Search Results (38)

Recently, aquatic life and human health are seriously threatened by the release of pharmaceutical drugs. For a sustainable ecosystem, emerging contaminants like antibiotics must be removed from drinking water and wastewater. To address this issue pure and cerium-doped titanium dioxide (CeT) nanoparticles were produced with stable tetragonal (anatase) lattices by room temperature sol–gel method and employing the inorganic titanium oxysulfate (TiOSO₄) as titanium precursor. The structural analysis by X-ray diffraction (XRD) revealed that at calcination temperature of 600 °C all (un and doped) powders were composed of crystalline anatase TiO₂ with the crystallite sizes in the range of 13.5–11.3 nm. UV–vis DRS spectroscopy revealed that the most narrowed bandgap value of 2.75 eV was calculated for the 0.5CeT sample containing the optimum dopant content of 0.5 weight ratio. X-ray spectroscopy (XPS) confirmed the presence of the impurity level Ce³⁺/Ce⁴⁺, which became responsible for the decrease in bandgap as well as for the photoinduced carriers recombination rate. Photocatalytic tests showed that the maximum decomposition of the model spiramycin (SPR) antibiotic pollutant was 88.0% and 77.0%, under UV and visible light, respectively. According to the reaction kinetics, SPR decomposition adhered to the Langmuir–Hinshelwood (L–H) model and via ROS experiments mainly hydroxyl radicals (OH^•) followed by photogenerated holes (h⁺s) become responsible for the pollutant degradation. In summary, this study elaborates on the role of xCeT nanoparticles as an efficient photocatalyst for the elimination of organic contaminants in wastewater. Full article

Ferrous oxalate dihydrate (α-FOD) was synthesized from Ecuadorian black sands for phenol removal from aqueous solutions. Visible light-driven photodegradation kinetics were studied by varying the initial pollutant concentration, solution pH, and α-FOD dosage and by adding peroxydisulfate (PDS), including quenching tests. A representative model of phenol photodegradation was obtained by the Langmuir–Hinshelwood mechanism over a large range of concentrations (apparent kinetic constant, k = 0.524 h⁻¹). Almost complete removal was reached within 1 h under dark + 9 h under visible irradiation. The degradation rate was slightly affected by pH in the range of 3 to 9, with a significant improvement at pH 11 (k = 1.41-fold higher). The optimal α-FOD dosage was ~0.5 g/L. Two regimes were observed when using PDS: first, a heterogeneous Fenton-like process during the first few minutes after PDS addition; second, pure photocatalysis to completely remove the phenol. When comparing the two systems, without and with PDS, the half-life time for pure photocatalysis was 2.5 h (after the lamp was switched on). When adding PDS (1.0 mM), the half-life time was reduced to a few minutes (5 min after PDS addition, phenol removal was 66%). The photocatalyst presented remarkable degradation efficiency up to five repeated cycles. Full article

Ensuring effective water purification is essential for addressing freshwater scarcity and achieving the United Nations Sustainable Development Goals (SDGs). An efficient hybrid mixture, composed of FeCr quantum dots doped into mesoporous silica SBA-15 support and activated carbon (AC) derived from olive mill solid wastes, has been developed for treating high optical density polluted aqueous environments. This hybrid, denoted as FeCr-SBA-15/AC, was examined for its efficacy in the adsorption and photo-Fenton degradation of met orange dye (MO), a model high-optical-density pollutant, under visible light exposure. Characterization of the prepared samples was conducted using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) surface area analysis, diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Key parameters investigated included catalyst dosage, dye concentration, solution pH, and H₂O₂ concentration. Remarkably, the FeCr-SBA-15/AC hybrid exhibited superior photocatalytic activity, achieving a degradation efficiency of 97% for MO under optimized conditions (catalyst dosage = 0.75 g L⁻¹, dye concentration = 20 mg L⁻¹, pH = 5.47, and 0.5 mL H₂O₂) after 180 min of irradiation with visible light. This performance surpassed that of FeCr-SBA-15 alone by 20%, due to the synergistic effects of adsorption and photo-Fenton. The adsorption of MO onto AC followed the Freundlich model equilibrium isotherm, while the experimental data for the hybrid mixture aligned well with the pseudo-first-order Langmuir–Hinshelwood kinetic model with a rate constant of 0.0173 min⁻¹. The leaching of Cr in the solution was very low—0.1 ppm—which is below the detection limit. These findings underscore the potential of the synthesized FeCr-SBA-15/AC hybrid as a cost-effective, environmentally friendly, and highly efficient photo-Fenton catalyst for treating wastewater contaminated by industrial effluents. Full article

