Trade-off between Fenton-like activity and structural stability of MILs(Fe)

Abstract

• Trade-off of activity and stability of MILs(Fe) catalyzed Fenton-like was evaluated. • Catalytic activity decline was determined by decontamination and OH formation. • Structural change and possible negative effects during operation were investigated. • Weak acid condition seems acceptable for MILs(Fe) based systems development. In this study, three typical MILs(Fe) catalysts were used for Fenton-like catalysis to investigate their stability and catalytic activity within 20-cycle used. Catalytic activity with various oxidants was evaluated by bisphenol S removal and OH generation. Possible negative effects were determined, and structural changes were characterized. The results indicate catalytic activity and stability of these three MILs(Fe) catalysts showed similar regularities under different conditions. At pH 3, MILs exhibited high catalytic activity initially, while the catalytic activity declined sharply prolonging operational time, due to the deactivation of surface active sites and decomposition of structure. Organics leaching and acute toxicity were relatively high in the effluent as well. Under weak acid condition, initial catalytic activity of MILs(Fe) was lower, while the decline of activity was much slower, that OH generation only declined 15.2%-27.1% within 20-cycle used. The leaching and acute toxicity were much lower as well. Under neutral condition, MILs(Fe) were stable, while the catalytic activity was unsatisfactory even in 1st cycle. The trade-off of catalytic activity and structural stability exists in some degree in MILs(Fe) based Fenton-like processes, and only comprehensively considering the trade-off is feasible to investigate them for wastewater treatment.