A flotation recovery method of silicon from metallurgical-grade silicon-refined slag (silicate) using sodium silicate (SS) as the depressant was proposed. The solution chemistry, contact angle, and zeta potential measurements were used to understand the interaction mechanisms of SS on the silicate. With SS addition, the content of recovered silicon increased from (72.12±5.08) wt.% to (81.14±1.77) wt.%. During the flotation process, SS was hydrolyzed into strongly hydrophilic H₂SiO₃ and HSiO₃^-, which could be physically or chemically adsorbed with silicate. This adsorption allowed the contact angle of the silicate surface to decrease from 6.62° to 0°, indicating the decreasing floatability of the silicate.