Removal of boron from wastewater by precipitation of a sparingly soluble salt

The removal of boron from wastewater has to be considered on a case-by-case basis because no boron compound is known to be precipitated quantitatively. Based on an industrial case, many methods were tested for the treatment of wastewater containing 50 g L−1 of sulfuric acid and 0.7 g L−1 of boron, and a well-adapted precipitation process consisting of the neutralization of boric and sulfuric acids by powdered calcium hydroxide is proposed. Experimental results show that under optimal conditions (50 g L−1 of powdered calcium hydroxide, a temperature of 90° C, and process time of 2 h), the residual boron concentration in solution was reduced from 700 to less than 50 mg L−1, a value never reached before by a precipitation process. © 2004 American Institute of Chemical Engineers Environ Prog, 2004