Diffusion Dialysis Process Research Articles

Mechanism underlying anion-sieving in poly(ionic liquid)-based membrane: Effective acid recovery from engineering waste

Anion exchange membranes (AEMs) are promising for recovering acid from different engineering effluent due to their lower energy consumption, positive environmental impact, and potential for providing clean water resources. Utilizing the diffusion dialysis (DD) process, AEMs effectively retain metal ions while selectively allowing fast proton permeation. Achieving high hydrophilicity, proton conductivity, and ion exchange capacity through exact control of polymeric structure and chemical composition is crucial for enhancing the efficiency of the acid recovery process. This study presents the findings on the impact of novel Poly(ionic liquid) on cellulose acetate-based AEMs for acid recovery through DD application. In this study, interconnected nanochannel AEMs with high acid permeability are engineered using a straightforward blending technique. Poly(3-butyl-1-vinylimidazolium bromide-co-methyl methacrylate-co-styrene) (poly([BVIM]-[Br]–co–MMA-co-Styrene, PIL) is blended with cellulose acetate to achieve ionic crosslinking, resulting in a mechanically stable membrane. The dosage of PIL within the membrane matrix plays a vital role in determining the prepared membranes' physicochemical properties and ion exchange capabilities, which exhibit excellent thermal stability. Remarkably, the optimal AEM (7.5 % PILM) exhibits a high acid dialysis coefficient (UH+) of 1.05 m/h and a separation factor (S) of 802, outperforming previously reported state-of-the-art AEMs and commercial membranes. These findings indicate that the prepared AEMs are highly effective for acid recovery through DD. Notably, our work stands out by introducing new AEMs with superior acid dialysis performance and selectivity.

Harnessing imidazole containing crosslinked AEM for HCl resurrection from industrial spent effluent by integrated diffusion dialysis and electrodialysis: Effect of small and macromolecular crosslinker

Herein, we report the preparation of crosslinked copolymer-based AEMs via a one-pot mechanism. AEMs were prepared by the nucleophilic substitution reaction of polyacrylonitrile-co-polyvinyl imidazole (PAN-co-PVI) copolymer (AN: VI = 63:37 mol/mol) with the small and macromolecular crosslinker. The AEM was then used for the separation and concentration of hydrochloric acid from its simulated waste mixture with ferrous chloride of the electroplating industry using diffusion dialysis (DD) followed by electrodialysis (ED). The separation has also been performed by the integrated approach of DD and ED processes. DD performance was carried out with three different crosslinked membranes namely M-PCMSt, M-XDC, and M-XDB synthesized using poly-chloromethyl styrene (PCMSt), xylene dichloride (XDC), and xylene dibromide (XDB) as crosslinker respectively. The DD performances were compared by measuring the diffusion coefficient and separation factor. M-PCMSt prepared using a macromolecular crosslinker (PCMSt) exhibited the highest crosslinking density and lowest extractable (%) in DMF due to strong network formation and lowest free volume. Due to its lowest water uptake and high mechanical strength in both water and acid swollen states, it was further used to concentrate the acid by ED and integrated the DD-ED process separately. A ∼2.49 and 1.575 times higher recovery was achieved by integrated process from DD and ED separately. Different parameters such as the effect of membrane-stack designing, current density, the effect of feed solution concentration, the effect of the volume ratio, flow rate of the circulating initial solution, and influence of gravity have been optimized. M-PCMSt shows the best separation behaviour with >92% recovered acid purity and ∼94.5 % acid recovery at 4 mAcm-2 current density which is better than polyethylene poly-(4-methyl styrene)-based interpolymer membrane.

