Activation of persulfates by natural magnetic pyrrhotite for water disinfection: Efficiency, mechanisms, and stability

Abstract

This study introduces natural occurring magnetic pyrrhotite (NP) as an environmentally friendly, easy available, and cost-effective alternative catalyst to activate persulfate (PS) of controlling microbial water contaminants. The E. coli K-12 inactivation kinetics observed in batch experiments was well described with first-order reaction. The optimum inactivation rate (k = 0.47 log/min) attained at a NP dose of 1 g/L and a PS dose of 1 mM, corresponding to total inactivation of 7 log cfu/mL cells within 15 min. Measured k increased > 2-fold when temperature increased from 20 to 50 °C; and > 4-fold when pH decreased from 9 to 3. Aerobic conditions were more beneficial to cell inactivation than anaerobic conditions due to more reactive oxygen species (ROS) generated. ROS responsible for the inactivation were identified to be SO > OH > HO based on a positive scavenging test and in situ ROS determination. In situ characterization suggested that PS effectively bind to NP surface was likely to form charge transfer complex (≡Fe(II)⋯OSOOSO), which mediated ROS generation and E. coli K-12 oxidation. The increased cell-envelope lesions consequently aggravated intracellular protein depletion and genome damage to cause definite bacterial death. The NP still maintained good physiochemical structure and stable activity even after 4 cycle. Moreover, NP/PS system also exhibited good E. coli K-12 inactivation efficiency in authentic water matrices like surface water and effluents of secondary wastewater.

Cu@Co-MOFs as a novel catalyst of peroxymonosulfate for the efficient removal of methylene blue

“…Sulfate radical (SO 4 c À )-based advanced oxidation processes (SR-AOPs) are known to be the most effective method to oxidize the bio-recalcitrant organic pollutants. [10][11][12] SR-AOPs are a kind of technology for the in situ generation of the SO 4 c À radical. Moreover, other reactive free radicals with high oxidation potential such as hydroxyl radicals ($OH) and superoxide radicals ($O 2 À ) could be produced by changing the reaction conditions.…”

Assessment of Sulfate Radical-Based Advanced Oxidation Processes for Water and Wastewater Treatment: A Review

“…Most of the experiments for Escherichia coli elimination have produced good results. The best results were obtained in those experiments in which a heterogeneous iron catalyst (ilmenite and pyrrhotite) was used, obtaining a complete disinfection in 20 min in both cases [120,123]. On the contrary, the combination of PMS/UV-A/Co 2+ has had a very low effect on the bacterial population [119], although these results may be due to interference in the treatment due to the composition of the wastewater used in the experiments, since the same process achieves within 60 min the complete elimination of microorganisms in other studies [124].…”

“…To the best of our knowledge, only the effectiveness of metallic catalysis, both heterogeneous and homogeneous, for the activation of PMS and PS in order to eliminate microorganisms from water has been analysed. Specifically, iron (in various forms and oxidation states) is the most commonly used transition metal, followed by Co 2+ [35,[119][120][121][122][123][124]. It seems necessary to expand the number of activation methods assessed in order to choose the most effective one for full-scale implementation.…”

“…However, the inactivation of other bacteria such as S. aureus, B. mycoides, Enterococcus sp. and various fungus species has also been studied, although to a lesser extent [119,120,126]. Table 8 summarizes the results of all the reports published so far about sulfate-based AOPs applied in disinfection.…”

“…On the contrary, the combination of PMS/UV-A/Co 2+ has had a very low effect on the bacterial population [119], although these results may be due to interference in the treatment due to the composition of the wastewater used in the experiments, since the same process achieves within 60 min the complete elimination of microorganisms in other studies [124]. The best inactivation rate of S. aureus has been achieved using natural magnetic pyrrhotite (NP) as a heterogeneous catalyst [120]. Among the homogeneous catalysts, Co 2+ has been the most effective activator [119,124].…”