Model Pollutant Research Articles

An analytical model for point source pollutants in an urban area with mesoscale wind and wet deposition

An analytical model for point source pollutants in an urban area with mesoscale wind and wet deposition

Unveiling the Photodegradation Mechanism of Monochlorinated Naphthalenes under UV‒C Irradiation: Affecting Factors Analysis, the Roles of Hydroxyl Radicals, and DFT Calculation

Polychlorinated naphthalenes (PCNs) are a new type of persistent organic pollutant (POP) characterized by persistence, bioaccumulation, dioxin-like toxicity, and long-range atmospheric transport. Focusing on one type of PCN, monochlorinated naphthalenes (CN‒1, CN‒2), this study aimed to examine their photodegradation in the environment. In this work, CN‒1 and CN‒2 were employed as the model pollutants to investigate their photodegradation process under UV-C irradiation. Factors like the pH, initial concentrations of CN‒1, and inorganic anions were investigated. Next, the roles of hydroxyl radicals (·OH), superoxide anion radicals (O2•‒), and singlet oxygen (1O2) in the photodegradation process were discussed and proposed via theory computation. The results show that the photodegradation of CN‒1 and CN‒2 follows pseudo-first-order kinetics. Acidic conditions promote the photodegradation of CN‒1, while the effects of pH on the photodegradation of CN‒2 are not remarkable. Cl−, NO3−, and SO32− accelerate the photodegradation of CN‒1, whereas the effect of SO42‒ and CO32‒ is not significant. Additionally, the contributions of ·OH and O2•‒ to the photodegradation of CN‒1 are 20.47% and 38.80%, while, for CN‒2, the contribution is 16.40% and 16.80%, respectively. Moreover, the contribution of 1O2 is 15.7%. Based on DFT calculations, C4 and C6 of the CN‒1 benzene ring are prioritized attack sites for ·OH, while C2 and C9 of CN‒2 are prioritized attack sites.

Two-Dimensional Time Fractional River-Pollution Model and Its Remediation by Unsteady Aeration

This study contains a mathematical model for river pollution and its remediation for an unsteady state and investigates the effect of aeration on the degradation of pollutants. The governing equation is a pair of nonlinear time-fractional two-dimensional advection-diffusion equations for pollutant and dissolved oxygen (DO) concentration. The coupling of these equations arises due to the chemical interactions between oxygen and pollutants, forming harmless chemicals. The Fractional Reduced Differential Transform Method (FRDTM) is applied to provide approximate solutions for the given model. Also, the convergence of solutions is checked for efficacy and accuracy. The effect of longitudinal and transverse diffusion coefficients of pollutant and DO on the concentration of pollutant and DO is analyzed numerically and graphically. Also, we checked the effect of change in the river’s longitudinal and transverse seepage velocity on pollutant and DO concentration numerically and graphically. We analyzed the comparison of change in the value of half-saturated oxygen demand concentration for pollutant decay on pollutant and DO concentration numerically and graphically. Also, numerical and graphical analysis examined the effect of fractional parameters on pollution levels.

A Python toolkit for integrating geographic information system into regulatory dispersion models for refined pollution modeling

AERMOD is designated as U.S. Environmental Protection Agency (EPA)'s preferred air dispersion model for refined transportation project hot-spot analyses beginning in 2020. One of the key challenges in its modeling process is spatially encoding roadway geometry, especially when simulating highways with complex geometric designs. This research proposed an open-source Python package, GTA, which enables conversion of publicly available roadway Geographic Information System (GIS) layers into defined sources, and source-based emission rates from MOtor Vehicle Emissions Simulator (MOVES) output for AERMOD modeling. The research selected a suburban area in Atlanta, and conducted a comprehensive analysis in terms of annual PM2.5 concentration results and the speed of preparing AERMOD input files for highway network modeling both manually and using software developed based on the proposed methodology. The results prove that the proposed methodology significantly expedites the AERMOD input preparation process, and facilitates convenient testing of multiple modeling configurations for multi-scenario or sensitivity analysis.

