Bipolar Membrane Electrodialysis Process Research Articles

Evaluation of treatment and recovery of leachate by bipolar membrane electrodialysis process

Recovery studies are frequently carried out for electrodialysis (ED) processes. In this study, beyond examining the recovery of leachate components in an electrodialysis process, the use of that process to treat leachate-containing wastewater was simultaneously tested. Leachates were initially pre-treated (ultra filtration+cation exchange) to prevent clogging and harmful effect to the bipolar electrodialysis membranes. Optimum operating conditions were determined at the end of the experimental studies. Online observations during the electrodialysis process included the temperature-dependent reaction time, conductivity and changes of molar concentrations of H+ and OH− ions in both the anolyte and catholyte compartments in which removed ions were collected. The most important contaminants in leachates are organic substances and nitrogen compounds. For this reason, representations of organic substances, such as the chemical oxygen demand (COD), and nitrogenous compounds, such as total Kheldahl nitrogen (TKN) and ammonia-nitrogen (NH3-N), were also monitored in the electrodialysis effluent. Under the optimum operating conditions, removal of NH3-N, TKN and COD were determined in the effluent at 96.2%, 92.8% and 86.7%, respectively. The conductivity value was determined to be 1.97mS/cm at the end of the study.

An innovative beneficial reuse of seawater concentrate using bipolar membrane electrodialysis

Because of the demand for acid solutions in seawater desalination pretreatment and the difficulty of transporting sulfuric acid or hydrochloric acid, seawater concentrate from an RO system was used as the feed for the production of mixed acid by bipolar membrane electrodialysis (BMED) after the removal of calcium ions and magnesium ions. In this experiment, the feasibility of the process was tested using a laboratory ED-cell with an effective area of 88cm2. Based on the configuration of the BP-C-A-BP, the mixed acid solution was produced in the acid compartment, and the base solution was produced in the base compartment. The results showed that 1mol/L mixed acid and sodium hydroxide could be produced continuously at a constant current density of 57mA/cm2 and a flow rate of 0.30L/h in the continuous-mode BMED. After the production of the acid and base solution, membrane fouling was inspected by measuring the stack resistance and using electron microscopy and surface elemental analysis. No visible fouling deposits on the surface of the CEMs (AEMs) were observed, and there was an increased stack resistance, thus proving that the BMED process for mixed acid production with pretreated RO concentrate is suitable for a long-term run.

Clean post-processing of 2-amino-1-propanol sulphate by bipolar membrane electrodialysis for industrial processing of 2-amino-1-propanol

2-Amino-1-propanol (AMP) is a key intermediate compound in the production of antibiotics, with increasing demand in industry. In this study, we propose a newly designed bipolar membrane electrodialysis (BMED) system with a novel three-compartment configuration for the processing of AMP from the AMP sulphate solution. The operational parameters were investigated for optimizing the performance of this novel BMED stack, compared to the traditional two-compartment BMED stack in the pilot scale experiment. The experimental results indicate that this novel type of BMED stack offers a better performance for AMP processing than the conventional two-compartment BMED stack. The optimum performance was observed at the current density ranging from 40 to 60mAcm−2 and a spacer thickness of 0.70mm. The corresponding current efficiency and energy consumption reached up to 53.4% and 3.135kWhkg−1, respectively. The two-compartment BMED stack was found to have a low current efficiency (39.8%) and a high energy consumption (3.864kWhkg−1). Pilot-scale experiments for an industrial application of this novel BMED stack have been applied, demonstrating that the BMED process is feasible and economically alternative for AMP purification in the industry.

Acid and base recovery from softened reverse osmosis (RO) brines. Experimental assessment using model concentrates

Managing high salinity concentrates generated during membrane water desalination processes is a primary need due to the potential threat to the receiving ecosystems that brine discharge represents. Brines from desalting techniques contain inorganic salts that may be further purified to increase their commercial value. This study presents a beneficial reuse strategy for reverse osmosis (RO) brines generated in a seawater desalination plant. Bipolar membrane electrodialysis (BMED) has been the selected technology for the conversion of RO concentrates into acid and base products.The viability results presented prove that BMED can be considered a technically feasible option for the production of 1.0M or higher concentrated acid and base with current efficiencies in the 60–90% range. Main factors affecting the current efficiency are proton and sulphate migration through anionic exchange membranes towards the acid stack and to a minor extent the migration of co-ions, Cl−, through cation exchange membrane towards the base stack. These results indicate that the application of the BMED process to real seawater RO brines needs the implementation of pre-treatment steps in order to eliminate interference compounds.From this work it can be further conclude that application of BMED process will contribute to ensure the recovery of valuable compounds.

