| With the rapid development of information industry while electronic products update more quickly, a large number of electronic waste are produced. The growing electronic waste poses a great threat to the earth’s ecological and human environment. It has become a crucial problem for the society how to effectively collect and reasonably safe disposal of electronic waste.The printed circuit board is a basic and indispensable part of all kinds of electronic products. It will be of great importance for resource, harmless and reduction of waste printed circuit boards due to their complex composition, environmental harmless, high recovery value.The aim of this thesis is to resource recycle of waste printed circuit boards. After heating and unsoldering the waste printed circuit boards, manual dismantling and sorting, the sorting out different components were crushing mill, detecting and comprehensive analysis by ICP-AES, XRD, elemental analyzer and GC-MS so to confirm the resources characteristics and possible environmental hazards. The results show that the components ratio of metals, organics and non-metals in waste printed circuit boards is4:4:2. The content of copper of all metals is the highest in various electric components except capacitance and solder. Gold distribution is much higher than that of other noble metals. The main elementary substances in waste printed circuit boards are Cu, Sn and Pb and so on. amorphous Al2O3and Sb2O3are high levels as well. Most pyrolysis products are phenol and some organic compounds containing benzene ring.At the previous work of this research group, metal powders were catalytic oxidation by PEG(Polyethylene glycol)-NOx in fully enclosed equipment, and the base metals were extracted. Some main factors on catalytic oxidation were optimized, and the reaction mechanisms were discussed. The results show that PEG-NOx as the catalytic oxidizer has good effect, copper as representative base metal elements was almost absolutely extracted.The extraction efficiency of copper was up to99%with NZ988as extractant, which presents good selective for only copper and stannum extracted but other elements not.The removal and preconcentration of Sn in stripping solution by expanded graphite (EG) was investigated to avoid interference of Sn to Cu, and absolutely extraction of Sn from waste printed circuit boards. The adsorptive characteristics of the produced EG were characterized and its experimental conditions of Sn adsorption, effects and mechanisms were studied as well. This study demonstrates that the expanded graphite is an effective and novel adsorbent for the removal of Sn as the removal ratio at optimized conditions reach to98%, but copper was hardly adsorbed. EG is not affected by environmental temperature, and removes Sn in waste board safely and efficiently.The EG and EG-PEG were used to improve the transfer efficiency of oxygen in NOX for improving catalytic oxidation efficiency and recycling of solvents. The experimental results show that the transfer efficiency of oxygen in NOX with EG-PEG is much higher than that of EG or PEG individually, which illustrators that PEG and EG are synergy on the transfer of oxygen in NOX. Adsorption rate of NOX with0.015g adsorbent EG and20mL PEG can reach to90%with0.025mol initial concentration of NOX at the temperature of0℃,0.5L/min flow velocity.To promote NOX transfer to NO, the catalytic oxidation efficiency of NOx with catalyst graphene oxide (GO) load Co3O4was prepared and investigated with PMS as adsorbent to catalytic oxidation NOX, where GO load Co3O4was characterized by morden analytical instruments such as XRD, FT-IR, RAMAN, SEM and TEM. The effect of some relative factors on catalytic oxidation efficiency was studied as well. It shows that the catalytic oxidation efficiency with GO load Co3O4as catalyst has improved significantly than using PMS as catalyst only. |
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