Preparation And Characterization Of Activated Carbon Modified By Nitric Acid From Solid Residues Of Printed Circuit Board

The recycling of printed circuit boards is a complex processing. Currently domestic and international countries developed vast research on the recycling of printed circuit board (PCB) particular emphasizing on more the metal recycling while less the nonmetal. It can be seen the composition of PCB which the macromolecule materials such as resin is about30%and plus the reinforcing material together with the fiber glass is about60%. The reinforcing material of PCB is mainly fiber glass which has high resource.This paper combining the superiority of the microwave and pyrolysis and according to the preparation of activated carbon, investigated the preparation and characterization of activated carbon modified by nitric acid from solid residues of PCB with microwave vacuum pyrolysis. which, in order to provide for theoretical basis recycling PCB.The effect on microwave time, microwave power, particle size, nitric acid concentrate and soak time on the adsorption properties of the activated carbon were discussed. Adopting different analysis, its result shown, the sequence of methylene blue were:microwave power>nitric acid concentrate>particle size>soak time>microwave time, the sequence of iodine were:microwave power>particle size>soak time>microwave time>nitric acid concentrate. Analyzing the best horizontal of each factor while considering the value of methylene blue and iodine, it could be gained the optimized experimental conditions were microwave time15min, microwave power633W, particle size1.5-2.0, nitric acid concentrate20%, and soak time16h and the value of methylene blue, iodine were94.8mg/g and496.6mg/g, respectively.The characterization of the optimized activated carbon was studied. The surface features of the optimized activated carbon were studied in virtue of ICP,XPS,FTIR and SEM. The results showed that the surface oxygen content increased (from5.01%to13.95%, respectively), while the metal contact and—C—C or the compounds of aromatic and aliphatic decreased obviously(from90.71%to86.05%, respectively)and the C=O species disappeared on the surface of the activated carbon; The functional groups on the activated carbon surface,such as carboxyl, phenol hydroxyl, lactonic and hydroxyl group, which the hydroxyl content increased obviously, while lactonic content decreased; The structure and morphology of the activated carbon is more irregular, while the differ of the holes and pores is smaller; The surface of activated carbon is oxidized significantly, some of which is subsidence and formed holes of varying size, while the around hole becomes smooth.It obtained the features of activated carbon was that the value of methylene blue and iodine were not ideal (the optimized activated carbon of the value of methylene blue and iodine were94.8mg/g and496.6mg/g.),which can be drawn the pore diameter and specific surface area during the adsorption process was not dominant, but the oxygen functional groups of activated carbon, increasing the content of the surface acidic groups, reducing the content of alkali groups, so improving the surface polarity and hydrophilicity of the activated carbon. Therefore, the activated carbon would attribute to the great advantage of the liquid phase adsorption. In this experiment, The activated carbon treating the wastewater recycling of the valuable metals is feasible; At the same time, the pyrolysis products from PCB which the gases could be used as coal gas applied in the city; the liquid is well engineering material for making chemical; It can achieved the dual effect of recovering resource and environmental protection.The treatment process of this experiment is innovative,which not noly recycled the metals,but also recycled the nonmetals.It can generated the economic and environmental benefits because of technoically practicable, less reagents(only to nitric acid),simply process and low cost.