A chromate of copper and cobalt (Φy) was synthesized and characterized. Φy activated peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP) in water. The Φy/PMS combination showed a high degrading capability toward CIP (~100% elimination in 15 min). However, Φy leached cobalt (1.6 mg L⁻¹), limiting its use for water treatment. To avoid leaching, Φy was calcinated, forming a mixed metal oxide (MMO). In the combination of MMO/PMS, no metals leached, the CIP adsorption was low (95% after 15 min of treatment). MMO/PMS promoted the opening and oxidation of the piperazyl ring, plus the hydroxylation of the quinolone moiety on CIP, which potentially decreased the biological activity. After three reuse cycles, the MMO still presented with a high activation of PMS toward CIP degradation (90% in 15 min of action). Additionally, the CIP degradation by the MMO/PMS system in simulated hospital wastewater was close to that obtained in distilled water. This work provides relevant information on the stability of Co-, Cu-, and Cr-based materials under interaction with PMS and the strategies to obtain a proper catalyst to degrade CIP.

In this study, a carbonaceous material was obtained from the thermal decomposition of a non-pretreated rice husk in a pyrolysis system with controlled nitrogen at 700, 800, 900, and 1000 °C. The characterization of the material was performed using various analytical techniques. The results of these characterizations indicate that the obtained carbonaceous material can achieve a surface area of 450 m²/g, with a microporous volume of 0.15 cm³/g. Furthermore, the presence of oxygenated function groups, predominantly hydroxyl (C-OH) and epoxy (C-O-C), along with amorphous silicon, was identified. Additionally, the material’s CO₂ adsorption capacity was assessed, revealing a maximum capacity of 1.0 mmol/g. The findings of this study suggest that the CO₂ adsorption effectiveness can be impacted by the presence of specific functional groups. These groups have been shown to enhance the material’s affinity for CO₂, along with its porosity and surface area. In this sense, a notable correlation was identified between the oxygenated function group content and CO₂ adsorption capacity. Also, the adsorption isotherm modeling showed an excellent fit to the Langmuir model, indicating monolayer adsorption on a homogeneous surface.

The hydrothermal method was used for the synthesis of lamellar chromates and vanadates of Cu and Ni (ΦY and ΦZ -types), which served as precursors for the subsequent synthesis of mixed metal oxides (MMO). These MMOs (named as CuV MMO, NiV MMO, CuCr MMO, and NiCr MMO) were characterized and evaluated for the catalytic oxidation of toluene, showing activity at temperatures below 400 °C. Among the studied materials, CuCr MMO demonstrated superior catalytic activity compared to CuV MMO, NiCr MMO, and NiV MMO, due to the higher reducibility of Cu or Cr in these materials. The temperatures required to achieve 90% conversion of toluene (T90) followed the order CuCr MMO (~275 °C) < CuV MMO (~330 °C) < NiV MMO (~370 °C) < NiCr MMO (~395 °C). Furthermore, the incorporation of Co to CuCr MMO (which produced CoCuCr MMO) significantly improved the catalytic performance, leading to toluene oxidation at even lower temperatures, T90: ~265 °C. For comparison, the MMO derived from the lamellar precursor exhibited superior catalytic performance relative to that obtained via simple mixing and calcination of the corresponding inorganic metal salt. This result highlights the relevance of the precursor’s structure in the subsequent catalytic activity. Finally, a stability test was performed on the best-performing catalytic material (CoCuCr MMO). Toluene conversion remained at ~100% for the first 4 h, then decreased to ~45%, remaining stable for up to 70 h of continuous reaction.