Ferrocene-Catalyzed Heterogeneous Fenton-like Degradation of Methylene Blue: Influence of Initial Solution pH

Ferrocene (Fc) was introduced to establish a heterogeneous Fenton-like system for the treatment of Methylene Blue (MB). Discoloration of MB was used to monitor the contributions of adsorption, homogeneous, and heterogeneous Fenton in the heterogeneous Fenton-like process. The dissolution and electrochemical character of Fc were investigated, as well as the effect of initial solution pH on the apparent removal of MB and processes that occurred in the system. pH 3 was verified to be the optimal condition for Fc and showed good redox reversibility. 100% discoloration of MB and 63.5% removal of COD were reached at pH 3, with only 0.2% Fc dissolved. Fc was found to play roles of catalyst as well as adsorbent in the Fc/H 2 O 2 system. Three processes including adsorption, Fenton catalyzed by Fc dissolved in solution (homogeneous Fenton), and Fc particles suspended in solution (heterogeneous Fenton) worked simultaneously. The efficiencies of the homogeneous Fenton and heterogeneous Fenton were up to the adsorption to some extent. The efficiency of homogeneous Fenton catalyzed by Fc dissolved in solution was about 76.66 times that of heterogeneous Fenton catalyzed by Fc particles at pH 5, but the bulk of MB was degraded in the heterogeneous Fenton catalyzed by Fc particles.