Investigation on novel chitin and chitosan from dung beetle Heteronitis castelnaui (Harold, 1865) and its potential application for organic dyes removal from aqueous solution

Chitosan, a natural polysaccharide, has attracted considerable attention as an environmentally friendly and highly efficient adsorbent for dye removal. It is usually produced by deacetylation or partial deacetylation of chitin. However, conventional sources of chitin and chitosan are limited, prompting the need for alternative sources with improved adsorption capabilities. Herein, this study focuses on exploring a novel chitin and chitosan source derived from the dung beetle and evaluates its potential for organic dye removal from aqueous solutions. The research involves the extraction and characterization of chitin and chitosan from dung beetle Heteronitis castelnaui (Harold, 1865) using various analytical techniques, including SEM, FT-IR, TGA, XRD, NMR, deacetylation degree and elemental analysis. The chitosan obtained was used for the formation of hydrogels with sodium alginate via cross-linking with calcium chloride. And then the prepared hydrogels were evaluated for its adsorption capacity through batch adsorption experiments using methylene blue as a model pollutant. The adsorption capacity for methylene blue was 1294.3 mg/g at room temperature with solution pH = 12, MB concentration of 1800 mg/L. Furthermore, the kinetics of the adsorption process were analyzed using pseudo-first-order and pseudo-second-order models to understand the rate of adsorption. The maximum adsorption capacities were determined using Langmuir and Freundlich isotherm models. This study provides valuable insights for the development of sustainable dye adsorption technologies, specifically investigating a novel chitosan source derived from the dung beetle.

Sunlight-driven charge separation for a heterojunction of nano-pyramidal CuWO4-MOF modified TiO2 nanoflakes for photocatalytic degradation of ciprofloxacin

The study presents a breakthrough of a balanced charge separation for heterojunction CuWO4-TiO2 cocatalyst to efficiently enhance visible light photocatalytic degradation of ciprofloxacin (CIP). A solvothermal-synthesized nanopyramid-like CuWO4 semiconductor was assembled before sol–gel treatment with TiO2 precursors to generate CuWO4-TiO2 nanocomposites. The optical, structural, and morphological properties of CuWO4-TiO2 were elucidated using UV–Vis DRS, XRD, FTIR, Raman spectroscopy, and TEM/SEM techniques. The UV–Vis DRS spectroscopy of as-synthesized CuWO4-TiO2 cocatalyst demonstrated enhanced visible light absorbance. The XRD patterns of CuWO4-TiO2 revealed a triclinic phase nanocrystal. The O-Ti–O functionality was confirmed by FTIR spectroscopy. The photoactive bands corresponding to anatase redshift were observed from Raman spectroscopy of CuWO4-TiO2 nanocomposite. The PL studies attributed this redshift to the elevated extra energy bands that aid electron/hole pair charge separation in a co-catalyst heterojunction CuWO4-TiO2 nanocomposite afforded by embedding CuWO4-MOF within TiO2 crystalline. The TEM showed that un-sintered CuWO4.MOF mimicked a pyramidal shape and converted to nanoflakes upon sintering, while TiO2 and CuWO4-TiO2 retained a tetragonal shape. The photocatalytic activity of CuWO4-TiO2 cocatalyst was studied using CIP, as a model pollutant. The innovative design of 5CuWO4-TiO2 charge separation nanocomposite completely degraded 10 mg L−1 CIP solution at pH = 6.31 (natural pH) and 9 under 120 min of sunlight irradiation.

Geospatial modelling of ambient air pollutants and chronic obstructive pulmonary diseases at regional scale in Pakistan.

Pakistan is among the South Asian countries mostly vulnerable to the negative health impacts of air pollution. In this context, the study aimed to analyze the spatiotemporal patterns of chronic obstructive pulmonary disease (COPD) incidence and its relationship with air pollutants including aerosol absorbing index (AAI), carbon monoxide, sulfur dioxide (SO2), and nitrogen dioxide. Spatial scan statistics were employed to identify temporal, spatial, and spatiotemporal clusters of COPD. Generalized linear regression (GLR) and random forest (RF) models were utilized to evaluate the linear and non-linear relationships between COPD and air pollutants for the years 2019 and 2020. The findings revealed three spatial clusters of COPD in the eastern and central regions, with a high-risk spatiotemporal cluster in the east. The GLR identified a weak linear relationship between the COPD and air pollutants with R2 = 0.1 and weak autocorrelation with Moran's index = -0.09. The spatial outcome of RF model provided more accurate COPD predictions with improved R2 of 0.8 and 0.9 in the respective years and a very low Moran's I = -0.02 showing a random residual distribution. The RF findings also suggested AAI and SO2 to be the most contributing predictors for the year 2019 and 2020. Hence, the strong association of COPD clusters with some air pollutants highlight the urgency of comprehensive measures to combat air pollution in the region to avoid future health risks.

