Catalysts enriched in Zinc ferrite (ZFO) were synthesized using coprecipitation and hydrothermal methods. Mixtures of crystalline nanoparticles (ZFO and α-Fe₂O₃, several allotropic varieties of FeO) were characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM, SEM), N₂ sorption, UV-visible spectrophotometry (UV-Vis) and X-ray photoelectron spectroscopy (XPS). After detailed characterizations, the catalytic performance of the solids (1 g/L) in the degradation of amoxicillin (AMX) (10 mg/L) as an antibiotic pollutant in water was evaluated. In addition, we used air as the oxygen source and adjusted the pH to 5.0. Consequently, the catalysts obtained via the hydrothermal method HT-ZFO had a high activity (100% of AMX removal in less than 100 min when an LED (75 W) light was used) compared to a similar mixture of oxides with graphene HT-ZFO-GO (a longer time of 150 min) that was necessary for the complete degradation of AMX. Impregnation with an aqueous solution containing 80 mg of GO obtained using Hummer’s method, reduced into RGO by an ultrasound treatment, enhances the initial reaction rate but is associated with a prolonged time for complete AMX removal (10 ppm in water) that we attribute to its spontaneous corrosion.

In this study, ultrasound treatment was used to exfoliate commercially available graphite flakes into reduced graphene oxide (rGO) dispersed in ethanol. After centrifugation, solid copper chloride trihydrate was added, resulting in a green liquor containing Cu(II), Cu(I), and rGO. These liquors exhibited good and rapid photocatalytic activity in the degradation of eosin and bromophenol blue dyes (elimination in a few seconds) under visible-light irradiation. UV–visible spectroscopy confirmed the presence of rGO and Cu species. The size and morphology of the rGO sheets were investigated by several methods (SAXS, wide-angle XRD, SEM, and TEM). Negative UV peaks indicated light emission, which was independently verified by fluorescence. Intense plasmon peaks, with absorbances greater than 10, were observed after adding copper chloride salt. These plasmons were eliminated by a high dilution before the described catalytic tests were performed.

Cu-ions dispersed on reduced graphene RGo prepared and characterized in a liquid state in ethanol. Either constant ultrasounds or a sequence of ultrasounds (15s working, 15s stop) were applied for 6 min or 2h overall time, at a power of 500 W. Commercial graphite in ethanol was introduced at a concentration of 0.04 g/mL and CuCl2 2.5 H2O concentrations between 0.012 and 0.04 g/mL were used. The structural characterizations performed by XRD, microscopic, and spectroscopic techniques, after a centrifugation at 5000 rpm applied 12 min before Cu-introduction, led to conclude that: 1) Without copper, negative peaks in UV spectra were detected with concentrated pure graphene solutions, indicating light emission as nicely confirmed next by fluorescence measurements, 2) After addition of copper chloride and equilibration for 2 min , very intense and narrow peaks of intensity larger than 10 were observed. These peaks due to collective excitations generating plasmons were suppressed at a higher dilution and also if the cell with one cm optical path was replaced by a narrower cell with a 0.2 cm path. When plasmons were suppressed, in the UV spectral range, a band gap due to the energy transition between the valence filled  orbitals and conducting empty * orbitals, was observed. The presence of Cu (II) and Cu (I) cations were evidenced by Visible NIR spectroscopy. The formed “green” liquors containing Cu (II) Cu (I) /graphene in ethanol were stable in air for months and had good photocatalytic visible properties as demonstrated by the decomposition of two dyes.

Nanoparticles of ZnFe2O4 or hematite of different sizes and shapes are obtained using the two-solvent method (cyclohexane, water) on SBA-15 silica batches. Calcination is performed in air at 700°C with a rate of 2°C by min and quenching for a rapid cooling down until room-temperature. The two inorganic oxides varieties are selected because they are less soluble in water than magnetite and a true heterogeneous reaction can be studied without having a significant parallel homogeneous reaction occurring because of the formation of Fe (II) ions by corrosion (limited Fenton reaction). Their photocatalytic activity is compared under visible light irradiation from a LED lamp, using O2 from air as an oxidizing agent. No H2O2 addition is necessary. We have studied the decomposition of the broad-spectrum antibiotic amoxicillin (AMX) by following the intensity of its signature peak in UV visible spectra and by HPLC chromatography with a C18 column. The photocatalytic activation was demonstrated by measurements performed in the dark also for 225 min. The photocatalytic reaction generates hydroxyl (°OH) and superoxide radicals that yield to a rapid AMX decomposition. An absorption of 7% of AMX occurs within the first 30 minutes of the catalytic test.

Nanoparticles of ZnFe₂O₄ and hematite with varied sizes and distributions were synthesized using the two-solvent method (cyclohexane, water) on SBA-15 silica batches. Calcination is performed in air at 700 °C (2 °C/min) with rapid quenching produced catalysts with distinct nanoparticle configurations, namely, internal zinc ferrite and external hematite. The choice of precursor was critical, and nitrate salts yielded only zinc ferrite nanoparticles, while chloride salts produced a mixture of hematite and zinc ferrite. The photocatalytic activity of these materials was evaluated under visible light irradiation from an LED lamp, using O₂ from air as an oxidizing agent without the addition of H₂O₂. Samples enriched with external hematite nanoparticles from chloride precursors achieved the highest activity, decomposing 30% of AMX in 225 min. In contrast, nitrate-derived samples with predominantly internal zinc ferrite nanoparticles exhibited lower catalytic activity. Characterization via TEM, XRD, N2 sorption, and Mössbauer spectroscopy confirmed the structural and magnetic properties of the nanoparticles. Mössbauer spectra, particularly at 12K and under a magnetic field, demonstrated the presence of hematite nanoparticles, distinguishing them from isolated Fe (III) cations. Zinc ferrite nanoparticles exhibited specific magnetic ordering, with Fe ions occupying tetrahedral and octahedral sites. The results demonstrate the critical role of nanoparticle, composition, and positioning in optimizing photocatalytic efficiency for water decomposition.