Nonradical electron transfer-based peroxydisulfate activation by a Mn−Fe bimetallic oxide derived from spent alkaline battery for the oxidation of bisphenol A

Abstract

Mn-Fe bimetallic oxide has been employed as an outstanding peroxydisulfate (PDS) activator, but the underlying mechanism is still controversial. In this work, Mn0.27FeO4.55 (MFBO) was synthesized using the recovered waste alkaline battery and its catalytic activity and mechanism for PDS activation were explored in detail. Results show that MFBO exhibited a higher catalytic activity than the individual single metal oxides (FeOx and Mn2O3) due to the synergistic effect between Fe and Mn elements. The removal efficiency of bisphenol A (BPA) with an initial concentration of 10 mg/L reached 97.8% within 90 min in the presence of 0.5 g/L MFBO and 2.0 mM PDS. Moreover, the MFBO maintained high stability and reusability even after being recycled for five times. With the aid of a series of experiments and ex-situ/in-situ characterizations, a non-radical PDS activation mechanism was proposed, in which organic contaminants would be oxidized through a direct electron transfer pathway mediated by the metastable reactive complexes (MFBO-PDS*). Notably, the MFBO/PDS system revealed selective oxidation towards different organic pollutants and the reaction rates were closely related to their structures and properties. The research provided an effective alternation process for application of the waste battery, as well as developed a novel perspective for removal of recalcitrant aqueous contaminants through a nonradical mechanism.