Hybrid of ZnFe layered double hydroxide/nano-scale carbon for activation of peroxymonosulfate to decompose ibuprofen: Thermodynamic and reaction pathways investigation

Abstract

Carbon black-incorporated ZnFe layered double hydroxide (C-ZnFe LDH) was utilized to activate peroxymonosulfate (PMS) in order to generate sulfate radical (SO 4 ⋅– ) for the treatment of ibuprofen (IBP)-polluted water in batch flow mode reactors. The utilization of C-incorporated ZnFe LDH enhanced the degradation efficiency of IBP (75.4%) in comparison with the carbon-free layered compound (60.6%) during the stirring time of 90 min. The decomposition of IBP by the C-ZnFe LDH/PMS process followed the pseudo-first order kinetic model with the reaction rate constant of 1.52 × 10 −2 min −1 . It was found that the basic pH of 9.0 favored the degradation of IBP (1.84 × 10 −2 min −1 ). Ethanol (EtOH) caused the most inhibitive impact on the decomposition of IBP among the studied scavenging agents. The activation energy of the degradation reaction ( E a ), enthalpy ( Δ H) and entropy ( Δ S) were obtained 11.32 kJ mol −1 , 8.7 kJ mol −1 and 144.7 J mol −1 K −1 , respectively. The bio-toxicity assessment on the reactor effluent showed significant decrease in the inhibition percent (%) from 79.1 to 15.8% within 240 min. Results showed high reusability potential of the C-ZnFe LDH accompanying insignificant release of both Zn and Fe ions (< 0.05 mg/L) in the process effluent. IBP degradation pathways were also proposed and illustrated. • Carbon@ZnFe layered double hydroxide was synthesized for peroxymonosulfate activation. • Sulfate radical was determined as the main oxidant for the decomposition of ibuprofen. • Bio-toxicity of ibuprofen-polluted water to living organisms decreased during treatment. • Degradation intermediates were identified and relevant pathways were illustrated.