P14 廃液中金属錯体のソノケミカル分解

抄録

In this study, the effect of the initial pH of solution on sonochemical degradation of EDTA, CuEDTA or ZnEDTA in an aqueous solution was observed. Also, the synergy effect of sonochemical degradation of metal complex and sulfurizing agent addition on the degradation rate was investigated. The frequency of ultrasound was 503kHz. During ultrasonic irradiation, the temperature of sample solution was kept at 298±2 K. The initial concentrations of EDTA, CuEDTA and ZnEDTA were 5.0x10^<-4>M. The pH adjustment of solutions was made by adding the buffer solution, hydrochloric acid solution, or sodium hydroxide solution. Sonochemical degradation rate constant of EDTA, CuEDTA or ZnEDTA under acidic condition was greater than that under base condition in all sample solution experiments. It is expect ed that sample compounds have higher hydrophobic property under acidic condition. As a result, they are likely to be concentrated at the surface layer of hot spot, which may enhance the degradation rates. Because of structural difference between CuEDTA and ZnEDTA, Cu^<2+> in CuEDTA reacted easily with Na_2S to form precipitates, CuS, whereas Zn^<2+> in ZnEDTA was not sulfurized at all. When ZnEDTA was sonicated with the addition of Na_2S, the degradation rate constant in the condition of stoichiometric Na_2S was greater than that in the condition of only sonication.