Abstract
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.
Highlights
A diffusion dialyzer using the commercial DF-120 anion exchange membranes (AEMs) developed by Tianwei Membrane Co., Ltd., (Weifang, China) has achieved extensive industrialization [6]
XPS analysis was conducted to evaluate the chemical compositions of chloromethyl polyethersulfone (CMPES) membrane substrate and PT-PES-5h AEM
PT-PES-5h reveal five peaks at binding energies of 531.4 eV (O 1s), 399.6 eV (N 1s), 284.9 eV (C 1s), 199.9 eV (Cl 2p) and 168.1 eV (S 2p); the PT-PES-5h AEM is stronger in the peak density of N element and weaker in that of Cl element, as compared with CMPES substrate
Summary
Acidic wastewater pollution emerging from the industrial production in the metallurgical, steel pickling and surface cleaning processes has become a serious problem [1,2,3,4,5]. The conventional methods represented by neutralization, crystallization, thermal decomposition and solvent extraction are facing various problems including high energy consumption and further pollution by disposal of salts. Diffusion dialysis (DD) employing anion exchange membranes (AEMs) is a promising alternative for acid recovery from acidic wastewater. A diffusion dialyzer using the commercial DF-120 AEM developed by Tianwei Membrane Co., Ltd., (Weifang, China) has achieved extensive industrialization [6]. As a spontaneous process merely driven by the concentration gradient, DD shows remarkable economic advantage, as compared with the above-mentioned conventional methods [6,7,8]
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