Tubular bag membrane for simple diffusion dialysis

Tubular bag membrane, designed from bionic aspect, is with a tortuous and long flowing channel in a dual-layer structure, which looks like an intestine in belly. The tubular bag membrane is in a large surface area with high packing density. Herein, one tubular bag membrane is prepared from polyvinyl alcohol (PVA), and the other tubular bag is prepared from PVA and quaternized poly (2,6-dimethyl-1,4-phenylene oxide) (QPPO). The bag has an effective area of 1261–1296 cm2, a channel length of 128 cm, and a volume of 650–675 mL. The tubular bag is immersed in a matrix solution to separate H2SO4/FeSO4 solution through a batch or semi-continuous diffusion dialysis (DD) process.Batch DD process shows an improved acid recovery ratio (RH) of 62.7% and a Fe2+ rejection ratio (ηFe) of 90.5% after 2 h. As for the semi-continuous DD process, the RH of 82.1% and ηFe of 90.6% are obtained after 6 h when the acid feed flows in bag PVA at 0.7 L m−2 h−1. In addition, acid with concentration of 1.66 mol‧L−1 can be recovered when water flows in bag QPPO/PVA at 1.6 L m−2 h−1. The tubular bag in DD process shows the advantages of simple structure, low weight, sufficient mass transfer and high separation ability. Hence, the tubular bag has strong potential to be applied in a large amount of matrix solution such as feed storage tank or salt lake.

Resourceful Treatment of Battery Recycling Wastewater Containing H2SO4 and NiSO4 by Diffusion Dialysis and Electrodialysis

Facing the increasing demand for batteries worldwide, recycling waste lithium batteries has become one of the important ways to address the problem. However, this process generates a large amount of wastewater which contains high concentration of heavy metals and acids. Deploying lithium battery recycling would cause severe environmental hazards, would pose risks to human health, and would also be a waste of resources. In this paper, a combined process of diffusion dialysis (DD) and electrodialysis (ED) is proposed to separate, recover, and utilize Ni2+ and H2SO4 in the wastewater. In the DD process, the acid recovery rate and Ni2+ rejection rate could reach 75.96% and 97.31%, respectively, with a flow rate of 300 L/h and a W/A flow rate ratio of 1:1. In the ED process, the recovered acid from DD is concentrated from 43.1 g/L to 150.2 g/L H2SO4 by the two-stage ED, which could be used in the front-end procedure of battery recycling process. In conclusion, a promising method for the treatment of battery wastewater which achieved the recycling and utilization of Ni2+ and H2SO4 was proposed and proved to have industrial application prospects.

Preparation and properties of polyvinyl alcohol (PVA)/amino-modified mesoporous silica (AMMS) composite membranes for diffusion dialysis

It is a plaguing problem of obtaining high ion flux while maintaining high selectivity during the diffusion dialysis (DD) process. However, functionalized mesoporous silica-based composite membrane is considered to be one of the effective candidates to solve it. Here, we report amino-modified mesoporous silica (AMMS) blended with pre-crosslinked polyvinyl alcohol (PVA) solution, after which a series of composite membranes were obtained to maintain high ion flux and selectivity. The fundamental properties of as-prepared membranes were tested, including water uptake (WR), alkali resistance, mechanical and thermal properties. The results of WR (181.7%–289.7%), alkali resistance (with swelling degree in the range of 250%–471% and mass loss in the range of 27.6%–35.3%), mechanical (with tensile strength (TS) in the range of 29.9–41.8 MPa and elongation at break (Eb) in the range of 135.3%–180.4%), and thermal (degradation temperature was higher than 200 °C) properties demonstrated that the as-prepared membranes possess higher water uptake and moderate alkali resistance and can be potentially applied in alkaline DD process. Further, microscopic morphologies of as-prepared membranes confirmed well dispersion of AMMS in PVA matrix and good compatibility between the two phases, which could be attributed to the hydrogen bonding between –NH2 of AMMS and –OH of PVA molecular. NaOH/Na2WO4 system was introduced to evaluate separation performance of as-prepared membranes via DD process and the effect of AMMS was detected preliminarily. The results indicated that amino-modified mesoporous silica (AMMS) blended with pre-crosslinked polyvinyl alcohol (PVA) membrane possessed high ion flux and selectivity simultaneously, and had strong practical application prospects. The mesopores and –NH2 groups of AMMS promoted the transport of OH− via hydrogen bonds synergistically.

