• Abstract
  High-salinity wastewater, generated from industrial processes such as oil refining, chemical manufacturing, and desalination plants, poses significant environmental and economic challenges due to its complex composition and high salt content. Traditional treatment methods, including evaporation and membrane filtration, often struggle with energy inefficiency or secondary pollution. The application of ion-membrane electrolysis as an innovative approach to treating high-salinity wastewater. By leveraging electrochemical principles and selective ion-exchange membranes, this technology offers potential solutions for salt recovery, organic degradation, and water purification. The mechanisms of ion-selective transport, energy efficiency, and scalability are discussed, along with challenges such as membrane fouling and corrosion. Case studies and recent advancements highlight the promising role of ion-membrane electrolyzers in sustainable wastewater management.

• 1. Introduction*
  High-salinity wastewater, characterized by dissolved solids exceeding 5,000 mg/L, is a critical issue in industries where water reuse and zero-liquid discharge (ZLD) are prioritized. Conventional treatments like reverse osmosis (RO) and thermal evaporation face limitations in handling high saline conditions, leading to high operational costs and membrane fouling. Ion-membrane electrolysis, originally developed for chlor-alkali production, has emerged as a versatile alternative. This technology utilizes ion-selective membranes to separate and control ion migration during electrolysis, enabling simultaneous water purification and resource recovery.

• 2. Principle of Ion-Membrane Electrolysis*
  The ion-membrane electrolyzer consists of an anode, cathode, and a cation-exchange membrane or anion-exchange membrane. During electrolysis:
• Cation-Exchange Membrane: Allows cations (e.g., Na⁺, Ca²⁺) to pass while blocking anions (Cl⁻, SO₄²⁻), directing ion migration toward respective electrodes.
• Electrochemical Reactions:
• Anode: Oxidation of chloride ions generates chlorine gas and hypochlorite, which degrade organics and disinfect the water.
  2Cl−→Cl2+2e−2Cl⁻ → Cl₂ + 2e⁻2Cl−→Cl2​+2e−
• Cathode: Reduction of water produces hydrogen gas and hydroxide ions, enhancing pH and promoting precipitation of metal ions.
  2H2O+2e−→H2+2OH−2H₂O + 2e⁻ → H₂ + 2OH⁻2H2​O+2e−→H2​+2OH−
• Salt Separation: The membrane facilitates selective ion transport, enabling brine concentration and freshwater recovery.

3. Applications in High-Salinity Wastewater Treatment*
a. Salt Recovery and Brine Valorization
Ion-membrane systems can concentrate brine streams (e.g., from RO reject) for salt crystallization or sodium hydroxide production. For instance, seawater desalination plants can recover NaCl as a byproduct.

b. Organic Pollutant Degradation
Electrochemical oxidation at the anode breaks down refractory organics via strong oxidants like ClO⁻ and HOCl. Studies show 90% removal of phenolic compounds in simulated HSW.

c. Heavy Metal Removal
Alkaline conditions at the cathode induce hydroxide precipitation of metals (e.g., Pb²⁺, Cu²⁺), achieving >95% removal efficiency.

d. Water Purification
Pilot-scale trials demonstrate freshwater recovery rates exceeding 80% with conductivity reduced from 150,000 µS/cm to <1,000 µS/cm.