Highly efficient absorption of nitric oxide by Ru^III(edta) aqueous solutions at low concentrations

In this paper, Ru^III(edta) was used as a highly efficient absorbent for the removal of NO due to its desirable properties of high NO affinity and oxygen insensitivity. The effects of the Ru^III(edta) concentration, reaction temperature, initial solution pH, oxygen concentration, inlet NO concentration, and liquid-to-gas ratio on denitration performance were examined. The results indicated that Ru^III(edta) showed excellent denitration performance at low concentrations and that an increase in the concentration of Ru^III(edta) resulted in an increase in NO removal efficiency. In addition, NO removal efficiency increased to its optimum value at first and then declined as both the reaction temperature and initial solution pH rose. The optimal reaction temperature and ideal initial solution pH were determined to be 45°C and 5.0 respectively. The suitable liquid-to-gas ratio was found to be 51.5 L/m³. NO removal efficiency was less affected by the oxygen concentration in the range of 0-12% due to a superior anti-oxidation performance at pH = 5.0. Furthermore, the NO removal efficiency decreased significantly as the inlet NO concentration increased. The addition of 5 wt% urea to an aqueous solution of Ru^III(edta) enhanced denitration performance, and an Ru^III(edta) and urea mixed solution were able to exceed 65.07% NO removal efficiency within 30 min under optimal experimental conditions. This work proposed an alternative absorbent for NO removal and provided fundamental data for industrial denitration with Ru^III(edta) absorbents.