Innovative low-energy enrichment of sulfuric acid using PVDF-HFP anion exchange membranes with acid-blocking properties

Abstract

In recent years, the electrodialysis (ED) technology has gained substantial attention for its role in recovering sulfuric acid from industrial wastewater. However, the typical anion exchange membranes (AEMs) have been known to exhibit notable proton leakage during ED, which can severely hinder the efficiency of acid concentration. To overcome this issue, we utilized a substrate made of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP). This choice capitalizes on the presence of fluorine-containing groups for enhanced acid stability and tertiary amine groups to minimize water content, resulting in a significant improvement in proton-blocking capabilities of the AEMs. It is worth noting that, through a combination of partial cross-linking and quaternization, these AEMs not only maintain their acid concentration performance but also substantially reduce energy consumption. Additionally, we conducted a thorough analysis of the delicate balance between current efficiency and energy consumption in acid recovery systems. In contrast to conventional AEMs and commercially available proton-blocking membranes such as ACM, we highlight the exceptional acid concentration capability (CH+ = 1.28 M) and the low energy consumption (3.3 kWh/kg) of AEM-1.2. This research breakthrough marks a significant advancement in the development of acid-blocking AEMs and strongly advocates for more efficient sulfuric acid recovery from industrial wastewater.