In the context of industrial effluent management, the application of electrodialysis (ED) for the recovery of sulfuric acid has attracted significant interest. Despite the technological promise, the employment of traditional anion exchange membranes (AEMs) is frequently marred by substantial proton leakage, a pervasive issue that markedly degrades the effectiveness of acid recovery. To address this challenge, we embarked on a novel approach utilizing a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) substrate. This innovative method harnessed the inherent properties of fluorine-containing groups within PVDF-HFP to provide robust acid stability, while incorporating tertiary amine groups to minimize water uptake resulted in the creation of a proton-blocking AEM. A distinguishing feature of this AEM is its thermally cross-linked diene structure, which not only preserves acid concentration properties but also considerably reduces water migration. Moreover, our investigation undertakes an exhaustive examination of the recycling concentration and water transport within the acid recovery framework, alongside the intricate interplay with energy expenditure. This investigation could facilitate the adoption of industrial acid recovery methods utilizing AEMs designed for minimal water uptake and enhanced acid-blocking capabilities.
Membrane-based methods offer a promising alternative for phosphoric acid concentration, addressing the limitations of conventional techniques. In this study, we employ a pervaporation system to achieve phosphoric acid concentration, evaluating its efficiency and stability under industrial-relevant conditions. Composite PVA-COF membranes were successfully prepared through vacuum filtration of TpPa-SO 3 H nanosheets and PVA on hydrophilic polytetrafluoroethylene (PTFE) support membranes and the followed crosslinking with glutaraldehyde. The incorporation of PVA effectively eliminates boundary defects and enhances the mechanical and operational stability of the composite membrane. The optimum COF-PVA composite membrane exhibits excellent rejection of NaCl (99.9 %) and an ultrafast water flux of 268.6 kg m −2 h −1 . The water flux surpasses that of most reported membranes. Moreover, the membrane exhibited outstanding acid resistance and durability in phosphoric acid concentration tests, maintaining stable operation for 420 min at 40 °C with no phosphorus leakage detected in permeate. The membrane demonstrated notable concentration efficiency, achieving an increase in phosphoric acid concentration from 20 % to 25 % during a sustained 180-min operational period at 70 °C. This work helps to explore the prospects for the application of pervaporation membranes in the fields of seawater desalination and phosphorus chemical industry. Synopsis The hybrid membrane composed of poly (vinyl alcohol) and covalent organic framework, which is characterized by high permeate flux, salt rejection rate and acid stability.
Proton blocking anion exchange membranes (AEMs), which are employed in electrodialysis technology, show promise in acid recovery from industrial waste. A series of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membranes were prepared using (3-aminopropyl)trimethoxysilane (APTMS) and weakly functionalized bases including N-butylimidazole (N-BuIm). Were networked to create AEMs with low leak rates. It was discovered that the appropriate concentration of siloxane crosslinker raised the membrane matrix's density and lowered the AEM matrix's hydrophilicity. Thermogravimetric measurements and water absorption have confirmed this, and the membranes in this series even swell up to 8.61 %. The maximum H + concentration concentrated by the cross-linked AEM (BPPO/5Si) during the ED with a current density of 10 mA ∙ cm −2 was 2.35 M, which was higher than the concentration concentrated by the uncross-linked AEM (BPPO/OSi), which was 1.90 M (beginning concentration: 1.00 M). The current efficiency was 44.8 % and the energy consumption was only 1.81 kW ∙h∙kg − 1 . A balance between proton blocking and SO 4 2− ions transport was achieved by the optimized AEM, which exhibited increased hydrophobicity and smaller ion clusters. The improved AEM was found to have fewer ionic clusters and greater hydrophobicity. For cross-linked AEMs, a trade-off between SO 4 2− ions transport and proton blocking was thus accomplished. This work is thought to offer direction for developing sophisticated proton blocking AEMs.
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