Degradation studies of bisphenol S by ultrasound activated persulfate in aqueous medium

Abstract

The degradation of recalcitrant organic pollutants by sulphate radical (SO₄^•-) represents one of the most recent developments in oxidation-based water treatment. In most cases, persulfate (PS) acts as a precursor of sulphate radicals. This study employed ultrasound-activated PS to generate reactive species, facilitating the degradation of bisphenol S (BPS), a well-known contaminant of emerging concern (CECs). An ultrasound with a frequency of 620 kHz and 80 W power was utilised for the degradation studies. The applied oxidation system successfully resulted in the complete degradation of BPS in both pure and real environmental water samples. Additionally, the Chemical oxygen demand (COD) was reduced to an acceptable limit in both matrices, with a reduction of 85 % in pure water and 73 % in river water. The degradation was monitored by varying chemical parameters such as pH, inorganic ions, and organics concentration. The results indicate that under specific pH conditions, the degradation efficiency followed the order of pH 3 > 4 > 7 > 11. The presence of coexisting matrices suppressed the efficiency by scavenging the reactive species. Utilizing high-resolution mass spectrometry (HRMS) analysis, this study identified seven intermediate products during identified during the degradation of BPS. Furthermore, a comprehensive mechanism has been deduced for the transformation and degradation process. All the results presented in this study underscore the applicability of the US/PS system in the removal of CECs.

Keywords: Advanced oxidation processes; Bisphenol S; Cavitation; Chemical Oxygen Demand; Persulfate.

Fig. 1

Effect of persulfate on the Sonochemical degradation, Frequency = 620 kHz, Power = 80 W, [BPS] = 10⁻⁵ mol dm⁻³, initial pH = 4. Inset: first order kinetics of degradation.

Fig. 2

Comparison of Total ion chromatogram (TIC) of US and US/PS treated solution of BPS; Frequency = 620 kHz, Power = 80 W, [BPS] = 10⁻⁵ mol dm⁻³, [PS] = 10⁻⁴ mol dm⁻³, Time: 60 min.

Fig. 3

Effect of radical scavengers on the degradation of BPS, Frequency = 620 kHz, Power = 80 W, [BPS] = 10⁻⁵ mol dm⁻³, [PS] = 10⁻⁴ mol dm⁻³, [scavenger] = 10⁻⁴ mol dm⁻³, and Time = 60 min.

Scheme 1

Generation of reactive species in US/PS system and the degradation of BPS.

Fig. 4

Degradation of BPS at varying pH; [BPS] = 10⁻⁵ mol dm⁻³; Freq = 620 kHz, power = 80 W; [PS] = 10⁻⁴ mol dm⁻³. Inset: effect of pH on the first-order degradation kinetics.

Fig. 5

Effect of SDS on the Degradation of BPS by US- persulfate system, Freq = 620 kHz; Power = 80 W; [BPS] = 10⁻⁵ mol dm⁻³; [PS] = 10⁻⁴ mol dm⁻³, pH = 4.

Fig. 6

Effect of different type organic matters such as a) humic acid, B) oxalic acid and C) glucose on the degradation of BPS, Frequency = 620 kHz; Power = 80 W; [BPS] = 10⁻⁵ mol dm⁻³ [PS] = 10⁻⁴ mol dm⁻³, and initial pH = 4.

Fig. 7

Effect of Bicarbonate ion on the US/ persulfate system, Frequency = 620 kHz; Power = 80 W; [BPS] = 10⁻⁵ mol dm⁻³; [PS] = 10⁻⁴ mol dm⁻³, initial pH = 4.

Fig. 8

Degradation of BPS in Pure water (PW) and River water (RW), Freq = 620 kHz; Power = 80 W; [BPS] = 10⁻⁵ mol dm⁻³; [PS] = 10⁻⁴ mol dm⁻³.

Fig. 9

COD reduction of BPS in River water and in pure water during sonolysis, Freq = 620 kHz; Power = 80 W; [BPS] = 10⁻⁵ mol dm⁻³; [PS] = 10⁻⁴ mol dm⁻³.

Fig. 10

The proposed degradation pathway of BPS by US/ persulfate system.