Polyaniline-Derived Nitrogen-Containing Carbon Nanostructures with Different Morphologies as Anode Modifier in Microbial Fuel Cells.

Anode modification with carbon nanomaterials is an important strategy for the improvement of microbial fuel cell (MFC) performance. The presence of nitrogen in the carbon network, introduced as active nitrogen functional groups, is considered beneficial for anode modification. In this aim, nitrogen-containing carbon nanostructures (NCNs) with different morphologies were obtained via carbonization of polyaniline and were further investigated as anode modifiers in MFCs. The present study investigates the influence of NCN morphology on the changes in the anodic microbial community and MFC performance. Results show that the nanofibrillar morphology of NCNs is beneficial for the improvement of MFC performance, with a maximum power density of 40.4 mW/m2, 1.25 times higher than the anode modified with carbonized polyaniline with granular morphology and 2.15 times higher than MFC using the carbon cloth-anode. The nanofibrillar morphology, due to the well-defined individual nanofibers separated by microgaps and micropores and a better organization of the carbon network, leads to a larger specific surface area and higher conductivity, which can allow more efficient substrate transport and better bacterial colonization with greater relative abundances of Geobacter and Thermoanaerobacter, justifying the improvement of MFC performance.

Catalytic Ozonation of Ibuprofen in Aqueous Media over Polyaniline-Derived Nitrogen Containing Carbon Nanostructures.

Catalytic ozonation is an important water treatment method among advanced oxidation processes (AOPs). Since the first development, catalytic ozonation has been consistently improved in terms of catalysts used and the optimization of operational parameters. The aim of this work is to compare the catalytic activity of polyaniline (PANI) and thermally treated polyaniline (PANI 900) in the catalytic ozonation of ibuprofen solutions at different pH values (4, 7, and 10). Catalysts were thoroughly characterized through multiple techniques (SEM, Raman spectroscopy, XPS, pHPZC, and so on), while the oxidation process of ibuprofen solutions (100 mgL-1) was assessed by several analytical methods (HPLC, UV254, TOC, COD, and BOD5). The experimental data demonstrate a significant improvement in ibuprofen removal in the presence of prepared solids (20 min for PANI 900 at pH10) compared with non-catalytic processes (56 min at pH 10). Moreover, the influence of solution pH was emphasized, showing that, in the basic region, the removal rate of organic substrate is higher than in acidic or neutral range. Ozone consumption mgO3/mg ibuprofen was considerably reduced for catalytic processes (17.55-PANI, 11.18-PANI 900) compared with the absence of catalysts (29.64). Hence, beside the ibuprofen degradation, the catalysts used are very active in the mineralization of organic substrate and/or formation of biodegradable compounds. The best removal rate of target pollutants and oxidation by-products was achieved by PANI 900, although raw polyaniline also presents important activity in the oxidation process. Therefore, it can be stated that polyaniline-based catalysts are effective in the oxidation processes.

Sorption of 4-n-nonylphenol, 4-n-octylphenol, and 4-tert-octyphenol on cyclodextrin polymers.

Alkylphenols are industrial pollutants commonly present in wastewater. They are difficult to eliminate by conventional treatment processes, ending up in the sludge of wastewater treatment plants. In this study, we propose to use cross-linked cyclodextrin-based polymers (ECP) as sorbents to treat three alkylphenols, namely, one nonylphenol (4-n-NP) and two octylphenols (4-n-OP and 4-tert-OP), present in aqueous solution by a batch method. The experiments were carried out with five cyclodextrin polymers (α-ECP, ß-ECP, γ-ECP, α,ß,γ-ECP, and HP-ß-ECP). Sorption results showed that all polymers, with the exception of α-ECP, had high sorption capacities between 60 and 100% of the alkylphenols in the concentration range studied (between 25 and 100 µg/L). In all cases, HP-ß-ECP has shown the highest removals, regardless of the structure of the molecule. The order obtained was HP-ß-ECP >> ß-ECP ~ α,ß,γ-ECP >> γ-ECP > α-ECP. The 4-tert-OP compound was the best adsorbed, regardless the material and the solution studied. Sorption results also indicated that (i) the sorption efficiency decreased with the increasing of alkylphenol concentration; (ii) sodium chloride had a strong negative effect on the sorption process; and (iii) the performance remained unchanged after five sorption-regeneration cycles. The main sorption mechanism of alkylphenols occurring in ECP was the inclusion within the cyclodextrin cavities. The obtained results proved that cyclodextrin polymers could serve as efficient sorbents for the removal of alkylphenols from real effluents.

Use of Chènevotte, a Valuable Co-Product of Industrial Hemp Fiber, as Adsorbent for Pollutant Removal. Part I: Chemical, Microscopic, Spectroscopic and Thermogravimetric Characterization of Raw and Modified Samples.

FINEAU (2021-2024) is a trans-disciplinary research project involving French, Serbian, Italian, Portuguese and Romanian colleagues, a French agricultural cooperative and two surface-treatment industries, intending to propose chènevotte, a co-product of the hemp industry, as an adsorbent for the removal of pollutants from polycontaminated wastewater. The first objective of FINEAU was to prepare and characterize chènevotte-based materials. In this study, the impact of water washing and treatments (KOH, Na2CO3 and H3PO4) on the composition and structure of chènevotte (also called hemp shives) was evaluated using chemical analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray computed nanotomography (nano-CT), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, solid state NMR spectroscopy and thermogravimetric analysis. The results showed that all these techniques are complementary and useful to characterize the structure and morphology of the samples. Before any chemical treatment, the presence of impurities with a compact unfibrillated structure on the surfaces of chènevotte samples was found. Data indicated an increase in the crystallinity index and significant changes in the chemical composition of each sample after treatment as well as in surface morphology and roughness. The most significant changes were observed in alkaline-treated samples, especially those treated with KOH.

Biosorbents from Plant Fibers of Hemp and Flax for Metal Removal: Comparison of Their Biosorption Properties.

Lignocellulosic fibers extracted from plants are considered an interesting raw material for environmentally friendly products with multiple applications. This work investigated the feasibility of using hemp- and flax-based materials in the form of felts as biosorbents for the removal of metals present in aqueous solutions. Biosorption of Al, Cd, Co, Cu, Mn, Ni and Zn from a single solution by the two lignocellulosic-based felts was examined using a batch mode. The parameters studied were initial metal concentration, adsorbent dosage, contact time, and pH. In controlled conditions, the results showed that: (i) the flax-based felt had higher biosorption capacities with respect to the metals studied than the hemp-based felt; (ii) the highest removal efficiency was always obtained for Cu ions, and the following order of Cu > Cd > Zn > Ni > Co > Al > Mn was found for both examined biosorbents; (iii) the process was rapid and 10 min were sufficient to attain the equilibrium; (iv) the efficiency improved with the increase of the adsorbent dosage; and (v) the biosorption capacities were independent of pH between 4 and 6. Based on the obtained results, it can be considered that plant-based felts are new, efficient materials for metal removal.