Elucidation of Structural, Morphological, Electrical Parameters, and Anti-Bacterial Activity of Polyaniline-Nanocomposite: New Paradigm of Controlling Bacterial Activity.

In this communication, we purpose an alternative electrical method to determine the anti-bacterial activity of compounds. Polyaniline/magnetite (Fe3O4/PANI) and polyaniline/hydrochloric acid (HCl/PANI) nanocomposites have been prepared. We have tested the anti-bacterial activity of Fe3O4/PANI and HCl/PANI nanocomposites by Agarwell Diffusion Assay and Bacterial Inhibition Assay method. The electrical characteristics of the prepared composites have been measured. The doping of 12% of Fe3O4 in PANI caused a substantial increase in anti-bacterial activity. The observed bacterial inhibition is in agreement with optimized values of resistivity, loss factor, quality factor, and spontaneous magnetization. Sample 2 associated with 12% Fe3O4-PANI composites has a high resistivity of 1.70×106Ω .m among all prepared composites. The magnetic character and insulating nature of Fe3O4 influenced the investigated parameters. The morphological variation of prepared composites is also consistent with electrical parameters. The alleviated energy zone formed by the magnetic behavior of Fe3O4 and interfacial polarization of PANI mitigates the polarization/field of charge carriers of bacteria. These effects altogether diminish the energy of bacterial zone revealed in the experiment. The tuning of electrical parameters provides an alternative to control bacterial growth in various compounds. The proposed method of electrical characterization for the detection of the anti-bacterial activity of the compounds can be very useful in terms of time and cost in contrast to the lab tests performed in biological labs. After implementing an electrical parameter standard equivalent to anti-bacterial activity, real-time detection can be performed by electrical parameters in the fields outside without any hassle, which otherwise is not possible for biological labs.

Magnetic hybrid gels for emulsified oil adsorption: an overview of their potential to solve environmental problems associated to petroleum spills.

Hydrogels (HGs) based on gelatin and crosslinked with gum Arabic have been prepared by the thaw-freezing method, employing two different concentrations of gum Arabic (15 and 50% w/w). Magnetic gels or ferrogels (FGs) were prepared by applying the breath in method to incorporate iron oxide magnetic nanoparticles to the HG matrix. The obtained HG and FG were characterized by XRD, FTIR, and SEM, and the FG composition was estimated by atomic absorption spectroscopy in terms of Fe content. The adsorption of crude oil onto HG and FG was explored achieving very satisfactory results. FG was regenerated by washing with toluene, maintaining efficiency of almost 90% after the fourth cycle. Equilibrium studies were performed to determine the capacity of the prepared FG for adsorption of crude oil from seawater synthetic solutions. The experiments were carried out as a function of different initial concentrations of oil residue (24 to 240 mg/L) exploring different contact times. Equilibrium data were found to fit very well with the Sips models. The kinetic data adsorption of oil onto the FG-15 was better fitted by a pseudo-second-order kinetic indicating that at the initial stages of adsorption, external mass transfer could control the whole rate of the crude oil uptake while intraparticle diffusion controlled the global rate of adsorption at later stages. The obtained results showed that the FG prepared by employing 15% of gum Arabic as the crosslinker (FG-15) has a high removal efficiency of crude oil reaching 1.53 g/g of FG at pH 5.5 and 0.59 g/g for oil/water emulsions in the order of 0.1 g/L. The magnetic properties extend its application. The reached data suggest that the materials presented here may be useful to further the design of systems or devices intended for the remediation of petroleum spills and/or its derivatives in marine water as well as other surfaces such as polluted rocks or soil.

Adsorption and catalytic oxidation of organic pollutants using Fe-zeolite.

In this work, a natural zeolite, modified and loaded with iron (NZ-A-Fe) as a heterogeneous catalyst, was characterized for its suitability as a permeable reactive barrier (PRB) material for treatment of aromatic hydrocarbons in groundwater. Adsorption and oxidation processes were analyzed. Batch adsorption tests for benzene, toluene and xylene (BTX) aqueous concentrated solutions were performed at neutral pH. Kinetic adsorption was described with the pseudo-second-order model. Experiments were performed using a stirred batch reactor with near 11 mM initial BTX concentration applying NZ-A-Fe as solid catalyst and H2O2 as an oxidant. BTX removal reached 80% in 600 min in these experimental conditions. Catalytic oxidation was described with a pseudo-first-order kinetic model. No significant iron leaching was detected during all the experiences. These investigations show that coupling adsorption with catalytic oxidation with this novel system is a promising procedure to simultaneously remove BTX from moderately concentrated aqueous solution at neutral pH in groundwater.

Microwave resonant and zero-field absorption study of doped magnetite prepared by a co-precipitation method.

Fe3O4 and ZnxFe3-xO4 pure and doped magnetite magnetic nanoparticles (NPs) were prepared in aqueous solution (Series A) or in a water-ethyl alcohol mixture (Series B) by the co-precipitation method. Only one ferromagnetic resonance line was observed in all cases under consideration indicating that the materials are magnetically uniform. The shortfall in the resonance fields from 3.27 kOe (for the frequency of 9.5 GHz) expected for spheres can be understood taking into account the dipolar forces, magnetoelasticity, or magnetocrystalline anisotropy. All samples show non-zero low field absorption. For Series A samples the grain size decreases with an increase of the Zn content. In this case zero field absorption does not correlate with the changes of the grain size. For Series B samples the grain size and zero field absorption behavior correlate with each other. The highest zero-field absorption corresponded to 0.2 zinc concentration in both A and B series. High zero-field absorption of Fe3O4 ferrite magnetic NPs can be interesting for biomedical applications.