Antonio Gascó

Biochar-supported rare earth oxides are herein assessed as heterogeneous catalysts for the UV-assisted Catalytic Wet Peroxide Oxidation (UV-CWPO) treatment of pharmaceuticals under mild conditions. Catalysts were synthesized by two different pyrolysis methods (activated carbon-assisted oxygen-limited pyrolysis in a muffle furnace, and inert-gas pyrolysis in a tubular furnace under nitrogen flow), and characterized by XRD, SEM, and N₂ adsorption–desorption isotherms. Their performance in assisting 385 nm UVA-LED CWPO treatment of acetaminophen (ACE), diclofenac (DCF), and metamizole (MTZ) was assessed under circumneutral pH conditions. The biochar-supported cerium-loaded catalyst prepared by oxygen-limited pyrolysis reported the highest activity, achieving 80% ACE and 70% DCF removals within 120 min of treatment, whereas MTZ was completely removed in less than 10 min, with only 16% of the removal attributable to adsorption. Superoxide radicals dominated the degradation mechanism, and photogenerated holes and hydroxyl radicals contributed moderately. Catalyst stability (minimal activity loss and negligible cerium leaching) was confirmed over five consecutive reuses. Degradation efficiency decreased ≈12–18% because of radical scavenging losses caused by the content of inorganic ions and organic matter in tap, river, and WWTP effluent waters. Treated effluents addressed lower toxicity than untreated solutions, reinforcing the environmental safety of this treatment strategy.

This study aims to demonstrate the feasibility of the use of chestnut waste as a green and circular material for developing iron-based photocatalysts for non-steroidal anti-inflammatory drug (NSAID) photodegradation. Four Fe-based catalysts and two pristine biochars were obtained upon a pyrolysis process at 500 and 700 °C and fully characterised. Due to the applied synthesis, iron is present in the form of isotropic grains of magnetite (Fe₃O₄), quite homogeneously dispersed onto the biochar. The textural properties of all the materials are mainly determined by the pyrolytic temperature, which results in macroporous materials at 500 °C and microporous ones at 700 °C. Fe-based catalysts were tested in Diclofenac (DFC) photodegradation. DFC removal was the result of both adsorption and photocatalytic reactions. Despite the good yield in DFC removal (80–100%), the formation of degradation by-products can partially invalidate the good effectiveness of this approach. However, the encouraging results of this study represent a step forward for the possible development of waste-derived biochar-based catalysts for in-field application.

This study investigates the synthesis of shape-controlled titanium dioxide (TiO₂) nanoparticles via a hydrothermal method, examining the influence of pH variation (8, 10, 12, and 14) and subsequent thermal treatments (200°C and 230°C) on phase transitions and morphological transformations. The resulting TiO₂ nanostructures—including nanorods, nanotubes, nanoflowers, elongated bipyramids, and irregular flower-like assemblies—undergo phase transitions from anatase to brookite. Their photocatalytic performance is assessed for aqueous pollutant degradation and NOx abatement. TiO₂ synthesized at lower pH (8-10), exhibiting anatase-phase nanotubular and elongated bipyramidal morphologies, achieves near-complete photodegradation of phenol, methomyl, and diclofenac in both Milli-Q and stormwater matrices. Conversely, brookite-rich TiO₂ phases, formed at higher pH (12-14), show limited liquid-phase activity but excel in NOx abatement, making them promising candidates for air purification applications. These findings highlight the pivotal role of phase composition and morphology in optimizing photocatalytic performance, offering a strategic approach for the scalable development of efficient TiO₂-based photocatalysts for environmental remediation.

This study reports the development of shape-controlled TiO₂ (B)/anatase heterostructures for the degradation of emerging environmental pollutants, including phenol, methomyl (insecticides), and diclofenac sodium (drug), under UV-visible-light irradiation in ultrapure water and alkaline stormwater. TiO₂ nanobelts were synthesized via a surfactant-free hydrothermal method, yielding structures with widths ranging from 40 to 80 nm and lengths extending up to several micrometers. The synthesized nanobelts were calcined at 400 °C, 600 °C, and 800 °C to form a TiO₂ (B)/anatase heterostructure. For comparison, calcination at 900 °C was also performed, resulting in the formation of pure anatase. The samples calcined at 800 °C (~92% anatase, ~8% nanobelts) exhibited enhanced photocatalytic efficiency, achieving significant total organic carbon (TOC) removal and complete mineralization in both water matrices. These findings contribute to a cost-effective method for developing efficient TiO₂ (B)/anatase heterostructures to avoid rapid charge carrier recombination, with strong potential for advanced wastewater treatment.

