Waste Printed Circuit Boards As Heterogeneous Fenton Catalyst For Refractory Organic Compounds Removal

With the rapid update of electrical and electronic products, treatement of waste printed circuit boards(WPCBs) has been a global issue from both the toxic and economic perspectives. Normal reuse methods such as pyrolysis or hydrometallurgy inevitably bring secondary environmental pollution and external cost. Regarding WPCBs as application-based material has been new thinking nowadays. Based on the fact that metals could accelerate H2O2 to generate reactive oxygen species at different levels, in this thesis, a novel method using WPCBs as catalyst to remove refractory organic compounds was deeply explored.WPCBs was certified to be capable of initializing Fenton-like reactions through the comparative experiments of WPCBs, H2O2 or WPCBs/H2O2 for the removal of pyridine. In addition, the catalytic ability of different solid catalysts(WPCBs, Cu(0), Cu O, Cu(OH)2·H2O, Cu3Mo2O9, Fe(0), Fe2O3, Fe2(Mo O4)3) for pyridine removal were compared which elucidated that WPCBs had better catalytic performance.WPCBs showed good catalytic activity in a wide solution p H range of 4.0-10.0 and 90% of pyridine could be removed. During the reaction, both heterogeneous WPCBs and homogeneous leached ions from WPCBs contributed to the removal of pyridine. Cu(0), which was the main metal existed in WPCBs, played a dominant role during the reaction. The effect of radical scavengers of pyridine removal established that ·OH and O2-· existed in the WPCBs/H2O2 system and the surface bounded ·OH were the main species. Glyceraldehyde and formamide were detected by GC-MS as the intermediates after reaction.From the perspective of WPCBs stability, Cu leached out into solution during the pyridine removal process. It is indicated that the leached Cu amount increased and then decreased under higher temperature. However, the maximum Cu leaching amount was not influenced by reaction temperature. By adding additional pyridine, H2O2 and WPCBs at the maximum Cu leaching amount point under 40 °C respectively, it was elucidated that under excessive H2O2 dose, the existing of abundant pyridine drove the successive Cu leaching process. By investigating the WPCBs adsorption capacity of Cu(II), Cu, Fe, and Pb leaching trends and p H variation during the reaction, it was demonstrated that the solution p H which increased at the later stage of reaction led to the leached Cu precipitated again. Futhermore, the maximum Cu leaching amount was of linear relationship with initial pyridine concentration.Pyridine removal kinetics was well fitted with Eley-Rideal model, indicating no adsorption intermediate between pyridine and WPCBs was formed.Phenol, methylene blue, methyl orange, congo red were also investigated as target organics using WPCBs/H2O2 and the results showed WPCBs had good catalytic performance of phenol and congo red.