The effect of thermal treatment on some characteristics of animal carbon

Abstract

The calcination of animal bone carbon and bone carbon waste was studied in order to characterize the processes' optima up to 1000°C. The thermal treatment in air and in vacuum, and subsequent weight loss determinations verified dehydration, dehydroxylation and decarbonization processes. The adsorption of nitrogen and water was measured to differentiate between these processes. The calcination course showed optimum weight losses up to 500°C and the final loss was reached at 700°C. The surface area of the vacuum-treated samples attained a limiting value at 300–350°C. Below 400°C the surface area of air-treated samples increased. Above 400°C the nitrogen adsorption showed a considerable decrease in surface area, denoting solid-state sintering above 500°C. This process of sintering was characterized by an exponential function between the surface areas and temperature, i.e. S=k e E/RT. from which the energies of sintering were calculated. The amount of water adsorbed and the surface area were correlated by the relation W=kS, i.e. the number of active sites for water chemisorption per unit area is constant. The dehydration, dehydroxylation, decarbonization and sintering processes are relatively retarded in the bone carbon waste.