Design of Visible Light Driven Bismuth based Catalysts for Degradation of Organic Pollutants

This Ph.D. thesis deals with the synthesis, immobilization of bismuth-based nanostructures and their photocatalytic evaluation for degradation of organic pollutants mainly dyes, with the aim to optimize synthesis and photo-evaluation conditions by focusing the practical application of heterogeneous photocatalysis. Initially, various bismuth based single structures α-Bi2O3, Bi5O7NO3 and heterostructures α/β-Bi2O3, β-Bi2O3/Bi5O7NO3 were synthesized by a simple and scalable route i.e. thermal decomposition of precursor salt. Properties such as crystallinity, composition, morphology and optical parameters were tuned by simply varying the calcination temperature. Heterostructures of α/β-Bi2O3, β-Bi2O3/Bi5O7NO3 are well crystallized, formed stable composites (originated from single precursor salt) and eventually improved the stability of β-Bi2O3 (a metastable form) in the heterojunction structure. Single structures and heterostructures were evaluated for photodegradation of various dyes (differ in chemical structures and ionic behaviors) under visible and UV light. Test were conducted on single dyes or mixed solution of 2/3 dyes to assess the photocatalytic mechanism and kinetics when dealing the mixed effluent. From the obtained results, it was observed that α/β-Bi2O3 and β-Bi2O3/Bi5O7NO3 heterostructures have higher photocatalytic response due to efficient cascade of electrons and holes within the tuned heterojunction and band alignments. Moreover, different dyes interact differently with the photocatalyst and resulted in changed kinetics, while mechanism of degradation depended upon their ionic behavior. Furthermore, during degradation of mixed solution; dyes that have higher interaction (with photocatalyst) and low absorptivity preferentially degraded earlier. Afterwards, α/β-Bi2O3 were used to investigate and distinguish coexisting processes during photocatalysis: (i) intense adsorption, (ii) dye photobleaching and sensitization assisted photodegradation and (iii) partial or complete mineralization. It was found that some dyes with Azo (N=N) and sulphonic groups have intense adsorption over photocatalyst surface and discoloration could occur without photocatalysis. Further, it was revealed that under controlled conditions, the other coexisted processes hardly occur during photocatalysis. Moreover, indigo carmine (IC) dye was found appropriate for preliminary photo-evaluation because its discoloration/removal process could be directly associated with photocatalytic oxidation by analyzing some identified spectral changes in UV-vis absorbance spectrum. Moreover, it was highlighted that dye chromophoric groups react readily and are easily attacked by the originated photocatalytic reactive species and partially mineralized, while further degradation of resulted intermediates containing phenyl groups, became more difficult to oxidize or reduce to achieve complete mineralization. In addition, to investigate and identify the mechanism and the path of photodegradation of the investigated dyes, two approaches were used: 1) the photo-evaluation of dyes in presence of quenchers of hole, atomic oxygen and hydroxyl radical i.e. triethyl amine (TEA), P-benzoquinone (BQ) isopropanol (IP) and, respectively and 2) Evolution of O2 after water oxidation. From the experimental results it was observed, that the photocatalytic activity eventually reduced in presence of quenchers as they quench the originated reactive radical species. Moreover, evolved O2 during water splitting confirmed that electrons and holes are well separated and able to generate reactive oxygen and radical species for photodegradation and partial mineralization of dyes. Thereafter, the work was focused to tackle the challenges of powder photocatalyst recovery and to explore a competing route, i.e. immobilized fixed support. Glass, steel mesh and sintered silica were used for photocatalyst immobilization to solve the problems associated to photocatalyst recovery, mass limitation and low interaction of pollutants with fixed photocatalyst supports. The immobilization/deposition of β-Bi2O3 over each support, was achieved by pneumatic spray pyrolysis and subsequent calcination at 450 °C. During photo-evaluation of different β-Bi2O3 immobilized supports; deposited sintered silica exhibited higher activity and competing response to β-Bi2O3 powder. The improved activity of sintered silica was associated to the rough, porous and hydrophilic nature of silica that have facilitated in providing higher interaction of deposited β-Bi2O3 films with dye molecules. Furthermore, β-Bi2O3 deposited sintered silica exhibited improved performance for photodegradation and mineralization of various dyes of different chemical structures and ionic behaviors and cyclic stability up to 3 cycles. Then, the work was focused to obtain single structure ferromagnetic bismuth ferrite (BiFeO3) and its heterostructure (BiFeO3/Fe2O3/Bi2Fe4O9); as they have the advantage of easy magnetic separation from aqueous solution. The single structure BiFeO3 and its heterostructures were obtained by using Sol-Gel method, in which precursor solution, containing dissolved Bi(NO3)3:5H2O and Fe(NO3)3:9H2O were preheated and calcined at 500°C with and without addition of Polyethylene Glycol (PEG) and NaOH in the precursor solution. From the XRD and UV-vis DRS analysis it was observed that addition of PEG and NaOH, assisted to obtain single nanostructure BiFeO3, simply by enabling the particles polymerization and inhibiting the formation of other compounds like Fe2O3 and Bi2Fe4O9. It was revealed that single phase BiFeO3 is antiferromagnetic in nature and have very low photocatalytic response, due to the low energy band gap and high electron and holes recombination rate. On the other hand, BiFeO3/Fe2O3/Bi2Fe4O9 heterostructure displayed high magnetic saturation and exhibited improved photoactivity. This is due to a low electrons and holes recombination rate because of tuned band alignment and charge transfer within the heterojunction interfaces. Cyclic stability and photocatalytic performance of BiFeO3/Fe2O3/Bi2Fe4O9 were found almost similar during photodegradation of various dyes up to 3 cycles. At the end, detailed analyses of the efficient heterostructure α/β-Bi2O3 and promising β-Bi2O3 immobilized silica were made, for the evaluation of bulk single and mixed dye solutions under natural sunlight and at varying IC dye concentrations. It was found that the mechanism and the photodegradation kinetics were almost similar amongst lab conditions and during sunlight irradiation and for bulk solutions of single and mixed dyes. Moreover, the experienced phenomena of the degradation and achieved kinetic rate at varying IC concentration were almost alike for both α/β-Bi2O3 and deposited β-Bi2O3 sintered silica. These results revealed that deposited β-Bi2O3 sintered silica could have the promising potential over α/β-Bi2O3 or any other powder photocatalyst under solar light irradiation. Moreover, cyclic stability and the photoactivity of both α/β-Bi2O3 and deposited β-Bi2O3 silica were almost identical up to 3 cycles