This study presents an efficient and environmentally sustainable synthesis of ZnO nanoparticles using a starch-mediated sol-gel approach. This method yields crystalline mesoporous ZnO NPs with a hexagonal wurtzite structure. The synthesized nanoparticles demonstrated remarkable multifunctionality across three critical applications. In photocatalysis, the ZnO NPs exhibited exceptional efficiency, achieving complete degradation of methylene blue within 15 min at pH 11, significantly surpassing the performance of commercial ZnO. Under neutral pH conditions, the nanoparticles effectively degraded various organic dyes, including methylene blue, rhodamine B, and methyl orange, following pseudo-first-order kinetics. The methylene blue degradation process was aligned with the Langmuir–Hinshelwood model, emphasizing their advanced catalytic properties. For supercapacitor applications, the ZnO NPs attained a high specific capacitance of 550 F/g at 1 A/g, underscoring their potential as energy storage solutions. Additionally, the nanoparticles demonstrated strong UV-induced antiradical activity, with an EC₅₀ of 32.2 μg/mL in DPPH assays. Notably, the cytotoxicity evaluation revealed an LC₅₀ of 1648 μg/mL, indicating excellent biocompatibility. This study highlights a sustainable approach for the synthesis of multifunctional ZnO NPs that offers effective solutions for environmental remediation, energy storage, and biomedical applications. Full article

The wastewater generated by the pharmaceutical industry poses a risk to the environment due to undesirable characteristics such as low biodegradability, high levels of contaminants, and the presence of suspended solids, in addition to the high load of organic matter due to the presence of drugs and other emerging products in the effluent. This study aims to reduce the impact of wastewater pollution by removing amoxicillin (AMO) antibiotics as an organic pollutant. In this concept, two synthesized catalysts, NiAl₂O₄ and ZnO, are sensitive oxides to light energy. The prepared materials were then characterized using X-ray diffraction, UV–vis solid reflectance diffuse, Raman spectroscopy, scanning electron microscopy, BET, and ATR-FTIR spectroscopy. The effects of principal operating parameters under sunlight, namely, the percentage of the mixture of NiAl₂O₄ and ZnO, the pH of the medium, and the initial concentration of the antibiotic were studied experimentally to determine the optimal conditions for achieving a high degradation rate. The results showed that photodegradation is higher at a pH of 6, with a weight percentage of the mixture of 50% for both catalysts in 1 g/L of the total catalyst dose. Then, the effect of the initial concentration of AMO on the photodegradation reaction showed an important influence on the photodegradation process; as the degradation rate decreases, the initial AMO concentration increases. A high degradation rate of 92% was obtained for an initial AMO concentration of 10 mg/L and a pH of 6. The kinetic study of degradation established that the first-order model and the Langmuir–Hinshelwood (LH) mechanism fit the experimental data perfectly. The study showed the success of using heterosystem photocatalysts and sustainable energy for effective pharmaceutical removal, which can be extended to treat wastewater with other organic emerging pollutants. On the other hand, modeling was introduced using Gaussian process regression (GPR) to predict the degradation rate of AMO under sunlight in the presence of heterogeneous ZnO and NiAl₂O₄ systems. The model evaluation criteria of GPR in terms of statistical coefficients and errors show very interesting results and the performance of the model used. Where statistical coefficients were close to one (R = 0.9981), statistical errors were very small (RMSE = 0.1943 and MAE = 0.0518). The results suggest that the model has a strong predictive power and can be used to optimize the process of AMO removal from wastewater. Full article

