Selectrodialysis for chloride-to-sulfate ion exchange in water treatment

Overview

This solution offers a membrane-based electrochemical process, termed selectrodialysis, designed to selectively exchange chloride ions for sulfate ions in product water streams. By leveraging monovalent-ion-selective ion exchange membranes, the technology targets the removal of chloride, which is primarily responsible for perceived saltiness, while retaining sulfate ions that have a higher taste threshold and therefore contribute less to salty taste. The result is a treated electrolyte or source water with a noticeably milder saline profile, which is relevant for drinking water applications and formulated electrolyte products where taste optimization is important.

Technical specifications

• Process type: Bench-scale electrodialysis system using alternating arrays of regular and monovalent-ion-selective ion exchange membranes.
• Ion selectivity: Designed to allow monovalent chloride ions to migrate across the membrane stack while retaining divalent sulfate ions introduced from a feed solution.
• Feed configuration: A source water containing sulfate is fed to one side of a cell pair, with sulfate ions migrating across the membrane to replace chloride in the product electrolyte stream.
• Prior demonstrated capability: The PI has previously shown that polyelectrolyte multilayer coatings can selectively transport monovalent ammonium over divalent calcium in an electro-driven process for nutrient recovery, providing a functional framework for monovalent-versus-divalent selectivity using synthetic membranes.
• Analytical validation: Ion concentrations are characterized using ion chromatography at Clarkson's analytical facility (CAARES).
• Operating parameters: Solution and operating conditions will be systematically identified to quantify the degree of chloride-to-sulfate replacement.

Technology readiness level

This technology is currently at an early-stage research and validation phase. The core concept builds on prior proof-of-concept work demonstrating monovalent ion selectivity in electro-driven membrane systems using polyelectrolyte multilayers. The proposed validation will translate this framework to a bench-scale selectrodialysis system employing commercially available monovalent-ion-selective membranes. Estimated project requirements are approximately $85,000 to cover supplies, analytical services, and a six-month graduate student stipend under PI supervision. Commercial deployment has not yet been demonstrated, and further work is needed to optimize operating conditions and quantify performance metrics.