# Application of Two-Compartment Bipolar Membrane Electrodialysis for Treatment of Waste Na2SO4 Solution

## TL;DR

This study explores using a two-compartment bipolar membrane system to recover sodium hydroxide from sodium sulfate waste, optimizing parameters for efficiency and concentration.

## Contribution

The study introduces a two-compartment bipolar membrane electrodialysis system optimized for NaOH recovery from Na2SO4 with detailed analysis of operational parameters.

## Key findings

- A NaOH recovery yield of 69.21% was achieved with a final concentration of 2.13 M at optimal conditions.
- The system showed energy consumption of 1.82 kWh/kg Na2SO4 processed and 4.72 kWh/kg NaOH produced.
- Reducing initial NaOH volume increased concentration to 2.85 M but raised energy consumption and water transport.

## Abstract

This study evaluated the performance of a constant-current two-compartment bipolar membrane electrodialysis (BMED) system comprising cation exchange membranes and bipolar membranes for the recovery of sodium hydroxide (NaOH) from sodium sulfate (Na2SO4) solution. Key operating parameters, current density, feed concentration, initial base concentration, and solution volume, were systematically varied to investigate their effects on ion transport, NaOH concentration, current efficiency, and energy consumption. At 450 A/m2 with 1.30 M Na2SO4, 0.10 M initial NaOH, and 1.00 L solution volume, the system achieved a NaOH recovery yield of 69.21%, a final concentration of 2.13 M, a current efficiency of 36.39%, and an energy consumption of 1.82 kWh/kg Na2SO4 processed, corresponding to 4.72 kWh/kg NaOH produced, indicating optimal energy efficiency and process stability. To maximize concentration, the highest NaOH concentration of 2.85 M was obtained at the same current density by reducing the initial NaOH volume to 0.50 L, although this led to increased water transport and higher energy consumption (2.31 kWh/kg Na2SO4; 5.99 kWh/kg NaOH), compromising process efficiency.