Large Laboratory-Plant application for the treatment of a Tannerywastewater by Fenton oxidation: Fe(II) and nZVI catalysts comparisonand kinetic modelling

This study reports a comparison among Conventional Fenton oxidation (CF) and Heterogeneous Fenton oxidation (HF) processes performed at large lab-scale on a Tannery Wastewater (TW). The heterogeneous Fenton process was carried out by using self lab-prepared nano zero-valent iron particles as solid catalyst. Two different catalyst/oxidant (Cat/Ox) (w/w) ratio were examined: a study on the pH solution influence on the process efficiency, monitoring the COD, TP, H2O2 and Cr(VI) variation over the reaction time was carried out. The process was conducted for 10 h in batch mode for the first 2 h, followed by 8 h in continuous mode. HF demonstrated better performance, with respect to CF, towards both the removal of Chemical Oxygen Demand (COD), up to 75.5 ± 2.1%, and Total Polyphenols (TP), up to 85.1 ± 0.7%, from the TW. The CF optimal operating parameters were Cat/Ox (w/w) = 0.2 and pH = 2.5 whereas to maximize the HF efficiency a larger Cat/Ox (w/w) ratio, i.e. 0.5, was necessary. In addition, a lower amount of iron sludge was produced by HF with respect to CF (17.5–21.6%). Finally, a kinetic model on the reactions occurring in the HF/TW system was proposed and successfully used to fit experimental data.