Waste acid recovery utilizing monovalent cation permselective membranes through selective electrodialysis

Selective electrodialysis(SED)has surfaced as a highly promising membrane separation technique in the realm of acid recovery owing to its ability to effectively separate monovalent ions through the utilization of a potential difference.However,the current SED process is limited by conventional commercial monovalent cation permselective membranes(MCPMs).This study systematically investigates the use of an independently developed MCPM in the SED process for acid recovery.Various factors such as current density,volume ratio,initial ion concentration,and waste acid systems are considered.The independently developed MCPM offers several advantages over the commercial monovalent selective cation-exchange membrane(CIMS),including higher recovered acid concentration,better ion flux ratio,improved acid recovery efficiency,increased recovered acid purity,and higher current efficiency.The SED process with the MCPM achieves a recovered acid of 95.9%and a concentration of 2.3 mol·L^(–1) in the HCl/FeCl_(2) system,when a current density of 20 mA·cm^(-2) and a volume ratio of 1:2 are applied.Similarly,in the H_(2)SO_(4)/FeSO_(4) system,a purity of over 99%and a concentration of 2.1 mol·L^(–1) can be achieved in the recovered acid.This study thoroughly examines the impact of operation conditions on acid recovery performance in the SED process.The independently developed MCPM demonstrates outstanding acid recovery performance,highlighting its potential for future commercial utilization.

Performance comparison of lithium fractionation from magnesium via continuous selective nanofiltration/electrodialysis

Although selective nanofiltration(SNF)and selective electrodialysis(SED)have been widely adopted in the field of Mg^(2+)/Li^(+)separation,their differences have not been illustrated systematically.In this study,for the first time,SNF and SED processes in continuous mode were studied for Li+fractionation from the same brine with high Mg/Li ratios and their differences were discussed in detail.For a fair analysis of the two processes,typical factors were optimized.Specifically,the optimal operating pressure and feed flow rate for SNF were 2.4 MPa and 140 L·h^(-1),respectively,while the optimal cell-pair voltage and replenishment flow rate for SED were 1.0 V and 14 L·h^(-1),respectively.Although the Li^(+)fractionation capacity of the two processes were similar,the selectivity coefficient of SNF was 24.7% higher than that of SED and,thus,the Mg/Li ratio in purified stream of the former was 19.0% lower than that of the latter.Due to higher ion driving force,SED had clear advantages in recovery ratio and concentration effects.Meanwhile,the specific energy consumption of SED was 20.1% lower than that of SNF.This study provided a better understanding and guidance for the application and improvement of the two technologies.

Using bipolar membrane electrodialysis to synthesize di-quaternary ammonium hydroxide and optimization design by response surface methodology

Bipolar membrane electrodialysis(BMED) has already been described for the preparation of quaternary ammonium hydroxide. However, compared to quaternary ammonium hydroxide, di-quaternary ammonium hydroxide has raised great interest due to its high thermal stability and good oriented performance.In order to synthesize N,N-hexamethylenebis(trimethyl ammonium hydroxide)(HM(OH)_2) by EDBM,experiments designed by response surface methodology were carried out on the basis of single-factor experiments. The factors include current density, feed concentration and flow ratio of each compartment(feed compartment: base compartment: acid compartment: buffer compartment). The relationship between current efficiency and the above-mentioned three factors was quantitatively described by a multivariate regression model. According to the results, the feed concentration was the most significant factor and the optimum conditions were as follows: the current efficiency was up to 76.2%(the hydroxide conversion was over 98.6%), with a current density of 13.15 m A·cm^(-2), a feed concentration of 0.27 mol·L^(-1) and a flow ratio of 20 L·h^(-1):26 L·h^(-1):20 L·h^(-1):20 L·h^(-1) for feed compartment, base compartment, acid compartment, and intermediate compartment, respectively. This study demonstrates the optimized parameters of manufacturing HM(OH)_2 by direct splitting its halide for industrial application.

