Search Results (155)

TiO₂/activated carbon (TiO₂/AC) was coated on mesh using the dip-coating method employing polyvinyl pyrrolidone (PVP) as a copolymer via a simple mixing method. The obtained catalyst was used to treat real wastewater from a building discharge with a horizontal photoreactor with a continuous flow system. The synthesis of 20%wt TiO₂/AC-coated mesh was performed with a fixed TiO₂:AC ratio of 1:0.05 wt/wt, as confirmed by employing various characterization techniques, which resulted in a composite TiO₂/AC characterized by XRD, FE-SEM, and EDS, confirming the uniform distribution of TiO₂/AC nanoparticles coated on mesh substrates. The influence of vital parameters on the best conditions of the photoreactor design, including flow rate (8.0 L/min), light intensity position (5.0 cm), and the number of mesh layers (20 mesh layers), was systematically examined during photocatalytic oxidation. The treatment efficiency of domestic building wastewater was evaluated using a TiO₂/AC coated on mesh under visible light irradiation for 120 min. The recirculating batch photoreactor was operated at a continuous flow rate of 8.0 L/min, corresponding to a total treated wastewater volume of 960 L. In real wastewater treatment, the optimized TiO₂/AC-coated mesh exhibited the highest activity, achieving approximately 68% BOD removal and 65% COD removal. This study indicates that TiO₂/AC-coated mesh can be a good candidate for building wastewater treatment systems using photocatalytic activity under visible light irradiation. However, the TiO₂/AC coating exhibited limited reusability, with BOD degradation decreasing to 53% after three cycles. Future work must develop a more stable binder to improve its durability and reusability. Full article

This study investigates the TiO₂ photocatalytic degradation of naproxen (NPX), a nonsteroidal anti-inflammatory drug, and spiramycin (SPM), a macrolide antibiotic, in aqueous solution. Experiments were conducted using a closed-loop falling thin-film photoreactor equipped with external UV lamps, with particular focus on the competitive degradation behavior when both pharmaceuticals are present simultaneously. Under optimized conditions such as natural pH, UV light intensity of 38 Wm⁻², and a recirculation flow rate of 25 L h⁻¹, the TiO₂-UV process achieved near-complete degradation of the parent compound (≥99%) for both compounds, whether treated individually or in combination. The degradation kinetics followed a pseudo-first-order model, consistent with heterogeneous photocatalytic systems at low pollutant concentrations. The apparent pseudo-first-order rate constants (k_app) were 0.025 min⁻¹ for NPX and 0.087 min⁻¹ for SPM in single-component systems. In competitive degradation, k_app ranged from 0.005 to 0.007 min⁻¹ for NPX and from 0.003 to 0.031 min⁻¹ for SPM, highlighting the influence of competitive adsorption and reactive-site interaction during simultaneous treatment. Mineralization efficiency differed between the compounds, reaching up to 67% for SPM and 41% for NPX when treated individually, suggesting the formation of more persistent by-products during naproxen degradation. Under competitive conditions, total mineralization rates ranged from 51% to 67% depending on the SPM/NPX molar ratio. Full article

Here, the degradation of a β-blocker drug (Nadolol (NAD)) and real pharmaceutical wastewater was achieved using magnetized cow bone waste-derived char (MCBWC)–alginate hydrogel beads via a periodate (PI) activation system in a continuous-flow fluidized-bed photoreactor. The removal of NAD by PI-based degradation systems has not been previously reported, and the degradation of real industrial wastewater in continuous-flow photoreactors remains underexplored. The fabricated beads exhibited a high surface area of 78.58 m² g⁻¹, a total pore volume of 0.19 cm³ g⁻¹, and an effective integration of all composite components. The MCBWC–alginate hydrogel beads/PI/light degradation system degraded 71.47% of NAD, which was higher than that of the sole photocatalysis and PI activation systems. Further, the optimal operating condition could achieve a NAD degradation efficiency of 97.1% and a total organic carbon (TOC) removal efficiency of 82.78%. Furthermore, the degradation system demonstrated the non-formation of toxic iodinated byproducts. The hydrogel beads demonstrated high stability, where the NAD degradation efficiency slightly decreased by only 2.85% across five successive experiments. Singlet oxygen and iodine-based radicals contributed to NAD degradation more than other reactive species. Bicarbonate showed the highest suppressive effect on the degradation performance, while adding 10 mg L⁻¹ of humic acid decreased the degradation efficiency to 85.58%. The degradation system could further degrade other pharmaceuticals (e.g., ibuprofen, paracetamol, carbamazepine, tetracycline) and real pharmaceutical wastewater, attaining 78.37% degradation efficiency of NAD and 44.25% TOC mineralization. This study presents a stable, effective, and continuous degradation system that can be employed in real-world industrial wastewater treatment applications. Full article

