Treatment of high boron concentration wastewater by chemical oxo-precipitation (COP) at room temperature

Chemical oxo-preceipitation (COP) process that combined the oxidant treatment and precipitation using metal salts was developed for boron containing water disposal under relatively milder conditions (room temperature, pH 10) than a precipitation process. Among the selected boron compounds in 1000 mg-B L, including boric acid (H3BO3), metaborate (NaBO2), borax (Na2B4O7) and perborate (NaBO3), the precipitation process using calcium chloride reduced 80% boron in perborate solution, and was unable to treat the rest of boron compounds immediately. COP then adopted the hydrogen peroxide (H2O2) to pretreat the boric acid and substantially increased the boron removal of chemical precipitation from less than 5% to 80%. In addition, of alkaline earth metals, barium ion was the most efficient precipitant increased the 80% of boron removal to 98.5% as the mole ratios of H2O2/B and Ba/B were adjusted to 1.5 and 1, respectively. The residue boron in end water of COP was 15 ppm-B, a value never reached by the conventional coagulation processes.