Water pollution, resulting from industrial effluents, agricultural runoff, and pharmaceutical residues, poses serious threats to ecosystems and human health, highlighting the need for innovative approaches to effective remediation, particularly for non-biodegradable emerging pollutants. This research work explores the influence of shape-controlled nanocrystalline titanium dioxide (TiO₂ NC), synthesized by a simple hydrothermal method, on the photodegradation efficiency of three different classes of emerging environmental pollutants: phenol, pesticides (methomyl), and drugs (sodium diclofenac). Experiments were conducted to assess the influence of the water matrix on treatment efficiency by using ultrapure water and stormwater (basic) collected from an urban drainage system as matrices. The size and shape of the nano-cuboids were accurately controlled during synthesis to assess their impact on photoactivity and selectivity. Regarding total organic carbon removal using TiO₂ nano-cuboids in basic environments, the results were particularly remarkable. TiO₂ nano-cuboids and truncated bipyramids synthesized in the 200–250 °C temperature range showed an enhanced photocatalytic efficiency when compared to alternative formulations. Diclofenac, methomyl, and phenol were fully mineralized from ultrapure water and basic stormwater. The TiO₂ nano-cuboids/nano-bipyramids demonstrated better selectivity and photoactivity in comparison to irregular TiO₂ nanoparticles. The differences in photoactivity and selectivity are explained in terms of charge carrier separation and trapping on the different crystal facets. Their performance demonstrates their potential as sustainable materials for the photodegradation of emerging pollutants in various water matrices.

Anaerobic digestion of animal manure generates biogas and removes biodegradable organic matter, while most of the nitrogen and phosphorous remains at very high levels after the process. A subsequent microalgae culture in the digestate provides nutrient uptake at very low operational and installation costs. However, the dark color of manure digestate prevents light penetration, reducing the rates of algae growth. Ozonation was researched as a strategy for color removal followed by microalgae culture. Although similar biomass production was achieved in treated and untreated digestates (1.09 vs. 0.99 g L⁻¹), the positive effect of ozonation was evidenced by the significantly higher rates of photosynthetically produced oxygen: 0.804 and 0.18 mg O₂ mg⁻¹ TSS min⁻¹, respectively, in ozonated and untreated digestates, revealing a four times higher rate of algae activity. However, this considerable higher activity was not correlated with better performance in nutrient removal since the microalgae treatment was assayed at a considerably reduced scale with a high ratio of illumination per volume. An operational costs analysis revealed that ozonation could be competitive against other strategies of color reduction such as dilution or coagulation/flocculation processes.

Wine lee generation, a by-product of the wine industry, implies economic challenges for producers in terms of management due to its high organic load and low pH value. Biological treatment based on controlled anaerobic digestion may emerge as a viable management alternative given its promising potential for biogas production thanks to the organic content of the substrate. However, the complex properties of wine lees may lead to microbial activity inhibition and process kinetics failure. Various solutions have already been explored, including co-digestion with other substrates, or the application of different pretreatments, to mitigate the effects of the accumulation of phenolic compounds, volatile fatty acids, antioxidants, or the acidic pH value of the medium. In this study, laboratory-scale batch reactors were established, adding iron- (magnetite) or carbon (graphite)-based microparticles to assess their impact on the kinetics of the process. The results demonstrate a significant improvement of 35% in the potential production of biomethane after four days of operation with graphite particles and 42% after five days using magnetite particles. Methane production rates, as determined by the Gompertz model, were 45.38 and 46.54 mL CH₄∙gVS⁻¹∙d⁻¹ for the application of graphite and magnetite microparticles to the medium, respectively, compared to the value of 33.46 mL CH₄∙gVS⁻¹∙d⁻¹ for the control trial, confirming kinetic process improvements of 36% and 39%, respectively. Evidences of the acceleration of the methanogenesis phase were detected along the essays; however, the strong inhibition mediated by the carboxylate accumulation was not avoided in any of the tested conditions.