Raul Berenguer

Expanded graphite (EG) electrodes gather several advantages for their utilization in microbial electrochemical technologies (MET). Unfortunately, the low microbial electroactivity makes them non‐practical for implementing them as electrodes. The objective of this work is to explore the enhancement of microbial electroactivity of expanded graphite (commercial PV15) through the generation of nanopores by CO ₂ treatment. The changes in properties were thoroughly analysed by TG, XRD, Raman, XPS, gas adsorption, SEM and AFM, as well as microbial electroactivity in the presence of Geobacter sulfurreducens . Nanopores remarkably enhance the microbially derived electrical current (60‐fold increase). Given the inaccessibility of micron‐sized bacteria to these nanopores, it is suggested that the electric charge exchanged by electroactive microorganisms might be greatly affected by the capability of the electrode to compensate these charges through ion adsorption. The increased microbial current density produced on activated PV15 opens the possibility of using such materials as promising electrodes in MET.

This work studies the removal of o-cresol from wastewater by using ozonation followed by adsorption onto sodium natural bentonite (Na-Bent). The degradation of o-cresol was followed by UV-Vis. During ozonation, 2-methylbenzoquinone (2-mBQ) and 2-methylhydroquinone (2-mHQ) were identified as two of the main by-products, while the pH decrease suggested the breakage of aromatic compounds into smaller organic acids. After 30 min treatment, the o-cresol degradation for 250–62.5 mg/L solutions was found between 64–85%, respectively. Next, the wastewater containing persistent o-cresol and by-products was contacted with Na-Bent adsorbent. The solutions and physicochemical properties of Na-Bent were analysed, before and after adsorption, by UV-Vis, FTIR, XRD and N₂ adsorption-desorption. Moreover, equilibrium and kinetic experiments were carried out to study the adsorptive properties of the Na-Bent. While sole ozonation or adsorption failed on the remediation of o-cresol solutions, the obtained results show that the contact of ozonated solutions with Na-Bent led to almost total removal of the o-cresol initial concentrations (between 96% and 99%). This excellent performance is assigned to the high volume of interlayer micropores and the suitable surface chemistry of this natural adsorbent.

This work presents a comprehensive study on the physico‐chemical and electrochemical properties of polyindenes (PIns) synthesized by Maghnite‐H ⁺ ‐catalysed polymerization of indene (benzocyclopentadiene) in CH ₂ Cl ₂ at different temperatures, and their oxidative derivatives by subsequent treatment with FeCl ₃ . The polymers are characterized by TG, FT‐IR, XPS and UV‐vis spectroscopies, as well as electrical conductivity and voltammetric measurements, analysing the influence of synthesis temperature and post‐oxidation. Results show that the PIns synthesized at different temperatures present quite similar thermogravimetric behavior and UV spectra. Nevertheless, FTIR and XPS reveal significant differences in chemical composition and polymer structure depending on this temperature. At higher temperatures, indenyl coupling proceeds via 1,2 carbon atoms to obtain more compact and less defective PIns with higher yields. At lower temperatures, polymerization through 1,3 carbon atoms may also occur, leading to polymers with a larger number of defects and oxygen functionalities and lower yields. FeCl ₃ treatment causes the introduction of some oxygen functionalities in the compact PIn60 and PIn80 polymers, without significantly affecting their molecular structure and electrical conductivity. Finally, cyclic voltammetry demonstrates that, despite not electro‐active, these partially oxidized PIns show enough electrical conductivity for different applications.

The hybridization of clay minerals with conducting polymers receives great interest for different potential applications, including environmental remediation. This work studies and compares the electrochemical properties of two different clays, montmorillonite (Mont) and diatomite (Diat), and their respective clay/PEDOT-PSS hybrid materials in H₂SO₄ medium. The hybrid materials were prepared by electropolymerization of EDOT in the presence of PSS. The physico-chemical and electrochemical properties of both clays were analyzed by different techniques, and the influence of the clay properties on electropolymerization and the electroactivity of the resulting clay/PEDOT-PSS hybrids was investigated. Specifically, the Fe²⁺/Fe³⁺ redox probe and the oxidation of diclofenac, as a model pharmaceutical emerging pollutant, were used to test the electron transfer capability and oxidative response, respectively, of the clay/PEDOT-PSS hybrids. The results demonstrate that, despite its low electrical conductivity, the Mont is an electroactive material itself with good electron-transfer capability. Conversely, the Diat shows no electroactivity. The hybridization with PEDOT generally enhances the electroactivity of the clays, but the clay properties affect the electropolymerization efficiency and hybrids electroactivity, so the Mont/PEDOT displays improved electrochemical properties. It is demonstrated that clay/PEDOT-PSS hybrids exhibit diclofenac oxidation capability and diclofenac concentration sensitivity.