Design of tropinium-functionalized anion exchange membranes for acid recovery via diffusion dialysis process

Diffusion dialysis (DD) process utilizing anion exchange membranes (AEMs) is an environmentally-friendly and energy-efficient technology. From acidic wastewater, DD is needed for acid recovery. This research reports the development of a series of dense tropinium-functionalized AEMs via solution casting method. Fourier Infrared transform (FTIR) spectroscopy verified the successful preparation of AEMs. The developed AEMs exhibited a dense morphology, featuring 0.98–2.42 mmol/g of ion exchange capacity (IEC), 30–81% of water uptake (WR) and 7–32% of linear swelling ratio (LSR). They displayed exceptional mechanical, thermal and chemical stability and were employed for acid waste treatment from HCl/FeCl2 mixtures via DD process. AEMs possessed 20 to 59 (10−3 m/h) and 166 to 362 of acid diffusion dialysis coefficient (UH+) and separation factor (S) respectively at 25 °C. Compared to DF-120 commercial membrane (UH+ = 0.004 m/h, S = 24.3), their DD efficiency was improved under identical experimental conditions.

Comparative Study of Different Ion-Exchange Membrane Types in Diffusion Dialysis for the Separation of Sulfuric Acid and Nickel Sulfate

The possibility of using various types of ion-exchange membranes in diffusion dialysis for the separation of sulfuric acid and nickel sulfate has been evaluated. The process of the dialysis separation of a real waste solution from an electroplating facility containing 252.3 g/L of sulfuric acid, 20.9 g/L of nickel ions and small amounts of zinc, iron, copper ions, etc. has been studied. Heterogeneous cation-exchange membrane containing sulfonic groups and heterogeneous anion-exchange membranes with different thicknesses (from 145 μm to 550 μm) and types of fixed groups (four samples with quaternary ammonium base and one sample with secondary and tertiary amines) have been used. The diffusion fluxes of sulfuric acid, nickel sulfate, and the total and osmotic fluxes of the solvent have been determined. The use of a cation-exchange membrane does not allow the separation of the components, since the fluxes of both components are low and comparable in magnitude. The use of anion-exchange membranes makes it possible to efficiently separate sulfuric acid and nickel sulfate. Anion-exchange membranes with quaternary ammonium groups are more effective in the diffusion dialysis process, while the thin membrane turns out to be the most effective.

Cu(I) catalyzed ATRP for the preparation of high-performance poly (vinylidene fluoride)-g-poly 2-(dimethylamino)ethyl methacrylate crosslinked anion exchange membranes for enhanced acid recovery

The exclusive selectivity feature of an anion exchange membrane (AEM) makes it a core component of the diffusion dialysis (DD) process. Herein, we have developed a novel synthetic route for the preparation of AEMs with a controlled graft length and density by grafting 2-(dimethylamino)ethyl methacrylate (DMA) chains from the backbone of poly(vinylidene fluoride) (PVDF) by Cu(I) catalyzed atom transfer radical polymerization to produce PVDF-g-PDMA copolymer, which is converted to AEM by the reaction with α,α’-dichloro-p-xylene (XDC). XDC induces positive charge on the membrane surface and increases the hydrophilicity of the membrane. It also acts as a crosslinker and helps to create a network structure in the membrane, which increases overall membrane stability. The AEMs are used to separate hydrochloric acid from its mixture with metal salts by diffusion dialysis. A representative AEM containing 12% w/w PDMA, abbreviated as ATM-2, show diffusion coefficient (UH+) and separation factors (S) of 0.049 m/h and 117, respectively during the separation of HCl from 2 M HCl + 0.09 M FeCl2 solution. ATM-2 also shows higher UH+ and S values for the separation of HCl with its mixture of different metal salts, i.e., NaCl, CuCl2, and AlCl3. ATM-2 membrane endures a small loss of 1.5% and 3.2% in UH+ and S values, respectively, after submerging in a 2 M acid/salt mixture solution for 60 days. This confirms the good acid stability of the AEM. The results indicate the reasonable potency of the prepared AEMs to be a suitable candidate for DD applications.