Dynamical analysis and numerical treatment of pond pollution model endowed with Caputo fractional derivative using effective wavelets technique

Dynamical analysis and numerical treatment of pond pollution model endowed with Caputo fractional derivative using effective wavelets technique

Insights into transition metal encapsulated inside carbon aerogel for accelerated electro-peroxone oxidation: Activity evaluation and reactive oxygen species generation

Transition metals have critical influences on the generation of reactive oxygen species in activating O3 and H2O2, as the binary oxidant sources in electro-peroxone (EP). To evaluate the catalytic activity of different metals and reveal the reactive oxygen species generation in heterogeneous EP, series of metals encapsulated inside carbon aerogel spheres (M@CS, M=Fe, Co, Ni, Zn) were fabricated for strengthening EP. Atrazine was used as model pollutant due to its low reactivity with O3, and the abatement trends followed Co@CS > Fe@CS > Ni@CS > Zn@CS. Co@CS exhibited the superior catalytic activity with maximum metal active site utilization (1.28 × 103 min-1 mol-1 per mole Co atom sites at pH 7) and minimum electric energy consumption (0.106 kWh/m3-log). The catalytic activity of M@CS was related to the adsorption energies for O3 and H2O2 (Fe@CS > Co@CS > Ni@CS > Zn@CS) and the graphitization degree (Co@CS > Fe@CS > Ni@CS > Zn@CS). Verified by theoretical calculation and in-situ Fourier transformed infrared, the metal effectively promoted the adsorption and decomposition of O3 and H2O2 into the surface oxygen intermediates, finally generating ·OH/·O2-/1O2. The carbon layer was conducive to the reduction of internal metal, ensuring catalyst durability. Electronic paramagnetic resonance and kinetic model revealed the occurrence, ratio and transient concentration of ·OH/·O2-/1O2 in M@CS/EP. M@CS/EP showed good performance for pollutant removal in coexistence of anions, humic acid and real water. This study provides guidance for selecting the metal–carbon catalyst in heterogeneous EP.

Efficient adsorptive removal of methyl green using Fe3O4/sawdust/MWCNT: Explaining sigmoidal behavior

The 4R concept (reduce, reuse, recycle and repurpose) in water management necessitates innovative adsorption techniques that utilize sustainable and natural materials. This study investigates the use of natural sawdust embedded in magnetic iron oxide to treat wastewater. The performance of the newly synthesized Fe3O4/sawdust adsorbent was also compared to the native Fe3O4 and Fe3O4/MWCNT. Methyl Green (MG) was used as a model pollutant due to its wide use and potential toxicity. The new adsorbents demonstrated a high removal efficiency that exceeds 97 % under ambient conditions. The study investigates the effect of pH on adsorption, revealing a significant shift in removal efficiency as pH increases, with an optimal pH of around 7. The pH dependence is explained based on the point-of-zero-charge of the Fe3O4 adsorbent and the structure of the dye. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) of adsorption were determined through a temperature study. The adsorption equilibrium was found to be endothermic, therefore preferring elevated temperatures. Because the adsorption data of the study exhibited S-shaped-like curves, sigmoidal models were used to describe the adsorption isotherms. This provided new insights into the competitive adsorption mechanisms acting on the heterogeneous Fe3O4/sawdust surfaces. The kinetics study indicates rapid and efficient adsorption with pseudo-second-order reaction. The half-life of the reaction was as low as 4.8 min. The findings suggest a rapid, highly efficient and sustainable method to remove organic pollutants from wastewater.

Effective hydrogen production and coupling degradation of organics (4-nitrophenol, methylene blue, and Rhodamine B) in wastewater by electrospun PAN@Fe0 composite nanofibers

The pursuit of clean energy generation and environmental preservation is of utmost importance for societal progress. However, couple clean energy production and pollution control is still a difficulty. In this study, a novel electrospun composite mat, with nano zero valent iron (Fe0, nZVI) encapsulated into polyacrylonitrile (PAN) nanofibers was acted as a catalyst. The activation energy (Ea) for the hydrolysis of NaBH4 to produce hydrogen is 22 kJ·mol−1, hydrogen atom utilization efficiency (HGE) of NaBH4 is 60.80%. Three kinds of organic dyes 4-nitrophenol (4-NP), methylene blue (MB), and Rhodamine B (RhB) were served as the model pollutant, to construct NaBH4-organic system for energy production and pollution reduction. The NaBH4-organic system demonstrates a collaborative capability to simultaneously remove organic pollutants and generate hydrogen, with a coupling equilibrium point between the two processes. The hydrogen generation rate (HGR) and HGE increased with the concentration of pollutants increased. The degradation of 4-NP, MB, and RhB followed pseudo-first-order kinetics, with RhB degrading dosage 20 and 44 times higher than 4-NP and MB, respectively. H2 and H· contributed to the organic degradation. nZVI directly participated in the formation H2 and H·. PAN@Fe0 possessed good recyclability and moderate cost. The degradation process adhered to the classical surface reaction controlled Langmuir-Hinshelwood (L-H) model. The integration of synergistic production capacity and pollutant degradation aligns well with the principles of green chemistry and sustainable development. This study demonstrates a novel approach to no precursor loss catalysts preparation, efficient production clean H2, advanced treatment of dye-containing wastewater, carbon neutral operation of sewage treatment plant.

