Degradation of Pb–EDTA complex by a H2O2/UV process

The degradation of PbEDTA in aqueous solution by a H2O2/UV process was studied. The effect of H2O2 content, pH of the solution and the presence of nitrate were investigated. PbEDTA degradation by a H2O2/UV process was shown to be accompanied by simultaneous lead precipitation. PbEDTA was decomposed rapidly in acidic solutions while lead precipitation was achieved only when the pH of the solution was higher than 6. The presence of nitrate in significant amounts (0.04 M) inhibited remarkably the degradation of the complex and metal precipitation. The degradation of CdEDTA and ZnEDTA was also studied. It was found that the decomposition of metal–EDTA complex and metal removal by the H2O2/UV process depend greatly on the nature of the metal. CdEDTA and ZnEDTA were decomposed rapidly but metal precipitation was not achieved. The major by-products of the degradation of metal–EDTA complexes observed were nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), oxalic acid and nitrate.