A novel conversion for blast furnace slag (BFS) to the synthesis of hydroxyapatite-zeolite material and its evaluation of adsorption properties

Blast furnace slag (BFS), as a byproduct from manufacturing iron, served as a cost-effective raw material for preparation of hydroxyapatite-zeolite composite material (HAP-ZE); this research introduces a way of synthesizing hydroxyapatite-zeolite composite material (HAP-ZE) using BFS with alkaline fusion and hydrothermal treatment. According to analysis with XRD, FT-IR, BET, ICP, FE-SEM, EDX and elemental mapping, the major phases in the HAP-ZE composite material synthesized under the most desirable conditions (at aging time of 6 h and at Ca/P ratio (starting gel) = 1.67) were identified to be zeolite and HAP with molar ratio of Ca/P = 1.61, Si/Al = 1.31, Na/Al = 1.75 and with a mean surface area of 44.22 m².g⁻¹. Moreover, the research found that the minor metals (Mg, Fe, K, etc.) generated from BFS have little influence on the synthesis of HAP-ZE. The thus obtained HAP-ZE material has a great adsorption performance in removing Mn²⁺, NH₄⁺ and phosphate ions mixed in water, on grounds of the higher ion-exchange capacities and abundantly existing Ca²⁺ ions in HAP-ZE structure. This novel process makes synthesizing HAP-ZE composite material from BFS possible and lays a great foundation for effective application of BFS.