Recovery and enrichment of acid from metallurgical wastewater model by electrodialysis integrated diffusion dialysis system using poly(ethylene) based IEMs

Abstract

Here in, we report an energy efficient and sustainable integrated approach for the recovery of different acids (viz. HCl, HNO3 and H2SO4) from metallurgical acidic effluent models. Taking advantage of high-permselectivity and counter-ion transport number in membrane driven processes, the pilot scale diffusion dialysis (DD) cell was integrated with electrodialytic (ED) cell in series and comparative performance is evaluated. The poly(ethylene) based inter-penetrating type cation and anion exchange membranes (In-CEM and In-AEM) was prepared and have counter-ion transport number (tm) in range 0.80–0.95 and ionic conductivities between 8 and 12 mS cm−1. The process efficacy was evaluated for the recovery of HCl, HNO3 and H2SO4 in terms of proton dialysis coefficient (vH+), separation factor (Sf) and metal-ion leakage (LFen+). The reclamation studies were corroborated based on the counter-ion diffusivity, thermodynamic parameters, dissociation coefficient and ion’s intrinsic transmembrane features for different acids. DD as an individual technology showed vH+ and Sf between 0.35 and 0.50 × 10-3 mh−1 and 6–7. In contrast, using integrated system, the vH+ and Sf were improved by ∼30 and ∼15 folds respectively. The highest achievable vH+ was 14 × 10-3 mh−1, 11 × 10-3 mh−1 and 10.2 × 10-3 mh−1 whilst, Sf was 88.6, 91.0 and 106.0 for HCl, HNO3 and H2SO4, respectively. Also, the autopsy analysis on the stability of IEMs and integrated assembly was evaluated and no significant change was observed which shows long-term durability of membranes. From these results, we anticipate that integrated systems with designed membrane stand out to be a competitive device model for acid enrichment application from industrial acidic wastewater.