CO₂ methanation is considered a key process in achieving carbon neutrality. Expanding on our previous study of supercritically dried Ni-Al aerogels, this work compares two gel-based catalyst families prepared via two different routes—supercritically dried Ni impregnated Al aerogel-based catalysts and oven-dried one-pot Ni-Al xerogel-based catalysts—to assess how the synthesis route affects catalyst structure and CO₂ methanation performance under light irradiation. The catalysts were subsequently characterized via different techniques, such as ICP-OES, N₂ adsorption–desorption isotherms, XRD, H₂-TPR, UV-vis DRS, XPS, and TEM. Catalytic activity was tested in a photoreactor at a range of temperatures from 300 °C to 450 °C and 10 bar pressure, and two different light sources were used (λ = 365 nm, λ = 470 nm). Both light sources enhanced catalytic activity in most cases; the xerogels with higher Ni loadings were the most active materials. These catalysts reached CO₂ conversions and CH₄ selectivities near 70% and 100%, respectively. The results indicate that drying gels is a promising method for synthesizing catalysts active in the Sabatier reaction, given the properties of the materials. Full article

The photocatalytic activity as a function of effective irradiance, photocatalytic quantum yield and reactant coverage was thoroughly assessed for the proper photoreactor (PhR) selection. The emitted wavelength and effective irradiance of several PhRs, equipped with fluorescent and light-emitting diode (LED) lamps, were tested in the photodegradation of methylene blue (MB) in the solid phase using an AgTiO₂ photocatalyst. Among all tested PhRs, the one equipped with the low-pressure Hg lamp enhanced the photodegradation of MB, as the Hg lamp emitted UV-type radiation, which promotes the simultaneous photoactivation of the TiO₂ and the surface plasmon resonance phenomenon of the Ag nanoparticles. It was determined that high values of effective irradiance promoted photocatalytic activity because of the greater amount of photogenerated species [e⁻/h⁺]. Also, it was determined that the effective irradiance used in the photocatalytic process slows down the recombination rate of the [e⁻/h⁺] into photocatalytic material. A kinetic photocatalytic model (KPM) was proposed to describe photocatalytic reactions as a function of effective irradiance, photocatalytic quantum yield and reactant coverage, considering photocatalytic pseudo-steady state according to the reactant equilibrium coverage (Langmuir isotherm) and the transfer processes of the photoinduced charge carrier species. Full article

Paracetamol (PAR) was selected as an emerging micropollutant model to evaluate the effectiveness of the photo-Fenton process using natural Bandjéli ore (BO) as a heterogeneous source of iron. An aliquot of 1 mL of the activated product was introduced into 200 mL of an aqueous solution of paracetamol at a defined concentration. The tests were conducted in a double-jacketed glass photoreactor (0.2 L), continuously stirred and equipped with two UVA PL-L lamps (36 W, λ = 365 nm), with the temperature maintained at 20 °C and the pH around 2.4. The photo-Fenton process was applied with different initial paracetamol concentrations (10–50 mg/L), different ${\mathrm{H}}_2{\mathrm{O}}_2/\mathrm{P}\mathrm{A}\mathrm{R}$ initial molar ratios (10:1 and 5:1), and different ferric ion concentrations (2.84–4.73 mg/L). Under these conditions, complete disappearance of the parent compound (paracetamol) was achieved in less than 3 h for iron contents below 5 mg/L, in compliance with the discharge standards applicable in France and Togo. Inhibition tests with propan-2-ol highlighted the predominant role of hydroxyl radicals and the secondary involvement of superoxide radicals in the subsequent stages. Taken together, these results demonstrate that Bandjéli iron ore is an effective, sustainable, and economically advantageous alternative to commercial iron salts for implementing the photo-Fenton process in the decontamination of water polluted by organic micropollutants. Full article

