Advisor(s)
Abstract(s)
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.
Description
Keywords
Advanced oxidation Cavitation Low frequency ultrasound Micropollutants Sonodegradation Water quality
Pedagogical Context
Citation
Zanias, Athanasios; Frontistis, Zacharias; Vakros, John; Arvaniti, Olga S.; Ribeiro, Rui S.; Silva, Adrián M.T.; Faria, Joaquim L.; Gomes, Helder T.; Mantzavinos, Dionissios (2020). Degradation of methylparaben by sonocatalysis using a Co–Fe magnetic carbon xerogel. Ultrasonics Sonochemistry. ISSN 1350-4177. 64, p. 1-7