Use of bipolar membrane electrodialysis (BME) in purification of l-ascorbyl-2-monophosphate

As a stable substitute of Vitamin C, l-ascorbyl-2-monophosphate (AMP) has many applications, such as skin protecting, skin treatment, and fish diary feed. For decades, several methods were developed for the production of AMP. However, no purification process with high yield, short route and limited waste production, was developed. As an environment friendly separation method, electrodialysis was introduced into the production of l-ascorbyl-2-monophosphate for the first time in this work. By achieving a ‘one-step’ removal of impurity ions, deacetalization of IAMP and recovery of KOH, the constant-voltage BME process provided an efficient and environment friendly purification method. The AMP-acid was obtained, and could further produce a series of AMP salts. In addition, the influence of potential difference per three-compartment unit was studies. Process under 6V/Unit and 5.3V/Unit achieved both high separation efficiency and low energy consumption, and the combined use of 5.3V/Unit and 6V/Unit in different stages was anticipated to be the optimum process with optimum energy consumption.

Recovery of acetic acid from simulated acetaldehyde wastewaters: Bipolar membrane electrodialysis processes and membrane selection

The recovery of acetic acid from simulated acetaldehyde wastewaters by BMED (bipolar membrane electrodialysis) process was studied in two steps. Firstly, selection of commercial membranes for acetic acid recovery was investigated through experimentation of diffusion dialysis, determination of membrane stability in acetic acid solution, and measurement of MER (membrane electrical resistance) of monomembranes and EIS (electrochemical impedance spectroscopy) of bipolar membranes. The results showed that Neosepta AMX and CMX membranes are the optimum monomembranes for BMED, and any bipolar membrane is suitable. Secondly, an improved BMED process was performed by changing the current density, adjusting the number of membranes, adding ion exchange resin in the cell, and including an additional cation exchange membrane. With the selected membranes, the optimum experimental condition in the BMED process was achieved, when two pieces of Neosepta AMX membranes and a current density of 10 mA/cm 2 was adopted. Furthermore, the addition of a strong acid 001 type cation exchange resin into the feed compartment and a strong base 201 type gel anion exchange resin into the cathode compartment could substantially decrease the voltage drop across the membrane stack and reduce corresponding energy consumption. Finally, a low energy consumption of 0.61 kWh/kg and a relatively high current efficiency of 56.72% were achieved for acetic acid recovery under the optimum condition.

Treatment of simulated brominated butyl rubber wastewater by bipolar membrane electrodialysis

A large amount of wastewaters containing sodium bromide (NaBr) is usually generated during the production of brominated butyl rubber; it can cause contamination of the environment. In this study, a method was reported to regenerate hydrobromic acid (HBr) and sodium hydroxide (NaOH) from a simulated NaBr wastewater by bipolar membrane electrodialysis (BMED). Sodium hydroxide may be recycled in the neutralization washing process of preparing the brominated butyl rubber. The effects of operation parameters, such as sodium bromide concentration, current density, and initial acid and base concentrations, on regeneration were analyzed, on the basis of proper energy consumption and current efficiency. The results indicated that a low energy consumption and a high current efficiency were achieved when the concentration of sodium bromide was in the range of 11,000–16,000 mg/L with both the initial concentration of the acid and base at about 0.10 mol/L. Additionally, it was also demonstrated that a high current density applied to the BMED stack usually resulted in both higher energy consumption and current efficiency. Finally, a discharged NaBr concentration of 133.9 mg/L, which was far below the discharge standard of water pollutants for industry, could be obtained from the initial concentration of 16,000 mg/L after the operation of BMED process for 3.5 h. Therefore, this process cannot only achieve the elimination of environmental pollution, but also the recycling of resources.

Cation-exchange membrane fouling and cleaning in bipolar membrane electrodialysis of industrial glutamate production wastewater

Bipolar membrane electrodialysis (BMED) was used to regenerate ammonium and sulfuric acid from industrial glutamate production wastewater. However, membrane fouling was observed during BMED process. The aim of present study was to identify the nature of fouling deposits for cation-exchange membranes (CEMs) and investigates the effect of various cleaning methods on the removal efficiency of fouling. A significant amount of fouling deposits were observed by scanning electron microscopy (SEM) on the CEM surface in contact with the base stream after processing five successive batches of BMED. Furthermore, the deterioration in physical and chemical membrane parameters indicated the presence of the inner membrane fouling. Elemental analysis mapping results showed that the fouling on CEM surface was identified as calcium hydroxide along with the mixtures of calcium carbonate and magnesium hydroxide. The effect of hydraulic cleaning, acid cleaning and a combination thereof with ultrasound on deposits removal was investigated. The combination of acid cleaning and ultrasound treatment has been proposed to be the most effective cleaning method, which removed the CEM fouling on the surface and in the interior membrane as well as restored the membrane performance efficiently. After 60 s of ultrasound treatment in 1% HCl solution, the cleaned membrane presented a plane and clean surface similar to an original one in the analysis of SEM. The results of surface elemental analysis and membrane parameters detection indicated that the chemical composition and the performance of cleaned membrane were very close to an original one.

