A Critical Review of Produced Water Management Using the Chlor-Alkali Process: Challenges and Future Prospects

The utilization of produced water (PW) as a feedstock for chlor-alkali (CA) processes offers significant potential for sustainable chemical production. This review article examines the technical feasibility of transforming PW into valuable products such as caustic soda, chlorine, and hydrogen gases through electrochemical processes. The high salinity of PW is identified as a potential advantage for reducing energy consumption in CA processes. However, the variable composition and presence of impurities, including multivalent cations like Ca²⁺, Mg²⁺, Sr²⁺, and Fe²⁺, and high total organic carbon (TOC) levels, necessitate advanced pretreatment. Effective pretreatment strategies involve a combination of physical and chemical methods, such as coagulation, chemical softening, microfiltration and activated carbon filtration, to achieve high contaminant removal efficiencies. The review evaluates different CA cell configurations, highlighting that diaphragm cells exhibit superior tolerance to impurities compared with membrane-based electrolyzers. Furthermore, the optimization of electrode materials and electrocatalysts is crucial to minimizing overpotentials and preventing deactivation. The review concludes by emphasizing key challenges and suggested future research directions focused on developing cost-effective, high-performance electrodes and diaphragm materials, improving feed brine quality, and enhancing energy efficiency through optimization, process integration and renewable energy utilization. SUMMARY: Electrolysis of highly saline-treated produced water generates caustic soda, chlorine, and hydrogen as valuable co-products. On-site production of caustic soda from electrolysis can be effectively used in the chemical softening of produced water. Integrating hydrogen fuel cells with chlor-alkali processes increases overall energy efficiency and mitigates environmental impacts.