Novel quaternized aromatic amine based hybrid PVA membranes for acid recovery

Semi-Interpenetrating Polymer Network Anion Exchange Membranes Based on Quaternized Polybenzoxazine and Poly(Vinyl Alcohol-Co-Ethylene) for Acid Recovery by Diffusion Dialysis

Acid recovery from acidic waste is a pressing issue in current times. Chemical methods for recovery are not economically feasible and require significant energy input to save the environment. This study reported a semi-interpenetrating polymer network (semi-IPN) anion exchange membranes (AEMs) for acid recovery by diffusion dialysis with excellent dimensional stability, high oxidation stability, good acid dialysis coefficient (UH +) and high separation factor (S). Semi-IPN AEMs are prepared by ring-open cross-linked quaternized polybenzoxazine (AQBZ) with poly(vinyl alcohol-co-ethylene), where AQBZ is obtained by Mannich reaction and Menshutkin reaction. All four proportions of semi-IPNs exhibit clear micro-phase separation, which is conducive to ion transport. The water uptake (WU) of the four semi-IPNs ranges from 14.2 % to 19.2 %, while the swelling ratio (SR) remains between 8.7 % and 11.3 %. These results indicate that the cross-linked structure in the designed semi-IPNs effectively control swelling and ensure dimensional stability. The thermal degradation temperature (Td5) of semi-IPN4:6 to semi-IPN7:3 varies from 309 °C to 289 °C, with an oxidation stability weight loss rate (WOX) ranging from 91.5 % to 93.5 %, demonstrating excellent thermal stability and oxidation stability. The semi-IPNs also show good UH + values ranging from 11.9-16.3*10-3 m/h and high S values between 38.6 and 45.9, indicating the promising potential of the semi-IPNs.

Guanidinium-based covalent organic framework membrane for single-acid recovery

Acids are extensively used in contemporary industries. However, time-consuming and environmentally unfriendly processes hinder single-acid recovery from wastes containing various ionic species. Although membrane technology can overcome these challenges by efficiently extracting analytes of interest, the associated processes typically exhibit inadequate ion-specific selectivity. In this regard, we rationally designed a membrane with uniform angstrom-sized pore channels and built-in charge-assisted hydrogen bond donors that preferentially conducted HCl while exhibiting negligible conductance for other compounds. The selectivity originates from the size-screening ability of angstrom-sized channels between protons and other hydrated cations. The built-in charge-assisted hydrogen bond donor enables the screening of acids by exerting host-guest interactions to varying extents, thus acting as an anion filter. The resulting membrane exhibited exceptional permeation for protons over other cations and for Cl^- over SO₄^2- and H_nPO₄^(3-n)- with selectivities up to 4334 and 183, respectively, demonstrating prospects for HCl extraction from waste streams. These findings will aid in designing advanced multifunctional membranes for sophisticated separation.

Anion Exchange Membrane Based on BPPO/PECH with Net Structure for Acid Recovery via Diffusion Dialysis

In order to improve the performance of the anion exchange membrane (AEM) used in acid recovery from industrial wastewater, this study adopted a new strategy in which brominated poly (2,6-dimethyl-1,4-phenyleneoxide) (BPPO) and polyepichlorohydrin (PECH) were used as the polymer backbone of the prepared membrane. The new anion exchange membrane with a net structure was formed by quaternizing BPPO/PECH with N,N,N,N-tetramethyl-1,6-hexanediamine (TMHD). The application performance and physicochemical property of the membrane were adjusted by changing the content of PECH. The experimental study found that the prepared anion exchange membrane had good mechanical performance, thermostability, acid resistance and an appropriate water absorption and expansion ratio. The acid dialysis coefficient (U_H⁺) of anion exchange membranes with different contents of PECH and BPPO was 0.0173-0.0262 m/h at 25 °C. The separation factors (S) of the anion exchange membranes were 24.6 to 27.0 at 25 °C. Compared with the commercial BPPO membrane (DF-120B), the prepared membrane had higher values of U_H⁺ and S in this paper. In conclusion, this work indicated that the prepared BPPO/PECH anion exchange membrane had the potential for acid recovery using the DD method.

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 (W_R) 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 (U_H⁺) and separation factor (S) respectively at 25 °C. Compared to DF-120 commercial membrane (U_H⁺ = 0.004 m/h, S = 24.3), their DD efficiency was improved under identical experimental conditions.

