Separation of sulfuric acid from spent acid using membrane based separation process-electrodialysis Synopsis of the thesis to be submitted in the partial fulfilment of the award of the degree of Doctor of Philosophy in Chemical Engineering (original) (raw)
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DESALINATION AND WATER TREATMENT, 2017
Five commercially available anion exchange membranes (AEMs) were evaluated in terms of their application to concentration of sulfuric acid by electro-electrodialysis. The membrane susceptibility to acid back diffusion decreased in the following order: ACM > FAB > AAV > AMI > AM-PP. The acid current efficiency decreased with acid concentration due to the proton leakage. The highest current efficiency in wide sulphuric acid concentration range were achieved with AAV and ACM membranes. The ability to concentrate sulphuric acid with tested AEMs raised as follows: AAV >ACM > AMI > AM-PP > FAB. The highest possible concentration of sulfuric acid achieved exceeded 3.5 mol dm-3 , however, the usable concentration range was found to be below 1.5 mol dm-3 .
Asian Journal of Chemistry, 2020
Cascaded electrodialysis system has been developed for increasing the concentration of sulfuric acid from aqueous solution using an interpolymer anion exchange (IPA) membrane. Enrichment process was carried out in a cascade of six electrodialyzers at 20.2 mA/cm2 current density. The performance of the process was evaluated rigorously in terms of current efficiency, voltage requirements and processability to enrich the acid concentration. The bench-scale experimental results exhibited the ability of membrane to perform as a low proton leakage membrane and to enrich the sulfuric acid concentration up to 27.93 wt. %. The higher values of current efficiencies were reported to be in the range of 50 to 60 %. Proton leakage through the membrane, acid back diffusion, concentration polarization and solution conductivity were considered to be the limiting factors for acid enrichment and their effects were found significant on current efficiency and voltage requirement.
Korean Journal of Chemical Engineering, 2018
Separation of sulfuric acid from a dilute solution involved a plate and frame type electrodialysis unit using a commercial anion exchange membrane. Experiments were conducted in batch with catholyte concentrations ranging from 1 to 5 wt%. Effect of applied current density, initial catholyte concentration and initial concentration difference of catholyte and anolyte on the molar flux was studied extensively. The maximum molar flux was estimated to be 10.52×10 8 mol cm 2 s 1 at 4.45 wt% catholyte concentration and applied current density of 30 mA cm 2. Current efficiencies were observed to be 75 to 85% at lower current density, which rose to more than 100% at 20 and 30 mA cm 2 , at equal initial concentration of catholyte and anolyte. Diffusive flux and flux due to membrane potential contributed very less compared to total flux in presence of applied electric current. An equation was developed to predict the practical molar fluxes, which fitted satisfactorily with minor standard deviation. Pristine and used membrane specimens were characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).
Journal of Membrane Science, 2016
In this paper, the consequences of traditional chemical cleaning on anion-exchange membrane structure and properties are thoroughly assessed. A homogeneous anion-exchange membrane (AEM1) and a heterogeneous one (AEM2) were subjected to ageing protocols in 2 M NaOH and 2 M HCl up to 700 h at room temperature. Moreover, both membranes were exposed to cleaning cycles in which they were soaked alternatively in 0.1 M HCl and 0.1 M NaOH (30 min each) from 100 to 400 h to simulate the cleaning-in-place (CIP) procedure commonly used in industrial electrodialysis stacks. Exposure to strong acidic conditions did not result in severe changes of the physicochemical properties of AEM1. In contrast, strong alkaline conditions resulted in the transformation of poly(vinyl chloride) (PVC), i.e. the polymeric binder of AEM1, into a polyene structure as a consequence of dehydrochlorination enhanced by the presence of quaternary ammonium groups. Additionally, a small part of the functional sites were degraded by E1 or E2 elimination reactions. On the other hand, the cleaning cycles caused entanglement modifications in the semi-interpenetrating polymer network structure of AEM1. This was a consequence of the constant changing of the equilibrating solutions nature, which led to membrane inflate-deflate sequences. Therefore, membrane toughness was deteriorated, thus leading to the formation of cracks and fractures, as observed before on the same type of membrane after industrial electrodialysis in which traditional CIP is performed through acid-base sequences. In contrast, the heterogeneous AEM2 suffered degradation in strong acid conditions, whereas it seemed to be more resistant than AEM1 in strong alkaline conditions. Regarding the HCl-NaOH cycles, modifications were more significant for AEM2. This investigation permitted to correlate membrane ageing resulting from such ex-situ acid-base cleaning cycles and that suffered after conventional electrodialysis during traditional CIP.
Hydrometallurgy, 1997
A performance study of four different cation-exchange membranes was conducted on laboratory and pilot scale (172 cm2/membrane, model CS-0 from Asahi Glass Co.) electrodialysis cells, using Neosepta CMS from Tokuyama Soda Co.; Morgane CRA from Solvay; Selemion CHV from Asahi Glass Co. and Nafion 117 from DuPont, coupled with a Morgane ARA 17-10 anion-exchange membrane. Comparisons were made of the sulphuric acid recovery rate, water transport, metal leakage and energy intake for these membranes. Proton permselectivity and metal leakage, co-and counter-ion transport numbers of the CMS membrane were investigated using Hittorf's method and radiotracer methods. This study shows that electrodialysis is suitable for the treatment of zinc hydrometallurgy effluents. However, R&D work must still be done in order to improve and optimize the technology for its use in future industrial applications. In particular, research efforts must concentrate on the synthesis of affordable and stable cation-exchange membranes showing high selectivity towards protons.
