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The degradation of recalcitrant organic pollutants by sulphate radical (SO 4 •- ) 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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Triphenylmethane (TPM) dyes are an important category of dyes with a variety of industrial applications and consequently, these are found in the aquatic environment at relatively higher concentrations. Here, we report the degradation of two important TPM dyes (para rosaniline (PRA) and ethyl violet (EV)) in an aqueous medium by ultrasound which is one among the Advanced Oxidation Processes (AOPs). The main objective of this work is to study the effect of various inorganic ions on the degradation and the product formation of TPM dyes from the sonochemical reactions. Using a typical concentration of 10 ppm dyes and an ultrasonic frequency of 350 kHz and power of 60 W, a complete degradation of EV and PRA was observed with a pseudo first order rate constant of 0.2339 min -1 and 0.1956 min -1 , respectively. The product analyses using high-resolution mass spectrometry (LC-Q-TOF-MS) revealed the formation of hydroxylated, de-alkylated, and other collapsed conjugated structure destructed products. The evolution of these products in the presence of various inorganic ions (Cl - , SO 4 2- , NO 3 - , and CO 3 - ) showed that only carbonate ions had a significant impact on the product evolution. The carbonate ions facilitated the formation of conjugated structure destructed product for both the dyes. This is attributed to the reactivity of carbonate radical, which facilitated the formation of carbon-centered radicals. This carbon-centered radical further undergoes reaction to cause the destruction of conjugated structures. This is confirmed by the identification of the corresponding product peaks in the mass spectra. The scavenging effect of carbonate ions was also reflected in the product study where there is a reduction in the formation of most of the hydroxylated products. One of the major inorganic species in any wastewater is carbonate ions and therefore the present result is very relevant to the understanding of oxidation based treatment protocol., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The sonochemical transformation of para-aminosalicylic acid (PAS), a widely used antibiotic and an identified Emerging Pollutant (EP) under the class of Pharmaceuticals and Personal Care Products (PPCPs), have been investigated in aqueous medium. Ultrasound having frequency of 350kHz and power of 80W was utilized for the degradation of PAS. A complete degradation (100%) of PAS after 60min and about 83% of COD removal after 120min of sonication, were obtained. Fourteen intermediate products were identified using LC-Q-TOF-MS. On a comparison with UV/H 2 O 2 method, it is understood that four products out of fourteen were nitro derivatives which are formed only in the sonolysis, and the rest are from hydroxyl radicals. The involvement of nitrite which is formed from the sonolysis of solution containing PAS, in the formation of the other four nitro products has been established from the control studies. Nitrite ion partially scavenge hydroxyl radical in the course of the reaction to form nitrite radical which is the reactive species for the production of nitro compounds. It is, therefore, proposed that in addition to hydroxyl radical, contribution of in-situ generated nitrite also plays an important role in the sonochemical transformation of PAS., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Ultrasound is extensively used in medical field for a number of applications including targeted killing of cancer cells. DNA is one of the most susceptible entities in any kind of free radical induced reactions in living systems. In the present work, the transformation of thymidine (dT) induced by ultrasound (US) was investigated using high resolution mass spectrometry (LC-Q-ToF-MS). dT was subjected to sonolysis under four different frequencies (200, 350, 620 and 1000 kHz) and at three power densities (10.5, 24.5 and 42 W/mL) in aerated as well as argon saturated conditions. A total of twenty modified nucleosides including non-fully characterized dT dimeric compounds were detected by LC-Q-ToF-MS. Out of these products, seven were obtained only in the argon atmosphere and two only in the aerated conditions. Among the identified products, there were base modified products and sugar modified products. The products were formed by the reaction of hydroxyl radical and hydrogen atom. Under aerated conditions, the reactions proceed via the formation of hydroperoxides, while in argon atmosphere disproportionation and radical recombinations predominate. The study provides a complete picture of sonochemical transformation pathways of dT which has relevance in DNA damage under ultrasound exposure., (Copyright © 2015 Elsevier B.V. All rights reserved.)

One-electron reduction of S-nitrosothiols (RSNO) has been studied using radiolytically produced reducing entity, the hydrated electron (e(aq)(-)), in aqueous medium. Both kinetics of the reaction and the mechanistic aspects of the decomposition of S-nitroso derivatives of glutathione, L-cysteine, N-acetyl-L-cysteine, N-acetyl-D,L-penicillamine, N-acetylcysteamine, L-cysteine methyl ester, and D,L-penicillamine have been investigated at neutral and acidic pH. The second-order rate constants of the reaction of e(aq)(-) with RSNOs were determined using a pulse radiolysis technique and were found to be diffusion controlled (10(10) dm(3) mol(-1) s(-1)) at neutral pH. The product analysis using HPLC, fluorimetry, and MS revealed the formation of thiol and nitric oxide as the major end products. It is therefore proposed that one-electron reduction of RSNO leads to the liberation of NO. There is no intermediacy of a thiyl radical as in the case of oxidation reactions of RSNOs. The radical anion of RSNO (RSN(*)O(-)) is proposed as a possible intermediate. The overall reaction could be written as RSNO + e(aq)(-) --H+--> RSH + (*)NO.