Production of antihypertensive and antidiabetic peptide fractions from quinoa(Chenopodium quinoa Willd.)by electrodialysis with ultrafi ltration membranes

Processing bioactive peptides from natural sources using electrodialysis with ultrafiltration membranes(EDUF)have gained attention since it can fractionate in terms of their charge and molecular weight.Quinoa is a pseudo-cereal highlighted by its high protein content,amino acid profile and adapting growing conditions.The present work aimed at the production of quinoa peptides through fractionation using EDUF and to test the fractions according to antihypertensive and antidiabetic activity.Experimental data showed the production of peptides ranging between 0.4 and 1.5 k Da.Cationic(CQPF)(3.01%),anionic(AQPF)(1.18%)and the electrically neutral fraction quinoa protein hydrolysate(QPH)-EDUF(~95%)were obtained.In-vitro studies showed the highest glucose uptake modulation in L6 cell skeletal myoblasts in presence of QPH-EDUF and AQPF(17%and 11%)indicating potential antidiabetic activity.The antihypertensive effect studied in-vivo in spontaneously hypertensive rats(SHR),showed a decrease in systolic blood pressure in presence of the fractionated peptides,being 100 mg/kg a dose comparable to Captopril(positive control).These results contribute to the current knowledge of bioactive peptides from quinoa by reporting the relevance of EDUF as tool to produce selected peptide fractions.Nevertheless,further characterization is needed towards peptide sequencing,their respective role in the metabolism and scaling-up production using EDUF.

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 wa stewater 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 se paration present limitations.

Research on Bipolar Membrane Electrodialysis for Ion Exchange of Molecular Sieves

In view of the problems associated with large amount of discharged wastewater and serious pollution in the existing technology for removing sodium species from molecular sieves,this research work introduces the bipolar membrane electrodialysis into the process of removing sodium species from molecular sieves,and proposes a novel method of cleanly removing sodium from molecular sieves.The results show that the technology for removing sodium ions from the molecular sieves with an indirect electrodialysis process is feasible,and can recover Na OH solution.The bipolar membrane electrodialysis is especially suitable for treating the USY,ZSM-5 and Beta molecular sieves with high acid-resistance,and the physicochemical properties and catalytic performance of the prepared molecular sieves are roughly equivalent to those of the ammonium ion-exchange method.In comparison with the ammonium ion-exchange method,the process is clean and environmentally friendly,which consumes less water,and does not discharge wastewater to exhibit a rosy prospect of industrial application.

TREATMENT OF INDUSTRIAL WASTEWATER FROM AN ALUMINA PLANT BY MEMBRANE (Ⅰ) ——Measurement of Limiting Current Density of Electrodialysis

In order to design the technological process of desalination by electrodialysis for the industrial wastewater of an alumina plant, the limit current density of the industrial wastewater is measured, and the equations of limit current density, voltage drop of the unit membrane pair at the limiting current and desalination ratio at the limiting current were obtained.

Concentration of mixed acid by electrodialysis for the intensification of absorption process in acrylic acid production

The absorption process in acrylic acid production was water-intensive.The concentration of acrylic acid before distillation process was low,which induced to large amount of wastewater and enormous energy consumption.In this work,a new method was proposed to concentrate the side stream of absorption column and thus increase the concentration in bottom product by electrodialysis.The influence of operating conditions on concentration rate and specific energy consumption were investigated by a laboratory-scale device.When the voltage drop was 1 V·cP^(-1)(1 cP=10^(-3) Pa·s),flow velocity was 3 cm·s^(-1) and the temperature was 35℃,the concentration rates of acrylic acid and acetic acid could be 203.3%and 156.6%in the continual-ED process.Based on the experimental data,the absorption process combined with ED was simulated,in which the diluted solution from ED process was used as spray water and the concentrated solution was feed back to the absorption column.The results shown that the flow rate of spray water was decreased by 37.1%,and the acrylic acid concentration at the bottom of the tower was increased by 4.56%.The ions exchange membranes before and after use 1200 h were tested by membrane surface morphology(scanning electron microscope),membrane chemical groups(infrared spectra),ion exchange capacity,and membrane area resistance,which indicated the membrane were stable in the acid system.This method provides new method for energy conservation and emission reduction in the traditional chemical industry.

