Slow-releasing permanganate ions from permanganate core-manganese oxide shell particles for the oxidative degradation of an algae odorant in water.

In this work, potassium permanganate particles (KMnO4) were modified with a manganese oxide (MnOx) shell comprising passages for the slow release of permanganate ions (MnO4-) in aquatic systems. The bare particle (KMnO4) and KMnO4 core-MnOx shell particles (CP-60) were characterized by attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The CP-60 were evaluated as a slow source of MnO4- for the oxidative treatment of pure and lake water containing dimethyl trisulfide (DMTS), a water odorant produced by cyanobacteria in many eutrophic waters. XPS and ATR-FTIR results confirmed the presence of MnOx surface shell (diameter ∼ 1 µm) on CP-60. SEM images revealed cracks on CP-60, which serve as outlets for MnO4-. Approximately 0.76 ±â€¯0.07 g KMnO4/g of CP-60 was released from the core of CP-60 after 120 min. The CP-60 degraded 88.9 ±â€¯2.5% and 70.8 ±â€¯6.3% of DMTS in pure water and lake water matrix within 120 min, respectively. The degradation was slightly more effective than the degradation using aqueous KMnO4 (74.2%) reported in literature. The release kinetics of the particles is consistent with a pseudo-first order equation with correlation coefficients of 0.99 and 0.97 in pure water and lake water matrix, respectively. The CP could serve as low cost slow-release particles for the degradation of micropollutants, even in cyanobacteria laden water. Notably, the in situ MnOx formed during the KMnO4 oxidation reaction can facilitate adsorption of organics and metal ions, improving water quality.

Interaction between bisphenol A and tannic acid: spectroscopic titration approach.

The interaction between tannic acid (TA) and bisphenol A (BPA), an endocrine disruptor, was studied by absorption and fluorescence titration techniques. The binding constants and corresponding thermodynamic parameters at different temperatures (294, 296, 298, 300 and 303 K) were determined. The intrinsic fluorescence of BPA was strongly quenched by TA and the quenching mechanism is attributed to static quenching. The thermodynamic data revealed that the formation of TA-BPA complex was exothermic, entropic-driven, and spontaneous. Furthermore, hydrogen and van der Waals interactions seem to be the major driving forces for the formation of the nonfluorescent TA-BPA complex.

Adhesion of bacterial exopolymers to alpha-FeOOH: inner-sphere complexation of phosphodiester groups.

Extracellular polymeric substances (EPS) constitute a heterogeneous mixture of polyelectrolytes that mediate biomineralization and bacterial adhesion and stabilize biofilm matrixes in natural and artificial environments. Although nucleic acids are exuded extracellularly and are purported to be required for biofilm formation, direct evidence of the active mechanism is lacking. EPS were extracted from both Bacillus subtilis (a gram-positive bacterium) and Pseudomonas aeruginosa (a gram-negative bacterium) and their interaction with the goethite (alpha-FeOOH) surface was studied using attenuated total internal reflection infrared spectroscopy. Correspondence between spectral data and quantum chemical calculations demonstrate that phosphodiester groups of nucleic acids mediate the binding of EPS to mineral surfaces. Our data indicate that these groups emerge from the EPS mixture to form monodentate complexes with Fe centers on the goethite (alpha-FeOOH) surface, providing an energetically stable bond for further EPS or cell adhesion.

Spectroscopic study of extracellular polymeric substances from Bacillus subtilis: aqueous chemistry and adsorption effects.

Reactions at ionizable functional groups in extracellular polymeric substances (EPS) from Bacillus subtilis are found to affect aqueous phase conformation and adsorption to mineral surfaces. Characterization by HPSEC, XPS, and FTIR indicates a wide range in apparent molecular mass (0.57-128 kDa), with functional group composition depending on cell growth phase (exponential vs stationary) and location in suspension (free vs cell-bound). ATR-FTIR spectroscopy shows complexation and dissociation of protons on acidic functional groups that result in alpha-helical protein conformation at pH < 2.6 and random coil (unordered) conformation at higher pH (>6). EPS exhibit higher affinity for adsorption to alpha-FeOOH than amorphous SiO(2) because of surface charge effects. Increased amide II band intensity and an amide I band shift to higher frequency indicate changes in protein structure upon adsorption. Goethite-EPS spectra show emergent vibrations consistent with P-O-Fe bonding, which suggests a role of phosphodiester groups in the adsorption reaction.