Preparation of Activated Carbon from Scrapped Poly(vinyl chloride)

Abstract

As a part of study to utilize waste plastic resins, the present study deals with the development of a new process to prepare a high quality activated carbon from PVC. To lower a reaction temperature and to raise an activated carbon yield Y(g(activated carbon)/g (PVC)), the study was carried out and discussed it by using the surface developing diagram, S_p(m²(activated carbon)/g(PVC)) [=Y×S_g(m²(activated carbon)/g(activated carbon))] vs. Y. Raw materials employed were PVC(powder), PVC(powder) containing metal chlorides (Cu, Fe : 0.1%) which were prepared from their ethanol solutions, and six kinds of industrial scrapped PVC which had once been shaped by pressing or extruding after blending with various organic and inorganic compounds to promote properties of a shaped PVC. Main results obtained are as follows:
1) Carbonization of PVC(powder) containing Cu in air or in HCl(5%)-air mixture marked by improved Y; Cl₂, formed from Deacon reaction (4HCl+O₂ → 2Cl₂+2H₂O) catalyzed by Cu, promotes dehydrochlorination and oxychlorination reactions.
2) Steam activation at ca. 800-900°C for 1-2h is preferable to that at a lower temperature than 700°C for a long time, irrespective of metal addition. The representative values of Y to prepare activated carbon with S_g=500-1000 m²/g are 15-25% for PVC containing 0.1% Cu and 10-18% for industrial scrapped PVC.
3) Adsorbed amount of I₂, UO₂²⁺ or PO₄^3- on activated carbon is proportional to each S_g, comparable to a commercial activated carbon prepared from coconut shell, and almost independent of raw PVC.