Apparent Kinetic Constants Research Articles

Kinetics of continuously catalyzed peroxymonosulfate in a fixed-bed reactor

Most studies have been conducted in batch reactors. Therefore, understanding the catalytic reaction kinetics and mass transfer in continuous catalytic reactors is essential for the design of heterogeneous catalysts and optimisation of catalytic degradation processes in heterogeneous systems. In this research, granular catalysts (Co-600/AlSi-0.25/AP) is used to investigate the kinetic constants and mass transfer resistance for the continuous catalytic decomposition of peroxymonosulfate (PMS) and degradation of p-nitrophenol (PNP) in a fixed bed reactor. The flow rate is 5 mL/min and reaction temperature is 30 °C, intrinsic kinetic constants of PMS decomposition and PNP degradation are 48 and 195 kg−1·min−1·L, respectively, which are 20–30 times of the apparent kinetic constants of PMS decomposition and PNP degradation in fixed bed reactors, respectively. The decomposition rates of PMS and PNP are controlled by mass transfer, and the reaction takes place in the diffusion-controlled regime. The mass transfer kinetic model based on the plug-flow model shows a good agreement between the calculated data and the experimental data. Which indicate that PMS decomposition and pollutant degradation in a fixed-bed reactor can be predicted by mass transfer kinetic modelling, guide the design of catalysts and the optimisation of heterogeneous catalytic reaction system in a fixed-bed reactor.

Adsorption Performance and Photocatalytic Activity of La-TiO2@kaolin Composites

Abstract La-TiO2@kaolin(LTK) composites were prepared via sol-gel method with kaolin, lanthanum nitrate and tetrabutyl titanate as raw materials. The samples were characterized by XRD, SEM/EDS, and UV-Vis. The visible light photocatalytic reduction activity and adsorption performance of samples for Cr(VI) were studied. The results showed that La doping can refine TiO2 grains, stabilize phase structure of anatase TiO2, and expand its absorption spectrum, thereby enhancing its photocatalytic reduction activity. Due to the composite of kaolin, the dispersion of TiO2 is improves and it is endowed with a large specific surface area lead to enhance its adsorption ability for Cr(VI). The adsorption equilibrium process of LTK for Cr(VI) conforms to the Langmuir equation model. The coupling effect of doping and composite modification improves the adsorption and visible light catalytic reduction activity of Cr(VI) over composite material samples. The adsorption-photocatalytic removal rate of LTK for Cr(VI) under visible light irradiation for 6 hours reached the highest of 96.5%. The apparent first-order kinetic constant of its photocatalytic reduction reaction was 2.6 times that of pure TiO2.

Self‐cleaning films of biopolymer polyhydroxybutyrate with different semiconductors incorporation: Development, characterization, and photocatalytic activity evaluation

AbstractSelf‐cleaning hydrophobic films were developed using polyhydroxybutyrate (PHB), enhanced with titanium dioxide (TiO2), bismuth oxyiodide (BiOI), and a BiOI/α‐Fe2O3 heterojunction. This is the first study to analyze the photoactivity of BiOI and BiOI/α‐Fe2O3 immobilized into PHB. Alternative solvents for dissolving PHB were investigated. Additionally, formation methods such as casting in Petri dishes, as well as controlled thickness casting through non‐solvent‐induced phase separation (NIPS), and evaporation‐induced phase separation (EIPS), were employed and compared. Despite differing morphologies, both NIPS and EIPS films exhibited similar photocatalytic activity, suggesting that only the catalyst on the external surface of the film is active. The highest pseudo first‐order apparent kinetic constant (0.1468 ± 0.0015 min−1 g−1) was found in films with the lowest polymer and catalyst concentrations analyzed (5% and 3% ). A double‐layer film preparation method was proposed to enhance photocatalytic activity, resulting in a 70% increase in the kinetic constant (0.2506 ± 0.0019 min−1 g−1). Double‐layer composite films with BiOI and BiOI/α‐Fe2O3 showed photocatalytic activity comparable to TiO2 under UV–visible light. Furthermore, their photocatalytic activity under visible light was confirmed, unlike TiO2, which exhibits a negligible kinetic constant in this wavelength range.