Community drinking water sources are increasingly contaminated by various point and non-point sources, with emerging organic contaminants and microbial strains posing health risks and disrupting ecosystems. This study explores the use of zinc oxide nanoparticles (ZnO-NPs) as a non-specific agent to address groundwater contamination and combat microbial resistance effectively. The ZnO-NPs were synthesized via a green chemistry approach, employing a sol-gel method with lemon peel aqueous extract. The catalyst was characterized using techniques including XRD, ATR-FTIR, SEM-EDAX, UV-DRS, BET, and Raman spectroscopy. ZnO-NPs were then tested for photodegradation of quinoline yellow dye (QY) under sunlight irradiation, as well as for their antibacterial and antioxidant properties. The ZnO-NP photocatalyst showed significant photoactivity, attributed to effective separation of photogenerated charge carriers. The efficiency of sunlight dye photodegradation was influenced by catalyst dosage (0.1–0.6 mg L⁻¹), pH (3–11), and initial QY concentration (10–50 mg L⁻¹). The study developed a first-order kinetic model for ZnO-NPs using the Langmuir–Hinshelwood equation, yielding kinetic constants of equilibrium adsorption and photodegradation of Kc = 6.632 × 10⁻² L mg⁻¹ and kH = 7.104 × 10⁻² mg L⁻¹ min⁻¹, respectively. The results showed that ZnO-NPs were effective against Gram-positive bacterial strains and showed moderate antioxidant activity, suggesting their potential in wastewater disinfection to achieve sustainable development goals. A potential antibacterial mechanism of ZnO-NPs involving interactions with microbial cells is proposed. Additionally, Gaussian Process Regression (GPR) combined with an improved Lévy flight distribution (FDB-LFD) algorithm was used to model QY photodegradation by ZnO-NPs. The ARD-Exponential kernel function provided high accuracy, validated through residue analysis. Finally, an innovative MATLAB-based application was developed to integrate the GPR_FDB-LFD model and FDB-LFD algorithm, streamlining optimization for precise photodegradation rate predictions. The results obtained in this study show that the GPR and FDB-LFD approaches offer efficient and cost-effective methods for predicting dye photodegradation, saving both time and resources. Full article

The MAP process involved placing acid-pretreated biomass (CPH) in a domestic microwave oven at 600 W for 15 min. This was followed by a doping process with iron salts (+2, +3) to obtain BCCPH-Fe. Characterization of BCCPH-Fe was carried out using surface analysis (BET), TGA analysis and FTIR. Subsequently, the photodegradation process was performed using three different light sources (solar, UV 254 nm and UV 356 nm), with tartrazine as the adsorbate. The effect of pH on photodegradation was studied, and the percentage of degradation was evaluated through equilibrium and kinetic studies. The amount of BCCPH-Fe, tartrazine concentration, and exposure time to the light source were also evaluated. The best conditions for the photodegradation process were: light source was 254 nm, pH of 5, 1 g of BCCPH-Fe over 100 mL of tartrazine, 25 ppm tartrazine concentration, and 40 h exposure time. Under these conditions, a 93.45% removal of tartrazine was achieved. The experimental data of the adsorption equilibrium best fit the Langmuir-Hinshelwood model, while the adsorption kinetics best fit the pseudo-first-order model. The apparent kinetic constant was 0.04053 [h⁻¹], and the correlation coefficient was 0.98667. In conclusion, photodegradation using BCCPH-Fe can be an effective method for the removal of tartrazine from wastewater, offering a sustainable alternative to traditional methods. Full article

This study synthesized NiAl-layered double hydroxide (LDH)/Cu-MOF photocatalyst using a simple impregnation method involving NiAl-LDH and Cu-MOF. The successful synthesis was confirmed through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), zeta potential measurements, thermogravimetric analysis (TGA), ultraviolet diffuse reflectance spectroscopy (UV-DRS), N₂ adsorption at −196 °C, and electrochemical impedance spectroscopy (EIS). Photocatalysts based on NiAl-LDH, Cu-MOF, and NiAl-LDH/Cu-MOF were used to remove methyl orange (MO) dye from contaminated water. The impact of various factors, including pH, dye concentration, and photocatalyst amount, on MO degradation efficiency was assessed. FTIR analysis was conducted both before and after dye degradation. The optimal degradation conditions were a photocatalyst dose of 25 mg and a pH of 3. Kinetic studies indicated that the degradation of MO dye onto NiAl-LDH/Cu-MOF followed a pseudo-first-order and an L–H or Langmuir–Hinshelwood model. The value of R² = 0.94 confirms the validity of pseudo-first-order and Langmuir–Hinshelwood (L–H) kinetic models for the photocatalytic degradation of MO dye. This study highlights the importance of developing novel photocatalysts with improved degradation efficiency to protect the water environment. Antibacterial activity was also performed with antibacterial sensibility testing by disk diffusion to determine minimal inhibitory and bactericidal concentrations. In short, NiAl-LDH/Cu-MOF can be helpful for various biomedical and industrial applications. Full article

A green synthesis method for producing zinc oxide nanoparticles (ZnO NPs) was presented using natural Gum Arabic (GA) as a natural stabilizing agent. For the first time, the as-synthesized ZnO NPs were employed to photodegrade the toxic Congo Red (CR) dye in an aqueous solution. The structural and morphological characterizations confirmed the successful synthesis of ZnO NPs. The ZnO NPs possessed an average crystallite size of 42.7 nm. In addition, it was found that a concentration of 20 mg L⁻¹ of CR dye yielded the most favorable photodegradation results, and 4 mg mL⁻¹ of the photocatalyst was the optimal amount. The results showed a maximum degradation percentage of 99.5% at pH 8 after 30 min of irradiation. This indicates that the as-synthesized ZnO NPs have remarkable photocatalytic properties. Moreover, the study demonstrated the suitability of the pseudo-first-order kinetic model for representing the photodegradation process through kinetic studies of the photocatalyst process of CR dye by ZnO NPs using the Langmuir-Hinshelwood (L-H) model. Full article

