Study on aluminum recovery and the preparation of activated carbon from Tetra Pak waste

Char and aluminum were obtained by pyrolysis of Tetra Pak waste and separated from each other. The activated carbon was prepared from the char as raw materials and K₂CO₃ as activator. The pyrolysis characteristics of Tetra Pak waste was investigated by thermogravimetric/differential thermal analyzer coupled with Fourier transform infrared spectrometer (TG/DTA-FTIR). The N₂-adsorption/desorption curves of activated carbon were determined by automatic gas adsorption instrument and the surface functional groups of activated carbon were characterized by FTIR. TG-FTIR was used to gain insight into the activation mechanism of activated carbon. Experimental results showed that the pyrolysis of paper and polyethylene and the melting of aluminum in Tetra Pak waste occurred at 365, 490 and 664 ℃, respectively. The filler CaCO₃ decomposed at 720 ℃. The specific surface area and total pore volume of activated carbon were 1 215 m ²/g and 0.768 cm ³/g, respectively, and the surface functional groups of activated carbon were mainly C=O、C—O—C and aliphatic C—H. The decomposition of CaCO₃ contained in char at 740 ℃ led to the formation of CO₂, and pores can be created via the in-situ reduction of CO₂ by char; K₂CO₃ began to be melted at 820 ℃, and the molten K₂CO₃ reacted with the carbon matrix to form CO and caused the loss of carbon. Both processes were involved in the formation of pores of activated carbon.