Removal of Mercury(Hg(Ⅱ)) from Seaweed Extracts by Electrodialysis and Process Optimization Using Response Surface Methodology

In this work,response surface methodology(RSM)was employed to model and optimize electrodialysis process for mercury(Hg(II))removal from seaweed extracts.Box-Behnken design(BBD)was utilized to evaluate the effects and the interaction of influential variables such as operating voltage,influent flow rate,initial concentration of Hg(II)on the removal rate of Hg(II).The developed regression model for removal rate response was validated by analysis of variance,and presented a good agreement of the experimental data with the quadratic equation with high value coefficient of determination value(R2=0.9913,RAdj 2=0.9678).The optimum operating parameters were determined as 7.17V operating voltage,72.54L h−1 influent flow rate and 5.04mgL−1 initial concentration of mercury.Hg(II)removal rate of 76.45%was acquired under the optimum conditions,which showed good agreement with model-predicted(75.81%)result.The results revealed that electrodialysis can be considered as a promising strategy for removal of Hg(II)from seaweed extracts.

Purification and Regeneration of Spent Electroless NickelPlating Baths by Electrodialysis

A method using electrodialysis to seperate phosphite from spent electroless nickel (EN) plating solution was studied. The major working parameters for the electrodialyzer with our selected membranes such as voltage, current and the flow rate of spent EN bath and condensed solution were optimized. Under the optimum operating conditions, spent EN bath could be effectively purified. And then the purified solution was replenished and reused for EN plating. The life of the EN bath was prolonged for more than 17 metal turnovers (M.T.Os). It showed that the electrodialysis method was one of the most effective means for purification and regeneration of spent EN plating baths and for saving resources and reducing waste.

Diffusion analysis and modeling of kinetic behavior for treatment of brine water using electrodialysis process

In this study,the removal of monovalent and divalent cations,Nat,Kt,Mg2t,and Ca2t,in a diluted solution from Chott-El Jerid Lake,Tunisia,was investigated with the electrodialysis technique.The process was tested using two cation-exchange membranes:sulfonated polyether sulfone cross-linked with 10%hexamethylenediamine(HEXCl)and sulfonated polyether sulfone grafted with octylamine(S-PESOS).The commercially available membrane Nafion®was used for comparison.The results showed that Nafion®and S-PESOS membranes had similar removal behaviors,and the investigated cations were ranked in the following descending order in terms of their demineralization rates:Nat>Ca2t>Mg2t>Kt.Divalent cations were more effectively removed by HEXCl than by monovalent cations.The plots based on the WebereMorris model showed a strong linearity.This reveals that intra-particle diffusion was not the removal rate-determining step,and the removal process was controlled by two or more concurrent mechanisms.The Boyd plots did not pass through their origin,and the sole controlling step was determined by film-diffusion resistance,especially after a long period of electrodialysis.Additionally,a semi-empirical model was established to simulate the temporal variation of the treatment process,and the physical significance and values of model parameters were compared for the three membranes.The findings of this study indicate that HEXCl and S-PESOS membranes can be efficiently utilized for water softening,especially when effluents are highly loaded with calcium and magnesium ions.

Study on concentration of β-Naphthalenesulfonic acid by electrodialysis

Anion-exchange membranes 3362W and AM-203 were evaluated for facilitating the concentration of β-Naphthalenesulfonic acid by electrodialysis. The effect of concentration, temperature, electric current and time on the electrodialysis process were studied. Experimental results indicated that electrodialysis was an effective method for concentrating β-Naphthalenesulfonic acid at 25℃. Higher efficiencies were not obtained at high temperature. The overall current efficiency was 80%～95%.

PREPARATION OF SA-Fe CATION EXCHANGE MEMBRANE AND IT’S APPLICATION IN ELECTRODIALYSIS FOR TREATING WASTEWATER

An insoluble SA-Fe membrane was prepared by being linked soluble sodium alginate with FeCl3. SEM was used to observe its surface structure. 1R spectrum indicated that Fe^3＋ was linked with -COOH and -OH in SA membrane. As a cationic exchanging membrane in electrodialysis the membrane was applied in treating inorganic wastewater with high concentration of inorganic ammonia and azote. The results of experiment showed that it was well-selective to ammonia and azote. The percentage of the removal of ammonia and azote in wastewater was up to 80%.

