Preparation Of Activated Carbons From Vacuum Pyrolysis Char Of Waste Printed Circuit Board

The recycling of waste printed circuit board (WPCB) is an important topic from the view of environmental protection and resources recovery. Recently, many studies were carried out focusing on the pyrolysis for the recycling of materials from WPCB. Results showed that the pyrolysis products included gaseous product, oil product and high level of solid residue. The gaseous product and oil product can be used as fuel or as feedstock to produce chemical products; the solid residue mainly consists of carbon and electronic components. Current recycling method mainly focuses on the recovery of the valuable metals; little attention has been paid to the recycling of carbon. As we all know, any materials with high carbon content can be used as precursor for the preparation of activated carbons (ACs). Due to the high carbon content in the pyrolyzed solid residue of WPCB (especially FR-1type), it can be considered as a candidate to prepare ACs.This work presents a detailed study about the preparation of high porous powder ACs from vacuum pyrolysis solid residue of flame retardant FR-1phenolic resin laminated board using either physical activation with CO2or chemical activation with KOH. We compared the pore properties of ACs prepared by both methods. The scanning electron microscope (SEM) was used to observe the surface morphology of obtained ACs. BET surface area and pore structures of ACs were determined by nitrogen adsorption at-196℃. Methylene blue (MB) and iodine (I2) adsorption experiments were employed to test the adsorption capacities of the resultant carbons.During CO2activation, the effects of preparation parameters such as activation temperature, activation hold time and CO2flow rate on the properties of resulting ACs were investigated. The results showed that the prepared ACs had well-developed porosities, with BET surface area up to1198m2/g and total pore volume of0.703cm3/g. The optimal MB and I2adsorption value were291.96and1113.05mg/g, respectively, at the following condition:an activation temperature of910℃, holding time of 140min and CO2flow rate of350mL/min.As for KOH activation, the effects of preparation parameters such as KOH/char ratio, activation temperature and hold time on the properties of prepared ACs were investigated. Results showed that the obtained product has high BET surface area of2289m2/g and total pore volume of1.317cm3/g at KOH/char ratio of5. The optimum conditions were as follows:KOH/char ratio of5, activation temperature of860℃and holding time of210min. Under above conditions, MB and I2adsorption values were1026and2704mg/g, respectively.According to the quality index of ACs set by China national standard GB/T13803.2-1999, it can be concluded that ACs prepared by both methods were First-grade products.