MoS2 nanosheets wrapped magnetic foamed recycled glass (NMG) for efficient photo-Fenton degradation of tetracycline: Sustainable mindset of “treating waste with waste”

Every year, tens of millions of tons of waste glass are buried on-site, causing serious resource waste and challenging environmental problems. Therefore, dealing with the problem of waste glass is a technical challenge with important economic significance. We used waste glass as a precursor to obtain foam recycled glass and then used a simple impregnation method to obtain magnetic foamed recycled glass (MG) and MoS2 nanosheets wrapped magnetic foamed recycled glass (NMG). Subsequently, we established an excellent NMG/H2O2 system for the efficient degradation of tetracycline (TC) under low-power light sources. The NMG/H2O2 system has a 92.2% removal rate of TC, accompanied by the apparent reaction kinetic constant is 0.01865 min−1. Meanwhile, the degradation mechanism of ·OH and 1O2 as the main active species was determined. Finally, the theoretical reaction sites of TC in the NMG/H2O2 system were obtained through density functional theory (DFT) calculation. The theoretical reaction sites were consistent with the reaction sites in the possible degradation pathways we obtained through the degradation fragment. In our work, we approach environmental issues with a “treating waste with waste” mindset, which combines economic and environmental considerations and may become the mainstream mindset in future environmental treatment.

Photocatalytic Degradation of Losartan with BiOCl/Sepiolite Nanocomposites

Developing highly active and available, environmentally friendly, and low-cost photocatalytic materials is one of the most popular topics in photocatalytic degradation systems. In the present study, a series of BiOCl/Sepiolite composite photocatalysts were prepared (in the range of 5%BiOCl/Sepiolite–30%BiOCl/Sepiolite). Their characterization was conducted using X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, nitrogen physical physisorption at the temperature of liquid nitrogen (77 K), and attenuated total reflectance-Fourier transform infrared spectroscopy. Results showed that composite photocatalysts possess superior efficiency than the parent materials for losartan, an antihypertensive agent, degradation in water, with the sample with only 10%wt. BiOCl shows the highest performance. The beneficial effect of the addition of sepiolite to BiOCl is derived from the increase in surface area, the prevention of particle aggregation, and the efficient separation of photogenerated species. Increasing catalyst concentration from 125 mg/L up to 500 mg/L was accompanied by an increase in the apparent kinetic constant from 0.077 min−1 to 0.197 min−1 while varying losartan concentration from 0.25 to 5.00 mg/L slowed down the removal efficiency. In addition, losartan degradation was only partially hampered in the case of bottled water, whereas it was practically stopped in a secondary wastewater effluent. Overall, this study serves as a useful guide for using geopolymers in photocatalytic applications.

Rational design of g-C3N4-based photocatalysts with intramolecular donor-acceptor structures for deep oxidation of emerging organic micropollutants

An in-situ route for the fabrication of intramolecular electron donor-acceptor (D-A) structured g-C3N4 photocatalysts is developed by the preorganization of urea with the precursor of electron donor units, such as 4-iodobenzaldehyde, 5-bromo-2-thiophenaldehyde and 5-bromo-2-furaldehyde, followed by thermal polymerization. In the resulting benzene unit-, thiophene unit- and furan unit-based D-A structured g-C3N4 photocatalysts, namely, BHCNx, SCNx, and OCNx, the incorporated electron donor units (i.e., benzene units, thiophene units and furan units) link with the electron acceptors (i.e., heptazine units) through CN and CN covalent bonds. In comparison of bulk g-C3N4, all D-A structured g-C3N4 display notably enhanced visible-light photocatalytic oxidation activity in the degradation of emerging organic micropollutants, p-nitrophenol (PNP) and methylparaben (MPB), in which the apparent first-order kinetic constant of the optimized BHCN2, SCN2, and OCN2 is 1.6, 3.0 and 6.8 times higher than bulk g-C3N4 for PNP degradation and 1.9, 3.4 and 2.6 times higher than bulk g-C3N4 for MPB degradation. Importantly, the micropollutants can be not only degraded but also mineralized completely. The catalysts are also robust in the removal of mixed emerging organic micropollutants in pharmaceutical wastewater, exhibiting potential of dealing with organic micropollutants in wastewater. Mechanism studies reveal that the unique intramolecular charge transfer process in the catalysts enhances visible-light harvesting capacity, boosts directional transfer of the photogenerated charges and increases adsorption towards oxygen molecules. These collective improvements can maximum utilization the photogenerated electrons and holes to yield plentiful reactive oxygen species for deep oxidization of the pollutants.