Since the signing of the Minamata Convention in 2013, attempts have been primarily focused on reducing the emission of elemental mercury (Hg⁰) from coal-fired power plants (CFPPs). The most cost-effective measure for controlling the emission of mercury involves oxidizing Hg⁰ to mercury oxides, which are then removed using wet flue gas desulfurization (WFGD). Thus, novel photocatalysts with the best properties of photocatalytic ability and thermal stability need to be developed urgently. In this study, titanium dioxide (TiO₂)-based photocatalysts were synthesized through the modification of three metal oxides: CuO, CeO₂, and Bi₂O₃. All the photocatalysts were further characterized using X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and ultraviolet-visible spectrometry. The photocatalytic oxidation efficiencies of Hg⁰ were evaluated under an atmosphere of N₂ + Hg⁰ at 100–200 °C. The photocatalytic reactions were simulated by kinetic modeling using the Langmuir–Hinshelwood (L–H) mechanism. The results showed that Bi₂O₃/TiO₂ exhibited the best thermal stability, with the best oxidation efficiency at 200 °C and almost the same performance at 100 °C. L–H kinetic modeling indicated that photocatalytic oxidation reactions for the tested photocatalysts were predominantly physical adsorption. Additionally, the activation energy (E_a), taking into account Arrhenius Law, decreased dramatically after modification with metal oxides. Full article

Chlorobenzene (CB) and Chloronaphthalene (CN) emissions from cement plant operations pose significant environmental risks. This study investigates the mass transfer effects of chlorinated aromatic Volatile Organic Compounds (VOCs), specifically CB and CN, in the gas phase of a continuous-tangential-flow annular photocatalytic reactor. The experiments involved introducing CB and CN into the reactor, and the degradation kinetics were analyzed using the Langmuir–Hinshelwood (L-H) model. The L-H model was applied to assess the impact of the flow rate, concentration, and relative humidity (% RH) on the degradation rate (DR). The results indicate that both the experimental and simulated degradation rates improved with increased flow rates (1 to 9 m³·h⁻¹) and inlet concentrations (30 to 216 mg·m⁻³). This enhancement of the DR correlates with the availability of active OH* species on the TiO₂ surface. The L-H model emphasizes the role of H₂O molecules in VOC removal kinetics. The degradation rates increased with a rising water content (5 to 55%), but adverse effects on VOC conversion were observed beyond a 55% RH. This study reveals a mass transfer effect, with internal diffusional limitations in the TiO₂ pores under operational conditions. The kinetics were predominantly controlled by chemical kinetics and catalyst pore availability. Furthermore, this study demonstrates a higher CB degradation than CN in the reactor and experimental conditions. For a concentration of 1.328 mM·m⁻³, the CB DR ranged from 0.70 to 2.84 µM·m²·s⁻¹, as the flow rate varied from 1 to 9 m³·h⁻¹. The CN DR varied from 0.60 to 2.20 µM·m²·s⁻¹ within the same flow rate range. Full article

Humic acid (HA), the most highly prevalent type of natural organic matter (NOM), plays an effective role in the generation of disinfectant byproducts such as trihalomethanes and haloacetic acid, which are well known to be definitive carcinogens. Therefore, the proactive elimination of HA from water and wastewater is a crucial means of preventing this pollutant from reacting with the chlorine incorporated during the disinfection process. This study investigated the UV light photocatalytic elimination of HA, employing a bentonite@Fe₃O₄@ZnO (BNTN@Fe₃O₄@ZnO) magnetic nanocomposite. The most significant variables pertinent to the photocatalytic degradation process examined in this work included the pH (3–11), nanocomposite dose (0.005–0.1 g/L), reaction time (5–180 min), and HA concentration (2–15 mg/L). The synthesized materials were characterized via field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating-sample magnetometer (VSM) techniques, all of which revealed outstanding catalytic properties for the BNTN@Fe₃O₄@ZnO. The conditions under which greater efficiency was achieved included a pH of 3, a nanocomposite dose of 0.01 g/L, and an HA concentration of 10 mg/L. Under these conditions, in just 90 min of photocatalytic reaction, an HA degradation efficiency of 100% was achieved. From the modeling study of the kinetic data, the Langmuir–Hinshelwood model showed good compliance (R² = 0.97) with the empirical data and predicted values. Thus, it can be concluded that the BNTN@Fe₃O₄@ZnO catalyst acts very efficiently in the HA removal process under a variety of treatment conditions. Full article

