The role of the anode material and water matrix in the electrochemical oxidation of norfloxacin.

The roles of the anode material, boron-doped diamond (BDD), with different boron (B) and substrate Silicon (Si) or Niobium (Nb) content, and one dimensionally stable anode (DSA®), were evaluated in the oxidation of norfloxacin (NOR) by electrochemical advanced oxidation process (EAOP). The effect of other components in real wastewater on the performance of EAOP was also studied. The anode materials were characterized by cyclic voltammetry, regarding diamond quality, electro-generation of oxidants and NOR oxidation mechanism (direct and/or indirect). The results showed that the anode material influences on the NOR oxidation pathway, due to distinct characteristics of the substrate and the coating. Apparently, low difference in diamond-sp³/sp2-carbon ratio (Si/BDD100 × Si/BDD2500) does not leads to significant differences in the EAOP. On the other hand, the variation in the sp³/sp2 ratio seems to be higher when Si/BDD2500 and Nb/BDD2500 are compared, which would explain the best current efficiency result for Si substrate. However, the Nb substrate presented a similar current efficiency and a 60% lower energy consumption. Dissolved organic matter (DOM) present in the real wastewater affect the EAOP-Nb/BDD due to HO and persulfate ions scavenged. However, when supporting electrolyte was added to a real wastewater spiked with NOR, the NOR decay reaches similar values found to the synthetic one. Due to the energy saving and mechanical properties, Nb substrate presents some technological advantages in relation to Si, which can facilitate the application to industrial levels.

Impedance Analysis of Polyaniline in Comparison with Some Conventional Solid Electrolytes.

Doped polyaniline (PANI) is well-known as an electronic (polaronic) conductor and mostly is used as semiconductor in various applications. However, in the literature there are examples of employment of the acid doped form of PANI as electrolytic filler in proton exchange membranes. In order to distinguish between two types of conduction, in the present study powdered samples of polyaniline, either in the form of emeraldine base (PANI-EB) or in the form doped with camphorsulfonic acid (PANI-CSA), were investigated using impedance spectroscopy both in the dry state and in contact with liquid water. The obtained spectra were compared with the spectra of such conventional solid electrolytes, as zeolites X and ZSM5 and a strong electrolyte boron orthophosphate, acquired in identical conditions. The most important dissimilarity between conventional electrolytes and PANI was that ion diffusion dominates in the impedance response of the formers, whereas the behavior of PANI is under control of electron/hole displacement and the diffusion part is quite inessential. This corroborates the results of analysis of temperature dependence of PANI conductivity, which revealed values of activation energy twice as large as typical solid electrolytes. Equivalent circuits, simulating the impedance responses of all materials, were built up and used to estimate a possible diffusion coefficient of cations in the comparable solids. It was found that the diffusion in a strong electrolyte such as BPO4 is ∼2 orders of magnitude faster than evaluated for zeolites and ∼4 orders higher than what was PANI estimation. A conclusion was made that the slow cation diffusion both in protonated and in base form of PANI makes them less efficient solid electrolytes than conventional materials.