Adsorption of Methyl Orange from an Aqueous Solution onto a BPPO-Based Anion Exchange Membrane

In this research, the development of a novel brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO)-based homogeneous anion exchange membrane (AEM) via the solution casting method was reported. Fourier transform infrared spectroscopy was used to confirm the successful development of the BPPO-based AEM. The prepared AEM showed excellent thermal stability. It exhibited an ion exchange capacity of 2.66 mg/g, a water uptake (W _R) of 68%, and a linear swelling ratio of 31%. Methyl orange (MO), an anionic dye, was used as a model pollutant to evaluate the ion exchange ability of the membrane. The adsorption capacity of MO increased with the increase in contact time, membrane dosage (adsorbent), temperature, and pH while declined with the increase in initial concentration of MO in an aqueous solution and molarity of NaCl. Adsorption isotherm study showed that adsorption of MO was fitted well to the Freundlich adsorption isotherm because the value of the correlation coefficient (R ² = 0.974) was close to unity. Adsorption kinetics study showed that adsorption of MO fitted well to the pseudo-second-order kinetic model. Adsorption thermodynamics evaluation represented that adsorption of MO was an endothermic (ΔH° = 18.72 kJ/mol) and spontaneous process. The AEM presented a maximum adsorption capacity of 18 mg/g. Moreover, the regeneration of the prepared membrane confirmed its ability to be utilized for three consecutive cycles. The developed BPPO-based AEM was an outstanding candidate for adsorption of MO from an aqueous solution.

Quaternized Diaminobutane/Poly(vinyl alcohol) Cross-Linked Membranes for Acid Recovery via Diffusion Dialysis

Diffusion dialysis (DD) using anion exchange membranes (AEM) is an effective process for acid recovery and requires the preparation of suitable materials for AEMs, characterized by unique ions transport properties. In this work, novel AEMs composed of quaternized diaminobutane (QDAB) and poly(vinyl alcohol) (PVA) were cross-linked by tetraethoxysilane (TEOS) via the sol–gel process. The prepared AEMs were systematically characterized by Fourier-transform infrared (FTIR) spectroscopy, ion-exchange capacity (IEC) analysis, thermo gravimetric analysis (TGA), water uptake, linear expansion ratio (LER), and mechanical strength determination, scanning electron microscopy (SEM), and DD performance analysis for acid recovery using a hydrochloric acid/iron chloride (HCl/FeCl₂) aqueous mixture and varying the QDAB content. The prepared AEMs exhibited IEC values between 0.86 and 1.46 mmol/g, water uptake values within 71.3 and 47.8%, moderate thermal stability, tensile strength values in the range of 26.1 to 41.7 MPa, and elongation from 68.2 to 204.6%. The dialysis coefficient values were between 0.0186 and 0.0295 m/h, whereas the separation factors range was 24.7–44.1 at 25 °C. The prepared membranes have great potential for acid recovery via diffusion dialysis.

Porous Anion Exchange Membrane for Effective Acid Recovery by Diffusion Dialysis

Diffusion dialysis (DD) employing anion exchange membranes (AEMs) presents an attractive opportunity for acid recovery from acidic wastewater. However, challenges exist to make highly acid permeable AEMs due to their low acid dialysis coefficient (Uacid). Here, a series of porous and highly acid permeable AEMs fabricated based on chloromethyl polyethersulfone (CMPES) porous membrane substrate with crosslinking and quaternization treatments is reported. Such porous AEMs show high Uacid because of the large free volume as well as the significantly reduced ion transport resistance relative to the dense AEMs. Compared with the commercial dense DF-120 AEM, our optimal porous AEM show simultaneous 466.7% higher Uacid and 75.7% higher acid/salt separation factor (Sacid/salt) when applied to acid recovery at the same condition. Further, considering the simple and efficient fabrication process as well as the low cost, our membranes show great prospects for practical acid recovery from industrial acidic wastewater.

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 (W_R) 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 (U_H⁺) 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 (U_H⁺ = 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.

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 (W_R) 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 W_R 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 (U_H⁺) (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.

Carbodiimide-assisted zwitterionic modification of poly(piperazine amide) thin-film composite membrane for enhanced separation and anti-depositing performances to cationic/anionic dye aqueous solutions

In this work, a novel method of carbodiimide-assisted zwitterionic modification was proposed and implemented to incorporate zwitterionic moieties onto poly(piperazine amide) membrane for improved water permeability and anti-depositing property, which are crucial for highly efficient nanofiltration of dye-contained effluents. Carboxyl groups of polyamide layer were firstly transferred into N-acylurea using excess l-ethyl-3-(3-(dimethylamino)propyl)-carbodiimide. Zwitterions were then incorporated through ring-opening reaction between tertiary amine groups of N-acylurea and 1, 4-butanesultone. Carbodiimide-assisted zwitterionic modification was verified by ATR-IR and XPS analyses and was found to not affect membrane pore size but significantly enhance membrane's permeation and anti-dye-deposition performances. Compared with those of virgin membrane, water permeabilities of the desired zwitterionic membrane to pure water, Congo red aqueous solution and Victoria blue B aqueous solution were higher by 42.9, 62.3 and 95.2 %, respectively, hydraulic resistances from irreversible deposition of Congo red and Victoria blue B molecules were dramatically lowered by 68.4 and 91.8 %, respectively. Furthermore, the perm-selectivity performance of the desired zwitterionic membrane in terms of molecular weight cut-off and pure water permeability was better than most of the reported zwitterionic membranes, and the separation and anti-depositing performances to both anionic and cationic dye aqueous solutions were better than commercial membrane NF270.

