Application and Breakthrough of Electrodialysis Technology in the Purification of 1,3-Propanediol

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As an important chemical raw material, 1,3-propanediol (PDO) is widely used in medicine, cosmetics, polyester fibers and other fields. With the maturation of bio-fermentation technology for 1,3-propanediol production, efficient and environmentally friendly purification has become a key industry focus. Relying on high desalination efficiency, low energy consumption and environmental friendliness, electrodialysis technology demonstrates outstanding advantages in 1,3-propanediol purification.

I. Technical Principle: Precise Separation via Directed Ion Migration

Electrodialysis is a membrane separation technology based on ion-exchange membranes. Under an external direct current electric field, ions migrate directionally according to the selective permeability of ion-exchange membranes, realizing separation between target products and salts. During PDO purification, organic acid salts (acetate, lactate) and inorganic salts (sodium chloride) in the fermentation broth migrate through anion and cation exchange membranes into the concentrate chamber, while uncharged PDO molecules are retained in the diluate chamber, achieving efficient desalination.

II. Process Innovation: Integrated Multi-Technology Synergy

1. Front-End Pretreatment: Anti-Fouling Barrier Design

For bacteria, proteins and colloids in PDO fermentation broth, a combined process of ultrafiltration + activated carbon adsorption is adopted. Ultrafiltration removes particles, colloids and macromolecules; activated carbon further reduces organic impurities. Experiments show that after pretreatment, broth turbidity ≤ 0.3 NTU, membrane service life exceeds 12 months, and membrane replacement cost is reduced by 40%.

2. Core Electrodialysis: Dynamic Parameter Optimization

Operating parameters are optimized via response surface methodology. At current density 15 mA/cm², stack voltage 60 V, diluate flow rate 300 L/h, the system reaches optimal performance: desalination rate ≥ 92%, energy consumption ≤ 0.8 kWh/kg (only 1/3 of evaporative crystallization). A one-stage three-pass stack configuration extends migration paths, raising concentrate salinity to 20% for subsequent resource utilization.

3. Back-End Refining: Crystal Morphology Control

The diluate (PDO ~12%) is concentrated to 25% at 60 °C, then cooled to 20 °C at 5 °C/h. Crystallization yield reaches 93.3%, product purity ≥ 98%. Compared with traditional processes, flocculants are reduced by 90%, crystal shape is more regular, filtration speed increases by 40%, greatly lowering production costs.

III. Resource Recycling: High-Value Utilization of By-Products

High-salt solution from the concentrate chamber (20% organic + inorganic salts) is processed by multi-effect evaporation crystallization to produce industrial-grade mixed salts, sold as nitrogen fertilizer or chemical raw materials. Waste activated carbon is regenerated by pyrolysis for reuse, reducing solid waste. One enterprise gains an additional 800 RMB per ton of fermentation broth from by-products, forming a closed resource cycle.

IV. Typical Case: Revolutionary Breakthrough in Bio-Fermentation

DuPont’s recombinant Escherichia coli fermentation couples PDO synthesis with glucose metabolism, achieving a yield of 135 g/L. However, high organic acid salts inhibit cell growth and product synthesis. After electrodialysis desalination, broth conductivity drops from 20,000 μS/cm to below 600 μS/cm, PDO loss ≤ 3.9%. Recovered organic acids are reused for biostimulants, forming an integrated fermentation–purification–resource utilization chain.

V. Future Outlook: Intelligent and Green Upgrading

Supported by IoT, electrodialysis systems are developing toward intelligent control. Real-time monitoring of conductivity, pH and transmembrane pressure, combined with AI algorithms, automatically adjusts current density (fluctuation ±5%), stabilizing desalination efficiency above 90%.

Bipolar membrane electrodialysis (BMED) enables in-situ conversion of salts into acids and bases. Organic anions combine with H⁺ to form acids; metal cations combine with OH⁻ to form bases (≈1 mol/L), which can be directly recycled into fermentation, further cutting costs and achieving zero liquid discharge.

Electrodialysis not only solves key purification challenges of 1,3-propanediol but also establishes a green manufacturing system through resource recycling. With improved membrane materials and integrated innovation, the technology will be widely applied in biomedicine and fine chemicals, providing a Chinese solution for global industrial upgrading.