Using the stopped-flow technique, the rate constants of the reaction of ozone with a number of amines have been determined. While the protonated amines do not react with ozone, the free amines react with rate constants of around 10⁶ dm³ mol⁻¹ s⁻¹ in the case of tertiary and secondary amines, while primary amines react more slowly. Mono-protonated EDTA reacts only with k=1.6×10⁵ and mono-protonated 1,4-diazabicyclo[2.2.2]octane (DABCO) with k = 3.5 × 10³ dm³ mol⁻¹ s⁻¹. In aqueous solution, tertiary amines react with ozone mainly by forming the aminoxide and singlet dioxygen [O₂(¹Δ_g)] and to a lesser extent the secondary amine and the corresponding aldehyde, a reaction which can be partially suppressed by tert-butyl alcohol. These data suggest that O-transfer [aminoxide plus O₂(¹Δ_g)] is in competition with an electron transfer which leads to the amine radical cation and an ozonide radical. In water, the latter gives rise to ˙OH which further reacts with the amine (and ozone). The amine radical cation deprotonates at a neighbouring carbon. The resulting radical adds dioxygen. Subsequent elimination of O₂˙⁻ and hydrolysis of the Schiff-base thus formed leads to the secondary amine and the corresponding aldehyde. In its reaction with ozone, O₂˙⁻ yields further ˙OH. Their reaction with the amines leads to the same intermediate as the free-radical pathway of ozone does, i.e. induces a chain reaction. This is interfered with by tert-butyl alcohol at the OH-radical stage. When complexed to Fe(III), EDTA reacts only very slowly with ozone (k = 330 dm³ mol⁻¹ s⁻¹). This explains why EDTA is not readily removed by ozonation in drinking-water processing.

In ozone reactions, singlet dioxygen [O₂(¹Δ_g)] is formed when ozone reacts by O-atom transfer. O₂(¹Δ_g) yields were determined for more than 50 compounds using as reference the reaction of hydrogen peroxide with hypochlorite. Close to 100% yields were found in the reaction of O₃ with sulfides, disulfides, methanesulfinic acid, and nitrite. In accordance with this, the only products are: methionine sulfoxide, methanesulfonic acid, and nitrate for the reaction of O₃ with methionine, methanesulfinic acid, and nitrite, respectively. In the case of aliphatic tertiary amines (trimethylamine, triethylamine, and DABCO), the O₂(¹Δ_g) yields range between 70 and 90%, the aminoxide being the other major product. With EDTA and nitrilotriacetic acid (NTA), the O₂(¹Δ_g) yield is around 20%. The interpretation of the data with DABCO required the determination of the quenching constant of O₂(¹Δ_g) by this amine, k_q = 1.8 × 10⁹ dm³ mol⁻¹ s⁻¹ in H₂O and D₂O, two orders of magnitude lower than previously reported. Aromatic tertiary amines give even lower O₂(¹Δ_g) yields [N,N-dimethylaniline (7%), N,N,N′,N′-tetramethylphenylenediamine (9%)]. Substantial amounts of O₂(¹Δ_g) are also formed with the DNA model compounds, 2′-deoxyguanosine (40%) and 2′-deoxyadenosine (15%, in the presence of tert-butyl alcohol as ˙OH scavenger). The pyrimidine nucleobases only yield O₂(¹Δ_g) when deprotonated at N(1). O₂(¹Δ_g) formation is also observed with hydrogen sulfide (15%), azide (17%), bromide (56%), iodide (12%), and cyanide ions (20%). The O₂(¹Δ_g) yield from the reaction of O₃ with phenols and phenolates is typically around 20%, but may rise closer to 50% in the case of pentachloro- and pentabromophenolate. Low O₂(¹Δ_g) yields are found with unsaturated acids such as dihydroxyfumarate (6%), muconate (2%), and acetylenedicarboxylate (15%). With saturated compounds, also, no O₂(¹Δ_g) (e.g. with propan-2-ol, acetaldehyde, acetaldehyde dimethylacetal and glyoxal) or very little O₂(¹Δ_g) (formic acid; 6%, at high formate concentrations) was detected. As shown with some examples, knowledge of the O₂(¹Δ_g) yield (in combination with that of other products) is a prerequisite for the elucidation of the mechanisms of O₃ reactions in aqueous solutions.