Water-bonding tubular membrane used in a 3D-printing dialyzer for diffusion dialysis

Tubular membrane used in diffusion dialysis (DD) is operated easily in simple structure with light weight. Nevertheless, some defects, including leakage, low membrane area and low packing density, still restrict the DD performances. Herein, inspired from bionic aspect, a water-bonding polyvinyl alcohol (PVA) tubular membrane is prepared, and then used in a 3D-printing dialyzer for a DD process. The tubular membrane shows a long length of 195 cm, and a satisfying tensile strength of 16.8 MPa and elongation at break of 306%. The 3D-printing dialyzer provides the tubular membrane with a smooth flowing channel, which is used to separate H2SO4/FeSO4 solution through batch and semi-continuous DD processes. Batch DD process shows an improved acid recovery ratio (RH) of 70.7% with the Fe2+ rejection ratio (ηFe) of 87.9% after 4 h. As for the semi-continuous DD process, the RH of 91.2% and ηFe of 86.1% can be obtained when the acid feed is flowing in the tubular membrane at 96 mL h−1. In addition, acid of 1.0 mol L−1 can be continuously (>10 h) recovered when the water is flowing at 196 mL h−1. Hence, long tubular membrane cooperated with the 3D-printing dialyzer can be potentially used in DD process to replace the traditional flat membrane dialyzers.

GO-anchored imidazolium based cross-linked composite anion exchange membranes for the enhancement in acid recovery via diffusion dialysis

To break the “trade-off” limitations regarding the acid reclamation and selectivity of the commercially available anion exchange membranes (AEMs), herein we report the preparation of specially designed 2D material incorporated dense AEMs to achieve high dialysis coefficient (UH+) and high separation factor (S) for separation of inorganic acids from its corresponding metal salt mixture by diffusion dialysis (DD). The composite AEMs were fabricated by incorporating graphene oxide (GO) into N-alkylated polyacrylonitrile-co-polyvinyl imidazole copolymer followed by crosslinking with hydrazine hydrate. The composite membranes exhibit higher hydrophilicity and increases the water uptake of the membranes. The combined effect of the impregnation of GO and the imidazolium ion on the acid recovery performance have been evaluated. The membrane B3 prepared by the quaternization of the copolymer with butyl bromide having 1.5 % (w/w) of GO in the polymer matrix exhibits the highest acid recovery performance with a UH+ and S value of 48 × 10−3 m/h and 87, respectively during the acid reclamation study of 1 M HCl + 0.2 M FeCl2 mixture. It also showed UH+ values of 37.11 × 10−3 m/h and 16.22 × 10−3 m/h for HNO3 and H2SO4 systems, respectively, with their respective salt mixtures. GO provides a well-organized slit like channels which intensifies the migration of H+ and increases the selectivity of the AEMs towards metal cations. We believe this engineering strategy can be employed to fabricate better AEMs for acid recovery (HCl, H2SO4 and HNO3) by DD process.

Lithium-Sodium Separation by a Lithium Composite Membrane Used in Electrodialysis Process: Concept Validation.

