Study On Vacuum Catalytic Pyrolysis Of Nonmetals In Waste Printed Circuit Boards And Fabrication Of Super-hydrophobic Surface

The rapid replacement of electronic and electrical equipment has re-sulted in a large volume of waste electronic and electrical equipment.As the core part of electronic and electrical equipment,printed circuit board is simultaneously abandoned.Waste circuit boards are both resource and harm.Metals in them can be separated and recovered by mechanical crush-ing,electronic separation and other technologies.The separated nonmetals will be burned directly or recycled as filler,but these methods may result in high energy consumption and secondary pollution.Therefore,it is urgent to develop an efficient and environmental-friendly technology for nonmetal re-cycling.Vacuum catalytic pyrolysis technology has the advantages of simple operation,high efficiency,low energy consumption and low pollution.It is a promising technology for the recycling of high molecular substances and the removal of organic bromide.Therefore,this thesis uses vacuum catalytic pyrolysis to recycle nonmetals in waste printed circuit boards.Kinetics and mechanism of vacuum catalytic pyrolysis,the composition of pyrolysis prod-ucts,and fabrication of super-hydrophobic surface by pyrolysis oil and gas were studied.Thermogravimetry analysis was used to study vacuum pyrolysis and vacuum catalytic pyrolysis kinetics of nonmetal in waste printed circuit boards.Results show that the starting and ending temperatures of vacuum pyrolysis of nonmetals are 286.9?C and 430.7?C.The average apparent activation energy is 146.23 k J·mol^-1.Vacuum pyrolysis behavior follows?esták-Berggren equation,meaning that the early stage is controlled by ran-dom nucleation and diffusion the later stage is controlled by phase boundary reaction.The addition of sodium hydroxide as a catalyst advances the start-ing temperature by 39.4?C and results in a weak weight loss peak higher than 400?C.The average activation energy of vacuum catalytic pyrolysis is 135.13 k J·mol^-1.Compared with that of vacuum pyrolysis,it drops by 11.10 k J·mol^-1.Vacuum catalytic pyrolysis behavior follows Jander diffusion model（m=2,n=2）,and the pyrolysis process is controlled by two-dimensional diffusion.The vacuum catalytic pyrolysis products of nonmetals are composed of pyrolysis residue,oil and gas.Pyrolysis residue is mainly composed of glass fiber and carbon residue.Pyrolysis gas is mainly composed of alkanes and olefins.Pyrolysis oil is mainly composed of phenol and its substitutes,and polycyclic compounds.Results show that during vacuum pyrolysis,91.6%of total bromine will enter pyrolysis oil and gas.Vacuum catalytic pyrolysis can significantly change the distribution of bromine.In the presence of 16.69%Na OH,only 4.4%bromine enters pyrolysis oil and gas,with pyrolysis oil and gas yield reaches 30.94%.And the bromine remained in pyrolysis residue can be removed by filtration.Vacuum catalytic pyrolysis oil and gas can be recycled as raw materi-als to fabricate super-hydrophobic surface.Results show that the optimal parameters are growth temperature 900?C,growth time 30 min and pore diameter 38μm.At this experimental condition,the maximum water contact angle of（150.9±0.8）°can be achievedis,indicating the super-hydrophobic property.The super-hydrophobic surface has the carbon fiber structure and graphite structure.Carbon atom percentage of the surface reaches 92.4%.Super-hydrophobic surfaces can resist strong acid,alkali and salt,and be applied to oil-water separation.In this paper,vacuum catalytic pyrolysis behavior and mechanism of nonmetals in waste printed circuit boards are discussed,and the composition of vacuum catalytic pyrolysis product is analyzed.Finally,vacuum catalytic pyrolysis oil and gas can be recycled to fabricate super-hydrophobic sur-faces.This study provides a theoretical basis and technical reference for the treatment and recycling nonmetals in waste printed circuit boards.