Papers by Keyword: Electrodialysis

Abstract: Membranes are used in various different applications in water treatment due to the wide array of properties that can be attained from different materials and polymers. A new hybrid membrane for the purification of water by electrodialysis has been manufactured and studied in this research. The membrane consists of two different materials: A host polymer matrix and a cation selective metal organic framework, MOF. For the polymer matrix, polyvinylidene fluoride, PVDF, was selected to act as the body that is meant to be the backbone of the membrane. It was dissolved in different solvents with different concentrations to determine the most stable matrix. Using scanning electraon microscope, SEM, imaging, it was found that 10% wt in dimethylformamide (DMF) provided the most suitable conditions for this work. As for the cation selective MOF, UIO-66 was selected and then synthesized using hydrothermal method and characterized using X-ray diffraction, XRD, and found to match previous literature. UIO-66 provides the membrane with cation selectivity, which allows the membrane to function in an electrodialysis system, so it was dissolved with the PVDF matrix to provide a hybrid membrane. Different amounts of the MOF in the membrane matrix were tested to find the most suitable distribution of the MOF over the surface of the membrane and was found to be around 2%. The membrane was tested with LiCl salt, before and after UIO-66 addition, in a half cell to measure the influence of the UIO-66 as a cation selective material and its effect on ion migration.

Abstract: Reverse Osmosis (RO) Brine is waste generated from the desalination process using the RO method. RO Brine is generally directly thrown back into the sea, even though it has the potential to be reprocessed because it still contains a variety of ions in it. The best method in RO Brine processing is Electrodialysis. But it has a problem of decreased membrane performance caused by the formation of fouling. The fouling problem can be overcome by doing a pretreatment process to eliminate impurities contained in RO Brine, one of which is Ca²⁺. The existence of Ca²⁺ can trigger the formation of CaSO₄ deposits. Therefore, it needs excess reagent Na2CO3 with a certain amount to eliminate the whole Ca²⁺. Currently, it isn’t yet known the best pretreatment conditions that can eliminate impurities ions and produce high concentrations of NaCl. Pretreatment trials are needed in various variations of reagents amount to reduce impurities. The purpose of this study is to find out the best RO Brine pretreatment process that will later be used for the electrodialysis process to produce high NaCl recovery. The best results were obtained in the pretreatment process with variations NaOH excesses by 15% and Na₂CO₃ by 30% from the ideal stoichiometry.

Abstract: This study aims to increase the efficiency of Li ion recovery via electrodialysis technique by manipulating several parameters. The membrane used for this study consists of a polymer matrix that acts as a backbone, and a metal organic framework (MOF) that acts as the cation selective agent. Polyvinylidene fluoride (PVDF) was chosen for this study due to its mechanical properties and chemical stability. UIO-66 was chosen as the cation selective MOF and prepared via hydrothermal method and characterized using XRD. The membrane matrix was synthesized using phase inversion casting technique. After casting, the membrane was characterized using XRD and FTIR to ensure that the MOF was successfully embedded. The investigated operation parameters are voltage applied, initial Li ion concentration, and time of operation. The tests were conducted at a selected value of each other controlled variable while manipulating only one variable at a time. The studied concentrations were 100, 200, 300, and 400 ppm, while the applied voltage varied from to 10 to 40 V with a 10 V step. The time parameter studeid was 1, 2, 3, and 4 hrs. This study aims to show the parameters’ effects on the recovery of the lithium ion. The highest recovery was recorded for each parameter.

Abstract: The extraction of copper (II) ions using di (2-ethylhexyl) phosphoric acid – based liquid membranes during a galvanostatic electrodialysis-electrolysis process was studied. Effects of the current density, copper (II) and hydrochloric acid concentration in the feed solution, carrier and admixture concentration in the liquid membrane, type of acid in the catholyte were studied, and the optimal conditions were determined. A practically complete removal of copper (II) from the feed solution containing 0.01 M CuCl₂ was achieved during 3.0 −4.0 h of electrodialysis. A possibility of effective transfer and electrodeposition of copper (II) from dilute solutions of sulfuric, hydrochloric, perchloric, nitric and acetic acids was shown. Adherent copper coatings with a fine-grained structure were obtained from dilute sulfuric acid solutions. A maximum stripping degree into the catholyte of 88 % and an electrodeposition degree of 73 % were achieved in the studied system.

Abstract: This chapter is devoted to organic-inorganic composite ion exchange resins and membranes. We ascertain interrelation between composition, morphology and porous structure of the materials on the one hand and ion transport through them on the other hand. The composites for different practical application (fuel cells, ion exchange columns, electrodialysis) are in a focus of attention. Porosity of a polymer constituent of the composite was determined with a method of standard contact porosimetry, which gives information about pores in a very wide diapason (from 2 nm to 200 μm). In this context, pore formation in ion exchange polymers during swelling is considered. A number of parameters, which are obtained from porosimetric measurements, can be used for interpretation of ion transport regularities, particularly evolution of electrical conductivity. Embedded non-aggregated nanoparticles, their aggregates and agglomerates affect differently porosity of the polymer constituent: they are able to block, stretch and squeeze pores, As a result, the composites demonstrates different rate of ion transport depending on amount and size of the inorganic particles. The approach to purposeful formation of one or other types of particles has been proposed.

