This work compares the ability of physical and chemical treatments, namely adsorption and electrochemical advanced oxidation processes, to remove tyrosol from aqueous medium. Adsorption on graphene nanoplatelets (GNPs) performed much better than that with a graphite intercalation compound. Adsorption isotherms were found to follow the Freundlich model (R2 = 0.96), which is characteristic of a chemisorption process. Successful electrochemical regeneration enables 5 successive adsorption/regeneration cycles before corrosion of GNPs occurs. Other typical aromatic contaminants that may coexist with tyrosol can be also adsorbed on GNPs. Percentage of regeneration efficiency of GNPs showed a higher affinity towards Lewis acids group compounds and a lower one towards Lewis base. The treatment of 100 mL of 0.723 mM tyrosol solutions in non-chlorinated and chlorinated matrices at pH 3.0 was carried out by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF). Trials were made with a BDD anode and an air-diffusion cathode at 10-30 mA cm-2. Hydroxyl radicals formed at the anode from water oxidation and/or in the bulk from Fenton's reaction between added Fe2+ and generated H2O2, along with active chlorine produced in chlorinated medium, were the main oxidants. Tyrosol concentration always decayed following a pseudo-first-order kinetics and its mineralization rose as EO-H2O2 < EF < PEF, more rapidly in the chlorinated matrix. The potent photolysis of intermediates under UVA radiation explained the almost total mineralization achieved by PEF in the latter medium. The effect of current density and tyrosol content on the performance of all processes was examined.

A carbon-neutral fuel is desired when it comes to solving the issues associated with climate change. A smart approach would be to develop new materials to produce such fuels, which could be integrated with renewables to improve the efficiency (e.g., solid oxide fuel cells (SOFCs) in smart grid and concentrated solar fuel technologies). In this study, we report the utilization of nonstoichiometric perovskite oxides, Ba₂Ca_0.66Nb_1.34−xFe_xO_6−δ (BCNF) (0 ≤ x ≤ 1), to split CO₂ into carbon, carbon monoxide, and oxygen at elevated temperatures. Powder X-ray diffraction shows the chemical stability of double perovskite-type BCNF after being exposed to 2000 ppm CO₂ in Ar at 700 °C. Furthermore, all x ≤ 0.66 BCNF members exhibit high chemical stability even under pure CO₂ at 700 °C. Scanning electron microscopy coupled with energy dispersive X-ray, Raman spectroscopy, temperature programmed oxidation (TPO) and mass spectroscopy (MS), and DFT analyses confirm the formation of solid carbon upon CO₂ exposure, which increases with increasing Fe in BCNF. Mössbauer spectroscopy of the as-prepared BCNF shows the presence of Fe³⁺, Fe⁴⁺ and Fe⁵⁺. Upon Ar exposure, the higher valent Fe component is reduced to Fe³⁺ and subsequent oxidation of Fe³⁺ seems to promote the CO₂ reduction. Overall, these promising results of BCNFs, displaying redox activity at significantly lower temperatures compared to state-of-the-art ceria for CO₂ reduction, show great potential for their use in renewable-driven fuel technologies.