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Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH.

ABSTRACT: Kinetics of phosphate removal by Fe(III) was investigated by both preformed and in situ formed hydrous ferric oxides (HFO) at pH 6.0-8.0. A pseudo-second-order empirical model was found to adequately describe phosphate removal in the two cases. The Elovich and intra-particle diffusion models, however, were only capable of describing phosphate adsorption to preformed HFO (PF-HFO). By using surface complexation kinetic models (SCKMs) to describe phosphate adsorption to PF-HFO, the adsorption rate constant (0.0386-0.205?mM^-1 min^-1 for SCKM-1 and 0.0680-0.274?mM^-1 min^-1 for SCKM-2) decreased with increasing pH while the protonation reaction rate constant in SCKM-2 (0.0776-0.0947?mM^-1 min^-1) increased over the pH range 6.0-8.0. Using the rate constants obtained from the process of phosphate adsorption to PF-HFO, the amount of active surface sites on the in situ formed HFO were calculated as 0.955?±?0.170, 1.46?±?0.39 and 2.98?±?0.78?mM for pH?=?6.0, 7.0 and 8, respectively. Generally, as the SCKMs incorporate phosphate complexation on HFO surface sites and protons competiting for the surface sites, they could provide a good description of the rate and extent of phosphate removal by both preformed and in-situ formed HFO over a wide range of conditions.

SUBMITTER: Mao Y

PROVIDER: S-EPMC5064408 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH.

Mao Yanpeng Y Yue Qinyan Q

Scientific reports 20161014

Kinetics of phosphate removal by Fe(III) was investigated by both preformed and in situ formed hydrous ferric oxides (HFO) at pH 6.0-8.0. A pseudo-second-order empirical model was found to adequately describe phosphate removal in the two cases. The Elovich and intra-particle diffusion models, however, were only capable of describing phosphate adsorption to preformed HFO (PF-HFO). By using surface complexation kinetic models (SCKMs) to describe phosphate adsorption to PF-HFO, the adsorption rate ...[more]

PMID: 27739456

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Project description:Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms, which drive the biogeochemical Fe cycle on the Earth's surface, are phylogenetically and ecologically diverse. However, no single organism capable of aerobic Fe(II) oxidation and anaerobic Fe(III) reduction at circumneutral pH have been reported so far. Here, we report a novel neutrophilic Fe(II)-oxidizing Rhodoferax bacterium, strain MIZ03, isolated from an iron-rich wetland in Japan. Our cultivation experiments demonstrate that MIZ03 represents a much more versatile metabolism for energy acquisition than previously recognized in the genus Rhodoferax. MIZ03 can grow chemolithoautotrophically at circumneutral pH by oxidation of Fe(II), H2, or thiosulfate as the sole electron donor under (micro)aerobic conditions (i.e., using O2 as the sole electron acceptor). In addition, it can reduce Fe(III) or nitrate under anaerobic conditions. Thus, this is the first report demonstrating the presence of a single bacterium capable of both Fe(II) oxidation and Fe(III) reduction at circumneutral pH. The observed physiology was consistent with its 4.9-Mbp complete genome encoding key genes for iron oxidation/reduction (foxEY and mtrABC), for nitrate reduction (narGHI), for thiosulfate oxidation (soxABCDXYZ), and for carbon fixation via the Calvin cycle. Our metagenomic survey suggests that there are more Rhodoferax members capable of Fe(II) oxidation and Fe(III) reduction. Such bifunctional Rhodoferax may have an ecological advantage in suboxic/anoxic environments at circumneutral pH by recycling of Fe as the electron donor and acceptor. IMPORTANCE The biogeochemical cycle of iron (Fe) via reactions of oxidation, reduction, precipitation, and dissolution is involved in the cycle of other ecologically relevant elements, such as C, N, P, S, As, Co, Ni, and Pb. The Fe cycle on the Earth's surface is driven by a variety of Fe(II)-oxidizing microorganisms and Fe(III)-reducing microorganisms. Here, we discovered a novel bacterium, Rhodoferax sp. strain MIZ03, capable of both Fe(II) oxidation and Fe(III) reduction at circumneutral pH, and we report its physiological characteristics and complete genome sequence. The unexpected capability of this bacterium provides novel insights into the Fe cycle in the environment. Moreover, this bacterium will help to better understand the molecular mechanisms of microbial Fe redox cycling as a model organism.

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Dataset Information

Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH.

Publications

Kinetic Modeling of Phosphate Adsorption by Preformed and In situ formed Hydrous Ferric Oxides at Circumneutral pH.

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