strength. The phosphinic resins show better extraction for these ions than the sulfonic resins, especially from high acid solution (4M HNO₃) due to the superior coordination ability of the phosphoryl oxygen. They also show a higher selectivity for the ions tested over sodium. For example, under conditions where sulfonic resins absorb 85% of the plutonium in solution, the phosphinic acid resins absorb 99.7%.     

Note: Zr(IV)-Immobilized Resin Prepared by Surface Template Polymerization for Fluoride Ion Removal

Abstract

A novel adsorbent Zr(IV)-immobilized resin was prepared to remove fluoride ions from tap water and industrial wastewater. In order to enhance both the kinetics and efficiency, large pathways were formed in the resin for fluoride ion adsorption and the Zr(IV)-phosphate complexes were immobilized on the polymer surface by surface-template polymerization. The Zr(IV)-immobilized resin had a fluoride adsorption capacity of 0.30 mmol/g. The morphology of the Zr(IV)-immobilized resin was evaluated by measuring the specific surface area, pore volume, and pore size distribution. The resin possessed large amounts of large macropores with diameters around 300 nm. The molecular structure at the fluoride adsorption sites was investigated by measuring the amounts of phosphorus, zirconium, and fluoride ion in the resin, and developing a model complex using computational chemistry. On the polymer surface, a fluoride ion/Zr(IV)/dioleyl phosphoric acid complex with an ideal F:Zr:P mole ratio of 3:1:3 could be formed.     

RADIUM SEPARATION THROUGH COMPLEXATION BY AQUEOUS CROWN ETHERS AND ION EXCHANGE OR SOLVENT EXTRACTION

ABSTRACT

The effect of three water-soluble, unsubstituted crown ethers (15-crown-5 (15C5), 18-crown-6 (18C6) and 21-erown-7 (21C7) on the uptake of Ca, Sr, Ba and Ra cations by a sulfonic acid cation exchange resin, and on the extraction of the same cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions has been investigated. The crown ethers enhance the sorption of the larger cations by the ion exchange resin, thereby improving the resin selectivity over calcium, a result of a synergistic interaction between the crown ether and the ionic functional groups of the resin. Similarly, the extraction of the larger alkaline earth cations into. xylene by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group IIa cation separations have been obtained using each of the three crown ethers as the aqueous ligands and the sulfonic acid cation exchange resin. Even greater separation factors for the radium - calcium couple have been measured with the crown-ethers and HDNNS solutions in the solvent extraction mode. The application of the uptake and extraction results to the development of radium separation schemes it discussed and a possible flowchart for the determination of ²²⁶Ra/²²⁸Ra in natural waters is presented.

     

Cyanide Recovery from Gold Extraction Process Waste Effluents by Ion Exchange II. Modelling of the Fixed Bed Operation

Abstract

An ion exchange operation in a fixed bed column is tested as a method to recover copper cyanide complexes from gold extraction process waste effluents. With this aim in mind, load and elution breakthrough curves are obtained using the anionic resin Lewatit MP500. A good performance of the resin in the load stage can be deduced from the breakthrough curves obtained in all the assays at two different pHs (12, 8.5). After load step operation, column elution was carried out using NaSCN 1.25 M as eluent. A good elution peak is obtained in all cases, indicating a good performance of the resin and the eluent in this stage. With the aim of testing the design of the industrial operation, a phenomenological model is tested by fitting experimental data to theoretical equations. The model used for the simulation of both steps incorporates axial dispersion, ion exchange equilibrium, and diffusion inside particles described by the linear driving force approximation, as well as taking into account the fact that the resistance to mass transfer controls the kinetics of the ion exchange process. The models are able to simulate the experimental load and elution results reasonably well.     

Diphonix® Resin: A Review of Its Properties and Applications

Abstract

The recently developed Diphonix® resin is a new multifunctional chelating ion exchange resin containing geminally substituted diphosphonic acid ligands chemically bonded to a styrene-based polymeric matrix. Diphonix can be regarded as a dual mechanism polymer, with a sulfonic acid cation exchange group allowing for rapid access, mostly non-specific, of ions into the polymeric network, and the diphosphonic acid group responsible for specificity (recognition) for a number of metal cations. The Diphonix resin exhibits an extraordinarily strong affinity for actinides, especially in the tetra- and hexavalent oxidation states. Therefore the resin has potential for applications in TRU and mixed waste treatment and characterization, and in the development of new procedures for rapid actinide preconcentration and separation from environmental samples. Metal uptake studies have been extended to alkaline earth cations, to transition and post-transition metal species, and to metal sorption from neutral or near neutral solutions. Also the kinetic behavior of the resin has been investigated in detail. In view of the above applications the influence of the most commonly occurring matrix constituents (Na, Ca, Al, Fe, hydrofluoric, sulfuric, oxalic and phosphoric acids) on the uptake of actinide ions has been measured. This review paper summarizes the most important results obtained in the studies on the properties of the Diphonix resin and gives an overview of the applications already in existence or under development in the fields of mixed waste treatment, actinide separation procedures, treatment of radwaste from nuclear power and fuel processing plants, and removal of iron from copper electrowinning solutions.

     

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.