The recent expansion of global Lithium Ion Battery (LIBs) production has generated a significant stress on the lithium demand. One of the means to produce this element is its extraction from different aqueous sources (salars, geothermal water etc.). However, the presence of other mono- and divalent cations makes this extraction relatively complex. Herein, we propose lithium-sodium separation by an electrodialysis (ED) process using a Lithium Composite Membrane (LCM), whose effectiveness was previously demonstrated by a Diffusion Dialysis process (previous work). LCM performances in terms of lithium Recovery Ratio (RR(Li+)) and Selectivity (S(Li/Na)) were investigated using different Li+/Na+ reconstituted solutions and two ED cells: a two-compartment cell was chosen for its simplicity, and a four-compartment one was selected for its potential to isolate the redox reactions at the electrodes. We demonstrated that the four-compartment cell use was advantageous since it provided membrane protection from protons and gases generated by the electrodes but that membrane selectivity was negatively affected. The impact of the applied current density and the concentration ratio of Na+ and Li+ in the feed compartment ([Na+]F/[Li+]F) were tested using the four-compartment cell. We showed that increasing the current density led to an improvement of RR(Li+) but to a reduction in the LCM selectivity towards Li+. Increasing the [Na+]F/[Li+]F ratios to 10 had a positive effect on the membrane performance. However, for high values of this ratio, both RR(Li+) and S(Li/Na) decreased. The optimal results were obtained at [Na+]F/[Li+]F near 10, where we succeeded in extracting more than 10% of the initial Li+ concentration with a selectivity value around 112 after 4 h of ED experiment at 0.5 mA·cm−2. Thus, we can objectively estimate that the concept of this selective extraction of Li+ from a mixture even when concentrated in Na+ using an ED process was validated.

Synthesis of Porous BPPO-Based Anion Exchange Membranes for Acid Recovery via Diffusion Dialysis.

Diffusion dialysis (DD) is an anion exchange membrane-based functional separation process used for acid recovery. TMA (trimethylamine) and BPPO (brominated poly(2,6-dimethyl-1,4-phenylene oxide) were utilized in this manuscript to formulate AEMs (anion exchange membranes) for DD (diffusion dialysis) using the phase-inversion technique. FTIR (Fourier transfer infrared) analysis, proton NMR spectroscopy, morphology, IEC (ion exchange capacity), LER (linear expansion ratio), CR (fixed group concentration), WR (water uptake/adsorption), water contact angle, chemical, and thermal stability, were all used to evaluate the prepared membranes. The effect of TMA content within the membrane matrix on acid recovery was also briefly discussed. It was reported that porous AEMs have a WR of 149.6% to 233.8%, IEC (ion exchange capacity) of 0.71 to 1.43 mmol/g, CR (fixed group concentration) that ranged from 0.0046 mol/L to 0.0056 mol/L, LER of 3.88% to 9.23%, and a water contact angle of 33.10° to 78.58°. The UH (acid dialysis coefficients) for designed porous membranes were found to be 0.0043 to 0.012 m/h, with separation factors (S) ranging from 13.14 to 32.87 at the temperature of 25 °C. These observations are comparable to those found in the DF-120B commercial membrane with UH of 0.004 m/h and S of 24.3 m/h at the same temperature (25 °C). This porous membranes proposed in this paper are excellent choices for acid recovery through the diffusion dialysis process.

Engineering robust RGO/PVA composite membrane for acid recovery via electron beam irradiation

As a cost-effective and eco-friendly approach to acid recovery, diffusion dialysis (DD) has attracted much attention but still suffers from dissatisfactory selectivity and low-efficiency, especially for low-concentration acidic wastewater. Herein, a robust graphene-based composite membrane was fabricated for high-selective acid recovery via DD process from low-concentration acidic solution by starting from graphene oxide (GO) and polyvinyl alcohol (PVA) mixed dispersion, which was treated by electron beam (E-beam) irradiation and vacuum-filtration in sequence. It was proved that the E-beam irradiation not only initiated the GO reduction, but also caused covalent PVA decoration on sheets, which endowed the obtained composite membrane with tolerance to intense ultrasonication and resistance to swelling in water. Tunable ability to block metal ion permeation and higher H+ permeation than coexisting metal ions also were substantiated, which contributed to around 5.1 × 10−3 m h−1 of H+ dialysis coefficients (UH+) from low-concentration mixed HCl solution (pH = 1, 0.2 mol L−1 metal chloride), rivaling that of commercial DD membrane (DF-120B) from high-concentration acid solution (≥1 mol L−1). More importantly, separation factor from the HCl/FeCl3 mixed solution reached up to 387.2, an order of magnitude higher than that of DF-120B membrane (24.3) and also superior to most of the reported DD membranes.

