Promoting mechanism of electronic shuttle for bioavailability of Fe(III) oxide and its environmental significance

Abstract

The biological reduction process of Fe(III) not only strongly affects the circulation of C, N, O, P and other elements in the environment, but also plays an important role in the transformation and degradation of organic and inorganic pollutants. Most Fe(III) oxides existing in nature have low bioavailability due to their poor solubility or strongly crystalline form with stable chemical properties. Addition of a substance having redox activity can form an electron shuttle cycle between Fe(III) oxide and the microorganism, which can not only enhance the bioavailability of Fe(III) and accelerate electron transfer, but also improve the removal efficiency of contaminants. This paper compares and analyzes several common redox active substances, for their promoting effect and limiting factors of Fe(III) bioavailability. Moreover, the mechanism by which the electron shuttle promotes the bioavailability of Fe(III) oxide is discussed. This review demonstrates that the electron shuttle promotes the Fe(III) bioreaction process for the degradation and removal of heavy metals, polycyclic aromatic hydrocarbons, azo dyes and other pollutants, which is of great environmental significance.