Water Leaching Dechlorination of Zinc-Containing Steel Dust Sludge
Zinc-containing steel dust sludge, a by-product of steelmaking, contains high levels of chlorine (Cl) along with valuable metals such as Fe, Zn, K, and Na. When recycled into the steel production process, Cl accumulates, causing sintering instability and severe corrosion of blast furnace linings. This study investigated water leaching for Cl removal from zinc-containing steel dust sludge. Under optimal conditions (liquid-to-solid ratio 5 mL/g, temperature 70 °C, time 60 min, rotation speed 160 r/min), the Cl leaching rate reached 87%. Furthermore, a three-stage countercurrent water washing process at a liquid-to-solid ratio of 6 mL/g and room temperature for 45 min achieved a Cl leaching rate exceeding 90%. The water washing also reduced the leaching toxicity of metals in the sludge to a certain extent. Characterization via XRD, SEM, FT-IR, and XPS revealed that water washing primarily dissolved soluble chlorides (NaCl, KCl, etc.), increasing the specific surface area from 2.71 to 10.11 m²/g and average pore size from 12.83 to 16.29 nm. These findings provide theoretical and technical support for efficient Cl removal from zinc-containing steel dust sludge, facilitating its safe resource utilization.