Sulfate Removal Process

Our flexible sulfate removal process consists of a sulfate precipitation stage at pH 11–13 using lime milk and aluminum, followed by a final neutralization stage using carbon dioxide. Gypsum precipitation can be included before the sulfate removal stage when required.

The process, built on easy-to-understand chemistry, can be applied to sulfate removal from gypsum saturated waters. Importantly, sulfate can be precipitated even when it is associated with highly soluble sodium and potassium sulfates. The sulfate concentration after treatment is typically 200–1000 mg/L. A level below 200 mg/L can be achieved with enhanced precipitation chemistry.

In addition to sulfate removal, the process includes advanced removal of metal impurities such as Ni, Cd, Cu, and Zn as metal hydroxides. The final product includes treated water with a low sulfate concentration for discharge or re-use, and stable, solid precipitate with a high buffer capacity.

Typical application areas:

• Non-ferrous concentrators    
• Gold plants    
• Coal mining    
• All mine sites using sulfidic ore    

Process solution examples:

• Control of sulfate in discharge water: effluent treatment plant to manage sulfate concentration in concentrators, mines, and process effluents    
• Reduction of scaling to improve plant availability: removal of sulfate and calcium prevents scaling and reduces scaling-related maintenance costs    
• Efficient water recycling: removal of gypsum saturation enables water recycling within the process and decreases fresh water intake requirements    
• Effluent volumes can be optimized by efficient overall plant water management