Effect of Silica Addition on Lead Ion Adsorption Ability of Alkali-Activated Blast Furnace Slag

Blast furnace slag is produced in large quantities as a by-product in the steel manufacturing process. In this study, a method for synthesizing lead ion adsorbent with high adsorption ability was investigated by alkali activation of the blast furnace slag. A sodium hydroxide aqueous solution was used as an alkali activator, and silica was added to the aqueous solution to improve the adsorption capacity. Alkali activation of the blast furnace slag with the sodium hydroxide aqueous solution yielded lead ion adsorbent. Addition of silica to the sodium hydroxide aqueous solution further increased the lead ion adsorption capacity. Langmuir adsorption isotherms revealed that the highest maximum adsorption capacity of 1658.1 mg-Pb/g was obtained when 5 g of silica was added to 50 mL of the sodium hydroxide aqueous solution. The adsorption capacity for lead ion decreased when more than 10 g of silica was added to the sodium hydroxide aqueous solution.