Growing environmental concern over plastic pollution has increased the need to address the persistence of PET-derived monomers, such as bis(2-hydroxyethyl) terephthalate (BHET) and terephthalic acid (TPA). This work examines the use of excimer radiation lamps combined with hydrogen peroxide (H₂O₂) to enhance advanced oxidation processes (AOPs) for their degradation. This approach stands out for its high selectivity, absence of mercury, and lower production of toxic byproducts. Experimental tests assessed how different operational factors affect pollutant degradation, such as the initial pollutant concentration (50–200 mg/L), the reaction volume (125–500 mL), and the H₂O₂:monomer mass ratio (0:1–6:1 for BHET and 0:1–4:1 for TPA). For BHET, the best results occurred with a 5:1 mass ratio, while TPA degraded optimally with a 3:1 ratio, with a 250 mL reaction volume and a 100 mg/L initial concentration for both compounds. Under these conditions, total degradation of the initial monomers was achieved in around 30 and 80 min for BHET and TPA, respectively, and at the end of the reaction, COD decreased by 46% and 32% relative to their initial values. In both cases, hydrogen peroxide was crucial since UV radiation alone led to much lower degradation efficiency. These results emphasize the need to optimize operational conditions for greater efficiency and establish a starting point for future use of excimer technology in the treatment of wastewater contaminated with PET and its derivatives. Additionally, the degradation data closely matched a pseudo-first-order kinetic model (R² ≈ 1), confirming its reliability for predictive analysis, which is of high importance for the simulation and optimization of the process. Full article

The presence of various drugs in wastewater has generated growing concern about the contamination of water bodies. This requires urgent attention and the development of effective methods for their degradation in aquatic ecosystems. The present study evaluates the efficiency of metformin (MET) degradation via various photochemical processes—photolysis, H₂O₂ photodecomposition, photocatalysis, and photo-Fenton—using iron-pillared bentonite clays (Fe-PILC) as a catalyst. The influence of radiation wavelength (254 nm and visible light) was investigated, while MET degradation, H₂O₂ consumption, and total organic carbon (TOC) removal were monitored as key response variables. Structural characterization confirmed successful pillaring, increasing the surface area of bentonite from 35 to 246 m²/g, with iron content at 11 wt. % quantified by atomic absorption spectroscopy. Fe₃O₄ and FeO were identified using XPS, and a 2.08 eV band-gap energy was revealed via diffuse reflectance spectroscopy. Experiments were conducted at environmentally relevant MET concentrations (13,000 ng L⁻¹) in a 0.1 L batch photoreactor at 25 °C. The results demonstrate that (i) photo-Fenton was the most efficient process to remove and mineralize MET (100% degradation after 10 min and 83% mineralization after 90 min); (ii) Fe-PILC is effectively activated at λ < 700 nm, enabling 75% mineralization under visible light; (iii) hydroxyl radicals and valence band holes were the primary oxidative species driving MET oxidation; and (iv) cyanoguanidine and carboxylic acids were identified as main oxidation by-products via UHPLC. Pseudo-first-order kinetic constants were determined for all processes, offering insight into their relative efficiencies. Notably, the rate constant for photo-Fenton under visible light (0.406 min⁻¹) was comparable to that under UV -light (0.545 min⁻¹), highlighting the potential of visible light-driven treatments. Therefore, this study demonstrated the metformin degradation capability of iron-pillared clays under both visible and UV light. Full article

