Fenton-type processes triggered by titanomagnetite for the degradation of phenol as model pollutant

Heterogeneous catalysts for the oxidation of toxic compounds are extremely important for many applications including environmental remediation. Here, we assessed the ability of Ti-substituted magnetite, i.e., titanomagnetite (FeIII(2-2x)FeII(1+x)TixO4) to promote Fenton-like heterogeneous reactions. Two titanomagnetites with x values respectively equal to 0.25 (TM0.25) and 0.75 (TM0.75), as well as unsubstituted magnetite (M, x = 0) were tested for the degradation of phenol under different conditions. Kinetic assessments over 1 hour reaction time showed that all the studied systems had the best performance at pH 3. This is the typical, optimal pH value of the Fenton reaction. Moreover, titanomagnetite-based systems were active at low loading and afforded the application of relatively low H2O2 doses. The titanomagnetites had lower ability than magnetite to induce phenol degradation at pH > 3. However, presumably because of the higher Fe(II) content, TM0.75 was less susceptible than M or TM0.25 to the loss in reactivity caused by air exposure. TM0.75 can thus be handled in ambient systems or O2-containing environments, which may be a key advantage from an application point of view.