Coagulation of colloidal particles with ferrate(vi)

Abstract

Coagulation and chemical oxidation have long been recognized as two major mechanisms of ferrate(vi) (i.e. FeO42−, an oxyanion containing Fe(vi)) in its environmental applications.

Preliminary Assessment of Ferrate Treatment of Metals in Acid Mine Drainage

“…Only 30% of total Mn and 65% of total Fe was in a particulate phase after a Fe(VI) dose of 100 μM (without NaOH); however, almost all the particles that did form were operationally defined as LP, indicating aggregation resulting from the low solution pH. Ferrate resultant Fe(III) particles have been found to have a point of zero charge (PZC) at pH 3.0 to 3.6 in natural water matrices with low dissolved organic carbon (Goodwill et al, 2015; Lv et al, 2018), suggesting optimal aggregation in that pH range. However, particle surface chemistry in the oxidized AMD matrix is expected to be complex due to the potential hydrolysis of Al and Fe (e.g., dual coagulation) (Johnson and Amirtharajah, 1983), leading to the formation of polymeric hydrolysis products (Duan and Gregory, 2003).…”

“…Ferrate [Fe(VI)] is an oxidant of increasing focus in environmental research (Sharma et al, 2016) that may have advantages in AMD. For example, Fe(VI) has a high oxidation potential at low pH (Sharma et al, 2016), rapidly oxidizes Mn (Goodwill et al, 2016b), and leads to the in situ formation of Fe oxides (Goodwill et al, 2015; Zheng and Deng, 2016) that may support coagulation (Lv et al, 2018). Ferrate has also been shown to not directly produce halogenated byproducts in common natural water matrices (DeLuca et al, 1983; Huang et al, 2016; Jiang et al, 2016), although the formation of brominated byproducts has been noted (Huang et al, 2016; Jiang et al, 2016).…”

Mechanistic Insight into Disinfection Using Ferrate(VI)

“…Meantime, ferrate(VI) oxidation decomposes NOM to promote particle aggregation. Efficient ferrate(VI) coagulation, integrated with ferrate(VI) oxidation, authorizes a dual-pathway treatment to remedy numerous contaminants for supporting water supply sustainability [59].…”

“…Even if ferrate(VI) oxidation of different pollutants has been widely investigated, fewer works were performed to evaluate the routes and comportments of ferrate(VI)-driven coagulation in water. Lv et al [59] Barışçı [68] tested the performance of ferrate(IV) prepared electrochemically [69] [70] [71] on both the decomposition of humic acid (HA) [72] [73] and the elimination of E. coli. In order to guarantee a total demobilization of E. coli, >1.5 mg/L ferrate(VI) concentration has to be injected for only E. coli [74] [78].…”

“…TEM images of particles in simulated natural water: (a) and (b) kaolin particles suspended in water before Fe(VI) coagulation; and (c) kaolin particles incorporated into ferrate(VI)-induced iron precipitates (3.0 mg/L Fe(VI)) (pH 7.5; DOC = 2.00 mg/L; and initial turbidity = 25.00 NTU)[59].…”