The application of the solar photocatalysis for the degradation of residual pollutants found in surface water was demonstrated. Semi-pilot scale flat-plate cascade reactor (FPCR) was used to study ...the degradation of model organic pollutants: enrofloxacin (ENRO), 17β-estradiol (E2) and 1H-benzotriazole (1H-BT) over TiO2 thin-film supported on glass fibers. A modular panel with full-spectra solar lamps with appropriate UVB and UVA irradiation levels was used as a simulation of sunlight. Pollutant degradation in FPCR was estimated using predictive models; intrinsic reaction rate constants (ki) for ENRO, E2 and 1H-BT independent of the reactor size, flow rate and irradiation conditions were determined: 9.60, 3.35 and 0.37 109 s−1 W−0.5 m1.5, respectively. Main degradation products (DPs), formed upon hydroxylation, ring opening and oxidation, were identified using LC-QTOF-MS. The ecotoxicological impact was assessed via T.E.S.T. and ECOSAR open-source tools showing the formation of less harmful DPs after sufficient reaction time. Pollutant degradation was simulated at four locations of interest, i.e. exhausts from urban wastewater treatment plants (UWWTPs) in Zagreb, Croatia (45°N), Krakow, Poland (50°N), Sevilla, Spain (37°N) and Ioannina, Greece (39.6°N). Results have proved that a simple flat-plate system with supported photocatalysts can be easily scaled up and incorporated at the outlet of UWWTP for the reduction of pollutant load and related toxicity. The exhaust canal in Zagreb with the estimated length of a photocatalytic layer of 122 m for the > 90% degradation of all target pollutants was discussed as the best installation site among studied locations.
A multi-disciplinary approach to the tentative application of TiO2 solar photocatalysis outdoors to reduce pollutant loads and toxicity in surface waters was demonstrated. Possible application at four selected locations in Europe, as an additional step in water treatment after urban wastewater treatment plants (UWWTPs) was discussed. Target pollutants were studied under environmentally relevant conditions (sunlight levels, water matrix, simulation of process on a real scale at selected geographical location), at both higher and low concentrations.
Display omitted
•Simulation of solar photocatalysis at different geographical location was done.•Targeted pollutants were rapidly degraded over TiO2 immobilized on glass fibers.•Intrinsic reaction rate constants independent of solar irradiation were determined.•Main degradation products of targeted pollutants were identified using LC-QTOF-MS.•In silico toxicity was assessed for photolysis and photocatalysis under sunlight.
This paper investigates the possibility of integrating the combination of nanofillers, titanium dioxide (TiO2) and carbon nanotubes (CNT) into the thermoplastic polymer matrix. This combination of ...fillers can possibly modify the physico-chemical properties of composites compared to the pure polymer matrix. The composites were blended using the extrusion method. The composite filament produced was used to manufacture static mixers on a 3D printer using the additive manufacturing technology fused filament fabrication (FFF). The aim of this work was to inspect the influence of the filler addition on the thermal and mechanical properties of glycol-modified polyethylene terephthalate (PET-G) polymer composites. The fillers were added to the PET-G polymer matrix in several ratios. Tensile test results showed an increase in the overall strength and decrease in the elongation at break of the material. Melt flow rate (MFR) showed a decrease in the viscosity with the initial filler addition and reaching a plateau after 2 wt% filler was added. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed minor changes in the thermal properties. Scanning electron microscope (SEM) results showed homogenous distribution of the filler in the matrix and strong filler–matrix adhesion. The results indicate suitable properties of new functional composites for the 3D printing of static mixers for application in tubular reactors.
In this study, equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin ...concentration, temperature and ionic strength on the sorption process were studied. The
K
d
parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin–Radushkevich (D–R) sorption models were applied to describe the equilibrium isotherms by linear and nonlinear methods. The estimated
K
d
values varied from 171 to 37,347 mL/g. The obtained values of
E
(free energy estimated from D-R isotherm model) were between 3.51 and 8.64 kJ/mol, which indicated a physical nature of ciprofloxacin sorption on studied sediments. According to obtained
n
values as measure of intensity of sorption estimate from Freundlich isotherm model (from 0.69 to 1.442), ciprofloxacin sorption on sediments can be categorized from poor to moderately difficult sorption characteristics. Kinetics data were best fitted by the pseudo-second-order model (
R
2
> 0.999). Thermodynamic parameters including the Gibbs free energy (Δ
G
°), enthalpy (Δ
H
°) and entropy (
Δ
S°) were calculated to estimate the nature of ciprofloxacin sorption. Results suggested that sorption on sediments was a spontaneous exothermic process.
