Evaluation of advanced oxidation processes for ß-blockers degradation: a review

This study summarizes the results of scientific investigations on the removal of the three most-often used ß-blockers (atenolol, metoprolol and propranolol) by various advanced oxidation processes (AOP). The free radical chemistry, rate constants, degradation mechanism and elimination effectiveness of these compounds are discussed together with the technical details of experiments. In most of AOP the degradation is predominantly initiated by hydroxyl radicals. In sulfate radical anion based oxidation processes (SROP) both hydroxyl radical and sulfate radical anion greatly contributes to the degradation. The rate constants of reactions with these two radicals are in the 109–1010 M−1 s−1 range. The degradation products reflect ipso attack, hydroxylation on the aromatic ring and/or the amino moiety and cleavage of the side chain. Among AOP photocatalysis and SROP are the most effective for degradation of the three ß-blockers. The operating parameters have to be optimized to the most suitable effectiveness.

K2S2O8 activation by glucose at room temperature for synthesis and functionalization of heterocycles in water

While persulfate activation at room temperature using glucose is primarily focused on kinetic studies of sulfate radical anion, utilization of this protocol in organic synthesis is rarely demonstrated. We reinvestigated...

GENERATION OF RADICALS IN FERROUS-PERSULFATE SYSTEM USING KRCL EXCILAMP

Generation of sulfate radical anion (SО4•–) and hydroxyl radical (•OH) in the ferrous-persulfate system (UV/PS/Fe2+), activated with KrCl excilamp (222 nm) radiation, was studied. To detect radicals and evaluate levels of their action, degradation experiments were conducted using the probe compounds, which trap the target radicals – terephtalic acid (TPA) and p-chlorobenzoic acid (pCBA). Deionized water (DW), natural water (NW) and wastewater (WW), containing a probe compound, were sequentially treated by direct UV, UV/PS and UV/PS/Fe2+ systems. The ferrous-persulfate system was shown to be the most efficient in terms of radical generation within the same water matrix: UV/PS/Fe2+ > UV/PS > UV. Comparing different water matrices, the lowest radical generation was observed in WW. Since TPA and pCBA were unsuitable compounds to assess the contributions of SО4•– and •OH by comparison of degradation degree with and without methanol and tert-buthanol, herbicide atrazine (ATZ) was taken as a model organic pollutant with comparable reaction rate constants with SО4•– and •OH. Scavenging experiments with ATZ and alcohols showed a major contribution of SO4•– during UV/PS/Fe2+ treatment of DW (79%) and NW (60%), whereas SO4•– and •OH contributed equally in WW. Direct UV irradiation (without persulfate and Fe2+) indicated the •OH production in WW, presumably, due to high photoreactivity of dissolved organic substance (DOM).

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH) of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time, DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4−) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O) and a sulfate radical anion (SO4 ⋅ −) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10−13 cm3 molecule−1 s−1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 1012 molecule cm−3 s), only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an organosulfate can lead to the formation of sulfate radical anion and produce inorganic sulfate. Fragmentation processes and sulfate radical anion chemistry play a key role in determining the compositional evolution of sodium methyl sulfate during heterogeneous OH oxidation.