Suppression of Thoracic Sulfuric Acid Mist in Zinc Electrowinning Using Sodium Lauryl Sulfate: An Industrial Pilot-Scale Study

Background and Objective: Sulfuric acid mist generated by oxygen bubble bursting at the electrolyte surface during zinc electrowinning presents significant occupational and environmental hazards. This study evaluated the effectiveness of sodium lauryl sulfate (SLS), an anionic surfactant, in suppressing thoracic sulfuric acid mist in an industrial pilot-scale zinc electrowinning system.,Materials and Methods: The pilot study was conducted at Zanjan Zinc Khales Sazan Industries Company (Iran) using industrial pilot electrowinning tanks. Four SLS concentrations (15, 20, 25, and 30 ppm) were tested. Thoracic acid mist was sampled at 30 cm above the electrolyte surface and at the workers’ breathing zone (1.5 m) using a Parallel Particle Impactor (PPI) sampler. Samples were analyzed by ion chromatography according to NIOSH 7908 method.,Results: Addition of SLS created a stable foam layer that acted as a physical barrier, significantly reducing acid mist emissions. At the SLS optimal concentration of 25 ppm, thoracic acid mist decreased from 0.36 to 0.015 mg/m³ at 30 cm and from 0.79 to 0.054 mg/m³ at 1.5 m, achieving over 90% reduction efficiency at both heights. Higher concentrations above 25 ppm showed decreased efficiency due to micelle formation and foam instability. Mist reduction was directly correlated with foam thickness.,Conclusions: SLS proved highly effective for suppressing thoracic sulfuric acid mist and offers a cost-effective, practical, and scalable solution for improving occupational health and regulatory compliance in zinc electrowinning. Limitations include the pilot-scale setting and lack of long-term assessment on zinc deposition and electrolyte chemistry. Future studies should explore integrated mist control strategies.