Recovery of calcium from BF slag and synthesis of zeolite a using its residue

The elution and recovery of Ca from blast furnace slag and the alkali hydrothermal synthesis of zeolite A using the residue from the elution treatment were investigated using a ball-milling-type reaction vessel. The superior elution was obtained by using citric and formic acid solutions from which Ca could be selectively eluted from the slag. Whereas hydrochloric acid solution and ion-exchanged water were ineffective for Ca elution. Ca ions eluted in the solution were recovered as calcium formate by evaporation of water. From the formic acid eluted slag residue after three elution treatment cycles of the slag for 7.2 ks, zeolite A was synthesized in 1 mol/L NaOH solution with a reaction time of 86.3 ks at 343 K, without the addition of any other materials.