Optimality Conditions for D.C. Vector Optimization Problems under D.C. Constraints

2000 Mathematics Subject Classification: Primary 90C29; Secondary 49K30.In this paper, we establish necessary optimality conditions and sufficient optimality conditions for D.C. vector optimization problems under D.C. constraints. Under additional conditions, some results of [9] and [15] are also recovered

Reponses Of A Metallic Bubble: A Self-Consistent Calculation Including Correlation And Exchange Effects

The Van der Waals energy of molecules interacting with metallic bubbles is determined from spherical-tensor theory by using the response field susceptibility of the spherical bubble. The correlation and exchange effects of the electron response inside the metal are included by using the local density approximation (LDA). The dependence of the Van der Waals energy on the first Euler angle is manifestation of the anisotropy of the interaction. In order to illustrate the non-locality and the correlation and exchange effects as well as the importance of the spherical bubble curvature and anisotropy of the interaction on the potential magnitudes, we present numerical results for typical systems (HF,HCl) molecules on (Ag,Al) surfaces.The Van der Waals energy of molecules interacting with metallic bubbles is determined from spherical-tensor theory by using the response field susceptibility of the spherical bubble. The correlation and exchange effects of the electron response inside the metal are included by using the local density approximation (LDA). The dependence of the Van der Waals energy on the first Euler angle is manifestation of the anisotropy of the interaction. In order to illustrate the non-locality and the correlation and exchange effects as well as the importance of the spherical bubble curvature and anisotropy of the interaction on the potential magnitudes, we present numerical results for typical systems (HF,HCl) molecules on (Ag,Al) surfaces