We disclosed an alternative method for controlled chloromethylation of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) in presence of paraformaldehyde, tri-methyl chlorosilane and Lewis acid catalyst. About 35–74% degree of chloromethylation (DCM) of PPO was achieved under optimized conditions. Reported method avoids the use of hazardous chemicals (such as chloromethyl methyl ether, and bromine) during preparation of AEM. AEMs with varied DCM were extensively characterized by measuring their physicochemical and electrochemical properties. Reported AEM-3 (DCM: 74%), was designed to possess all the required properties such as good water uptake (26.2%), ion-exchange capacity (1.61 meq·g −1), high permselectivity (0.98), and conductivity (7.67 × 10 −2 S cm −1) due to high molality of quaternary ammonium groups. Chronopotentiometry study of prepared membranes confirmed their homogeneous and alkaline nature suitable. Most optimized AEM-3 with splendid alkaline, oxidative and hydrolytic stabilities is a good candidate for electrodialysis.
Chromic acid recovery by electro-electrodialysisI. Evaluation of anion-exchange membrane
Journal of Membrane Science, 2005
Electro-electrodialysis (EED) is a promising technology for economic recovery of chromic acid in plating shops. It could potentially achieve chromic acid recovery, removal of metallic impurities and purification of static rinses in one step. There are however, process limitations. These are mainly, the poor stability of the applied anion-exchange membrane (AEM) against the oxidative chromic acid solution and the increase of the AEM resistance, especially at the starting phase of the process, due to the formation of polychromates in the membrane.
Desalination, 2003
Natural organic matter (NOM) is thought to be a major source of fouling during membrane filtration of natural waters. The organic matter present in surface waters was characterized in terms of its molecular weight distribution, acidity and electrokinetic properties. The fouling potentials of anion exchange membranes were predicted by the characterization. Changes in the physicochemical properties of anion exchange membranes were also examined during electrodialysis (ED) process of solutions containing NOM. The ED performances were evaluated for the three anion exchange membranes (AMX, AM-1 and ACM) in the presence of NOM. Fouling phenomena in terms of current efficiency and NaC1 flux were in good agreement with the fouling potentials predicted by the characterization results. Observations of the molecular weight distribution and the constituents of NOM revealed that the hydrophobic NOM fraction with high molecular weights deposited mainly on the membrane surface, providing fouling effects on the anion exchange membrane.
Canadian Journal of Chemical Engineering, 1994
In this work some mixtures of sulphuric and nitric acids have been separated and concentrated by selective electro-dialysis (SED) using heterogeneous membranes. Selective membranes can now be used for the separation of acids since anion exchange membranes with reduced transport number to multivalent ions are commercially available. The electric performance of the system has been analyzed and a correlation between current density, hydrodynamic parameters and concentration was established. The modelling of the SED experiments can be achieved with a good fitting for various membrane configurations of industrial interest.Experimental results show that at operation times lower than 40 minutes, the selective anion exchange membranes efficiently exclude the sulphate anions. The nitrate anions fall to zero concentration at 60 minutes of operation and then the sulphate anions begin to cross through the membrane.On a untilisé une technique d'électrodialyse sélective (SED) avec des membranes héterogènes pour la séparation de plusieurs mélanges d'acides nitrique et sulphurique. Des membranes sélectives aux anions sont actuellement disponibles avec des valeurs réduites des nombres de transport aux ions multivalents. On a étudié le rendement electrique du systéme et établie une corrélation en fonction de la densité de courant, des conditions hydrodynamiques et de la concentration des solutions utilisées. La modélisation des expériences d'électrodialyse sélective peut être réalissé en obtenant des résultats semblables aux expérimentaux pour plusieurs configurations des membranes ayant un intérêt industriel.Les résultats expérimentaux montrent que pour des temps d'opération inférieures à 40 minutes les anions sulphate sont exclus par la membrane avec une bonne efficacité. Lorsque la durée des expériences atteint 60 minutes la concentration des anions nitrate descend jusqu'à zero et alors les anions sulphate commencent à être transférés à travers la membrane.
Separation and Purification Technology, 2002
Two modified membranes are used for the treatment of industrial effluent by electrodialysis. This surface modification of membrane using both immersion and electrodeposition method improves the selectivity for monovalent ions against to divalent. In this work both neutralisation of the effluent and acid enrichment are achieved. The immersion method appears more efficient when not more than two compounds are inside the solution. On the other hand, electrodeposition technique should be used allowing to attain 2.8 N acid concentration. It was noticed that polyethyleneimine plays two different roles according to the modification method. The multilayer was formed by adsorption using immersion method though electrodeposition technique permits PEI to penetrate into the pores and play a role of an effective carrier for proton.