Water from Madín Dam in Mexico has been shown to contain a wide variety of pollutants such as drugs, pesticides, personal care products and compounds that are released into the environment as waste from production processes. In this work, the effect of the main process variables on the percentage of total organic carbon (TOC) removal in water samples from the Madín reservoir was studied by applying a photo-Fenton treatment catalyzed with iron-pillared clays. The catalyst was characterized by XRD, N₂ physisorption, DRS and XPS. The sampling and characterization of the water from the Madín reservoir was carried out according to Mexican standards. The system for treatment tests was 0.1 L of reaction volume and a controlled temperature of 23–25 °C, and the reaction system was kept under constant stirring. After 4 h of treatment time under UV light, the TOC removal was 90%, and it was 60% under Vis light. The main ROS involved in the photo-Fenton process driven by UVC light were hydroxyl radicals, while hydroperoxyl radicals predominate in the Vis-light-driven process. Evidence of superoxide anion participation was not found. The toxicity of untreated and treated water was assessed on Danio rerio specimens, and it was observed to be reduced after the photo-Fenton treatment.

This work aimed to demonstrate Cu₂O/Al₂O₃ as a catalyst of the photo-Fenton process in the UV and visible spectra. Cu₂O nanoparticles were synthesized by laser ablation in liquid and supported on Al₂O₃. The catalytic activity of the resulting solid was assessed in the mineralization of bisphenol A (BPA). The studied variables were type of Al₂O₃$\left(\alpha \mathrm{and} \gamma \right)$, Cu content (0.5 and 1%), and H₂O₂ concentration (1, 5, and 10 times the stoichiometric amount). The response variables were BPA concentration and total organic carbon (TOC) removal percentage. The presence of Cu₂O nanoparticles (11 nm) with an irregular sphere-like shape was confirmed by transmission electron microscopy (TEM) and their dispersion over the catalytic surface was verified by energy-dispersed spectroscopy (EDS). These particles improve ·OH radical production, and thus a 100% removal of BPA is achieved along with ca. 91% mineralization in 60 min. The BPA oxidation rate is increased one order of magnitude compared to photolysis and doubles that for H₂O₂ + UV. An increase of 40% in the initial oxidation rate of BPA was observed when switching from α-Al₂O₃ to γ-Al₂O₃. 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, acetaldehyde, and acetic acid are the BPA oxidation by-products identified using LC/MS and based on this a reaction pathway was proposed. Finally, it was also concluded that the synthesized catalyst exhibits catalytic activity not only in the UV spectrum but also in the visible one under circumneutral pH. Therefore, Cu₂O/Al₂O₃ can be recommended to conduct a solar photo-Fenton reaction that can degrade other types of molecules.

In this investigation, metronidazole was degraded in an aqueous solution through electro-oxidation. A DiaClean^® cell was used to accommodate a stainless-steel electrode as a cathode and a boron-doped diamond (BDD) electrode as anode. This setup provides several electrochemical advantages, including low currents, a high operational potential, and, frequently, low adsorption compared to conventional carbon materials. The physicochemical parameters were estimated after 180 min of treatment, applying different current densities. The concentration of metronidazole was monitored by HPLC to assess degradation, resulting in 30.67% for 30 mA cm⁻², 79.4% for 50 mA cm⁻², and 100% for 100 mA cm⁻². The TOC mineralization percentages were 12.71% for 30 mA cm⁻², 14.8% for 50 mA cm⁻², and 29.9% for 100 mA cm⁻². Also, biodegradability indices of 0.70 for 30 mA cm⁻², 0.81 for 50 mA cm⁻², and 0.93 for 100 mA cm⁻² were obtained. The byproducts found were formic acid and acetic acid. A pseudo-first order kinetic model was thus obtained due to the quasi-stable concentration achieved through hydroxyl radicals, given that they do not accumulate in the medium, due to their high rate of destruction and short lifespan.

In this work, gold-photo-catalyzed CO₂ transformation was conducted and the effect of three variables with two levels was investigated: support (TiO₂ and hydroxyapatite from bovine bone (BB)), Au content (5 and 10%) and activation wavelength (254 and 380–700 nm). Reactions were conducted in a stirred tank reactor by bubbling CO₂ (9 × 10⁻³ dm³/min) in 0.1 dm³ of 0.5 M NaOH solution. The catalysts were synthesized using AuCl₃, TiO₂ and BB. Au nanoparticles were obtained by reduction with Hetheroteca inuloides, thus eliminating calcination and hydrogenation to reduce the gold species. By TEM, the particle size distribution was determined, and the synthesized nanoparticle sizes varied in the range of 9 to 19 nm, depending on the support and Au content. By UV–Vis spectroscopy, the energy band gaps of the prepared materials were 2.18 eV (10% Au/BB), 2.38 eV (5% Au/BB), 2.42 eV (BB), 3.39 eV (5% Au/TiO₂), 3.41 eV (10% Au/TiO₂) and 3.43 eV for pure TiO₂. Methanol and formic and acetic acids were identified during the process. Selectivity toward methanol was found to be improved with the 10% Au/BB catalytic system.

This study investigated the electro-mineralization of chloroquine (CQ) in a filter-press-type flow reactor using two BDD electrodes operating in batch recirculation mode. The optimal operating parameters were established using response surface methodology (RSM) and central composite rotatable design (CCRD) with three parameters: current density (j), initial pH (pH₀), and volumetric flow rate (Q), with the mineralization efficiency of (CQ) and specific energy consumption (SEC) as responses. Optimal operating parameters were j = 155.0 mA/cm², pH₀ = 9.75, and Q = 0.84 L/min within a reaction time of 9 h, leading to a maximum mineralization efficiency of CQ of 52.59% and a specific energy consumption of 15.73 kW/mg TOC, with a total operating cost of USD 0.18 per liter. Additionally, an ultra-high-performance chromatography study identified three by-products (4-amino-7-choloroquinoline, formic acid, and acid acetic) of CQ degradation. Furthermore, the phytotoxicity test indicates that the electrochemical wastewater proposed decreased the effluent’s phytotoxicity, and an increase in the percentage of Vigna radiata germination was observed. The carbon footprint of optimized electrochemical mineralization of chloroquine is 2.48 kg CO₂ eq., representing a 48% reduction in cumulative energy demand (CED) when the source of energy is a mixture of fossil fuels (50%), wind (25%), and photovoltaic (25%) energy.