Preparation of activated carbon (AC) from 8 species of coal whose coking property and ratios (1.8~7.7) of fixed carbon (FC) to volatile matter(VM) being differ widely, was studied to find the most suitable process or conditions to obtain a large surface area Sg(m2(AC)/g(AC)) and a high yield Y(g(AC)/g(raw coal)). The value of Sp= YSg(m2(AC)/g(raw coal)) or Se= YSg/α(m2(AC)/g(sum of FC and ash)) was used as a criterion, which was expected to attain a high value as possible. The two-step activation process which was the combination of carbonization of coal to char with flowing air, HCl-air mixture gas, CO2(dry method), and/or cone. H2SO4(wet method), and activation of char with steam, as well as other process of direct activation of coal were tried and compared, changing such experimental conditions as carbonization atmosphere, carbonization temperature and time(4°C/min, 300~400°C, mainly 3 hrs for dry method; 150°C, lhr for wet method), activation atmosphere(H20-N2, CO2, H2O-CO2-N2; mainly 10% H2O-N2), activation temperature, and time(700~1000°C, mainly 900°C; 0.5~7hrs). Drying at 110°C for lhr in air was selected as the weight criterion of raw coal(-12/+24 mesh, average diameter 1.0 mm). The main results obtained are as follows : (1) The coking property and the ratio of FC/VM of coal in the direct activation process and the carbonization methods in the two-step activation process, namely the physicochemical properties of coal and char, controlled the pore developing process (Sp, vs. Y; Se vs. Y/α) through the activation. The basic carbon structure of AC, found by X-ray diffraction analysis, had been determined by the structure of coal or char prior to activation. (2) To prepare AC of large Sg in high yield, the direct activation and two-step activation by dry carbonization were excellent for raw coal whose FC/VM was below 3 or the content of FC+Ash was below 75%, and the two-step activation by wet carbonization was suitable for raw coal of high degree of coalification. The typical performance in this study was to prepare AC with Sg=500~1000 m2/g, whose yield being 40~70%, comparable to commercial ACs. (3) Steam(10% H2O-N2) activation at relatively high temperature (900°C) for 0.5~2hrs was preferable to a low temperature and long-time operation. Pretreatment of char with an inactive gas(N2) at 900°C improved the yield of AC during activation, forming partially hard carbon in char. (4) Adsorption capactityfa) of prepared AC for I2, UO22+ and PO42- in liquid phase was independent of raw coal and preparation methods, and showed proportionality toward Sg as follows : q(mg(I2)/g(AC)) =1.20Sg…(A), q(mg(U)/g(AC)) =0.18Sg…(B) or q(mg(PO42-)/ g(AC))=0.012Sg…(C). (5) Catalytic activity of prepared ACs for air oxidation of Fe8+ in sulfuric acid solution was comparable to that of commercial AC prepared from coconut shell. As reported previously. the ACs prepared from poly(vinyI chloride) and polycarbonate gave the same adsorption abilities as shown in Eqs. (A) and (B), but only half in Eq. (C), and no catalytic activity toward air oxidation of Fe2+. © 1979, The Chemical Society of Japan. All rights reserved.