Cationic covalent organic framework membranes with stable proton transfer channel for acid recovery

Diffusion dialysis (DD) based on the anion exchange membranes (AEMs) is considered as a promising technology for acid recovery. Two-dimensional (2D) cationic covalent organic frameworks (COF) with uniform pores and intrinsic cationic-type skeleton structures are excellent candidates for the synthesis of the AEMs. However, the sustaining of crystallinity and porosity in acid environments is still a key challenge for the existing COF, which severely restricts their applicability in the acid recovery. Herein, by introducing OH functionalities adjacent to the Schiff base centers, we synthesized the acid-stable cationic COF (DhaTGCl) layers with intralayer hydrogen bond on the surface of hydrolytic polyacrylonitrile (HPAN) ultrafiltration membrane. The strong electrostatic repulsion, endowed bycationic guanidine-based knots, as well as well-aligned proton channel, constructed by OH functionalities, rendered extremely high separation factor (S) of 4589 ± 684.2 for HCl recovery from HCl/FeCl2 solution. The membrane maintained high selectivity toward H+/Fe2+ after 10 cycles during DD process, while the one without OH degraded during cycling experiments. Our results imply that building the intralayer H-bonding interactions could be a promising approach for expanding the application of the COF membranes for acid recovery.

Influence of hydrophobic components tuning of poly (aryl ether sulfone)s ionomers based anion exchange membranes on diffusion dialysis for acid recovery

In this work, AEMs based on poly(arylene ether sulfone)s skeletons were tailored with three kinds of hydrophobic components: biphenol (BP) with conjugate double benzene rings , bisphenol A (BPA) containing isolated double benzene rings and fluorene-9-bisphenol (FBP) with Cardo ring skeleton of four benzene rings. A series of quaternized poly(arylene ether sulfone)s (QPAES) membranes were fabricated successfully including QPAES-BP, QPAES-BPA and QPAES-FBP. The obtained membranes were applied in diffusion dialysis (DD) process of simulated waste acid (1.0 mol L-1 HCl and 0.2 mol L-1 FeCl2) to figure out the influence of hydrophobic structures on DD performance. The dialysis coefficients (UH+) were in the range from 12.13 × 10-3 m h-1 to 13.28 × 10-3 m h-1, while the separation factors (S) were in the range from 67.33 to 126.37. The resultant membranes show much better performance compared with the commercial TWDDA1 membrane (UH+ = 8.5 × 10-3 m h-1, S = 18.5). Interestingly, the membrane structures and properties revealed that the rigid aromatic component induced low water swelling, strong mechanical property and microphase separation, the nature of the structure offers high UH+ as well as high S. The results show that the fabricated membranes are potential candidates for the acid recovery in diffusion dialysis, especially the QPAES-BP membrane tuned with rigid linear conjugated hydrophobic component.

Innovative BPPO Anion Exchange Membranes Formulation Using Diffusion Dialysis-Enhanced Acid Regeneration System.

Recycling of acid from aqueous waste streams is crucial not only from the environmental point of view but also for maturing the feasible method (diffusion dialysis). Anion exchange membrane (AEM)–based diffusion dialysis process is one of the beneficial ways to recover acid from aqueous waste streams. In this article, the synthesis of a series of brominated poly (2, 6–dimethyl-1, 4–phenylene oxide) (BPPO)-based anion exchange membranes (AEMs) through quaternization with triphenylphosphine (TPP) were reported for acid recovery via diffusion dialysis process. The successful synthesis of the prepared membranes was confirmed by Fourier transform infrared (FTIR) spectroscopy. The as-synthesized anion exchange membranes represented water uptake (WR) of 44 to 66%, ion exchange capacity of (IEC) of 1.22 to 1.86 mmol/g, and linear swelling ratio (LSR) of 8 to 20%. They exhibited excellent thermal, mechanical, and acid stability. They showed homogeneous morphology. The acid recovery performance of the synthesized AEMs was investigated in a two compartment stack using simulated mixture of HCl and FeCl2 as feed solution at room temperature. For the synthesized anion exchange membranes TPP–43 to TPP–100, the diffusion dialysis coefficient of acid (UH+) was in the range of 6.7 to 26.3 (10−3 m/h) whereas separation factor (S) was in the range of 27 to 49 at 25 °C. Obtained results revealed that diffusion dialysis performance of the synthesized AEMs was higher than the commercial membrane DF–120B (UH+ = 0.004 m/h, S = 24.3) at room temperature. It showed that the prepared AEMs here could be excellent candidates for the diffusion dialysis process.

