Synthesis and characterization of SnO2 crystalline nanoparticles: A new approach for enhancing the catalytic ozonation of acetaminophen.

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.

The catalytic destruction of antibiotic tetracycline by sulfur-doped manganese oxide (S-MgO) nanoparticles.

The present study evaluates the efficacy of S-doped MgO (S-MgO) as compared with the plain MgO as a catalyst for destructive removal of tetracycline (TTC) in aqueous solutions. The S-MgO had around 6% S in its structure. Doping MgO with S caused increase in surface oxygen vacancy defects. Adding S-MgO (12 g/L) to a TTC aqueous solution (50 mg/L) caused removal of around 99% TTC at the neutral pH (ca. 5.1) and a short reaction time of 10 min. In comparison, plain MgO could remove only around 15% of TTC under similar experimental conditions. Diffusing O2 into the TTC solution under the reaction with S-MgO resulted in a considerable improvement of TTC removal as compared to diffusing N2. Complete removal of TTC and 86.4% removal of its TOC could be obtained using 2 g/L S-MgO nanoparticles. The removal of TTC increased with the increase in solution temperature. The presence of nitrate, sulfate and chloride did not considerably affect the removal of TTC using S-MgO while TTC removal significantly decreased at the presence of bicarbonate and phosphate. The S-MgO was a stable and reusable catalyst exhibiting much higher catalytic activity than plain MgO for the TTC destruction. Accordingly, S-MgO is an emerging and efficient catalyst for catalytic decomposition and mineralization of such pharmaceutical compounds as TTC under atmospheric temperature and pressure.