The flow regime inside the channel of 3D printed microreactors is defined by the surface properties of the channel walls. Polylactide (PLA) and acrylonitrile/butadiene/styrene (ABS) are two polymers ...that are the most common in additive manufacturing using fused filament fabrication, commonly known as “3D printing”. With the aim of developing new materials for the 3D printing of microreactors whose channel surface hydrophobicity could be modified, PLA and ABS were blended with cheaper and widely used polymers-high-density polyethylene (PE-HD) and low-density polyethylene (PE-LD). Polymer blend surfaces were treated with inductively coupled plasma (ICP) and coated by fluorocarbon-based material (CFx) plasma deposition treatment in order to modify surface hydrophobicity. It has been shown that the modification of surface morphology of PLA polymer blends can be achieved by ICP etching and CFx coating, while this was not possible for ABS polymer blends under the conducted treatment conditions. The treated surface of PLA/PE-HD 90/10 showed a contact angle of 121.6° which is 36° higher than the contact angle measured on the untreated surface. Surfaces that have achieved contact angles higher than 120° have an “island like” surface morphology. Samples with higher “islands” showed higher contact angles, that confirmed that the hydrophobicity also depends on the height of the “islands”. Furthermore, it has been found that etching time significantly impacts the contact angle values and surface morphology of the PLA polymer blends, while the CFx coating time does not have significant impact on the surface properties.
In this work, we present the application of solar photocatalysis for air purification including toxic substances such as ammonia and methane normally related to emissions from agriculture (e.g., ...poultry and cattle farms), landfills, etc. The study was done in three different laboratory and semi-pilot scale reactors: annular reactor (AR), mini-photocatalytic wind tunnel (MPWT), and photocatalytic wind tunnel (PWT). Reactors present a physical model for estimation of air-borne pollutant degradation over TiO
2
-based photocatalytic layer in respect to optimal operating conditions (relative humidity, air/gas flow, and feed concentration). All studies were performed under artificial solar irradiation with different portions of UVB and UVA light. The application of solar photocatalysis for air purification was evaluated based on thorough monitoring of pollutants in inlet and outlet streams. The kinetic study resulted with intrinsic reaction rate constants:
k
p,int,NH3
= (3.05 ± 0.04) × 10
−3
cm
4.5
mW
−0.5
g
−1
min
−1
and
k
p,int,CH4
= (1.81 ± 0.02) × 10
−2
cm
4.5
mW
−0.5
g
−1
min
−1
, calculated using axial dispersion model including mass transfer considerations and first-order reaction rate kinetics with photon absorption effects. The results of photocatalytic oxidation of NH
3
and CH
4
confirmed continuous reduction of pollutant content in the air stream due to the oxidation of NH
3
to N
2
and CH
4
to CO and CO
2
, respectively. The application of solar photocatalysis in outdoor air protection is still a pioneering work in the field, and the results obtained in this work represent a good basis for sizing large-scale devices and applying them to prevent further environmental pollution. In the current study, a TiO
2
P25 supported on a glass fiber mesh was prepared from commercially available materials. The system designed in this way is easy to perform, operate, and relatively inexpensive.
A series of semi-transparent W-incorporated TiO2 thin films (TxW; x = 0,1,2,5, and 10) were fabricated by anodizing co-sputtered titanium-tungsten (WiTi1−i (0 ≤ i ≤ 0.05)). Field emission gun ...scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Grazing incidence X-ray diffraction, and Raman spectroscopy were used to characterize TxW thin films, which confirmed the anatase form of TiO2 as well as the presence of W in the thin films. Optoelectronic and photoelectrochemical characterization showed that TxW thin films are markedly beneficial for reducing photo generated charges recombination. T1W exhibited the maximum charge carrier lifetime (0.29 µs) which is over two times of pristine T0W (0.13 µs). Methylene blue (MB) and imidacloprid (IMI) were selected as the target pollutants for the study of photocatalytic effectiveness of TxW under solar light. T1W showed maximum removal efficiency for MB at pH8. Moreover, response surface methodology analyses revealed that IMI removal efficiency enhanced about three times at pH 4 with adding 255 µM of H2O2.
Display omitted
•Fabrication of semi-transparent TxW thin films by anodizing co-sputtered WiT1−i films.•Enhancement charge carrier life time through W incorporation into TiO2 structure.•Photocatalytic activity association of with the ratio of W in TxW thin films.•Improvement MB removal efficiency with increasing pH.•IMI removal efficiency optimization using response surface methodology.
The work is focused on the assessment of possible methods for intensification of photocatalytic degradation of common water borne pollutants. Solar photocatalysis poses certain limitations for large ...scale application with several possible reactor designs which have shown an optimal performance. In the current study, a comparison between two types of pilot scale reactors was made: a flat-plate cascade reactor (FPCR) and tubular reactor with a compound parabolic collector (CPC). Apart from the reactor design, another aspect of possible intensification was a photocatalyst formulation. The efficiency of photocatalytic films that consisted of pure TiO2 nanoparticles was compared to the efficiency of films that consisted of TiO2/CNT composites. Intensification assessment was performed via detailed kinetic modelling, combining the optical properties of films, irradiation conditions and reactor mass balance. Intensification was expressed via intensification indices. Results showed the advantage of the CPC-based reactor design and an unbiased effect of sensitizing agent (CNT) in the photocatalytic film formulation.