Alkylated Imidazole Moieties in a Cross-Linked Anion Exchange Membrane Facilitate Acid Recovery with High Purity

An anion exchange membrane (AEM) is applied for acid recovery through the diffusion dialysis (DD) process. However, a specially designed AEM is required to achieve a high dialysis coefficient of ac...

Higher Acid Recovery Efficiency of Novel Functionalized Inorganic/Organic Composite Anion Exchange Membranes from Acidic Wastewater.

In this work, the synthesis of a series of the functionalized inorganic/organic composite anion exchange membranes (AEMs) was carried out by employing the varying amount of inorganic filler consist of N-(trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride (TMSP-TMA+Cl−) into the quaternized poly (2, 6-dimethyl-1, 4-phenylene oxide) (QPPO) matrix for acid recovery via diffusion dialysis (DD) process. Fourier transform infrared (FTIR) spectroscopy clearly demonstrated the fabrication of the functionalized inorganic/organic composite AEMs and the subsequent membrane characteristic measurements such as ion exchange capacity (IEC), linear swelling ratio (LSR), and water uptake (WR) gave us the optimum loading condition of the filler without undesirable filler particle aggregation. These composite AEMs exhibited IEC of 2.18 to 2.29 meq/g, LSR of 13.33 to 18.52%, and WR of 46.11 to 81.66% with sufficient thermal, chemical, and mechanical stability. The diffusion dialysis (DD) test for acid recovery from artificial acid wastewater of HCl/FeCl2 showed high acid DD coefficient (UH+) (0.022 to 0.025 m/h) and high separation factor (S) (139-260) compared with the commercial membrane. Furthermore, the developed AEMs was acceptably stable (weight loss < 20%) in the acid wastewater at 60 °C as an accelerated severe condition for 2 weeks. These results clearly indicated that the developed AEMs have sufficient potential for acid recovery application by DD process.

Development of high performance anion exchange membranes for diffusion dialysis process

Development of high performance anion exchange membranes for diffusion dialysis process

Regulation of Polyvinyl Alcohol/Sulfonated Nano-TiO2 Hybrid Membranes Interface Promotes Diffusion Dialysis.

It is important to emphasize that the adjustment of an organic–inorganic interfacial chemical environment plays an important role during the separation performance of composite materials. In this paper, a series of hybrid membranes were prepared by blending polyvinyl alcohol (PVA) solution and sulfonated nano-TiO2 (SNT) suspension. The effects of different interfacial chemical surroundings on ions transfer were explored by regulating the dosage content of SNT. The as-prepared membranes exhibited high thermal and mechanical stability, with initial decomposition temperatures of 220–253 °C, tensile strengths of 31.5–53.4 MPa, and elongations at break of 74.5–146.0%. The membranes possessed moderate water uptake (WR) values of 90.9–101.7% and acceptable alkali resistances (swelling degrees were 187.2–206.5% and weight losses were 10.0–20.8%). The as-prepared membranes were used for the alkali recovery of a NaOH/Na2WO4 system via the diffusion dialysis process successfully. The results showed that the dialysis coefficients of OH− (UOH) were in a range of 0.013–0.022 m/h, and separate factors (S) were in an acceptable range of 22–33. Sulfonic groups in the interfacial regions and –OH in the PVA main chains were both deemed to play corporate roles during the transport of Na+ and OH−.