Enhanced degradation of phenol via a zero-valent iron – sodium percarbonate (ZVI-SPC) Fenton-like system: toward environmentally relevant water treatment conditions

This work reports the fundamentals about the performance of a Fenton-like system based on zero-valent iron (ZVI) and sodium percarbonate (SPC), employing phenol (5 – 50 μM) as model contaminant. The influence of operational parameters (pH, temperature, initial SPC concentration, and ZVI amount), as well as the effect of common water constituents and selective scavengers, were systematically studied and compared with the performance of the ZVI-H2O2 treatment. At pH 4.0 and room temperature, the CO2* (i.e., CO2(aq) and the unstable species H2CO3) from SPC promoted the corrosion of ZVI, yielding faster phenol oxidation rates with ZVI-SPC than with ZVI-H2O2. This effect is diminished with pH < 4.0 or at elevated temperatures due to the lower [CO2*] in solution. Regarding the effects of anions and humic acids (investigated as water-matrix components), no appreciable negative effects were observed, except for H2PO4− that would hinder the process through the formation of insoluble FePO4(s) and concomitant ZVI passivation. Scavenger experiments revealed that hydroxyl radicals (HO•) were the predominant reactive species, followed by carbonate radicals (CO3•−). Overall, the ZVI-SPC process demonstrated higher or equal performance than traditional ZVI-H2O2 systems, which warrants further investigations into a promising, low-cost, and safer alternative that could potentially remove emerging contaminants under near-environmental conditions.