Degradation of Pb--EDTA complex by a H(2)O(2)/UV process.

The degradation of PbEDTA in aqueous solution by a H(2)O(2)/UV process was studied. The effect of H(2)O(2) content, pH of the solution and the presence of nitrate were investigated. PbEDTA degradation by a H(2)O(2)/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 H(2)O(2)/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.

Degradation of organolead species in aqueous solutions by electron beam irradiation.

Electron beam irradiation of aqueous solutions containing different lead compounds (Pb(2+), (CH(3))(3)Pb(+), (C(2)H(5))(3)Pb(+)) was carried out. Formate and hydrogen peroxide were used as radical scavengers to elucidate the influence of the different species generated by water radiolysis. The precipitation of Pb(2+), only observed in the presence of formate, was attributed to COO(*-) but the nature of the precipitate is still unclear. Organolead compounds were shown to be efficiently degraded, probably converted into Pb(2+), using doses around 4 kGy. In the absence of scavengers, the degradation occurred according to the alkyl group stability. Both trialkyllead compounds were shown to be degraded by HO(*). On the contrary, the contribution of hydrogen atoms (H(*)) was shown to be highly dependent on the nature of the alkyl group, i.e. negligible for (C(2)H(5))(3)Pb(+) and more important for (CH(3))(3)Pb(+).