Reaction of aqueous Mn(II) with hexagonal birnessite at pH 7.5 causes reductive transformation into feitknechtite (β-MnIIIOOH) and manganite (γ-MnIIIOOH) through interfacial electron transfer from adsorbed to structural Mn(IV) atoms arrangement product Mn(III) MnOOH, summarized by + Mn(IV)O2 2 H2O → Mn(III)OOH H+. Feitknechtite is the initial product, subsequently converted more stable polymorph during ongoing reaction Mn(II). production observed concentrations orders magnitude below...

We investigated the effect of pH (5.5-8.5) on mineralogical transformation hexagonal birnessite induced by reaction with aqueous Mn(II) (50-2200 μM), using batch sorption experiments, X-ray diffraction analyses, absorption and infrared spectroscopic measurements. Samples reacted at < 7.0 exhibited disrupted stacking sheets, but no products were observed. At 7.5, under anoxic conditions caused reductive into manganite (γ-MnOOH), whereas 8.0 8.5, conversion hausmannite (Mn3O4) occurred....

Birnessite, a phyllomanganate and the most common type of Mn oxide, affects fate transport numerous contaminants nutrients in nature. Birnessite exhibits hexagonal (HexLayBir) or orthogonal (OrthLayBir) layer symmetry. The two types birnessite contain contrasting content vacancies Mn(III), accordingly have different sorption oxidation abilities. OrthLayBir can transform to HexLayBir, but it is still vaguely understood if how reverse transformation occurs. Here, we show that HexLayBir (e.g.,...

Attachment of live cells Shewanella putrefaciens strain CN-32 to the surface hematite (α-Fe(2)O(3)) was studied with in situ ATR-FTIR spectroscopy at variable pH (4.5-7.7) and contact times up 24 h. The IR spectra indicate that phosphate based functional groups on cell wall play an important role mediating adhesion through formation inner-sphere coordinative bonds sites. attachment mode microbial P varies pH, involving either a change protonation or coordination sites as is modified. At all...

We present a combined experimental and theoretical study to demonstrate that the electrocatalytic activity of NiFe layered double hydroxides (NiFe LDHs) for oxygen evolution reaction (OER) can be significantly enhanced by systematic cobalt incorporation using coprecipitation and/or intercalation. Electrochemical measurements show modified LDH possesses an OER relative pristine LDH. The Co-modified exhibits overpotentials in range 290-322 mV (at 10 mA cm-2), depending on degree content. best...

We investigated the effects of Shewanella putrefaciens cells and extracellular polymeric substances on sorption As(III) As(V) to goethite, ferrihydrite, hematite at pH 7.0. Adsorption solution concentrations between 0.001 20 μM decreased by 10 45% in presence 0.3 g L−1 EPS, with being affected more strongly than As(V). Also, inactivated induced desorption from Fe(III)-(hydr)oxide mineral surfaces. ATR-FTIR studies ternary As(V)-Shewanella−hematite systems indicated concurrent attachment...

We employed Mn-54 radiotracers to characterize the extent and dynamics of Mn atom exchange between aqueous Mn(II) vernadite (δ-Mn(IV)O2) at pH 7.5 under anoxic conditions. Exchange atoms solid liquid phase is rapid, reaching dynamic equilibrium in 2-4 days. propose that during initial stages reaction, occurs through consecutive comproportionation-disproportionation reactions where interfacial electron transfer from adsorbed lattice Mn(IV) generates labile Mn(III) cations rapidly...

We used a combination of batch studies and spectroscopic analyses to assess the impacts aqueous Mn(II) on solubility speciation Zn(II) in anoxic suspensions hexagonal birnessite at pH 6.5 7.5. Introduction into pre-equilibrated Zn(II)-birnessite leads desorption 6.5, but enhances sorption XAS results show that adsorbs as tetrahedral octahedral triple-corner-sharing complexes layer vacancy sites when reacted with absence Mn(II). Addition causes no discernible change surface triggers...

Proteins are of ubiquitous interest in the Life Sciences but Geosciences as well because significant role these compounds play biogeochemical cycling trace and nutrient elements. Structural changes resulting from adsorption proteins onto mineral surfaces may alter protein biological function other environmental interactions. Iron oxides major sinks a range elements including organic compounds. In this study, broadly studied model BSA hematite surface was characterized pH, ionic strength,...

Stormwater runoff is a significant source of heavy metals, including cadmium (Cd), chromium (Cr), and nickel (Ni), which pose ecological human health problems.Various filter media have been evaluated for metal removal from stormwater via adsorption, most involving chemical-or energy-intensive processes.Aluminum-based drinking water treatment residuals (WTR), non-hazardous byproduct treatment, are an inexpensive sorbent metals.However, the low permeability WTR problem requires mixing with...

Summary Assessing the accumulation and transport of trace metals in soils associated toxicological risks on a national scale requires generally applicable sorption equations. Therefore Freundlich equations were derived for Cd, Zn Cu using multiple linear regression batch data from literature with wide variety soil experimental characteristics, metal concentrations ranging over five orders magnitude. Equations based both total dissolved free activities solution. Free calculated taking into...

In this study, the reactivity of lead (Pb(II)) on naturally occurring Mn(III,IV) (oxyhydr)oxide minerals was evaluated using kinetic, thermodynamic, and spectroscopic investigations. Aqueous Pb(II) more strongly adsorbed to birnessite (delta-MnO1.7) than manganite (gamma-MnOOH) under all experimental conditions. The isoteric heat Pb adsorption (delta HT) or 94 kJ mol-1 at a surface loading 1.1 mmol g-1, decreased with increasing density. This indicated that an endothermic process possessed...