Application of Fe(VI) in abating contaminants in water: State of art and knowledge gaps

Abstract

The past two decades have witnessed the rapid development and wide application of Fe(VI) in the field of water de-contamination because of its environmentally benign character. Fe(VI) has been mainly applied as a highly efficient oxidant/disinfectant for the selective elimination of contaminants. The in situ generated iron(III) (hydr)oxides with the function of adsorption/coagulation can further increase the removal of contaminants by Fe(VI) in some cases. Because of the limitations of Fe(VI) per se, various modified methods have been developed to improve the performance of Fe(VI) oxidation technology. Based on the published literature, this paper summarized the current views on the intrinsic properties of Fe(VI) with the emphasis on the self-decay mechanism of Fe(VI). The applications of Fe (VI) as a sole oxidant for decomposing organic contaminants rich in electron-donating moieties, as a bi-functional reagent (both oxidant and coagulant) for eliminating some special contaminants, and as a disinfectant for inactivating microorganisms were systematically summarized. Moreover, the difficulties in synthesizing and preserving Fe(VI), which limits the large-scale application of Fe (VI), and the potential formation of toxic byproducts during Fe(VI) application were presented. This paper also systematically reviewed the important nodes in developing methods to improve the performance of Fe(VI) as oxidant or disinfectant in the past two decades, and proposed the future research needs for the development of Fe(VI) technologies.

Three Kinetic Patterns for the Oxidation of Emerging Organic Contaminants by Fe(VI): The Critical Roles of Fe(V) and Fe(IV)

“…These findings have profound implication in Fe­(VI) technologies for mitigation of EOCs in water and wastewater industries. Given that Fe­(V) and Fe­(IV) are much more reactive than Fe­(VI), ,, the generation of more Fe­(V) and Fe­(IV) from Fe­(VI) is one of the promising approaches for more efficient destruction of EOCs in Fe­(VI) applications. If the in situ production of Fe­(V) and Fe­(IV) can be well harnessed, better EOCs removals and lower Fe­(VI) dosages are expected in practices for improving the efficiency of Fe­(VI) treatment and saving the operation costs associated with water treatment.…”

“…It was well documented that Fe­(V) and Fe­(IV) are 2–6 orders of magnitude more reactive than Fe­(VI), and the difference between the reactivity of Fe­(IV)/Fe­(V) and Fe­(VI) toward a specific EOC heavily relies on the species of EOCs under specific experimental conditions. , Moreover, solution chemistry and operating parameters can influence the difference extent in their reactivity toward a specific EOC. Although our previous work demonstrated the involvement of Fe­(V) and Fe­(IV) in the oxidation of the target EOC by Fe­(VI), the contributions of Fe­(V) and Fe­(IV) during EOCs oxidation by Fe­(VI) under different experimental conditions were not systemically assessed.…”

On the Origins of Some Spectroscopic Properties of “Purple Iron” (the Tetraoxoferrate(VI) Ion) and Its Pourbaix Safe-Space

“…In an effort to identify toxic products which resulted from treating PPCP (pharmaceuticals and personal care products) wastes, Barisci & Dimoglo [163] described the mechanistic pathways of the reactions between ferrate(VI) and antibiotics, analgesics, β-blockers, lipid regulators, anti-psychotics and cytostatic drugs in detail, a rarity in the literature of wastewater science. This area of knowledge should be added to the "gaps" highlighted by Professor Guan Xiahong (Tonji University, Shanghai, China) and colleagues from various institutes (2021) in their review of ferrate(VI) [164].…”

Influence of Elevated Temperature and Pressure on Treatment of Landfill Leachate by Potassium Ferrate(VI)

“…The green oxidant, e.g., H 2 O 2 , potassium peroxysulfate (2KHSO 5 × KHSO 4 × K 2 SO 4 ), potassium persulfate (K 2 S 2 O 8 ), and ozone (O 3 ), is added in order to promote oxidation of organic compounds in landfill leachate (Anglada et al, 2011;Rivas et al, 2005;Xu et al, 2012;Zhai et al, 2016). Potassium ferrate(VI) is an emerging green water treatment agent frequently proposed for wastewater treatment (Wang et al, 2021). The results of recent study has shown that potassium ferrate(VI) can be successfully applied also for treatment of landfill leachate (Thomas et al, 2020).…”

“…The results of recent study has shown that potassium ferrate(VI) can be successfully applied also for treatment of landfill leachate (Thomas et al, 2020). Potassium ferrate(VI) may oxidize organic compounds by electron or/and oxygen transfer mechanisms (Rush & Bielski, 1989;Chen et al, 2018;Luo et al, 2020aLuo et al, , 2020bWang et al, 2021). Thus, reactivity of potassium ferrate(VI) depends on pH value.…”