Reductive dissolution of arsenic-bearing ferrihydrite

Fast microbial reduction of ferrihydrite colloids from a soil effluent

“…However, terrestrial and aquatic humic substances also inhibit microbial respiration under anoxic conditions (Minderlein and Blodau, 2010) and enhance the toxic effect of metals (Stone et al, 2007). Surface coverage with phosphate and arsenate lowers the mineral solubility (Majzlan, 2011) and decreases the reductive (and non-reductive) dissolution (Biber et al, 1994), which was also confirmed with respect to microbial Fe(III) reduction (Borch et al, 2007;Erbs et al, 2010;O'Loughlin et al, 2010). Depending on speciation, the presence of dissolved arsenic decreased the rates of microbial Fe(III) reduction.…”

Influence of size, morphology, surface structure, and aggregation state on reductive dissolution of hematite nanoparticles with ascorbic acid

“…In general, many smaller particles/aggregates than the pore size of the filter (10-1000 times smaller than the pore size) may be retained when most particles/aggregates larger than the pore size are retained, because particles/aggregates smaller than the pore size become attached to the larger particles/aggregates when filtration occurs above and within a filter pore (Stumm and Morgan, 1996). Besides this, Penn and co-workers demonstrated that 0.2 lm nylon filter can separate ferrihydrite nanoparicles (average diameter: 3.5 nm) from acidic aqueous solution (pH 3.75 buffered with 40 mM Na-acetate) completely (Jentzsch and Penn, 2006;Erbs et al, 2008;Erbs et al, 2010). Hence we employed the same procedure as these previous studies to separate the hematite nanoparticles from the solution.…”

Structure and composition of Fe–OM co-precipitates that form in soil-derived solutions

“…A high proportion of surface-near Fe sites would also contribute to the pronounced tailing at higher ∆E Q as observed in our study (Figure 2A,C), provided that the crystallite sizes of the Fe-OM co-precipitates are comparably small. Referring to Fe oxide precipitation experiments with DOM (Eusterhues et al, 2008), Si (Cismasu et al, 2014) and As (Erbs et al, 2010;Rancourt et al, 2001), small crystallite sizes can be assumed for the Fe-OM coprecipitates in our study. The absence of distinct reflexes in the X-ray diffractograms indicates the absence of enhanced scattering domains and therefore supports this assumption ( Figure EA-14).…”

“…The significant presence of As exclusively in the Ah-derived Fe-OM co-precipitates (As/Fe ~ 0.06, Figure 1B) very likely contributed to these differences. Incorporated As is known to increase structural disorder and thus ∆E Q (Rancourt et al, 2001) and decrease crystallite interactions and thus B hf (Erbs et al, 2010).…”