A novel dual S-scheme heterojunction photocatalyst KBCN/t-BiVO4/m-BiVO4 induced by phase-transformed bismuth vanadate for highly efficient degradation of ciprofloxacin in full-spectrum: Degradation pathway, DFT calculation and mechanism insight

A novel KBr-g-C3N4/t-BiVO4/m-BiVO4 (15KBCN/mtBVO-P, P means PVP) heterojunction photocatalyst is synthesized using a hydrothermal method with the assistance of surfactant polyvinylpyrrolidone (PVP). Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and X-ray powder diffraction (XRD) confirm the formation of the heterostructure and changes in the crystal structure. Under sunlight illumination, 15KBCN/mtBVO-P exhibits the strongest photocatalytic degradation performance for ciprofloxacin (CIP), reaching 95.3 % within 240 min, the apparent kinetic constant is approximately 3.4, 2.4, and 3.3 times higher than CN, t-BVO, and m-BVO. The outstanding CIP degradation rate is observed under simulated solar and visible light, with over 93.0 % and 85.8 % in 60 min and 120 min. The enhanced photocatalytic performance is attributed to the in-situ generation of the mixed-phase BiVO4 by precise crystal phase regulation. Furthermore, the charge transport and photocatalytic degradation mechanism of 15KBCN/mtBVO-P is revealed. Degradation pathways and ecotoxicity of CIP and its degradation products were elucidated through LC-MS/MS technology, DFT calculations, and QSAR models. This study presents a pioneering perspective on the fabrication and development of g-C3N4-based dual S-scheme heterojunction photocatalysts for practical application.

Novel CQDs/BiOI Microspheres with Gradient Oxygen Vacancies for Efficient Photocatalytic Performance Boosting by the Synergism of Reactive Oxygen and Iodine Species

AbstractThe synergy of reactive oxidative species (ROSs: ⋅OH, ⋅O2− and 1O2) and reactive iodine species (RISs: ⋅I and ⋅I2−) is conclusive to driving organic pollutant degradation in various aquatic environments. Over the past years, rational design of Vis‐NIR responsive photocatalyst with enhanced photocatalytic performance has attracted drawing attention. Herein, CQDs/BiOI composites with up‐conversion photoluminescence (UCPL) properties and oxygen vacancies was constructed for tetracycline (TC) and oxytetracycline (OTC) degradation. The apparent kinetic constant of the 4‐CQDs/BiOI is 2.13 and 2.38 times on pure BiOI. The excellent photodegradation efficiency can be attributed to the enhanced light absorption originated from the up‐conversion property and improved charge separation efficiency. Furthermore, the iodine free radicals (⋅I) and superoxide free radicals (⋅O2−) played a crucial role in the photodegradation procedure. I− from BiOI could be partially oxidized to form ⋅I. At the same time, the electron capture traps formed by Oxygen vacancies can promote the production of ⋅O2−. Remarkably, the removal efficiency of TC and OTC was still maintained at 80 % by 4‐CQDs/BiOI under different water quality conditions due to the synergy of ⋅O2− with ⋅I. This work sheds light on a new treatment for the synergistic degradation of pollutants in complex water by RISs and ROSs.

Nanostructures of Prussian blue supported on activated biochar for the development of a glucose biosensor

This work emphasizes the utilization of biochar, a renewable material, as an interesting platform for anchoring redox mediators and bioreceptors in the development of economic, environmentally friendly biosensors. In this context, Fe(III) ions were preconcentrated on highly functionalized activated biochar, allowing the stable synthesis of Prussian blue nanostructures with an average size of 58.3 nm. The determination of glucose was carried out by indirectly monitoring the hydrogen peroxide generated through the enzymatic reaction, followed by its subsequent redox reaction with reduced Prussian blue (also known as Prussian white) in a typical electrochemical-chemical mechanism. The EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-Hydroxysuccinimide) pair was employed for the stable covalent immobilization of the enzyme on biochar. The biosensor demonstrated good enzyme-substrate affinity, as evidenced by the Michaelis-Menten apparent kinetic constant (4.16 mmol L−1), and analytical performance with a wide linear dynamic response range (0.05–5.0 mmol L−1), low limits of detection (0.94 μmol L−1) and quantification (3.13 μmol L−1). Additionally, reliable repeatability, reproducibility, stability, and selectivity were obtained for the detection of glucose in both real and spiked human saliva and blood serum samples.