Performing a Three-Step Process for Conversion of Chitosan to Its Oligomers Using a Unique Bipolar Membrane Electrodialysis System

Chitosan, a linear polysaccharide composed of beta-1,4 linked d-glucosamine residues, can be depolymerized into oligomers by enzymatic reaction with chitosanase. Recently, bipolar membrane electrodialysis (BMED) has been used for chitosan solubilization and for terminating the enzymatic reaction by action of electrogenerated acid and base, respectively. The aim of the present study was to test a complete "3-in-1" process using a three-compartment BMED configuration to perform simultaneously the solubilization of chitosan, the inactivation of chitosanase, and the demineralization of the oligomers. In addition, the BMED process was compared to a conventional process using chemical acid and base. The BMED method was found to be as effective as the conventional method for solubilizing the chitosan and for inactivating the chitosanase. Furthermore, the use of BMED allowed a demineralization rate of 53% of the chito-oligomer solution in the diluate compartment. A global process of chitosan hydrolysis into its oligomers using a BMED system was proposed. This technology has great potential for industrial application in chitosan oligomer preparation, because it is convenient and ecological and it produces chito-oligomers with a lower mineral content compared with the conventional method.

Membrane fouling caused by amino acid and calcium during bipolar membrane electrodialysis

AbstractBACKGROUND: Bipolar membrane electrodialysis (BMED) has been widely applied in the recovery/production of organic acids and in the treatment of wastewater containing ammonium sulfate, sodium nitrate, sodium acetate and ammonium nitrate. However, membrane fouling is still one of the major problems in the electrodialysis process. Since calcium and amino acid are present naturally in fermentation wastewater, this study was carried out to determine the effects of calcium and amino acid on membrane fouling when simulated fermentation wastewater containing ammonium sulfate was treated by BMED.RESULTS: Calcium formed a scale on the cation exchange membrane (CEM) surface in contact with the base cell, but this had no significant adverse effect on the BMED performance. Amino acid, however, caused CEM fouling of the inner membrane, which hampered the BMED process. The coexistence of calcium and amino acid aggravated the membrane fouling, as observed morphologically on the CEM surface on the base cell side. Elemental mapping analysis showed that the membrane foulant was composed of calcium hydroxide and amino acid.CONCLUSION: The CEM fouling caused by calcium and that due to amino acid, which were distributed differently on the membrane, had different effects on the BMED performance. The coexistence of amino acid and calcium deteriorated the CEM fouling during BMED. Copyright © 2008 Society of Chemical Industry

Effect of some parameters on the improvement of the bipolar membrane electrodialysis process

A study of electrodialysis with biploar membranes of NaNO 3 solutions to produce nitric acid and soda wasperformed with the object of stressing the role of the auxiliary ion-exchange membranes used to equip the bipolarmembrane electrodialysis cell. Efficiencies of the recovery of acid largely depend on the anion-exchange membraneproperties. In relation to such effects, characterization of several industrial anion-exchange membranes wasperformed. Our results of BPM electrodialysis led to select the AD-Solvay membrane. A stack of cells equipped withthis membrane was used to study the efficiency of HNO 3 and NaOH production under the influence of theconcentrations of the solutions that were flowing across the cell compartments. Measurements were performedseparately for the effects of salt, acid and base solutions. It is shown that with increasing salt concentration the faradicyields of both acid and base increase and tend towards limiting values. The increase of initial acid and baseconcentration reduces the faradic yields as well as the ratio of the final to the initial acid and base concentration. Asimilar investigation was made by changing the volume of the NaNO 3 solution that circulates across the saltcompartment. With increasing volumes of salt solutions, concentrations vary from an initial value of 0.1M to 3.9 Nfor acid and 4.5 N for base. Some measurements of acid production were made in the case of bipolar membraneelectrodialysis of a mixed NaNO 3–NaCl salt solution.

Complete Decalcification of Saline Effluent by Associating a Carboxylic Resin with a Chelating Resin

Abstract Saline effluent from the glucose industry can be reused as resin regenerants after treatment by a bipolar membrane electrodialysis process preceded by chromatographic decalcification. Ca2+/Na+ isotherms measured on two weak acidic resins showed that the chelating resin has a higher selectivity for calcium. The decalcification process was optimized by combining rough decalcification on a carboxylic resin, followed by a finishing step on a chelating one. This chromatographic system led to the expensive chelating resin being spared and to the treatment of 60% more volume of effluent than with the carboxylic resin alone.