Preparation of Sorbent with a High Active Sorption Surface Based on Blast Furnace Slag for Phosphate Removal from Wastewater

A new method has been presented, which leads to a significant improvement of the adsorption ability of blast furnace slag (BFS). An ultra-high pressure water jet mill cavitation disintegrator and a controlled vacuum freeze dryer were used to disintegrate amorphous BFS. Specific surface areas of both BFS and disintegrated slag (BFS-D) were measured using the S method. BFS-D was obtained with an average particle size of 198 nm and with 27-times bigger free specific surface area than that of original BFS. The BFS-D was tested as an adsorbent of phosphate from aqueous solutions. Adsorption data were analysed using the Freundlich and Langmuir adsorption isotherms. The BFS-D after phosphate adsorption was characterized using FTIR. The theoretical adsorption capacity of the BFS-D was 30.49 mg P/g, which represents an increase by 126.7% compared to the original BFS. Surface precipitation of hydroxyapatite was dominant retention mechanism.