Polar peripheral substituent-regulated organic/inorganic hybrid photocatalysts promoting the degradation of phenolic pollutants

Constructing surface hybrid inorganic semiconductor photocatalysts with π conjugated structure is considered as an efficient way to improve the photocatalytic performance. Herein, by using porphyrin as light harvester and electron donor, BiOI as electron acceptor and active center, novel inorganic/organic (porphyrin/BiOI) hybrid photocatalysts with improved performance were prepared using impregnation method in non-covalent way. To explore the effects of porphyrin peripheral substituents on the performance of hybrid photocatalysts, four porphyrin/BiOI hybrids with different polar groups (–COOH, –OH, –NH2, –NO2) on the porphyrin substituents were prepared and their performances in the photocatalytic degradation of four phenolic pollutants were evaluated. All porphyrin/BiOI hybrids showed greatly improved photocatalytic activities compared to BiOI, and TCPP/BiOI hybrid containing –COOH groups was the best one. Under visible light irradiation, TCPP/BiOI could realise 100% photodegradation of 4-chlorophenol (4-CP) within 60 min, whose apparent kinetic constant was about 9.4 times that of BiOI. Substantial experimental results and theoretical calculation suggest that the different photocatalytic performances of the porphyrin/BiOI hybrids containing different porphyrin peripheral groups (–NO2 < –NH2 < –OH <–COOH) are highly correlated with the orientation of the dipole moment and the polarity of porphyrin substituent. This work illustrates that fine-tuning of the sensitizer molecular structure is essential to improve the photocatalytic activity of organic molecule-sensitized semiconductors.

Influence of visible light LEDs modulation techniques on photocatalytic degradation of ceftriaxone in a flat plate reactor

In this paper, the effect of light modulation on photocatalytic ceftriaxone (CEF) degradation in aqueous solution was investigated. The experimental set-up consisted of a fixed bed photocatalytic reactor with a flat plate geometry and visible LEDs for irradiation. Fe-N-codoped TiO2 photocatalyst was immobilized on a polystyrene plate (PS) by solvent casting method to achieve a structured photocatalyst (Fe-N-TiO2/PS), which was loaded in the photoreactor. Raman and UV–Vis diffuse reflectance spectroscopy confirmed the presence of Fe-N-TiO2 on the PS surface and its uniform distribution on the polymer support. Various LEDs dimming techniques were tested with fixed and variable duty-cycle values. In particular, the following modulations were used: fixed duty-cycle (FD), sinusoidal variable duty-cycle (S-VD), triangular variable duty-cycle (T-VD), square wave variable duty-cycle (SW-VD), saw-tooth variable duty-cycle (ST-VD), pulse variable duty-cycle (P-VD), and pseudo-sinusoidal variable duty-cycle (PS-VD). The optimal light modulation was the S-VD, with an average fed current between 25 and 75 mA and a period of 30 s. Indeed, by using S-VD modulation, the highest value of the apparent CEF degradation kinetic constant (resulting 0.0082 min−1) and the highest total organic carbon (TOC) removal (70 %) were achieved. By comparing the electric energy consumption (EE/O) with S-VD modulation used in this work with those found in other literature studies dealing with the photocatalytic ceftriaxone degradation, a significant decrease of EE/O was evidenced. Moreover, toxicity test showed that the photocatalytic treatment allowed to significantly reduce the toxicity of CEF solution when compared to untreated effluent.

Sliver-doped α-MnO2 to enhance peroxymonosulfate activation for efficient degradation of sulfamethoxazole: Cooperation between radical and non-radical mechanisms

The application of metal doping has emerged as a prominent approach for modifying transition-metal-based heterogeneous catalysts in activating peroxymonosulfate (PMS). Herein, silver-doped α-MnO2 (Ag-α-MnO2) was synthesized via a one-step hydrothermal approach and utilized for activating PMS to degrade sulfamethoxazole (SMX). The catalyst was systematically characterized and examined to determine that the efficientdispersionof Ag increased thespecific surface area and pore volume of α-MnO2. The degradation experiments demonstrated that SMX could be efficiently degraded by a combination of PMS and Ag-α-MnO2 within 60 min. The apparent kinetic rate constant was 0.039 min−1, which was approximately ten times higher than that of α-MnO2. The impacts of external water conditions on catalytic performance and the stability of Ag-α-MnO2 were subsequently investigated. Density functional theory calculations revealed that Ag as a crucial active center reduced the PMS adsorption energy, promoted electron transfer, and orchestrated electron distribution. EPR spectra, quenching experiments, electrochemical tests, and XPS analysis were performed to validate the radical and non-radical mechanisms, including SO4−, OH, O2− and 1O2. The two redox cycles of Ag+/Ag0 and Mn4+/Mn3+ on the surface of Ag-α-MnO2 contributed to the activation of PMS. Additionally, probable degradation pathways for SMX were presented. This study provides an initially valuable insight into the cooperative mechanism of PMS activation for SMX degradation employing Mn-based catalysts doped with precious metal silver.