Impact of LED radiation intensity on gold nanoparticles photodeposition on TiO2 with physicochemical and photocatalytic characterization

This study investigates the influence of LED radiation intensity on the photodeposition of gold nanoparticles onto TiO2 substrates, examining their physicochemical properties and photocatalytic activities. Utilizing a range of radiation intensities and wavelengths, TiO2-Au composites were synthesized and characterized through techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The deposition process, markedly enhanced by shorter wavelengths and higher intensities, efficiently formed gold nanoparticles. This research distinctly highlights observable morphological changes in the nanoparticles; increased radiation intensity not only augmented the size but also altered their shape from spherical to hexagonal. These morphological transformations significantly improve the composites’ light absorption and catalytic properties due to the surface plasmon resonance of the gold nanoparticles. Photocatalytic assessments, using metronidazole as a model pollutant, demonstrated that composites prepared with higher LED intensities showed significantly enhanced degradation capabilities compared to those synthesized with lower intensities. The findings underscore that manipulating photodeposition parameters can critically influence the structural and functional properties of TiO2-Au composites, potentially advancing their applications in environmental remediation and solar energy utilization.

Degradation of Malachite Green Dye by Solar Irradiation Assisted by TiO2 Biogenic Nanoparticles Using Vaccinium corymbosum Extract

The green synthesis of metal oxide nanoparticles (NPs) offers an alternative to chemical procedures, which can be harmful to human health due to exposure to hazardous substances and harsh synthesis conditions. The following work synthesized titanium dioxide nanoparticles (TiO2 NPs) using a green synthesis method. As a precursor, food-grade TiO2 was used with blueberry extract. This approach makes the process safer, cheaper, and simpler, requiring minimal effort to achieve effective TiO2 NP synthesis. The TiO2 NP characterization was performed by solid-state techniques, such as Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). According to the XRD diffractograms, TiO2 NPs were obtained in the anatase phase with incidence peaks of 25.28 (101). TEM confirmed their pseudo-spherical shape with an average size of 170 nm. The 3.2 eV bandgap of TiO2 NPs enables UV absorption, making them ideal for efficient photocatalytic degradation under sunlight. On the other hand, the photocatalytic activity of TiO2 NPs was examined using malachite green (MG) dye as a pollutant model under direct sunlight. After 30 min, a degradation of 94% was achieved. The kinetic analysis identified parabolic diffusion and modified-Freundlich kinetics as primary mechanisms, emphasizing diffusion and adsorption in electron transfer. The main reactive oxygen species (ROS) involved in the photodegradation of MG dye were h+ and OH•.

Customization of indium-based MOFs for enhanced adsorptive and photocatalytic of organic pollutants: Morphology involvement on performance and mechanism

Metal-organic frameworks (MOFs) as photocatalysts are promising candidates for environmental wastewater treatment owing to their tunable crystal structure, well-ordered donor–acceptor interface, and exceptional porosity. However, precise control over size and morphologies of MOFs to enhance adsorptive and photocatalytic performance is still a considerable challenge. Herein, the MIL-68(In)–NH2 (MN) MOFs with special acicular structure are customized by a facile method, in which the growth of crystal nuclei is inhibited and regulated by pyridine. The formation mechanism of MN with different morphologies and size is introduced, and their photocatalytic activities are systematically explored by degrading model pollutants tetracycline (TC) and dyes under visible light irradiation. Benefiting from its high specific surface area and the exposed large lattice spacing facet, the wool-ball morphology MN (MN-W) with surface acicular nanostructure presents an optimum photocatalytic performance compared to other MN morphologies. The MN-W also exhibits excellent adsorption capacity, remarkable cyclic stability, and good practical organic wastewater treatment capability. The possible photodegradation mechanism and pathways are elucidated, demonstrating that h+ is the primary reactive species, followed by •OH and •O2– radicals, responsible for the degradation of TC. This work is anticipated to tailoring design and modulate MOF photocatalysts for boosting the photocatalytic performance towards organic effluents remediation.

