Mechanistic Consideration of Zinc Ion Removal by Zero-Valent Iron

Abstract

Mechanism of zinc iron removal by zerovalent iron was discussed through zinc removal responses to several operational conditions of a packed column reactor with zero-valent iron powder. The adsorption isotherm observed implied that a kind of chemisorption was responsible for zinc removal. Zinc removal by zero-valent iron was enhanced by dissolved oxygen and ferric ion addition. However, it was deteriorated under acidic pH. In addition, zinc adsorbed on zero-valent iron was eluted by a reducing agent such as citric acid, whereas the zinc was not eluted by diluted sulfuric acid. Consequently, the zinc removal mechanism by zero-valent iron was inferred to be as follows: Zero-valent iron was firstly corroded and oxidized into ferric ion by dissolved oxygen. The ferric ion was precipitated as iron hydroxide onto the surface of the zero-valent iron powder. Zinc ion was adsorbed on and/or coprecipitated with the iron hydroxide. The iron hydroxide was finally oxidized and transformed into iron oxides.

The specific reactive surface area of granular zero-valent iron in metal contaminant removal: Column experiments and modelling

“…A decrease in the specific reactive surface area of conductive oxides for example magnetite, which facilitate electron transfer and hence copper cementation, could have occurred. Unlike Cu 2þ , Zn 2þ cannot be reduced by elemental iron: an important Zn 2þ removal mechanism is inclusion into the iron oxyhydroxide structure (Kishimoto et al, 2011). Zn 2þ removal may require the formation or transition of oxygenated, flow-dependent iron oxyhydroxides and these would require a period of time for nucleation.…”

“…This is possibly due a reduction in the rate of ferric iron production, as oxygen is a reactant in the ferrous to ferric corrosion process (Sung and Morgan, 1980). As the rate of this corrosion pathway has been reduced so has the inclusion of Zn 2þ into the w a t e r r e s e a r c h 7 7 ( 2 0 1 5 ) 2 4 e3 4 associated corrosion minerals (Kishimoto et al, 2011). This change in oxide formation has less influence on Cu 2þ removal as Cu 2þ can react with ZVI by a reduction pathway (Ku and Chen, 1992;Wilkin and McNiel, 2003;Rangsivek and Jekel, 2005).…”

“…A reduction in the concentration of dissolved oxygen reduces the rate of iron corrosion and ferric iron formation and hence co-precipitation of contaminant metals into the iron oxyhydroxide layer (Kishimoto et al, 2011;Sung and Morgan, 1980). The effect is more pronounced for the removal of metal cations that are not reducible by elemental iron, such as Zn 2þ : a corrosion process becomes an important removal mechanism in this case (Statham unpublished data), hence the greater decrease in reactive area for Zn 2þ relative to Cu 2þ was expected.…”

Application of a Dialysis-Based pH Control System to a Microbial Fuel Cell Using Ferric-EDTA Electron Acceptor

“…The overall oxidation reaction from Fe (II)-EDTA to Fe (III)-EDTA will be expressed as equation (4) according to the analogy of Fe 2+ oxidation by molecular oxygen [12].…”

Removal of zinc from contaminated groundwater by zero-valent iron permeable reactive barrier

“…Many theoretical and experimental studies concerning the migration of heavy metals through PRB were achieved [5][6][7][8][9][10]. The removal of organic and inorganic pollutants from groundwater by zero-valent iron (ZVI) and apatite was investigated.…”