Bipolar membrane electrodialysis integrated with in-situ CO_(2)absorption for simulated seawater concentrate utilization,carbon storage and production of sodium carbonate

In the context of carbon capture,utilization,and storage,the high-value utilization of carbon storage presents a significant challenge.To address this challenge,this study employed the bipolar membrane electrodialysis integrated with carbon utilization technology to prepare Na_(2)CO_(3)products using simulated seawater concentrate,achieving simultaneous saline wastewater utilization,carbon storage and high-value production of Na_(2)CO_(3).The effects of various factors,including concentration of simulated seawater concentrate,current density,CO_(2)aeration rate,and circulating flow rate of alkali chamber,on the quality of Na_(2)CO_(3)product,carbon sequestration rate,and energy consumption were investigated.Under the optimal condition,the CO_(3)^(2-)concentration in the alkaline chamber reached a maximum of 0.817 mol/L with 98 mol%purity.The resulting carbon fixation rate was 70.50%,with energy consumption for carbon sequestration and product production of 5.7 k Whr/m^(3)CO_(2)and1237.8 k Whr/ton Na_(2)CO_(3),respectively.This coupling design provides a triple-win outcome promoting waste reduction and efficient utilization of resources.

Hybrid Donnan dialysiseelectrodialysis for efficient ammonia recovery from anaerobic digester effluent

Ammonia recovery from wastewater is crucial,yet technology of low carbon emission and high ammonia perm-selectivity against complex stream compositions is urgently needed.Herein,a membrane-based hybrid process of the Donnan dialysiseelectrodialysis process(DDeED)was proposed for sustainable and efficient ammonia recovery.In principle,DD removes the majority of ammonia in wastewater by exploring the concentration gradient of NH4 t and driven cation(Nat)across the cation exchange membrane,given industrial sodium salt as a driving chemical.An additional ED stage driven by solar energy realizes a further removal of ammonia,recovery of driven cation,and replenishment of OHtoward ammonia stripping.Our results demonstrated that the hybrid DDeED process achieved ammonia removal efficiency>95%,driving cation(Nat)recovery efficiency>87.1%for synthetic streams,and reduced the OH-loss by up to 78%compared to a standalone DD case.Ammonia fluxes of 98.2 gN m^(-2)d^(-1)with the real anaerobic digestion effluent were observed using only solar energy input at 3.8 kWh kgN^(-1).With verified mass transfer modeling,reasonably controlled operation,and beneficial recovery performance,the hybrid process can be a promising candidate for future nutrient recovery from wastewater in a rural,remote area.

Anion exchange membranes with a semi-interpenetrating polymer network using 1,6-dibromohexane as bifunctional crosslinker

An anion exchange membrane(AEM)is generally expected to possess high ion exchange capacity(IEC),low water uptake(WU),and high mechanical strength when applied to electrodialysis desalination.Among different types of AEMs,semi-interpenetrating polymer networks(SIPNs)have been suggested for their structural superiorities,i.e.,the tunable local density of ion exchange groups for IEC and the restrained leaching of hygroscopic groups by insolubility for WU.Unfortunately,the conventional SIPN AEMs still struggle to balances IEC,WU,and mechanical strength simultaneously,due to the lack of the compact crosslinking region.In this work,we proposed a novel SIPN structure of polyvinylidene difluoride/polyvinylimidazole/1,6-dibromohexane(PVDF/PVIm/DBH).On the one hand,DBH with two cationic groups of imidazole groups are introduced to enhance the ion conductivity,which is different from the conventional monofunctional modifier with only one cationic group.On the other hand,DBH has the ability to bridge with PVIm,where the mechanical strength of the resulting AEM is increased by the increase of crosslinking degree.Results show that a low WU of 38.1%to 62.6%,high IEC of 2.12—2.22 mmol·g^(-1),and excellent tensile strength of 3.54—12.35 MPa for PVDF/PVIm/DBH membrane are achieved.This work opens a new avenue for achieving the high-quality AEMs.

