Fe3+-NTA as iron source for solar photo-Fenton at neutral pH in raceway pond reactors

Amal Mejri; Paula Soriano-Molina; Sara Miralles-Cuevas; José Antonio Sánchez Pérez

doi:10.1016/j.scitotenv.2020.139617

Fe³⁺-NTA as iron source for solar photo-Fenton at neutral pH in raceway pond reactors

Sci Total Environ. 2020 Sep 20:736:139617. doi: 10.1016/j.scitotenv.2020.139617. Epub 2020 May 23.

Authors

Amal Mejri¹, Paula Soriano-Molina², Sara Miralles-Cuevas², José Antonio Sánchez Pérez³

Affiliations

¹ Laboratory of Wastewater Treatment and Recycling, Research and Technology Center of Water, University of Carthage, BP 273, 8020 Soliman, Tunisia; National School of Engineers of Sfax, University of Sfax, Soukra road, Km 4, 3038 Sfax, Tunisia.
² Solar Energy Research Centre (CIESOL), Ctra de Sacramento s/n, Almería ES04120, Spain; Chemical Engineering Department, University of Almería, Ctra de Sacramento s/n, Almería ES04120, Spain.
³ Solar Energy Research Centre (CIESOL), Ctra de Sacramento s/n, Almería ES04120, Spain; Chemical Engineering Department, University of Almería, Ctra de Sacramento s/n, Almería ES04120, Spain. Electronic address: jsanchez@ual.es.

PMID: 32485381
DOI: 10.1016/j.scitotenv.2020.139617

Abstract

This work presents, for the first time, a kinetic study of the solar photo-Fenton process at neutral pH mediated by the Fe³⁺-NTA complex (molar ratio 1: 1) applied to remove contaminants of emerging concern (CECs). To this end, wastewater treatment plant (WWTP) secondary effluents were treated in a raceway pond reactor (RPR) at pilot plant scale with 0.1 mM Fe³⁺-NTA and 0.88 mM H₂O₂ under average solar UVA irradiance of 35 W/m². Sulfamethoxazole and imidacloprid, at 50 μg/L of initial concentration each, were selected as model CECs. Up to 40% of the sum of both model CECs was removed from simulated WWTP effluent by the Fe³⁺-NTA Fenton-like process, and >80% was removed by solar photo-Fenton. The effect of liquid depth in the reactor was evaluated, showing an increase of the treatment capacity from 12 mg CEC/m²·h to 18 mg CEC/m²·h when liquid depth increased from 5 to 15 cm. Afterwards, these results were validated with real WWTP effluents and compared with the results obtained with the Fe³⁺-EDDS complex under the same operating conditions. The same CEC removal rates were obtained with Fe³⁺-NTA and Fe³⁺-EDDS at 5 cm of liquid depth (kinetic constants of 0.110 min^-1 and 0.046 min^-1 for sulfamethoxazole and imidacloprid, respectively). Conversely, at 15 cm of liquid depth, the degradation rates were lower with Fe³⁺-NTA (kinetic constants of 0.034 min^-1 for sulfamethoxazole and 0.017 min^-1 for imidacloprid), whereas with Fe³⁺-EDDS the values were 0.076 min^-1 and 0.047 min^-1 for sulfamethoxazole and imidacloprid, respectively. Regarding process cost estimation, the use of NTA as iron chelate for solar photo-Fenton at neutral pH at pilot plant scale resulted very cost-effective (0.13-0.14 €/m³) in comparison with the use of EDDS (0.46-0.48 €/m³) at the two liquid depths tested.

Keywords: Advanced oxidation process; Chelating agents; Contaminants of emerging concern; Cost; EDDS; Real wastewater.