D.B. Nothaft, P. Lu, H. Zong, W. Liessmann Jr., K. Goskonda, K. Issapour
Uplift Geosystems LLC, Maryland, United States
Keywords: Electrodialysis, zinc, bipolar, membranes, galvanizing
The Department of War manages zinc as a strategic and critical material through the National Defense Stockpile due to its uses in corrosion protection, alloying, and batteries. Hot-dip galvanizing is a one of the main surface treatments for corrosion protection of steel. Prior to dipping the steel in a molten zinc kettle, the steel must have surface oxides removed through acid cleaning (pickling). Many US galvanizing plants truck iron- and zinc-rich hydrochloric acid from the pickling process offsite for deep-well injection as hazardous waste. Bipolar electrodialysis (BPED) is an energy-efficient acid/base regeneration technique that can also contribute to zero-liquid discharge operations. Uplift Geosystems is developing modular processing units that leverage BPED to regenerate hydrochloric acid in addition to iron and zinc byproducts. The process has lower energy usage than thermal approaches and uses no consumable reagents. In addition, our electrodialysis stack innovations have led to increases in output acid concentrations twofold over electrodialysis industry standard, better meeting the needs of the galvanizing industry. To date, we have shown >14 weight% HCl production in bench-scale testing. Overall, BPED shows promise for substantially lowering the costs for galvanizing plants using hydrochloric acid pickling, while separating valuable zinc for domestic refining.