Diffusion Dialysis for Acid Recovery from Acidic Waste Solutions: Anion Exchange Membranes and Technology Integration

Inorganic acids are commonly used in mining, metallurgical, metal-processing, and nuclear-fuel-reprocessing industries in various processes, such as leaching, etching, electroplating, and metal-refining. Large amounts of spent acidic liquids containing toxic metal ion complexes are produced during these operations, which pose a serious hazard to the living and non-living environment. Developing economic and eco-friendly regeneration approaches to recover acid and valuable metals from these industrial effluents has focused the interest of the research community. Diffusion dialysis (DD) using anion exchange membranes (AEMs) driven by an activity gradient is considered an effective technology with a low energy consumption and little environmental contamination. In addition, the properties of AEMs have an important effect on the DD process. Hence, this paper gives a critical review of the properties of AEMs, including their acid permeability, membrane stability, and acid selectivity during the DD process for acid recovery. Furthermore, the DD processes using AEMs integrated with various technologies, such as pressure, an electric field, or continuous operation are discussed to enhance its potential for industrial applications. Finally, some directions are provided for the further development of AEMs in DD for acid recovery from acidic waste solutions.

Fabrication and characterization of pyridinium functionalized anion exchange membranes for acid recovery

In the present work, the fabrication of pyridinium functionalized anion exchange membranes (AEMs) for acid recovery using diffusion dialysis (DD) processes was developed using brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO) as a polymer backbone and 4-methylpyridine (MP) as an ion exchange element. The electrochemical and physiochemical properties of the developed AEMs were tested under various concentration of MP into the polymer matrix. Water uptake (W_R) of 17.18% to 30.55%, ion exchange capacity (IEC) of 1.94-2.24 mmol/g and linear swelling ratio (LSR) of 6.87-14.89% were obtained. In addition, the new membranes exhibited dense morphology, higher thermal and chemical stability in addition to dimensional and mechanical sturdiness. Acid dialysis coefficient (U_H) in the range of 0.011-0.066 m/h was obtained. In addition the developed AEMs had a separation factor (S) in range of 24.87-77.61 resulting in enhanced DD performance compared to commercial membrane DF-120B under comparable experimental conditions. The new prepared membranes showed potential for successful application in acid recovery via diffusion dialysis.

Supplementing multi-functional groups to polysulfone membranes using Azadirachta indica leaves powder for effective and highly selective acid recovery

Moderate and eco-pleasing ion-exchange trade membranes are in need to recover acid from industrial waste. Present study is focused on incorporation of plant waste (Azadirachta indica, neem leaves powder (NP)) of different composition as filler to polysulfone (PSf) membrane matrix to achieve acid recovery. Membranes were characterized, their chemical, mechanical and thermal stabilities and effectiveness in acid recovery via diffusion has been inspected. Multi-functional groups (-COOH, -NH₂, -OH, -OAc, -C = O) present in different components of NP contributes in their own means in H⁺ ion transportation through membrane in acid recovery. They assisted formation of hydrogen bond and provided channels for ion permeation, and facilitated selective transportation of H⁺ ion over Fe²⁺ ions and explained mechanism is in accordance with Grotthuss-type and vehicle mechanism. Membrane with 15% of NP showed better performance in terms of ion exchange capacity (IEC) and acid recovery, at optimum concentration of NP, composite the membrane showed highest IEC values of 3.9771 mmol/g, U^H+ value of ≈46.499 × 10^-3 m/h and greater separation factor ≈154, which is higher than commercially available DF-120 membrane. An original thought of utilizing NP in membrane matrix opens up promising opportunities for extremely straightforward, easy, cost-effective and greener methods of recovery acid.

BPPO-Based Anion Exchange Membranes for Acid Recovery via Diffusion Dialysis

To reduce the environmental impact of acids present in various industrial wastes, improved and robust anion exchange membranes (AEMs) are highly desired. Moreover, they should exhibit high retention of salts, fast acid permeation and they should be able to operate with low energy input. In this work, AEMs are prepared using a facile solution-casting from brominated poly-(2,6-dimethyl-1,4-phenylene oxide) (BPPO) and increasing amounts of 2-phenylimidazole (PI). Neither quaternary ammonium salts, nor ionic liquids and silica-containing compounds are involved in the synthesis. The prepared membranes showed an ion exchange capacity of 1.1–1.8 mmol/g, a water uptake of 22%–47%, a linear expansion ratio of 1%–6% and a tensile strength of 0.83–10.20 MPa. These membranes have potential for recovering waste acid via diffusion dialysis, as the acid dialysis coefficient (U_H) at room temperature for HCl is in the range of 0.006–0.018 m/h while the separation factor (S) is in the range of 16–28, which are higher than commercial DF-120B membranes (U_H = 0.004 m/h, S = 24).

Preparation and characterization of click-driven N-vinylcarbazole-based anion exchange membranes with improved water uptake for fuel cells

Novel click mediated AEM with improved water uptake.