This work investigated the effective precipitation recovery of boron by chemical oxo-precipitation (COP), which uses hydrogen peroxide (H2O2) to transform aqueous boron to easy-precipitating perborates at room temperature. By using barium hydroxide (Ba(OH)(2)) as a precipitant, the boron removal enhanced with treatment time and the boron level was eventually reduced from 1000 ppm to 3 ppm in four hours. The transformation of the precipitates from amorphous to crystalline was assumed to be responsible for such high boron removal. The aqueous data and the characterization of the precipitates, including elemental analysis, dissolved oxygen, XRD and Raman microscopy, reveal that the phase transformation of perborate species in the precipitates carried out with time during the COP. Mechanisms of COP that describe the precipitates transformation from BaB(OH)(3)OOB(OH)3 and Ba(B(OH)(3)OOH)(2) to BaB(OH)(2)(OO)(2)B(OH)(2) were proposed. (C) 2015 Elsevier Ltd. All rights reserved.