Optimization of methylparaben degradation by sonocatalysis

Başak Savun-Hekimoğlu; Nilsun H Ince

doi:10.1016/j.ultsonch.2019.104623

Optimization of methylparaben degradation by sonocatalysis

Ultrason Sonochem. 2019 Nov:58:104623. doi: 10.1016/j.ultsonch.2019.104623. Epub 2019 May 31.

Authors

Başak Savun-Hekimoğlu¹, Nilsun H Ince²

Affiliations

¹ Institute of Environmental Sciences, Bogazici University, 34342 Istanbul, Turkey.
² Institute of Environmental Sciences, Bogazici University, 34342 Istanbul, Turkey. Electronic address: ince@boun.edu.tr.

PMID: 31450296
DOI: 10.1016/j.ultsonch.2019.104623

Abstract

Sonocatalytic degradation of methylparaben (MPB) in the presence of a low-cost clay mineral (sepiolite) was optimized using a multivariable center composite design protocol based on response surface methodology (RSM). Using the data generated with varying MPB concentrations, pH, frequency and catalyst dose, two semi-empirical expressions were developed to describe the relation between the apparent reaction rate constant of the parent compound and the most significant control variables. It was found that ultrasonic power, pH, sepiolite dose and its interactions with time and pH were the most significant parameters influencing the rate of MPB decay under high frequency ultrasound. The models also showed that the rate constant was a convex function of time, as it decreased during the first 35-min of sonolysis and increased thereafter, indicating the formation and depletion of competing oxidation byproducts. Finally, the models predicted that the rate of MPB decay was a maximum either at alkaline pH and a high sepiolite dose (k = 1.68 × 10^-1 min^-1), or at acidic pH and a considerably lower dose of the mineral (k = 1.48 × 10^-1 min^-1).

Keywords: Bubble coalescence; Factorial design; Hydrogen-bonding; Sepiolite; Van der Waals attraction.