Application of reverse micelle sol-gel synthesis for bulk doping and heteroatoms Surface Enrichment in Mo-Doped TiO 2 nanoparticles

TiO 2 nanoparticles containing 0.0, 1.0, 5.0, and 10.0 wt.% Mo were prepared by a reverse micelle template assisted sol-gel method allowing the dispersion of Mo atoms in the TiO 2 matrix. Their textural and surface properties were characterized by means of X-ray powder diffraction, micro-Raman spectroscopy, N 2 adsorption/desorption isotherms at -196 °C, energy dispersive X-ray analysis coupled to field emission scanning electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV-Vis spectroscopy, and ζ-potential measurement. The photocatalytic degradation of Rhodamine B (under visible light and low irradiance) in water was used as a test reaction as well. The ensemble of the obtained experimental results was analyzed in order to discover the actual state of Mo in the final materials, showing the occurrence of both bulk doping and Mo surface species, with progressive segregation of MoO x species occurring only at a higher Mo content

Optimality conditions for a bilevel optimization problem in terms of KKT multipliers and convexificators

In this paper we investigate a bilevel optimization problem by using the optimistic approach. Under a non smooth generalized Guignard constraint qualification, due the optimal value reformulation, the necessary optimality conditions in terms of convexificators and Karush-Kuhn-Tucker (KKT) multipliers are given.</p

Measurement of the serum level of Elabela for the early detection of acute kidney injury in hospitalized Iraqi COVID-19 patients

Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is caused coronavirus disease 2019 (COVID-19) affecting people worldwide. The angiotensin converting enzyme2 (ACE2) represents a receptor of SARS-CoV-2 on the infected host cell. Apelin or its receptor agonists suppress the production of angiotensin-converting enzyme (ACE) and angiotensin II (Ang-II) and is characterized by a protective effect against SARS-CoV-2. Objective: The study aims to assess the serum level of Elabela biomarker as an early detector for Acute Kidney Injury (AKI) in patients with COVID-19. Cases and Methods: This is a case-control study which included 45 hospitalized adult patients in multiple centers (public hospitals) receiving COVID-19 cases in Baghdad. These cases had a positive real-time or reverse transcription polymerase chain reaction (RT-PCR) of nasal/oropharyngeal swabs. Excluded from the study were those with a negative PCR and comorbidities and 43 apparently healthy adult subjects as controls. The age range of the cases and controls was (20 to 60) years Result: There are no a statistically significant differences between the two groups in terms of age and gender distribution. Statistically significant differences were found in terms of eGFR, S. Creatinine, D. dimer, NEU×103 /µL, LYM×103 /µL and ELA biomarker. Significant negative correlations were found between Elabela with D. dimer and NEU×103 /µL, and between eGFR with S. creatinine, D. Dimer, and NUT×103 /µL. Conclusion: The Elabela biomarker can be used for the early detection of acute kidney injury in COVID-19 patients

Bi2O3/Nylon multilayered nanocomposite membrane for the photocatalytic inactivation of waterborne pathogens and degradation of mixed organic pollutants

Worldwide there is an increasing demand for clean water and sanitation systems and any different solutions are under evaluation, including advanced oxidation processes such as photocatalysis. This work describes the scalable synthesis process of an electrospun composite membrane made of Nylon and embedded α/β-Bi2O3 nanoparticles that can be activated by visible light instead of UV light typically used with other nanomaterials (e.g. TiO2). As a proof of concept, the efficacy of the α/β-Bi2O3 electrospun composite membrane in the visible light inactivation of pollutants and pathogens was demonstrated in a Continuous-flow Photocatalytic Membrane Reactor, highlighting the great potential of this advanced photocatalytic process for clean water and sanitation