Kinetic constants and transformation products of ornidazole during ozonation

Ornidazole (ONZ), a nitroimidazole antibiotic detected in water bodies, may negatively impact the aquatic ecosystem. Its reaction kinetics during ozonation which is a feasible and applicable technology to control the contamination of emerging contaminants, however, has not been reported in literature. In this study, we measured the apparent second-order kinetic constant of ONZ with ozone molecules via the excessive ozone method and the competing method which led to an average value of 103.8 ± 2.7 M−1 s−1 at pH 7. The apparent second-order kinetic constant of ONZ with HO• was calculated to be 4.65 × 109 M−1 s−1 with the concept of Rct measured via para-chlorobenzoic acid as a probe. The transformation products (TPs) of ONZ during ozonation at pH 3 and pH 11 were separately analyzed with HPLC-MS/MS and some unique products were found at pH 11, reflecting the influence of HO•. The toxicity of individual TPs was predicted with the tool of T.E.S.T. It was found that 62% of 21 identified TPs could be more toxic than ONZ in terms of at least one acute toxicity endpoint, including chlorinated amines and N-oxides. The analysis with a respirometer further revealed that the toxicity of mixing TPs generated at HO• rich conditions was slightly lower than O3 dominated conditions. In general, this study provides the basic kinetic data for designing ozonation processes to eliminate ONZ and the important reference for understanding the toxicity evolution of ONZ during ozonation.

The role of 2‐iminopyrrolyl copper(I) complexes in the Reversible‐Deactivation Radical Polymerization of methyl methacrylate

The role of 2‐iminopyrrolyl copper(I) complexes in the Reversible‐Deactivation Radical Polymerization (RDRP) of methyl methacrylate (MMA) is described. Mononuclear 2‐iminopyrrolyl copper(I) complexes [Cu{κ2N,N′‐NC4H3‐2‐C(H)=NR′}Ln] 1–7 (R′ = C6H5, Ln = (PPh3)2 (1); R′ = 2,6‐Me2C6H3, Ln = (PPh3)2 (2); R′ = 2,6‐iPr2C6H3, Ln = (PPh3)2 (3); R′ = 4‐NMe2C6H4, Ln = (PPh3)2 (4); R′ = CH3, Ln = (PPh3)2 (5); R′ = CH3, Ln = (PMe3)2 (6); R′ = CH3, Ln = PiPr3 (7)) were synthesized by the reaction of the in situ prepared sodium salts of precursors HL1–5 with [Cu(NCMe)4]BF4 with the respective phosphines. In their absence, the binuclear complex [Cu{κN,κN'‐NC4H3‐2‐C(H)=NCH3}]2 8 was formed instead, which, when treated with one equivalent of PR3 yielded the binuclear complexes [Cu2{κN,κN'‐NC4H3‐2‐C(H)=NCH3}2PR3] 9 (R = Ph) and 10 (R = Me).All complexes, except 8, were active in the RDRP of MMA using the initiator tert‐butyl‐α‐bromoisobutyrate (tBiB‐Br), achieving apparent propagation kinetic constants (kp') in the range of 0.5–7.5 × 10−5 s−1, at 90 °C and with a [MMA]0:[complex]0:[tBiB‐Br]0 ratio of 500:1:1. All reactions yielded poly (methyl methacrylate)s with molecular weights ( ) and dispersities higher than expected for Controlled Radical Polymerization processes. Complex 7 achieved the best results, with values being only 1.2‐fold higher than theoretically expected. Experimental and density functional theory (DFT) studies suggest that this system operates via Atom Transfer Radical Polymerization/Organometallic Mediated Radical Polymerization (ATRP/OMRP) mechanisms interplay.