The synthesis of TiO2 using a nanocrystalline cellulose template improves its photocatalytic performance

Using cellulose nanocrystals (CNCs) as a template in the production of TiO2 has a positive impact on its crystal and porous structure, ultimately improving its photocatalytic performance. In this study, TiO2 photocatalysts with mesoporous anatase structures were prepared by acid-catalyzed hydrolysis using sulfate-ester-modified CNCs as the template. The effects of CNC concentration on the structure and performance of TiO2 were investigated in detail. The addition of CNCs was found to inhibit TiO2 transformation from the anatase to rutile phase, and abundant hydroxyl and sulfate ester groups on the CNCs provide narrow confined spaces for the crystal growth of TiO2, leading to the generation of smaller crystals with more exposed (001) crystal faces. Moreover, the CNCs act as a template for the pore structure remaining after calcination, thus increasing the specific surface area of the TiO2. Among the numerous samples evaluated, that prepared with a CNC concentration of 0.15 wt% and calcined at 600 °C had the highest percentage of (001) crystalline surface exposure. In photodegradation tests using phenol as a model pollutant, a degradation rate of 97.4 % and mineralization rate of 79.9 % were achieved with 60 min of light exposure. Thus, this study provides a clear approach for the directional synthesis of mesoporous TiO2 from biomass template materials.

Simple precipitation synthesis and solar light-driven photocatalytic degradation of Ag3PO4 floating photocatalysts

Abstract A highly efficient and stable photocatalyst, Ag3PO4, was prepared using a simple co-precipitation method at room temperature. The precursors used in this process were AgNO3 and K2HPO4. The resulting Ag3PO4 photocatalyst forms irregularly-shaped spheres with diameters ranging from 300 to 1 μm. The shape of the Ag3PO4 photocatalyst slightly changes when different surfactants (PVA, PVP, PEG) are used. The powdered Ag3PO4 photocatalyst exhibits excellent visible light-driven photocatalytic performance. It is capable of decomposing rhodamine B (RhB) as a model pollutant in just 5 min under visible light irradiation. This performance is quite remarkable. Interestingly, Ag3PO4 floating composite sheets have been achieved using polystyrene (PS) and fumed silica Aerosil 200. After three cycles, the decolorization of RhB dyes remains at 87% with the 30% Ag3PO4@PS/Aerosil 200 sheet. This indicates that the Ag3PO4@PS/Aerosil 200 photocatalyst is highly reusable and stable.

Solar-driven remediation of antibiotics in synthetic and real reverse osmosis brine: Addressing lattice oxygen demand and electron transfer for improved purification

This study investigated the significance of integrated advanced oxidation process with reverse osmosis (RO) to ensure the purification and elimination of micropollutants, primarily pharmaceuticals prior to the discharge of brine to the environment. To envisage this, TiO2 based solar driven photocatalysis was employed, highlighting the crucial role of oxygen vacancy formation in the lattice of TiO2 for enhancing the purification of antibiotic contaminants from RO brine. The study elucidated how variations in oxygen environments such as oxygen rich yellow TiO2 (Y-TiO2) and oxygen vacancy black TiO2 (B-TiO2) influence photodegradation reaction kinetics taking ofloxacin (OFX) and tetracycline (TC) as model pollutants. The B-TiO2 exhibited 8.5 times higher photodegradation for OFX compared to Y-TiO2, proving significance in tuning of oxygen environment in lattice. The photodegradation efficiency plot showcases B-TiO2′s efficacy, demonstrating 99.8 % and 99.4 % for OFX and TC, respectively. Additionally, the study investigated the photocatalytic degradation mechanism, identifying predominant charge carriers and reactive species involved, while also assessing the durability of photodegradation processes. The impact of pH on the photocatalytic performance of B-TiO2 in degrading antibiotics explored, spanning pH levels from 2.5 to 10.5. An exploration on band alignment formation in B-TiO2 explains the effectiveness of it over Y-TiO2. Lastly, efficacy of B-TiO2 in degrading antibiotics in real RO brine with high level of salinity (60,200 ppm TDS) is demonstrated, which resulted with photodegradation efficiency of 31.25 % for OFX and 67.8 % for TC, proving applicability of integrated system as a sustainable purification approach. Moreover, the blockage of chloride ions quenching demonstrated improvements in photodegradation emphasizing the influence of chloride ions in high saline conditions.