A photocatalyst comprised of Ag nanoparticles dispersed on an anatase matrix has been prepared using a simple hydrothermal method without additional thermal treatment. The prepared material was ...characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV-Vis spectroscopy, and N2 adsorption–desorption isotherms. The prepared catalyst activity was evaluated by photocatalytic degradation of C.I. Reactive Violet 2 (RV2) aqueous solution under UVA and visible light illumination. SEM revealed the non-uniform dispersion of silver particles throughout the matrix composed of fine particles. According to XRD analysis, the matrix was composed of pure anatase with a crystallite size of 8 nm calculated through the Scherrer equation. HRTEM micrograph analysis showed that anatase nanoparticles possess a spherical morphology and a narrow size distribution with an average particle size of 8 nm with more active anatase {100} crystal surface exposed, while silver nanoparticles were between 60 and 90 nm. A bandgap of 3.26 eV has been calculated on the basis of the DRS UV-Vis spectrum, while a specific surface area of 209 m2g−1 has been established from adsorption isotherms. Thus, through a simple synthesis approach without subsequent thermal treatment, the agglomeration of nanoparticles and the reduction of specific surface area have been avoided. Prepared nano Ag/anatase photocatalyst exhibits excellent efficiency for the photodegradation of RV2 under UVA and visible irradiation.
During the last decades, heterogenous photocatalysis has shown as the most promising advanced oxidation process for the removal of micropollutants due to degradation rate, sustainability, ...non-toxicity, and low-cost. Synergistic interaction of light irradiation, photocatalysts, and highly reactive species are used to break down pollutants toward inert products. Even though titanium dioxide (TiO2) is the most researched photocatalyst, to overcome shortcomings, various modifications have been made to intensify photocatalytic activity in visible spectra range among which is modification with multiwalled carbon nanotubes (MWCNTs). Therefore, photocatalytic oxidation and its intensification by photocatalyst’s modification was studied on the example of four micropollutants (diclofenac, DF; imidacloprid, IMI; 1-H benzotriazole, BT; methylene blue, MB) degradation. Compound parabolic collector (CPC) reactor was used as, nowadays, it has been considered the state-of-the-art system due to its usage of both direct and diffuse solar radiation and quantum efficiency. A commercially available TiO2 P25 and nanocomposite of TiO2 and MWCNT were immobilized on a glass fiber mesh by sol-gel method. Full-spectra solar lamps with appropriate UVB and UVA irradiation levels were used in all experiments. Photocatalytic degradation of DF, IMI, BT, and MB by immobilized TiO2 and TiO2/CNT photocatalysts was achieved. Mathematical modelling which included mass transfer and photon absorption was applied and intrinsic reaction rate constants were estimated: kDF=3.56 × 10−10s−1W−0.5m1.5, kIMI=8.90 × 10−11s−1W−0.5m1.5, kBT=1.20 × 10−9s−1W−0.5m1.5, kMB=1.62 × 10−10s−1W−0.5m1.5. Intensification of photocatalysis by TiO2/CNT was observed for DF, IMI, and MB, while that was not the case for BT. The developed model can be effectively applied for different irradiation conditions which makes it extremely versatile and adaptable when predicting the degradation extents throughout the year using sunlight as the energy source at any location.
This work reports the effectiveness of TiO2 photocatalysts modified by defect engineering methods. The prepared photocatalysts were characterized by X-ray diffraction (XRD), UV–Vis diffuse ...reflectance spectroscopy (DRS), photoluminescence (PL) measurements and electron spin resonance (ESR) technique. The immobilized photocatalyst layer was prepared using an abrasive material as a support and a mineral binder. To the best of our knowledge, this is the first time that such type of the immobilized photocatalytic layer has been prepared and tested. A home-made flat-plate photoreactor (FPP) with artificial light sources was used for the degradation of an aqueous solution of imidacloprid using an immobilized TiO2. The effects of different operating variables such as irradiation source, recirculation flow rate, irradiated surface area and photoreactor volume on the photocatalytic performances were investigated. The hydrodynamic behavior of the flat-plate photoreactor (FPP) was studied utilizing a residence time distribution (RTD) technique using the axial dispersion model. Based on kinetic measurements it was found that the photocatalytic degradation of imidacloprid under the conditions used in this study can be described by a complex kinetic model that follows pseudo-zero order kinetics at the beginning of the degradation, and with the progress of the reaction at higher irradiation times changes to the pseudo-first order. Liquid chromatography - quadrupole time‐of‐flight mass spectrometry (LC‐QTOF‐MS) was used to identify imidacloprid degradation by-products as a function of irradiation time. Theoretical modeling of the geometry and electronic structure of imidacloprid in aqueous solution was performed using density functional theory (DFT) calculation. Based on the results of theoretical simulations and experimental measurements, the possible pathway for photodegradation of imidacloprid in aqueous phase after irradiation with UVA was proposed and discussed.
Display omitted
•The TiO2 photocatalysts were modified using the deffect engineering methods.•This is the first report utilizing abrasive material as support and mineral binder to prepare the photocatalyst.•Hydrodynamic behaviour of the flat-plate photoreactor was studied.•Imidacloprid electronic structure is investigated by DFT calculation.•Possible pathway for imidacloprid photodegradation under UVA irradiation was proposed.
PDF