The photoelectrocatalytic degradation and mineralization of sulfamethazine (SMT), a sulfonamide drug, were explored in aqueous solution. Working electrodes with TiO₂ coatings on Ti substrates (TiO₂/Ti) were used, which were produced by the dip coating method. TiO₂ film electrodes were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) following annealing at 500 °C for 1.5 h. To photoelectrochemically characterize them, photocurrents vs. applied potential curves were used. The photoelectrocatalytic efficiency (PEC) of the TiO₂/Ti electrodes regarding the oxidation of SMT has been assessed with reference to degradation and mineralization under different experimental conditions. The selected drug molecule was effectively degraded following the Langmuir–Hinshelwood (L-H) kinetic model. The degradation efficiency was shown to increase with increasing applied potential bias up to +1.5 V vs. Ag/AgCl. It was found to be more favorable in acidic environments compared to alkaline ones. A decrease in the destruction rate constant was recorded when the pH was increased from 3 to 5.6 (natural pH) and 9. The decomposition rate was shown to first increase and subsequently reach a saturation value at high concentrations of SMT, indicating that the degradation also depends on other parameters (e.g., the rate of the charge or the mass transfer on the electrode double layer). The results of the photoelectrocatalytic experiments were compared to those of electrochemical (EC) and photocatalytic (PC) degradation of SMT. A significant enhancement was recorded in the case of the PEC degradation, leading at +1.5 V to an increase of the apparent rate constants of degradation, k, and mineralization, k_TOC, of 153 and 298%, respectively, compared to the simple photocatalytic process. Full article

This study investigates the potential of a combined photocatalysis–adsorption approach to effectively degrade near wash yellow (NWY), a commonly used and highly persistent dye in the textile industry, notorious for its challenging treatment and removal from wastewater due to its colorfastness. A chitosan–glycerol (CTiG) film combined with titanium dioxide was examined in both batch and continuous-flow experiments under visible solar irradiation. The results show that this combination was more effective than a pure chitosan film (60%) or chitosan–glycerol film (63%), with up to 83% degradation of NWY achieved in just 60 min of visible solar irradiation. The kinetics of the film were evaluated using both pseudo-first-order and Langmuir–Hinshelwood kinetic models. The rate constant values (k, min⁻¹) decreased with increasing NWY concentration from 20 to 80 mg/L, and k was found to be greater than twice as high under visible solar irradiation as it was in the dark. The Langmuir–Hinshelwood model’s K_LH (reaction rate constant) and K_L (adsorption coefficient) values were 0.029 mg/L·min and 0.019 L/mg, respectively. The optimal conditions for NWY degradation were found to be 4% TiO₂ to chitosan ratio, glycerol/chitosan ratio of 40%, and a pH of 7. In the continuous-flow model, the CTiG film was submerged in an 8 L NWY solution (80 mg/L) and degraded at a rate of 22.6 mg NWY/g film under natural sunlight. This study contributes to the development of effective and sustainable methods for the degradation of dyes from textile industry wastewater. Full article

Pesticide residues, when present in agricultural wastewater, constitute a potential risk for the environment and human health. Hence, focused actions for their abatement are of high priority for both the industrial sectors and national authorities. This work evaluates the effectiveness of the photocatalytic process to decompose two frequently detected pesticides in the water effluents of the fruit industry: thiamethoxam-a neonicotinoid compound and flonicamid-a pyridine derivative. Their photocatalytic degradation and mineralization were evaluated in a lab-scale photocatalytic batch reactor under UV-A illumination with the commercial photocatalyst Evonik P25 TiO₂ by employing different experimental conditions. The complete degradation of thiamethoxam was achieved after 90 min, when the medium was adjusted to natural or alkaline pH. Flonicamid was proven to be a more recalcitrant substance and the removal efficiency reached ~50% at the same conditions, although the degradation overpassed 75% in the acidic pH medium. Overall, the pesticides’ degradation follows the photocatalytic reduction pathways, where positive charged holes and hydroxyl radicals dominate as reactive species, with complete mineralization taking place after 4 h, regardless of the pH medium. Moreover, it was deduced that the pesticides’ degradation kinetics followed the Langmuir-Hinshelwood (L-H) model, and the apparent rate constant, the initial degradation rate, as well as the L-H model parameters, were determined for both pesticides. Full article