Catalytic oxidative degradation of bisphenol A using an ultrasonic-assisted tourmaline-based system: Influence factors and mechanism study

Abstract

Abstract Tourmaline was utilized as a heterogeneous catalyst for the oxidation of bisphenol A (BPA) with synergetic H 2 O 2 -catalytic ability and ultrasonic irradiation. Higher tourmaline concentration, an appropriate H 2 O 2 dose and a lower pH favored BPA depletion. The removal of 5.0 mg L −1 BPA reached 98.4% at 120 min under the following optimized reaction conditions: sonication (40 kHz, 500 W), tourmaline concentration 5.0 g L −1 , H 2 O 2 50 mM and pH 2.0. This high BPA removal could be caused by coordinating heterogeneous and homogeneous processes, based on the observed iron leaching and H 2 O 2 conversion data at different pHs. A retarded first-order kinetic model was employed to describe BPA degradation. The strong inhibition of BPA removal by radical scavengers indicated that the attack of hydroxyl radicals was mainly responsible for BPA removal. In view of the X-ray photoelectron spectroscopy (XPS) results during the reaction, a possible mechanism involving accelerated transfer in the Fe(III)/Fe(II) cycle on the tourmaline surface was proposed. Moreover, eight intermediates were evidenced by GC–MS and LC–MS/MS analyses, and a reaction pathway was also proposed, including the processes of hydroxylation, oxidative skeletal rearrangement, demethylation and dehydration.