Degradation of methylparaben by sonocatalysis using a Co-Fe magnetic carbon xerogel

Athanasios Zanias; Zacharias Frontistis; John Vakros; Olga S Arvaniti; Rui S Ribeiro; Adrián M T Silva; Joaquim L Faria; Helder T Gomes; Dionissios Mantzavinos

doi:10.1016/j.ultsonch.2020.105045

Degradation of methylparaben by sonocatalysis using a Co-Fe magnetic carbon xerogel

Ultrason Sonochem. 2020 Jun:64:105045. doi: 10.1016/j.ultsonch.2020.105045. Epub 2020 Feb 25.

Authors

Athanasios Zanias¹, Zacharias Frontistis², John Vakros¹, Olga S Arvaniti¹, Rui S Ribeiro³, Adrián M T Silva³, Joaquim L Faria³, Helder T Gomes⁴, Dionissios Mantzavinos⁵

Affiliations

¹ Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece.
² Department of Chemical Engineering, University of Western Macedonia, GR-50100 Kozani, Greece.
³ Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
⁴ Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5300-253 Bragança, Portugal.
⁵ Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece. Electronic address: mantzavinos@chemeng.upatras.gr.

PMID: 32120238
DOI: 10.1016/j.ultsonch.2020.105045

Abstract

The degradation of methylparaben (MP) through 20 kHz ultrasound coupled with a bimetallic Co-Fe carbon xerogel (CX/CoFe) was investigated in this work. Experiments were performed at actual power densities of 25 and 52 W/L, catalyst loadings of 12.5 and 25 mg/L, MP concentrations between 1 and 4.2 mg/L and initial pH values between 3 and 10 in ultrapure water (UPW). Matrix effects were studied in bottled water (BW) and secondary treated wastewater (WW), as well as in UPW spiked with bicarbonate, chloride or humic acid. The pseudo-first order kinetics of MP degradation increase with power and catalyst loading and decrease with MP concentration and matrix complexity; moreover, the reaction is also favored at near-neutral conditions and in the presence of dissolved oxygen. The contribution of the catalyst is synergistic to the sonochemical degradation of MP and the extent of synergy is quantified to be >45%. This effect was ascribed to the ability of CX/CoFe to catalyze the dissociation of hydrogen peroxide, formed through water sonolysis, to hydroxyl radicals. Experiments in UPW spiked with an excess of tert-butanol (radical scavenger), sodium dodecyl sulfate or sodium acetate (surfactants) led to substantially decreased rates (i.e. by about 8 times), thus implying that the liquid bulk and the gas-liquid interface are major reaction sites. The stability of CX/CoFe was shown by performing reusability cycles employing magnetic separation of the catalyst after the treatment stage. It was found that the CX/CoFe catalyst can be reused in up to four successive cycles without noteworthy variation of the overall performance of the sonocatalytic process.

Keywords: Advanced oxidation; Cavitation; Low frequency ultrasound; Micropollutants; Sonodegradation; Water quality.