Fluoride removal from secondary effluent of the graphite industry using electrodialysis:Optimization with response surface methodology

Response surface methodology was utilized to model and optimize the operational variables for defluoridation using an electrodialysis process as the treatment of secondary effluent of the graphite industry. Experiments were conducted using a Box-Behnken surface statistical design in order to evaluate the effects and the interaction of the influential variables including the operational voltage, initial fluoride concentration and flow rate. The regression models for defluoridation and energy consumption responses were statistically validated using analysis of variance (ANOVA);high coefficient of determination values (R^2 = 0.9772 and R^2 = 0.9814;respectively) were obtained. The quadratic model exhibited high reproducibility and a good fit of the experimental data. The optimum values of the initial fluoride concentration, voltage and flow rate were found to be 13.9 mg/L, 13.4 V, 102.5 L/h, respectively. A fluoride removal efficiency of 99.69% was observed under optimum conditions for the treatment of the secondary effluent of the graphite industry.

Study on the recovery of ionic liquids from dilute effluent by electrodialysis method and the fouling of cation-exchange membrane

With the wide application of ionic liquids(ILs)in various fields,developing efficient techniques to recover ILs from effluent is an urgent demand for the cost reduction and the environmental protection.In this study,an electrodialysis(ED)method was used to recover 1-butyl-3-methylimidazolium chloride([Bmim]Cl)IL from aqueous solution as model effluent.The influences of initial IL concentration and applied voltage on the current efficiency,removal ratio,desalination ratio,membrane flux and specific energy consumption during the ED process were investigated.It was found that the removal ratio and desalination ratio increases with the increasing of initial IL concentration and applied voltage.The current efficiency decreases with the increasing of initial IL concentration and the current efficiency reached the maximum value of 94.3%at 25 V.Besides,as the applied voltage increases,the membrane flux increases and the specific energy consumption decreases.Moreover,the fouling of cation-exchange membrane was also discovered after the desalination of IL.The deposits on the surface or into the membrane which is probably caused by[Bmim]+was characterized by scanning electron microscopy,elemental analysis and Fourier transform infrared.

Multistage-batch bipolar membrane electrodialysis for base production from high-salinity wastewater

Bipolar membrane electrodialysis(BMED)is considered a state-of-the-art technology for the conversion of salts into acids and bases.However,the low concentration of base generated from a traditional BMED process may limit the viability of this technology for a large-scale application.Herein,we report an especially designed multistage-batch(two/three-stage-batch)BMED process to increase the base concentration by adjusting different volume ratios in the acid(Vacid),base(Vbase),and salt compartments(Vsalt).The findings indicated that performance of the two-stage-batch with a volume ratio of Vacid:Vbase:Vsalt=1:1:5 was superior in comparison to the threestage-batch with a volume ratio of Vacid:Vbase:Vsalt=1:1:2.Besides,the base concentration could be further increased by exchanging the acid produced in the acid compartment with fresh water in the second stage-batch process.With the two-stage-batch BMED,the maximum concentration of the base can be obtained up to 3.40 mol∙L^(-1),which was higher than the most reported base production by BMED.The low energy consumption and high current efficiency further authenticate that the designed process is reliable,cost-effective,and more productive to convert saline water into valuable industrial commodities.

San copolymer membranes with ion exchangers for Cu(Ⅱ)removal from synthetic wastewater by electrodialysis

Heterogeneous membranes were obtained by using styrene-acrylonitrile copolymer（SAN）blends with low content of ion-exchanger particles（5 wt.%）. The membranes obtained by phase inversion were used for the removal of copper ions from synthetic wastewater solutions by electrodialytic separation. The electrodialysis was conducted in a three cell unit, without electrolyte recirculation. The process, under potentiostatic or galvanostatic control, was followed by p H and conductivity measurements in the solution. The electrodialytic performance,evaluated in terms of extraction removal degree（rd） of copper ions, was better under potentiostatic control then by the galvanostatic one and the highest（over 70%） was attained at8 V. The membrane efficiency at small ion-exchanger load was explained by the migration of resin particles toward the pores surface during the phase inversion. The prepared membranes were characterized by various techniques i.e. optical microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and differential thermal analysis and contact angle measurements.