Convenient-style electrodeionization system with novel configuration and inflow mode for small-scale high purity water preparation

Abstract

Electrodeionization (EDI) is a promising sustainable and eco-friendly technology for deep desalination, essential for preparing high purity water (HPW). Its miniaturization and simplification are crucial for the application of small-scale HPW machines in decentralized HPW supply scenarios. In this study, a two-stage Convenient-style EDI (Conv-EDI) system with the countercurrent flow mode and special resin-filling strategy was proposed, which eliminates the need for many components found in conventional EDI systems. The influences of total inflow (Q_tot), inflow ratio of dilute and concentrate stream (Q_D/Q_C), total applied current (I_tot), and the distribution of current between two stacks (I₁/I₂) were studied, respectively. Initially, the inflow pattern had great influence on the back diffusion phenomenon and the competitive electromigration among H⁺, OH⁻, and other ions in the dilute stream. Optimal conditions were determined to be a Q_tot of 25 L·h⁻¹ and a Q_D/Q_C of 3/2. Meanwhile, the operation mode of the Conv-EDI stack was determined by the applied current, and the optimal I_tot and I₁/I₂ were 0.30 A and 1/1, respectively. Furthermore, the system demonstrated excellent long-term stability and anti-scaling performance over 20 days of continuous operation. It could operate stably with raw water containing hardness of ~3.4 mg·L⁻¹, and the highest resistivity HPW of 15.52 MΩ·cm could be produced with the energy consumption of ~0.19 kWh·m⁻³ and the total process of 2.43 USD·m⁻³. In summary, the Conv-EDI system offers a practical and efficient solution for small-scale HPW production, advancing the miniaturization of EDI technology and potentially transforming decentralized HPW supply systems.