Hierarchically structured TiO2-based composites for Fenton-type oxidation processes

A novel hierarchically structured composite aimed as a stable catalyst for the heterogeneous Fenton-type (HFT) oxidation process was developed by using a cost-effective and versatile technique. Prussian Blue nanoparticles (PBNP) were dispersed onto aligned macroporous TiO2 (rutile) monoliths prepared via directional freezing of aqueous dispersions of TiO2 nanoparticles. The catalytic performance was evaluated in the HFT oxidation of an azo dye frequently used as a model contaminant, Orange G (OG). Experiments were carried out in a liquid batch-recycle reactor, in which the liquid flow rate was set to ensure negligible external mass transfer resistance. The catalyst exhibited good activity to form highly oxidative radicals from hydrogen peroxide decomposition, which readily discolored OG. Significant reduction of the time required to attain complete discoloration and improvement in TOC removal were achieved by adjusting operating conditions and oxidant dosage strategies. Almost complete OG conversion at around 90 min and 34.4% of TOC removal after 4 h were achieved by using the best evaluated strategy. The catalyst activity was tested under specific operating conditions and remained unaltered during 42 cycles of 4 h each (total 168 h). The fresh and used PBNP/TiO2 catalysts and the support were thoroughly characterized by several techniques. Results supported the excellent stability exhibited by the catalyst in the OG HFT oxidation. [Display omitted] •Prussian Blue nanoparticles are well-dispersed on structured TiO2 porous scaffolds.•The composite is highly active in heterogeneous Fenton-type reactions.•An increase in temperature and a H2O2 dosage strategy allow duplicating TOC removal.•Complete discoloration of Orange G solution and 34.4% of TOC removal are achieved.•The composite shows remarkable stability throughout 42 reaction cycles of 4 h each.