Mineralogical transformations of 2-line ferrihydrite were studied under oxic and Fe-reducing conditions to establish the role, if any, of 6-line ferrihydrite (“well” organized ferrihydrite) in the reaction pathway and as a final product. In oxic experiments, concentrated suspensions (0.42 mol/L Fe in 0.1 mol/L NaClO4) of freshly synthesized 2-line ferrihydrite, with and without 3% Ni, were aged...

Biochar contains quinones and aromatic structures that facilitate extracellular electron transfer between microbial cells and insoluble minerals. In this study, granulated biochar (1.2-2 mm) and powdered biochar (<0.15 mm) were amended to two ferrihydrite (in situ ferrihydrite and ex situ ferrihydrite) enrichments to investigate the effect of biochar with different particle sizes on dissimilato...

The natural nanomineral ferrihydrite is an important component of many environmental and soil systems and has been implicated as the inorganic core of ferritin in biological systems. Knowledge of its basic structure, composition, and extent of structural disorder is essential for understanding its reactivity, stability, and magnetic behavior, as well as changes in these properties during aging....

[1] Ferrihydrite, an antiferromagnetic iron oxyhydroxide with resulting magnetization due to uncompensated spins, is of great importance for the cycling of many trace metals in the environment. Four ferrihydrite samples prepared with 1.3 to 3.5 wt% of Si at different synthesis temperatures (7.5 C, 22 C, 50 C, and 75 C) were studied by temperaturedependent hysteresis loops, ZFC/FC susceptibility...

Understanding the chemical interactions that occur in complex natural systems is fundamental to their management In this work the distribution of cadmium in the presence of phthalic acid (H2Lp), ferrihydrite, and bacteria cells (Comamonas spp., heat killed) was measured and modeled for systems with incrementally increasing complexity. In binary systems, cadmium adsorption onto bacteria or ferri...

The distribution of Cd in the presence of phthalic acid (H2Lp), ferrihydrite and bacteria (Comamonas spp.) was investigated in biologically active systems involving H2Lp biodegradation. Tests showed that Cd sorption onto bacteria, ferrihydrite and bacteria–ferrihydrite mixture increased with pH in all systems, irrespective of H2Lp degradation or not. The use of bacterial growth medium, Bushnell...

Iron(III) (oxyhydr)oxides can represent the dominant microbial electron acceptors under anoxic conditions in many aquatic environments, which makes understanding the mechanisms and processes regulating their dissolution and transformation particularly important. In a previous laboratory-based study, it has been shown that 0.05 mM thiosulfate can reduce 6 mM ferrihydrite indirectly via enzymatic...

Observations in enrichment cultures of ferric iron-reducing bacteria indicated that ferrihydrite was reduced to ferrous iron minerals via sulfur cycling with sulfide as the reductant. Ferric iron reduction via sulfur cycling was investigated in more detail with Sulfurospirillum deleyianum, which can utilize sulfur or thiosulfate as an electron acceptor. In the presence of cysteine (0.5 or 2 mM)...

Ferrihydrite is effective in arsenic removal because of the considerable amount of active hydroxyl groups. Solid–liquid separation of the arsenic adsorbed ferrihydrite from aqueous solution is important for the arsenic treatment technology. Coagulation is a promising process for ferrihydrite separation. Effects of different coagulants on arsenic adsorbed ferrihydrite settlement were investigate...

Metal partitioning in ferrihydrite suspensions may reach equilibrium only after a long reaction time. To determine key factors controlling the kinetics, we measured Cu and Pb uptake as a function of ferrihydrite morphology, reaction temperature, metal competition, and fulvic acid concentration over a period of 2 months. X-ray microscopy, which was used to probe ferrihydrite morphology in suspen...