Abstract: The processes of Zn²⁺ and Pb²⁺ extraction by bulk liquid membranes containing di (2-ethylhexyl) phosphoric acid and tri-n-octylamine during galvanostatic electrodialysis accompanied by electrodeposition of the metals were studied. The effects of the current density as well as of composition of the liquid membranes and aqueous solutions on the rate of zinc (II) and lead (II) transport were determined. It was demonstrated that a practically complete removal of zinc (II) and more than 90 % extraction of lead (II) from the feed solutions containing 0.01 M ZnSO₄ or 0.01 M Pb (NO₃)₂ was achieved during 1.0 − 5.0 h of electrodialysis. A possibility of effective transfer of zinc (II) into dilute solutions of sulphuric, hydrochloric, perchloric and acetic acids was shown. Adherent zinc and lead coatings with a fine-grained structure have been deposited on the platinum cathode. More than 75% of zinc (II) and about 60% of lead (II) was deposited from solutions of sulfuric acid and perchloric acid, respectively.

Abstract: Reducing the negative environmental impact and securing the efficient use of water resources are key factors in the mining-metallurgical industry. At the enterprises of non-ferrous metallurgy the residual waters contaminated by a substantial amount of ions of heavy metals, sulphates and other impurities are formed. A promising way of their deep treatment consists in membrane technologies. This paper presents the results of pilot testing of ultrafiltration, electrodialysis, reverse osmosis and ion exchange technologies for purification residual waters of metallurgical enterprise of the Middle Ural. The possibility of using these technologies to achieve the final result – obtaining treated water, that meets the standards for fishery water bodies, is presented. It is reasonable to use the resulting water for the technical needs of the enterprise, which will significantly reduce the fresh water consumption and the environmental load, providing the ecological and economic benefits.

Abstract: A novel method for Co (II) and Pb (II) recovery from acidic solutions is presented. The extraction of Co (II) and Pb (II) ions using the bulk liquid membranes during a galvanostatic electrodialysis process accompanied by cathodic electrodeposition of the metals was studied. Solutions of di (2-ethylhexyl) phosphoric acid (D2EHPA) with admixtures of tri-n-octylamine (TOA) in 1,2-dichloroethane were used as the liquid membranes. Effects of current density, Co (II) and Pb (II) concentrations in the feed solution, sulfuric or nitric acid concentration in the feed solution, D2EHPA and TOA concentration in the liquid membrane, of the type and concentration of acid in the cathodic solution were studied, and optimal conditions were determined. It is demonstrated that a practically complete (98-99%) removal of Co (II) and Pb (II) from the feed solutions containing 0.01 mol∙L^-1 CoSO₄ or 0.01 mol∙L^-1 Pb (NO₃)₂ is achieved during 1.0 − 4.0 h of electrodialysis. A possibility of effective transfer of Pb (II) into dilute solutions of perchloric and nitric acids was demonstrated. The liquid membranes ensure the recovery of Co (II) ions into dilute solutions of perchloric, sulphuric, hydrochloric and nitric acids. Adherent, compact cobalt and lead electrodeposits with a fine-grained structure were obtained in the studied systems.

Abstract: Cation and anion exchange membranes were prepared by radiation-induced graft polymerization of ethyl styrenesulfonate and chloromethyl styrene, respectively, onto poly (ethylene-alt-tetrafluoroethylene) (ETFE) films, followed by hydrolysis in the former case and quaternization in the latter case. The degree of grafting as well as the ion exchange capacity (IEC) and the conductivity of the prepared membranes were investigated. Furthermore, the cation and anion exchange membranes were tested in an electrodialysis cell using CsNO₃ aqueous solution in the dilute compartment. It was found that the high-IEC membranes enhanced the electrodialysis speed, while the low-IEC membranes showed the high percent removal.

Abstract: The wastewater contained Cu²⁺ which the concentration ranged from 10 to 50 mg/L are used as the target, to investigated the influences of experiment conditions on the treatment efficiency by electrodialysis enrichment experiments, the authors designed the electrodialysis device, and copper sulfate solutions are used as the objectives. The experiments were investigated when the membrane adsorbed bubbles and removing bubbles, the results show that removing bubbles can improve the efficiency of the concentration and desalination. During the electrodialysis process, the intensity of light chamber has effects on the current intensity, the study in this paper proposed a optimization program for the existing electrodialysis devices.