A novel sol-gel method was employed in this study to efficiently synthesize SnO2 nanoparticles to catalyze the ozonation of acetaminophen (ACT) from aqueous solutions. The influence of various parameters including Sn source, type of capping and alkaline agents, and calcination temperature on the catalytic activity of the SnO2 preparations was investigated. The SnO2 nanoparticles prepared by tin tetrachloride as Sn source, NaOH as gelatin agent, CTAB as capping agent and at calcination temperature of 550 °C (SnNaC-550) exhibited the maximum performance in the catalysis of ACT. The optimized catalyst (SnNaC-550) had spherical-homogeneous and cubic-shaped nanocrystalline particles with 5.5 nm mean particle size and a BET surface area of 81 m2/g, which resulted in 98% degradation and 84% mineralization of 50 mg/L ACT at 20 and 30 min reaction time, respectively when combined with ozonation (COP). Based on the radical scavenger experiments, •OH was the major oxidizing agent involved in the removal of ACT. LC/MS analysis showed that short-chain carboxylic acids were the main intermediates. Furthermore, the SnNaC-550 catalytic activity was preserved after four successive cycles. Collectively, the new method has the potential to efficiently synthesize stable and reusable SnO2 nanoparticles to catalyze the ozonation of ACT from aquatic environments.@en

Degradation of tetracycline (TTC) with a heterogeneous Fenton-like pyrite/H₂O₂ process by pyrite from mine waste as a mineral catalyst was investigated. The study focused on identifying the main oxidizing agents and degradation mechanisms along with operational variables including solution pH, pyrite and H₂O₂ concentration, contact time, solution temperature, and initial TTC concentration. Catalyst characterization tests revealed that pyrite is a mesoporous powder with a high degree of FeS₂ purity. Radical scavenger tests demonstrated that ^•OH was the main oxidizing agent generated by both solution and surface phase reactions. During the pyrite/H₂O₂ process, more than 85% of TTC was mineralized in 60 min and the maximum TTC removal was attained in the solution at an acidic pH value (4.1). The most abundant transformation products of TTC, formed by the attack of ^•OH radicals, were simple chain carboxylic acids. Cultured cells of human embryonic kidney (HEK) were used for the cytotoxicity assessment of raw and pyrite/H₂O₂ treated TTC solutions. The results illustrated that the viability of HEK cells was enhanced considerably after treating TTC solutions under optimal conditions. Accordingly, pyrite originating from mine waste is a practically effective and cost-effective catalyst in heterogeneous Fenton-like systems for mineralization and degradation of emerging contaminants such as antibiotics.

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Pyrite mine waste was used as a non-toxic and natural catalyst for the activation of peroxydisulfate (PDS) and peroxymonosulfate (PMS) to oxidize tetracycline (TTC), one of the most extensively used antibiotics worldwide, in contaminated water. The results demonstrated that PMS was activated more effectively than PDS by using pyrite. Scavenging experiments indicated that both OH^[rad] and SO₄^[rad]− were the main oxidative species in the pyrite/PMS process, while SO₄^[rad]− was more dominant. A high degradation of 98.3 % and significant mineralization (up to 46 %) of TTC (50 mg/L) were achieved using pyrite activated PMS at a reaction time of 30 and 60 min, respectively. In-vivo toxicity of raw and pyrite/PMS treated TTC solutions was evaluated using biochemical and histopathological assays. The results revealed that the pyrite/PMS process significantly decreased the nephrotoxicity (90 %) and hepatotoxicity (85 %) effect of TTC. Catalyst reusability was evaluated under cycling conditions. No significant decrease in process efficiency was measured between the first and fourth cycle (<3% decrease in TTC removal). In conclusion, mine waste pyrite nanoparticles can be considered as a non-toxic and clean catalyst to activate PMS for an effective detoxification, degradation, and intermediate mineralization of TTC, as a refractory water pollutant.

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