Integration of concentration and electro-driven membrane system for effective water-saved acid recycling performance

Abstract

Diffusion dialysis (DD) has shown promise in waste acid reclamation, while it presents excessive water consumption and incomplete acid recovery because mass transfer is concentration-gradient dependent. This study demonstrated the nonlinear relationship between mass transfer and water consumption in DD, and then constructed an integrated concentration and electro-driven membrane system for enhanced acid recovery and water-saved. Results showed that selective-electrodialysis achieved 80% secondary acid recovery via applying a cell potential-difference of 0.6 V at a 14.9-fold reverse concentration-difference. The integrated system hence achieved 93% acid recovery under conditions that reduced the water consumption in DD unit by 50%, while the concentrated acid reached ∼13% higher than the initial concentration of waste acid. Also, the system represented excellent heavy metal rejection (∼90%) and it demonstrated clear benefits as less alkali reagent was required and less nitrate was released into the environment, highlighting its vast potential for industrial waste acid reclamation.