Preparation of Activated Carbon from Various Plastics

Abstract

Tsushima, Okayama-shi 700 Japan The investigation was carried out to prepare activated carbon in high yield from waste plastics, e. g., copolymers of poly (vinylidene chloride) (PVDC)-poly(vinyl chloride) (PVC) or poly (acrylonitrile) (PAN), PVC, polycarbonate (PC), polyester, polyethylene (PE), polystyrene (PS), etc.
The thermal decomposition characteristics (initiation temp. and rate pattern of weight decrease), possibility of carbonization and the effects of activation during carbonization process of these plastics were examined at increasing or constant temperature below 1000°C in flowing N2, CO₂, H₂O (10%)-N2, air, Cl2 and/or HCl chiefly to elevate the activated carbon yield Y (g/g (plastic)) and specific surface area Sg (m2/g(activated carbon prepared)).
The results obtained are as follows:
(1) From PVDC copolymers and polyester, activated carbon (ca.700 m2/g (SO) is obtained merely by the thermal decomposition below 700°C. From PVC and PC, activated carbon 1000 m2/g (Sig)) is prepared by the activation in H₂O or CO₂ stream at temperatures higher than 800°C after carbonization.
(2) The carbonization in Cl2 stream is very efficient. For example, from PS, which does not give carbon by the thermal decomposition, activated carbon (2050 m2/g (Sg)) is obtained by the Cl2 treatment.
(3) The facility of preparation of activated carbon is in the order of. PVDC-copolymers >PVC> PC, polyester, from the comparison of their carbon yields, rac (cec: carbon content in plastic).
(4) Iodine adsorbed amount per unit sursce area of the above activated carbon is comparable to that of commercially activated carbon.
(5) By plotting the surface area Sp=(YS, ; m2ig (plastic)) or Se (=Spicre; m2/g (carbon in plastic)) vs. Y (or rac) or Sg, the relations between Y and surface-area developing rate (change of Sg with change of pore diameter distribution) during the activation process can easily be elucidated. These diagrams are very useful for the reasonable comparision and/or judgement of the preparation conditions.