This study explores a hybrid advanced electrochemical oxidation process (EAOP) intensified by solar irradiation and ozone for the treatment of wastewater containing COVID-19-related pharmaceuticals. Pilot-scale trials were performed in a 30 L compound parabolic collector (CPC)-type photoreactor with a boron-doped diamond (BDD–BDD) electrode configuration. Under optimal conditions (50 mg L⁻¹ paracetamol, 0.05 M Na₂SO₄, 0.50 mM Fe²⁺, pH 3.0, and 60 mA cm⁻²), the solar photoelectro-Fenton (SPEF) process achieved 78% chemical oxygen demand (COD) reduction within 90 min, with catechol and phenol detected as the main aromatic intermediates. When applied to a four-drug mixture (dexamethasone, paracetamol, amoxicillin, and azithromycin), the solar photoelectro-Fenton (SPEF–ozone (O₃)) system reached 60% degradation and 41% COD removal under solar conditions. The results highlight the synergistic effect of ozone and solar energy in enhancing the electrochemical oxidation process (EAOP) performance and demonstrate the potential of these processes for scalable and sustainable removal of pharmaceutical contaminants from wastewater. Full article

In this work, the photocatalytic reduction of CO₂ was innovatively tested with the simultaneous removal and mineralization of a textile contaminant, methylene blue (MB), which acts as a sacrificial agent. The process was carried out in a flow regime under atmospheric conditions, using a liquid-phase photoreactor under UVA illumination with a duration of 24 h per test. Two commercial TiO₂-based photocatalysts, P25 and P90 from Evonik, were used and surface modified through the photodeposition of metallic nanoparticles of Pt, Au, and Pd, as they did not show gas-phase products from CO₂ reduction on their own. The optimal pH was 5, the decreasing order of activity by metal was Pt > Au > Pd, and the optimal MB concentration was 20 ppm. The major products were CH₄ and H₂ in the gas phase. The presence of CH₄ was only detected in the presence of a CO₂ flow. In the liquid phase, carboxylic acids were also detected in small amounts, and in the test, 100 ppm of MB ethanol was additionally detected. A 100% degradation of MB and 72.5% mineralization was achieved under the conditions of highest CH₄ production (20 ppm MB at pH 5 with 4 g·L⁻¹ P25-0.70%Pt). Full article

Conventional wastewater treatment plants (WWTPs) have limited efficiency in removing emerging pollutants (EPs), meaning these pollutants persist and lead to widespread ecological contamination. In this study, real effluents from a WWTP were characterized using TOC and Py-GC/MS, which indicated the presence of various organic compounds that could be indicative of micro-nanoplastics (MNPs) or plastics additives. To address this challenge, we propose the use of a photocatalytic membrane reactor (PMR) as an advanced treatment system capable of achieving high degradation efficiency under mild operating conditions. Preliminary experimental tests were conducted using various commercial photocatalysts (TiO₂, WO₃, Nb₂O₅), four UV lamps, and oxidants (air, O₂) using added Gemfibrozil (GEM) as a drug model compound. Real effluent samples collected from WWTP were tested with and without pretreatment to remove coarse particles prior to photocatalysis. Mineralization was achieved in both cases, but it occurred at a higher rate for the pretreated effluent. The mineralization of GEM and EPs in real effluent was achieved within five hours under UV irradiation using titanium dioxide (TiO₂) as a low-cost photocatalyst in a PMR. The results highlight the potential of photocatalytic systems, and particularly PMRs, as a promising technology for removing recalcitrant pollutants in real effluents offering a viable solution for improved environmental protection. Full article

This study explores the visible-light-driven photolysis of Ferrioxalate complexes for the degradation of Toluidine Blue (TB), a persistent phenothiazine dye, using a 1 L recirculating batch-loop photoreactor. The reactor system incorporated two tubular photochemical units (35 cm × 3 cm each) in series: the first equipped with an immersed blue fluorescent lamp (12 W, 30 cm-tube), and the second with dual external blue LED lamps (18 W total, 30 cm) encasing a double-walled glass cell. Continuous flow between the units was maintained via a peristaltic pump. Experimental investigations were used to evaluate the effects of key parameters such as Fe(III) and oxalate concentrations, initial TB load, pH, light source, flow rate, ligand type, dissolved gas type, external H₂O₂ addition, and the presence of various inorganic ions. The results demonstrate efficient dye degradation, with ~75% TB removal within 1 h under combined fluorescent and LED irradiation, where each reactor contributing comparably. The optimal performance was achieved at pH 4, with a 10 oxalate-to-Fe(III) molar ratio (1 mM:0.1 mM) and a flow rate of 25 mL s⁻¹. Among various ligands tested (oxalate, acetate, citrate, EDTA), oxalate proved to be the most effective. The presence and type of anions significantly influenced degradation efficiency due to their potential scavenging effects. Although the process achieved high dye removal, TOC analysis indicated only moderate mineralization, suggesting the accumulation of non-colored intermediates. External H₂O₂ addition moderately improved TOC removal, likely due to enhanced hydroxyl radical generation via the Fenton mechanism. These findings highlight the promise of Ferrioxalate-based photochemical systems under visible light for dye removal, while also emphasizing the need for further research into by-product identification, mineralization enhancement, and toxicity reduction to ensure safe effluent discharge. Full article