Z-scheme MnO2/Mn3O4 heterojunctions with efficient peroxymonosulfate activation for organic pollutant removal

The exploration of efficient heterogeneous catalysts for persistent organic pollutant removal is extremely attractive. In the present work, MnO2/Mn3O4 photo-Fenton catalysts were designed by a facile hydrothermal route to activate peroxymonosulfate (PMS) under visible light irradiation for organic pollutant degradation. The optimized MnO2/Mn3O4 heterojunction shows excellent Rhodamine B (RhB) removal efficiency, whose apparent kinetic constant is 11.9 and 5.36 times as high as the MnO2 and Mn3O4. Meanwhile, there is a neglectable attenuation in catalytic performance after 5 recycling runs. Based on the active species trapping experiments, the non-radical process contributes more than the radical process during RhB degradation. Moreover, factors including the dosage of PMS, initial RhB concentration, initial pH, the presence of various anions, different organic pollutants, and water sources are investigated. Systematical characterizations reveal that the enlarged specific surface areas and the efficient charge separation aroused from the Z-scheme mechanism are attributed to the enhanced photo-Fenton performance. The present work contributes to the construction of the Mn-based photo-Fenton catalyst with efficient PMS activation capacity for environmental remediation.

Synthesis of Ta2O5 by introducing graphene quantum dot with excellent photocatalytic performance for degradation of tetracycline

Wide band gap, weak adsorption ability, poor electronic conductivity and insufficient charge transportation limit the applications of Ta2O5 in photodegradation of antibiotics. The paper reports synthesis of Ta2O5 photocatalyst by introducing glycine-functionalized graphene quantum dot (GGQD). The introduction of GGQD effectively prevents the hydrolysis of Ta(V) and finally leads to the formation of small Ta2O5 nanorods. The modification of graphene sheets on the Ta2O5 surface enhances the adsorption towards tetracycline. The presence of Ta4+ self-doped oxygen vacancy narrows the band gap of Ta2O5, optimizes the band position and creates new defect energy level. These improve the light absorption capacity to visible light and promotes the photogenerated charge transfer. The graphene as electron trap suppresses the recombination of photogenerated charge carriers. The graphene as light sensitizer expands the absorption to visible light. The synergy of these multiple structure engineering realizes an excellent photocatalytic performance of Ta2O5 for solar-light driven tetracycline photodegradation. The photodegradation efficiency of 60 min solar-light irradiation is 6.6 times higher, apparent kinetic constant is 19.3 times higher and photocurrent density is 13.4 times over Ta2O5. The study also paves an avenue for construction of metal nanomaterials with desirable photoelectric properties in catalysis, energy storage and conversion and sensing.

Physical characterizations of Sn1-xZn2xCr2O5 nanocomposites and their adsorption performance towards methylene blue

Herein, the structure, thermal stability, optical, magnetic characteristics, and adsorption performance towards methylene blue (MB) of Sn1-xZn2xCr2O5 nanocomposites (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1), prepared by the hydrothermal method, were investigated. The crystal structures, elemental chemical compositions and surface morphology were conducted using XRD, TEM, EDX, and SEM techniques. The structural parameters significantly depend on the elemental composition. For example, a tetragonal SnO2 phase was formed at x = 0, and 0.2, while a spinel-structured ZnCr2O4 was formed at x ≥ 0.4 beside the orthorhombic CrO3 phases. The mass magnetic susceptibility and magnetization of the Sn1-xZn2xCr2O5 nanocomposites displayed a weak room temperature ferromagnetism behavior. The maximum surface area (100.89 m2/g), evaluated via the Brunauer-Emmett-Teller method, was achieved for Sn0.6Zn0.8Cr2O5 nanocomposite. The optical band gap and Urbach energy show opposite trends and are slightly influenced by Zn content. Moreover, the impact of the Zn2+ ratio on the structure, optical, thermal stability, and magnetic characteristics was correlated. The adsorption performance of the Sn1-xZn2xCr2O5 nanocomposite (0 ≤ x ≤ 0.6) revealed an excellent removal efficiency (max ∼87.64%) towards MB dye with apparent rate kinetic constant of 44.9 × 10–2 min–1.

