(545ao) Boron Removal By a Co-Precipitation Method with Formation of Ettringite-like Compounds

A new type of boron removal method using co-precipitation technique was developed. Materials containing aluminum, calcium, and sulfate were added to a waste water containing boron to form ettringite-like compounds such as chalesite (Ca₆(Al)₂(SO₄)₂[B(OH)₄](OH)₁₂・26H₂O). We used PAdeCS as a calcium source, and aluminum sulfate as a aluminum and sulfate source. The addition of 4wt% of the materials with the stoichiometric condition (Ca: Al: SO4 = 3: 1: 1) resulted in 98% removal of boron in the model solution of which the initial boron concentration was 100 ppm in 60 min. The final boron concentration in the treated water was lower than 2 ppm, which is far below the regulated concentration of effluent in Japan (8 ppm). The born removal capacity was in the range of 0.2-0.4 μg/g, which was much higher than the one for ion-exchange process using ettringite. This is so because the boron in the feed solution will be captured and uptaken into the crystal structure of chalesite.