INNOVATIVE APPROACHES TO SYNTHESIS OF GT 267-004, A SEQUESTRANT FOR C. DIFFICILE TOXIN

GT 267-004 is a nonabsorbed, nonantibiotic, high molecular weight anionic polymer that is undergoing clinical evaluation as a Clostridium difficile toxin sequestrant. The active pharmaceutical ingredient (API) is a mixed salt form that consists of approximately 30 to 50% potassium and 70 to 50% sodium as the counterions on the polymer. The initial polymerization process results in an aqueous polymer solution with the polymer in the 100% sodium form. This article describes the use of two innovative approaches, electrodialysis (ED) and ion exchange using ion exchange resins (IXR), to convert the single-salt polymer to the mixed-salt form. Electrodialysis experiments were conducted using a stack of five cells, each of which contained two cation and one anion exchange membranes. The electrodialysis was run in batch mode with a sodium chloride solution as the concentrate stream and a potassium chloride solution as the diluate stream. The ED process was monitored on-line by measuring the conductivity of the streams. Yield loss of the API through the ED membranes was minimal. The ED process was found to be fast, efficient, and reproducible. The ion exchange experiments were conducted using a strong acid cation resin in the potassium form. By using a fixed bed column mode, an appropriate amount of ion exchange was carried out to produce the mixed-salt API in the effluent stream. The resin bed could be regenerated using KCl solution and reused for subsequent batches of polymer solution. The recovery of the API in the product solution was excellent. The ion exchange route was used to synthesize radio-labeled API for clinical trials.     

Studies on transport properties of short chain aliphatic carboxylicacids in electrodialytic separation

An electrodialysis process was employed to investigate the concentration of formic, acetic and propionic acid solutions under different experimental conditions. In this process interpolymer-type ion-exchange membranes were used due their high chemical stability and durability. The effects of concentration, electric current and time on the electrodialysis process were studied. A mathematical equation representing the water transport behavior of the electrodialysis process for concentrating acids under the influence of different current densities was developed. This equation is valid for any electrodialysis process with ion-exchange membranes used under similar operating conditions. The reliability of the water transport equation was tested through comparison with the experimental data. Results indicate that electrodialysis is an effective method for concentrating shorter chain aliphatic carboxylic acid solutions. Ionic transportation, power consumption and current efficiency data reveal the following trend of the electrodialysis process's efficiency during concentration of carboxylic acid solutions: formic acid > acetic acid > propionic acid.     

Exergy analysis of a combined RO, NF, andEDR desalination plant

A brackish water desalination plant in California that incorporates RO, NF, and EDR units was analyzedthermodynamically using actual plant operation data. Exergy flow rates were evaluated throughout the plant, and the exergy flow diagrams were prepared. The rates of exergy destruction and their percentage are indicated on the diagram so that the locations of highest exergy destruction can easily be identified. The analysis shows that most exergy destruction occurs in the pump/motor and the separation units. The fraction of exergy destruction in the pump/motor units is 39.7% for the RO unit, 23.6% for the NF unit, and 54.1 % for the EDR unit. Therefore, using high-efficiency pumps and motors equipped with VFD drives can reduce the cost of desalination significantly. The plant was determined to have a Second Law efficiency of 8.0% for the RO unit, 9.7% for the NF unit, and 6.3% for the EDR unit, which are very low. This indicates that there are major opportunities in the plant to improve thermodynamic: performance by reducing exergy destruction and thus the amount of electrical energy supplied, making the operation of the plant more cost effective.     

Separation of copper ions by electrodialysis using Taguchi experimental design

With the aid of atomic absorption, a systematical and analytical evaluation method called Taguchi's quality engineering has been applied for the separation of copper ions from a solution using a laboratory electrodialysis set-up to evaluate the optimal experimental conditions and hence to achieve the highest removal percentage and the best robustness of the quantitation from the least number ofexperimental runs. Fourparameters at three levels were studied: concentration (100, 500, 1000 ppm), temperature (25, 40, 60°C), flow rate (0.07, 0.7, 1.2 mL/s) and voltage (10, 20, 30 V). Two types of different membranes with different ion-exchange capacities were used. The optimal levels thus determined for the four influential factors were: concentration 1000 ppm, temperature 60°C, flow rate 0.07 mL/s and voltage 30 V. It has also been found that using a membrane pair with higher ion-exchange capacity improves performance. The highest removal percentage was found to be 94.94% and 97.33% for the two types of membranes.     

