Removal of phosphate in dissolution-coagulation process of layered double hydroxide

Pyroaurite-like compounds with a series of crystal quality were synthesized in a strong alkali solution with pH above 13. The characterization of the synthesized compounds was carried out in terms of the crystal quality, specific surface area and intercalated anions of the compounds. The crystal quality of the compounds decreased with increase in the aging time. The lower crystal quality compound showed larger dissolution than the higher crystal quality one in a solution depending on buffering capacity of the solution. Removal of phosphate using the dissolution followed by coagulation and/or precipitation process of the compounds was demonstrated. Phosphate removal property of the compounds was examined as a function of the crystal quality of the compounds, buffering capacity of the solution and competitive anion in the solution. The phosphate removal was increased depending on decrease of the crystal quality of the compound and increase of the buffering capacity of the solution. The significance of crystal quality of the compounds on the phosphate removal was elucidated.