Mineralisation behaviour during heterogeneous photo-Fenton treatment of amoxicillin in a rotating Fe2O3-impregnated disc reactor: the controlling role of oxidant stoichiometry
Year: 2026
Type: preprint
Abstract: Conventional biological treatment does not remove antibiotic residues, and in Jordan this matters more than in most places, because reclaimed effluent supplies a large share of the water used for irrigation. Heterogeneous photo-Fenton treatment is one candidate for a tertiary polishing step: the iron stays on a recoverable support, so the process avoids the sludge that homogeneous Fenton chemistry produces. We treated amoxicillin (AMX) in a closed 1 L rotating catalytic disc reactor holding ten Fe 2 O 3 -impregnated mesh discs (0.435 mmol Fe g -1 ; 93 g in total), irradiated by three UV-C lamps at 254 nm and turned at about 20 rpm. Seven runs were carried out at 100, 500 and 1000 mg L -1 AMX and pH ≈ 3, at peroxide doses of roughly 140 µL and 1.0 mL, and followed by total carbon (TC) or non-purgeable organic carbon (NPOC) for up to 17 h. Peroxide is consumed by every route that makes a hydroxyl radical, and 35 mol of it are needed per mol of AMX for complete mineralisation. The fractional carbon removal a run can achieve is therefore capped by the fraction f of that demand actually supplied. Our doses gave f = 1.4–20.4%, so complete mineralisation was unattainable before the experiments began. Every apparent carbon removal nevertheless exceeded its cap, in one case by a factor of 13.6, and cannot therefore be attributed to mineralisation. The carbon increases of up to 87.6% cannot be attributed to intermediates either, since fragmentation redistributes carbon without generating it. What the reactor can achieve, and how its carbon data should be read, are both governed by oxidant stoichiometry rather than by catalyst loading or irradiation time.
Source: ChemRxiv
Institution: Al-Balqa Applied University
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7222631789