REDUCTION REACTION OF FE3+ ION BY ACTIVAT ED CARBON

Activataed carbon is widely used as the adsorbent and the catalyst of oxidation. However, there are little studies about the reduction react ion by activated carbon. In this paper, the effect of the solution con ditions and the pretreatment of activated carbon on the reduction of F e3+ was investigated. The experiments were carried out as follows : Ac tivated carbon was added to the HCI solution containing Fe3+ and the t ime course of Fe2+ concentration was measured by o-phenanthroline meth od. When the reaction was carried out in an atmosphere of nitrogen, ac tivated carbon was added to the HCI solution and degassed with an aspi rator and then Fe3+ solution was added after passing the N2 gas. In th e presence of dissolved oxygen, the time course of Fe2+ concentration displayed a maximum curvature, but it displayed increasing curvature i n an atmosphere of nitrogen (Fig. 2). Consequently, activated carbon c an reduce Fe3+ to Fe2+ in the presence or absence of dissolved oxygen and oxidize Fe2+ to Fe3+ if oxygen is dissolved. Reducing ability of t he activated carbon decreased by the acid treatment in the presence of oxygen (Table 2, Fig. 3) and by the Fe3+ treament (Fig. 6). However, reducing ability was restored by drying the treated carbon (Figs. 4, 5 , 6) and the degree of restoration of reducing ability increased with an increase in the drying temperature (Fig. 4). Initial reduction rate was not affected by the presence of dissolved oxygen (Fig. 7), Fe2+ ( Fig.8) and acid concentration (Fig. 9). These results suggest that at the begining of the reaction, only reduction reaction proceed even if oxygen is dissolved.