Pyridine is a recalcitrant organic compound present in industrial wastewater that causes severe effects on the environment and the health of living beings, as it is considered a toxic, mutagenic, teratogenic, and carcinogenic agent. Therefore, this research explored the efficacy of a zinc oxide catalyst, doped with platinum nanoparticles and supported alumina through the precipitation method, for the photocatalytic degradation of pyridine using a fluidized bed reactor. A Box–Behnken experimental design was used to analyze the effect of the pH (4–10), the pyridine concentration (20–300 ppm), and the amount of catalyst (20–100 g). The X-ray diffraction (XRD) characterization results confirmed the hexagonal structure of the zinc oxide and the successful incorporation of platinum. Scanning electron microscopy (SEM) revealed a nano-bar morphology upon catalyst doping, favoring the photocatalytic activity. Pyridine removal of 57.7% was achieved under the following conditions: a pH of 4, 160 ppm of pyridine, and 100 g of catalyst. The process followed a pseudo-first-order model, obtaining the reaction constant k₁ = 1.943 × 10⁻³ min⁻¹ and the adsorption constant k₂ = 1.527 × 10⁻³ L/mg. The results showed high efficiency and stability of the catalyst in the fluidized bed reactor for pyridine degradation, especially under acidic conditions, representing a promising technological alternative for treating industrial wastewater contaminated with N-heterocycles such as pyridine. Full article

The development of three types of UV radiation-based photoreactors using light-emitting diodes (LEDs) is presented. In this work, three pattern irradiation arrangements, direct radiation, internal radiation, and external radiation, were tested for deactivation of a typical model contaminant in wastewater under the same conditions. All photoreactors allow the adjustment of optical power and irradiation time and include a sensor for temperature monitoring in the solution. In this case, phenol was used as a model contaminant with TiO₂ as a photocatalyst in a batch-type reactor at pH 7. The results showed that the highest degradation efficiency was achieved after 120 min, reaching 97.79% for the internal-radiation photoreactor, followed by 90.17% when the direct-radiation photoreactor was used, and 85.24% for the external-radiation photoreactor. Phenol degradation served as the basis for validating reactor performance, given its persistence and relevance as an indicator in advanced oxidation processes. It was concluded that the arrangement of LEDs in each photoreactor significantly influences phenol degradation under the same reaction conditions. Full article

This work analyzes the performance of a photoreactor built with UV-LED technology. For this task, a UV-LED wavelength of 365 nm was used as an irradiation source, and it was electrically and spectrally characterized to ensure correct operation. To evaluate the functionality, the photoreactor was tested on the degradation of Rhodamine B (Rh B), a dye commonly used in the textile industry. The experiment was conducted under optimal conditions, using a concentration of 17 ppm of Rh B and 100 mg of zinc oxide (ZnO) as a photocatalyst in a glass reactor. The mixture was continuously stirred for 120 min, achieving 99.42% efficiency. The results showed that the UV-LED photoreactor performs well in activating ZnO for the removal of Rh B from the solution, highlighting its potential for treating textile industry wastewater. The use of LEDs offers advantages such as energy efficiency and lower environmental impact compared to traditional UV lamps. ZnO, known for its reactivity under UV light, acted as a stable photocatalyst, ensuring complete degradation of the dye without producing harmful by-products. This method provides an efficient approach to dye removal in wastewater treatment, promoting cleaner and more sustainable industrial practices. Full article