High ozone rate constants (in water) cannot be determined directly by stopped-flow techniques. Competition experiments with buten-3-ol (k = 7.9 × 10⁴ dm³ mol⁻¹ s⁻¹; Dowideit and von Sonntag, Environ. Sci. Technol., 1998, 32, 1112), based on reasonably long-lived intermediates, have been set up with 1,4-dimethoxybenzene (DMB; intermediate at 250 nm measured at 3 s) and 1,3,5-trimethoxybenzene (TMB; intermediate at 260 nm, measured at 10 s). They yielded k(O₃ + DMB) = 1.3 × 10⁵ and k(O₃ + TMB) = 9.4 × 10⁵ dm³ mol⁻¹ s⁻¹, respectively. A competition of 1,3,5-trimethoxybenzene with indigotrisulfonate, monitored by the bleaching of the indigo derivative at 600 nm, yielded a rate constant of 9.4 × 10⁷ dm³ mol⁻¹ s⁻¹ for this compound. This convenient and highly reactive competitor now allows us to determine other very high ozone rate constants. As an example, its reaction with DABCO (k = 1.7 × 10⁶ dm³ mol⁻¹ s⁻¹) has been determined. Its direct reaction with ozone (by following the decay of the absorption at 260 nm) can only be determined in a pH range where DABCO is still largely protonated [k(O₃ + DABCO/H₂ ²⁺) < 30 dm³ mol⁻¹ s⁻¹; k(O₃ + DABCO/H⁺) = 3.5 × 10³ dm³ mol⁻¹ s⁻¹], and the rate constant of the fully deprotonated amine can only be arrived at by extrapolation [k(O₃ + DABCO) = 3.2 × 10⁶ dm³ mol⁻¹ s⁻¹].

Polymeric carbon nitride doped with copper through a solid-state reaction was characterized by several techniques, among them are UV-visible spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, etc. The material is a semiconductor with a wide band gap of 2.74 eV. Sites of both Cu(I) and Cu(II) were detected, apparently only coordinated by the polymer. The material comprises crumpled nanosheets, and is substantially an amorphous layered material with a prevalent 2D structure with low inter-planar interactions, as shown by X-ray diffractometry and TeraHertz spectroscopy. Photo-oxidation of benzyl alcohol was used to probe the active sites of the material, comparing them with the non-doped material. The higher activity and selectivity toward salicylic alcohol of the non-doped material can be due to both a more localized electron transfer and a longer lifetime of the hole–electron pair. Cu-CN favored the oxidation of hydroxymethyl group. Therefore, the presence of copper can favor different reaction pathways with respect to the non-doped material.

OH radicals generated in the pulse radiolysis of N₂O-saturated water react with formamide (by H-abstraction) and with cyanide (by addition and rearrangement) to give the same radicals, the main radical being the ^·CONH₂ radical 1 (85–95%), the other most likely being the HC(O)NH^· radical 2 (5–15%). Quantum-chemical calculations support the preferred formation of 1 from formamide as well as from cyanide. Radical 1 reduces tetranitromethane (TNM) to the nitroform anion (2.8 × 10⁸ dm³ mol⁻¹ s⁻¹). In the presence of oxygen, it rapidly adds oxygen (2.7 × 10⁹ dm³ mol⁻¹ s⁻¹) to give the corresponding peroxyl radical ^·OOCONH₂ (3) which absorbs more strongly in the wavelength region 250–400 nm than radical 1 [ε(320 nm) ≈ 180 dm³ mol⁻¹ cm⁻¹]. Peroxyl radical 3 deprotonates in basic solution (pK_a ≈ 9.6), and its anion rapidly eliminates O₂ ^·− (10⁶ s⁻¹) to give cyanic acid. Product studies under γ-radiolysis conditions show that in the absence of O₂ less than half of radical 1 decays by disproportionation to produce cyanate and formamide. In basic solution and in the presence of O₂, the G values of cyanate and H₂O₂ confirm that all of the peroxyl radical 3 decays by O₂ ^·−-elimination.

Meropenem (MER), a carbapenem, is considered a last-resort antibiotic. Its presence in water bodies, together with other antibiotics, has brought about environmental problems related to the destruction of natural microorganisms and the development of antibiotic-resistant bacteria. Herein, the degradation of MER by heterogeneous photocatalysis using TiO₂ immobilized on fiberglass substrates is reported. Morphological characterization of the substrates was performed by Scanning Electron Microscopy (SEM). Three pH values (4.0, 5.7, and 7.9) were tested for the treatment of MER solutions (100 mg/L). The best rate constants and MER removals were obtained at pH 4.0 (0.032 min⁻¹; 83.79%) and 5.7 (0.032 min⁻¹; 83.48%). Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removals of 25.80% and 29.60% were achieved for the treatment at a pH value of 5.7. The reuse and regeneration of the plates were also tested. The activity of the substrates was maintained until the fourth cycle of reuse, nonetheless, a decrease in MER removal was observed for the 5th cycle. After the fourth cycle of reuse, the activity of the substrates was recovered by a regeneration procedure involving a wash stage of the substrates with a 1% H₂O₂ solution in an ultrasonic bath.