Microwave Assisted Degradation Of Nonmetallic Materials From Waste Print Circuit Boards

Non-metallic materials in Waste Printed Circuit Board(WPCB)are one of the research focuses in the recycling of electronic waste.WPCB belongs to hazardous waste.Non-metallic materials account for 70%~80% of the total mass of WPCB.They are mainly composed of epoxy resin,glass fiber and brominated flame retardant,which have good recycling value.Nowadays,the recycling treatment of non-metallic materials has become a research focus and hotspot in the field of electronic waste.Its harmless treatment has dual significance of environmental protection and resource utilization.Traditional recovery methods are incineration and landfill,which are harmful to the environment and human body.Compared with physical method and pyrolysis method,chemical treatment of WPCB non-metallic materials consumes less energy,does not produce toxic and harmful substances in the disposal process,and can be recycled using solvents without secondary pollution.Therefore,chemical treatment may become the future research and development direction of WPCB non-metallic materials.In this paper,the effective separation of epoxy resin and glass fiber can be achieved by dissolving non-metallic materials by chemical method,and the highly recycled recycling of epoxy resin and glass fiber can be realized.In this paper,WPCB non-metallic materials were studied,nitric acid solution was used as solvent,and microwave-assisted chemical method was used to carry out the research.The decomposition experiments,kinetics and recycling were studied in detail,as follows:(1)In the decomposition experiment,single factor experiment and orthogonal experiment(four factors and three levels)were used to optimize the decomposition process of WPCB nonmetallic materials.The main factors of microwave-assisted decomposition of WPCB nonmetallic materials are reaction time,reaction temperature,solid-liquid ratio,nitric acid concentration and microwave power.From single factor experiment and orthogonal experiment,the optimum technological parameters are as follows: the optimum concentration of nitric acid: 7~9 mol/L,reaction time: 8~12 h,reaction temperature:80~90 ?,solid-liquid ratio: 1:5,microwave power: 300 W.Orthogonal experimental analysis showed that the order of factors affecting the decomposition rate of non-metallic materials was nitric acid concentration>temperature>time>solid-liquid ratio.(2)Kinetics experiments during decomposition showed that the apparent activation energy and reaction series of WPCB nonmetallic materials decomposed under microwave heating were lower than those of traditional oil bath heating.The apparent activation energy and the apparent reaction order were 50.96 KJ/mol and 2.04 respectively when microwave heating was used,while the apparent activation energy and the apparent reaction order were90.51 KJ/mol and 3.22 respectively under the traditional heating mode.Therefore,using microwave as heating condition is beneficial to the decomposition of WPCB nonmetallic materials.(3)In the recycling experiment,polypropylene(PP)composites were prepared by melt blending using WPCB non-metallic materials and glass fibers as reinforcing materials.The results show that compared with pure PP,both of them can improve the flexural and tensile properties and melt flow rate of the composites.However,the impact properties of the composites will also be reduced by the addition of both.When non-metallic materials are used as additives,the maximum increase of tensile strength can reach 15.5%,and when recycled glass fibers are used as additives,the maximum increase of bending strength and melt flow rate can reach 58.4% and 62.0%,respectively.Reasonable distribution of WPCB non-metallic materials and recycled glass fibers as PP reinforcement fillers can not only reduce the pressure of hazardous waste on the environment,realize the reuse of resources,but also reduce the cost of composite materials.