Photocatalytic paint for phage inactivation in dairy industry: inactivation constants and efficiencies

A photocatalytic paint, formulated with commercial carbon doped anatase TiO2, was tested for the inactivation of sixteen bacteriophages infective to lactic acid bacteria. Phages were deposited on borosilicate glass plates coated with paint and subjected under radiation typically used for indoor illumination (λ = 360–720 nm). Inactivation assays for a total time of 20 h in a laboratory photoreactor at constant temperature and relative humidity were performed. Plaque Forming Units (PFU) as function of time were followed demonstrating that eight phages were completely inactivated in a short time (1.5–5 h, phage reductions higher than 2.79 log orders) whereas the eight remaining phages partially reduced their infectivity with varied log reductions and assay times (reductions of 2.33–5.88 log orders within 4–20 h). Apparent inactivation kinetic constant (kT) ranged from 0.30 to 7.52 1/h. The highest and lowest photonic inactivation efficiency were of 4.06 × 1012 PFU/Einstein and 3.00 × 109 PFU/Einstein, respectively; whereas the quantum inactivation efficiencies varied between 9.17 × 1012 PFU/Einstein and 6.00 × 109 PFU/Einstein. Results demonstrated the efficiency of photocatalytic paint to inactive phages in short times. Application of this paint on diverse surfaces of dairies using the own illumination system would contribute to the diminution of phage concentration in the environment, thus reducing the risk of phage attacks to bacterial strains belonged to starter cultures.

Visible-light-driven AgI/Bi4O5I2 S-scheme heterojunction for efficient tetracycline hydrochloride removal: Mechanism and degradation pathway

The existence of excessive tetracycline hydrochloride (TCH) in the ecological environment has seriously threatened human health, so there is an urgent need to develop a high-performance photocatalyst that can efficiently and greenly remove TCH. Currently, most photocatalysts have the problems of fast recombination of photogenerated charge carriers and low degradation efficiency. Herein, S-scheme AgI/Bi4O5I2 (AB) heterojunctions was constructed for TCH removal. Compared with the single component, the apparent kinetic constant of the 0.7AB is 5.6 and 10.2 time as high as the AgI and Bi4O5I2, and the photocatalytic activity only decreases by 3.0% after four recycle runs. In addition, to verify the potential practical application of the fabricated AgI/Bi4O5I2 nanocomposite, the photocatalytic degradation of TCH was performed under different conditions by regulating the dosage of photocatalyst, the TCH concentration, pH, and the existence of various anions. Systematical characterizations are conducted to investigate the intrinsic physical and chemical properties of the constructed AgI/Bi4O5I2 composites. Based on the synergetic characterizations by in situ X-ray photoelectron spectroscopy, band edge measurements, as well as reactive oxygen species (ROS) detections, the S-scheme photocatalytic mechanism is proved. This work provides a valuable reference for developing efficient and stable S-scheme AgI/Bi4O5I2 photocatalyst for TCH removal.

An energy autonomous and portable pilot unit for the photocatalytic treatment of wastewater

An energy-autonomous and portable pilot unit was designed and manufactured. The unit was placed on a wheeled support consisting of a photovoltaic panel, four (4) metallic photo-reactors, each equipped with 6 W UV-A lamps, two (2) peristaltic pumps of 5 W, and an external recirculation tank. The annular space of reactors was packed with ZnO-coated Duranit spheres. The pilot unit was assessed with regard to the degradation capacity of phenol solution and effluents collected from wastewater treatment plant (WWTP). Measurements of the UV-light intensity were combined with the 2-flux radiation model to determine the radial profile of UV-radiant flux across the annular photoreactor. The experimentally measured transient responses of phenol concentration, total organic, and inorganic carbon were fitted with one-dimensional (1D) numerical models to estimate the apparent 1st order kinetic constant of photo-degradation processes. On average, the energy demand of the unit was counterbalanced by the electric power generated by the photovoltaic panel. The repeated use of the same photocatalysts in all experiments confirmed the long-term energy efficiency of the unit. The apparent kinetic constants of phenol, intermediates species, and total organic carbon (TOC) degradation were found to be governed by the corresponding mass-transfer coefficients of relevant species from the bulk liquid to the active catalyst surface. At early times, the total inorganic carbonates (TIC) concentration increases, and at late times the fast mass-transfer of dissolved CO2 to gas phase compensates for the production of inorganic carbon. Preliminary tests showed that the photocatalytic unit is capable of reducing the COD and TOC of WWTP effluents and occasionally, the concentration of nitrates and ammonia may also decrease.