Photocatalytic Denitrification of Nitrate Using Fe-TiO2-Coated Clay Filters

In this work, 3D-structured clay filters were prepared and coated with iron-doped tita- nium dioxide (Fe-TiO2) using 3D printing and sol–gel soaking and calcination techniques. Three- dimensional printing was employed to mold and shape the clay filters before annealing. The coated and uncoated filters were characterized for different properties, i.e., morphology, optical properties, and crystalline structure, using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), UV/Vis diffused reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The FESEM images show uniform coatings of round-shaped Fe-TiO2 on the tiny pore of the clay filter. The optical energy band gap of the obtained coating was around 2.8 eV, estimated by Tauc’s plot, compared with 3.2 eV of pristine anatase TiO2. The XRD spectra data processed through XRD software revealed the coatings of TiO2 on the filter surface with the obtained phase of anatase. The photocatalytic performance of bare and coated filters was initially tested for the degradation of indigo carmine (IC) dye and the obtained results suggested the photocatalytic degradation of IC dye by the Fe-TiO2 clay filter compared with the bare filter. Afterward, the deni- trification of nitrate NO3 at various concentrations was performed using Fe-TiO2-coated clay filters and analyzing the total nitrogen (TN) analysis and reduction of NO3 to nitrite (NO2−), nitrogen monoxide (NO), and nitrogen gas (N2). The TN analysis revealed up to 81% denitrification efficiency of the 30 ppm NO3 solution with the photocatalytic response of the Fe-TiO2-coated filter. The results revealed that the Fe-TiO2-coated clay filter has a high potential for denitrification applications under natural sunlight

Calculus of Tangent Sets and Derivatives of Set Valued Maps under Metric Subregularity Conditions

In this paper we intend to give some calculus rules for tangent sets in the sense of Bouligand and Ursescu, as well as for corresponding derivatives of set-valued maps. Both first and second order objects are envisaged and the assumptions we impose in order to get the calculus are in terms of metric subregularity of the assembly of the initial data. This approach is different from those used in alternative recent papers in literature and allows us to avoid compactness conditions. A special attention is paid for the case of perturbation set-valued maps which appear naturally in optimization problems.Comment: 17 page

A method for verification of treatment times for high-dose-rate intraluminal brachytherapy treatment

Purpose: This study was aimed to increase the quality of high dose rate (HDR) intraluminal brachytherapy treatment. For this purpose, an easy, fast and accurate patient-specific quality assurance (QA) tool has been developed. This tool has been implemented at Bahawalpur Institute of Nuclear Medicine and Oncology (BINO), Bahawalpur, Pakistan.Methods: ABACUS 3.1 Treatment planning system (TPS) has been used for treatment planning and calculation of total dwell time and then results were compared with the time calculated using the proposed method. This method has been used to verify the total dwell time for different rectum applicators for relevant treatment lengths (2-7 cm) and depths (1.5-2.5 cm), different oesophagus applicators of relevant treatment lengths (6-10 cm) and depths (0.9 &amp; 1.0 cm), and a bronchus applicator for relevant treatment lengths (4-7.5 cm) and depth (0.5 cm).Results: The average percentage differences between treatment time TM with manual calculation and as calculated by the TPS is 0.32% (standard deviation 1.32%) for rectum, 0.24% (standard deviation 2.36%) for oesophagus and 1.96% (standard deviation 0.55%) for bronchus, respectively. These results advocate that the proposed method is valuable for independent verification of patient-specific treatment planning QA.Conclusion: The technique illustrated in the current study is an easy, simple, quick and useful for independent verification of the total dwell time for HDR intraluminal brachytherapy. Our method is able to identify human error-related planning mistakes and to evaluate the quality of treatment planning. It enhances the quality of brachytherapy treatment and reliability of the system