用壳聚糖膜分离水溶液中的钛与钪的研究

用壳聚糖膜的电渗析法研究了水溶液中的Tio2十与SC3十的分离，讨论了电压、浓度、酸度对分离的影响．研究发现，电荷相同而电价不同的离子，如TiO2十与SC3十用电渗析法难以分离，而将其中的TiO2十转变为阴离子络合物则可实现TiO2十与SC3十的分离，且在适当的条件下可完全分离     

An evaluation of a hybrid ion exchange electrodialysis process in the recovery of heavy metals from simulated dilute industrial wastewater

Hybrid ion exchange electrodialysis, also called electrodeionization (IXED), is a technology in which a conventional ion exchange (IX) is combined with electrodialysis (ED) to intensify mass transfer and to increase the limiting current density and therefore to carry out the treatment process more effectively. It allows the purification of metal-containing waters, as well as the production of concentrated metal salt solutions, which could be recycled. The objective of this paper was to investigate the ability of the IXED technique for the treatment of acidified copper sulphate solutions simulating rinsing water of copper plating lines. A single-stage IXED process at lab-scale with a small bed of ion exchanger resin with a uniform composition was evaluated, and the treatment performance of the process was thoroughly investigated. The IXED stack was assembled as a bed layered with the ion exchanger resin (strong acid cation-exchange Dowex™) and inert materials. The stack configuration was designed to prevent a non-uniform distribution of the current in the bed and to allow faster establishment of steady-state in the cell for IXED operation. The influence of operating conditions (e.g. ion exchanger resin with a cross-linking degree from 2 to 8% DVB, and current density) on IXED performance was examined. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of IXED on (i) the abatement yield of the metal cation, which is a fundamental purification parameter and an excellent indicator of the extent of IXED, (ii) the current yield or the efficiency of copper transport induced by the electrical field and (iii) the energy consumption. The experimental results showed that the performance at steady-state of the IXED operation with a layered bed remained modest, because of the small dimension of the bed and notably the current efficiency varied from 25 to 47% depending on the conditions applied. The feasibility of using the IXED in operations for removal of heavy metals from moderately dilute rinsing waters was successfully demonstrated.     

Acid precipitation coupled electrodialysis to improve separation of chloride and organics in pulping crystallization mother liquor

Inefficient separation of inorganic salts and organic matters in crystallization mother liquor is still a problem to industrial wastewater treatment since the high salinity significantly impedes organic pollutant degradation by oxidation or incineration. In the study, acidification combined electrodialysis (ED) was attempted to effectively separate Cl^- ions from organics in concentrate pulping wastewater. Membrane's rejection rate to total organic carbon (TOC) was 85% at wastewater intrinsic pH=9.8 and enhanced to 93% by acidifying it to pH=2 in ED process. Negative-charged alkaline organic compounds (mainly lignin) could be liberated from their sodium salt forms and coagulated in acidification pretreatment. Neutralization of the organic substances also made their electro-migration less effective under electric driving force and in particular improved separation efficiency of chloride and organics. After acid-ED coupled treatment (pH=2 and J=40 mA·cm^-2)[TOC] remarkably reduced from 1.315 g·L^-1 to 0.048 g·L^-1 and[Cl^-] accumulated to 130 g·L^-1 in concentrate solution. Recovery rate of NaCl was 89% and the power consumption was 0.38 kW·h·kg^-1 NaCl. Irreversible fouling was not caused as electric resistance of membrane pile maintained stably. In conclusion, acidic-ED is a practical option to treat salinity organic wastewater when current techniques including thermal evaporation and pressure-driven membrane separation present limitations.     

Electrodialysis Application of the Ultrafiltration Permeate of Milk Before and After Reverse Osmosis

Ultrafiltered (UF) milk permeate was concentrated by reverse osmosis (RO). UF and UF + RO samples were then desalted by electrodialysis (ED) to three levels of desalination: 1, 2.5, and 4 % of ash in the dry matter. Ions were analyzed by a new high‐performance liquid chromatography method, which enables simultaneous estimation of cations and anions. ED of UF permeate has some advantages over that of UF + RO samples, including a shorter ED time and a higher average salt flow rate, but RO treatment of UF permeate before ED enables the processing of larger volumes of UF permeate. Therefore, ED of milk permeate, particularly after RO, improves the handling characteristics and may offer advantages for further processing of secondary dairy products.     

Zinc salt recovery from electroplating industry wastes by electrodialysis enhanced with complex formation

ABSTRACT

In this work, the possibility and effectiveness of a zinc salt recovery from simulated zinc electroplating wastes by electrodialysis enhanced with citric acid were discussed. It was concluded that zinc recovery exceeded 86%, with current efficiency in the range from 84.9% to 93.7%. Moreover, high iron retention coefficients equal to 92.4% and 94.5% respectively for experiments were observed. Lower value of retention coefficient was determined for copper ions (72.7% and 58%). It was found that electrodialysis enhanced with complex formation can be used for selective zinc recovery from wastewater.     

Novel anion exchange membrane with low ionic resistance based on chloromethylated/quaternized-grafted polystyrene for energy efficient electromembrane processes

A novel anion-exchange membrane has been manufactured by chloromethylation and subsequent quaternization of polystyrene within a graft copolymer films based on UV-oxidized polymethylpentene. Particular attention is given to the kinetics of chloromethylation and the influence of the reaction conditions on the properties of the anion-exchange membranes. By means of variation of the polystyrene content and its crosslinking degree we have obtained membranes that have an ion-exchange capacity from 1.1 to 2.9 mmole g⁻¹, anion transport numbers between 91.0 and 95.5% and specific ionic conductivities ( ranging from 2 to 25 mS cm⁻¹. The developed membranes due to their low thickness and high conductivities have a remarkably low surface ionic resistance of around 0.6 Ω cm². It was calculated that the use of the developed materials will increase the efficiency of reverse electrodialysis energy production by 8–10% compared to the state of the art membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48656.