BiVO4/sulfur-doped g-C3N4 nanocomposite as photocatalyst for degradation of ciprofloxacin under visible light irradiation

In recent years, the use of antibiotics has greatly increased, which has caused environmental pollution. We offer a photocatalyst based on BiVO4/sulfur-doped g-C3N4 nanocomposite, which was made by a one-step thermal condensation method from thiourea and bismuth vanadate to degradate ciprofloxacin (CIP). The BiVO4/sulfur-doped g-C3N4 photocatalyst was analyzed by certain techniques including XRD, FTIR, BET, FESEM, EDX, TEM, DRS, photoluminesence, and Mott-Schottky to determine various physicochemical properties. The photocatalytic degradation of CIP, as a model pollutant, under visible LED light irradiation was tested to investigate the catalytic performance of nanocomposite. Response Surface Methodology (RSM) was employed to optimize operational parameters, including photocatalyst dosage (50–150 mg), CIP concentration (10–30 mg/L), initial pH of the solution (3–11), and irradiation time (12–120 min). The BiVO4/sulfur-doped g-C3N4 nanocomposite, with a narrow bandgap of 2.15 eV, exhibited exceptional photocatalytic performance in degrading CIP. The optimal conditions for CIP removal were photocatalyst dosage of 120.9 mg, CIP concentration of 10 mg/L, and initial solution pH of 3, resulting in 93.5 % removal efficiency after 105 min of irradiation. The photocatalytic degradation kinetics of CIP followed a pseudo-first-order model with a rate constant (K) of −0.0221 L/min, indicating rapid degradation process. The photocatalyst maintained excellent performance after 5 reuses, with only a 3 % reduction in efficiency. XRD analysis confirmed the structural stability of the nanocomposite after reuse.

Effective removal of textile dye via synergy of adsorption and photocatalysis over ZnS nanoparticles: Synthesis, modeling, and mechanism

In this work, we prepared sulfur-zinc nanoparticles (ZnS-TGA) functionalized with thioglycolic acid by a hydrothermal method and tested their photodegradation ability by solar irradiation. ZnS-TGA were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), UV–Vis spectrophotometer and photoluminescence spectroscopy. In the characterization of these nanoparticles, thioglycolic acid proved to be a strong capping ligand, with a specific surface area of 36.82 m2/g and an average size of 7.15 nm. To test the photocatalytic degradability of the product, methylene blue (MB) was used as a model pollutant. Various operational variables were investigated, including pH, amount of nanoparticles, dye concentration, contact time and temperature. The equilibrium adsorption tests, and the statistical physical calculations allowed the analysis of the energetic and steric variables of the adsorption of MB dye molecules on the surface of these nanoparticles. The equilibrium data were well fitted with Langmuir-Freundlich (L-F) and the adsorption kinetics with pseudo-first order. The maximum adsorption capacity of the MB dye removal process was 30.92 mg g−1 at pH 7 and 298 K, and this process was spontaneous and exothermic. The dye molecules and the surface of the nanoparticles exhibited physical interactions with adsorption energies of 23.31–25.92 kJ/mol. The photocatalytic activity of these nanoparticles resulted in a dye degradation efficiency of 91.1 % in 180 min. The photocatalytic efficiency remained almost unchanged after five consecutive degradation cycles, resulting in a methylene blue degradation of 85 %. According to these results, these environmentally friendly nanoparticles have the potential to purify industrial and urban liquids contaminated with harmful organic compounds such as dye molecules.

Ground-reflected light: The invariance principle and the effect of luminaire height, emission pattern, and non-uniform albedo

The weighted contribution of ground-reflected component of light emissions from artificial sources gradually increases as the transitioning from bad-shielded to modernized light sources with low or zero direct uplight takes place in cities or towns. In this work, we demonstrate that the modeling of reflected light on a large domain for Lambertian flat surfaces does not require information about the height of the light sources and directional distribution of photons their produce. This kind of "invariance principle" becomes invalid when the homogeneity condition for the surface albedo is violated. However, we have shown that an analytical solution exists also for position-dependent albedo and even for angle-dependent reflectance which is the effect we now include to the light pollution models for the first time. This effect is known from the observation of sunbeams entering uneven surfaces at different zenith angles. Here in analogy with that daylight model we derive formulae for ground surfaces illuminated by artificial lights located at different heights above the surrounding terrain.