Deterination of Ferrate/Proxymonosulfate and Ferrate/Hydrogen peroxide for sulfamethoxazole removal from municipal wastewater treatment effluent.

Abstract

Entering farmaceticals, antibiotics and their byproducts into the water bodies raised many environmental concerns recently. Advanced oxidation processes (AOPs), due to their high oxidation potential and the formation of more potent radicals, have attracted many interest in removal of antibiotics from wastewater. Therefore, the main objective of this study was to eliminate sulfametoxazole using potassium ferrate/peroxy monosulfate and potassium ferrate/hydrogen peroxide processes. The present research was an experimental study carried out by a Jartest system using a 1 liter volume reactor. The effect of different variables including pH (3-9), time (0-90 min), concentration of oxidizing agents [Fe (VI), (0-10 mg/l)], H2O2 (0-30 mg/l ), molecular ratio of Fe (VI)/PMS (1:2 - 1:10), and Fe (VI)/H2O2 (1:5.5- 1:1.7)] and different concentrations of antibiotics were investigated. The SMX concentration was measured using high performance liquid chromatography at 270 nm. In order to reduce the number of experiments, response surface methodology was used to design the experiments, analyze and optimize the results. Kinetic study, and the amount of mineralization was studied under optimal experimental conditions. Finally, the intermediate products of the oxidation processes were identified by the LC-MS/MS device. Data analysis was performed using Excel (2016) and (3.2.2) R software. The results of individual Fe (VI) and H2O2 processes showed 45.32% and 33.31% of SMX degradation, respectively. Complete removal efficiency (100%) of the SMX at a concentration of 2200 μg/L was achieved by PMS/Fe (VI) process at pH 5 and 25 min (optimum conditions). Concerning the Fe (VI)/ H2O2 process, the removal efficiency was 81.77 % after 90 minutes. It was also found that time, molar ratio and pH had a significant effect on SMX degradation in both processes. The TOC removal and mineralization also indicated that the SMX removal efficiency was higher than mineralization. The highest constant rate of antibiotic degradation was observed at pH = 3, which for each Fe (VI) and H2O2 processes was 1.99 × 10-2 and 4.3 × 10-3 (min-1), respectively. In case for Fe (VI)/PMS and Fe (VI)/H2O2 processes degradation rates were 4.8× 10-2 and 1.95 × 10-2 (min-1), respectively. Eight compounds were identified in the Fe (VI) process; while in Fe (VI)/PMS process, in the two sampling times at 2 and 10 minutes, 12 and 14 compounds were identified as intermediate products of SMX degradation. The most important decomposition mechanisms in the Fe (VI) process were oxidation and hydroxylation. Also in the Fe (VI)/PMS process, Sulfate radical was the most important factor in SMX decomposition and production of intermediate products. In general, the results of experiments showed that Fe (VI) based advanced oxidation processes can be used as an effective treatment method for SMX removal from aqueous media. Among the processes investigated in this study, Fe (VI)/PMS process due to its higher removal efficiency than other processes is recommended as an effective and rapid method for removal of antibiotics from aqueous media.