On line continuous chemical synthesis of ferrate(VI): Enhanced yield and removal of pollutants

Abstract

This paper presents a new process to synthesize ferrate(VI) (FeVIO4−2) continuously through the oxidation of ferric ion (Fe3+) by hypochlorite (OCl-) under alkaline condition. Synthesis was performed under different experimental conditions ([OH-] = 5.0 – 16.0 M, and T = 20 – 45 °C) to obtain optimum yield of ferrate(VI). Under the most favorable condition (i.e., ([Fe3+] = 0.10 M, [OCl-]: [Fe3+] = 10.0, [OH-] = 10.0 M, and T = 40 °C), the yield of ferrate(VI) in the newly designed reactor increased by about 11% in 60 min compared to conventional reactor (or increased in [FeO42-] from 4.0 × 10−2 M to 4.5 × 10−2 M). The rapid mixing under flow condition in the closed coil of the new reactor improved the reaction efficiency and yield. When [Fe3+] was varied in the range from 0.10 to 0.20 M in the reactor under the same condition, the optimum concentration of Fe3+ was at 0.16 M, which increased the concentration of FeO42- to 6.8 × 10−2 M. Applying ultrasound power density (5.0–25.0 W/L) in the reaction process further increased the yield by about 12% (or increased [FeO42-] from 6.8 × 10−2 M without ultrasound to 7.6 × 10−2 M at 15.0 W/L). Overall, operating the newly designed reactor under ultrasound could increase the concentration of synthesized ferrate(VI) from 4.0 × 10−2 M to 7.6 × 10−2 M. At pH 7.0, the prepared ferrate(VI) completely removed atrazine (ATZ), sulfachloropyridazine (SCP), ibuprofen (IBP), and naproxen (NAP)) in water.