Carbonization of iron-treated Loy Yang coal

Abstract Carbonization of untreated and iron-treated Loy Yang coal was carried out at selected temperatures in the range of 200°C–700°C. The electrical conductivity was higher in all the iron-treated samples, except for the sample prepared at 700°C, which was identical. Arrhenius plots of the conductivity of carbons treated above 500°C exhibited considerable non-linearity but showed that the conductivity increase was caused by a change in the pre-exponential factor rather than in the activation energy. Mossbauer measurements revealed that the three, initially dispersed, paramagnetic iron species were transformed into magnetite and then principally, α - and γ -iron between 400°C and 600°C. The electrical conductivity depended strongly on the concentration of carboxyl groups and suggested a model in which conduction between the π -electron reservoirs was via an electron hopping mechanism along hydrogen-bonded cross-links. The enhanced removal of the carboxyl groups by the presence of iron aids the destruction of these poorly conducting links during carbonization.