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Representation the various stages of the sulfate process used for the manufacture of TiO2. Reprinted with permission from Ref. [15]. Copyright 2004 Royal Society of Chemistry.
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Despite the recent synthesis and identification of a diverse set of new nanophotocatalysts that has exploded recently, titanium dioxide (TiO2) remains among the most promising photocatalysts because it is inexpensive, non-corrosive, environmentally friendly, and stable under a wide range of conditions. TiO2 has shown excellent promise for solar cel...
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Conventional photocatalysts are primarily stimulated using ultraviolet (UV) light to elicit reactive oxygen species and have wide applications in environmental and energy fields, including self-cleaning surfaces and sterilization. Because UV illumination is hazardous to humans, visible light-responsive photocatalysts (VLRPs) were discovered and are...
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... Since incorporation of metallic and non-metallic components into photocatalysts improves their catalytic efficiency towards various water pollutants and makes the environment clean. On a commercial scale, the production of these photoreactors using advanced developed blueprints will open new horizons for WWT (Ramos-Delgado et al. 2016). ...
Water is a vital component of our existence. Many human activities, such as improper waste disposal from households, industries, hospitals, and synthetic processes, are major contributors to the contamination of water streams. It is the responsibility of every individual to safeguard water resources and reduce pollution. Among the various available wastewater treatment (WWT) methods, smart nanomaterials stand out for their effectiveness in pollutant removal through absorption and adsorption. This paper examines the application of valuable smart nanomaterials in treating wastewater. Various nanomaterials, including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), nanoadsorbents, nanometals, nanofilters, nanocatalysts, carbon nanotubes (CNTs), nanosilver, nanotitanium dioxide, magnetic nanoparticles, nanozero-valent metallic nanoparticles, nanocomposites, nanofibers, and quantum dots, are identified as promising candidates for WWT. These smart nanomaterials efficiently eliminate toxic substances, microplastics, nanoplastics, and polythene particulates from wastewater. Additionally, the paper discusses comparative studies on the purification efficiency of nanoscience technology versus conventional methods.
Graphical Abstract
... Titania (TiO 2 ) nanostructures have been, and remain, of significant research interest due to their unique physical and chemical properties as well as their potential application in a wide range of fields including paint pigment, catalysis, photocatalysis, photoluminescence, gas sensors, and solar and fuel cells. [1][2][3][4][5][6][7][8][9][10][11][12] Among commercially available nanostructured titania, Evonik's Aeroxide TiO 2 P25 (formerly sold by Degussa), and hereafter referred to as P25, stands out. P25 synthesized via flame pyrolysis of TiCl 4 , is attractive because of its high photocatalytic activity. ...
... Procedure is one-pot, facile, and easily scalable When exposed to water, the 1D NFs self-assemble into quasi-2D flakes and nanobundles With increasing reaction time, the quasi-2D flakes form amorphous nanoparticles and amorphize Sudhakar et al., Matter 6,[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] September 6, 2023 ª 2023 Elsevier Inc. ...
... As a result, they are used in a number of important applications in a wide range of fields, including paint pigment, catalysis, photocatalysis, photoluminescence, gas sensors, and solar and fuel cells. [1][2][3][4][5][6][7][8][9][10][11] Among these, pigment titania (p-TiO 2 ) is the most important. Pigment TiO 2 is produced such that the particle size is 0.2-0.3 ...
Water stable, one-dimensional (1D) materials are few and far between and none are titania based. Herein, we react inexpensive, water-insoluble titanium-based precursors—TiC, TiB2, and TiN—with 25 wt % tetramethyl ammonium hydroxide aqueous solution at 80°C for 2 to 5 days under ambient pressures to produce short (≈100 nm) 1D titania-based lepidocrocite (1DL) nanofilaments (NFs) with minimal cross sections of ≈ 5 × 7 Å2. The NFs self-assemble into nanobundles that, in turn, self-assemble into ribbons/fibers micrometers long. The NFs also self-assemble into quasi-2D flakes that are more or less amorphous. With time, amorphous nanoparticles (NPs)—themselves composed of 1DL NFs attached to the 2D layers—form, rendering the system amorphous. Using X-ray diffraction, photoelectron, and Raman spectroscopies, selected area diffraction, and transmission and scanning electron microscopy, we conclude that, regardless of precursor chemistry, processing conditions, or final morphologies, the 1DL NFs are the essential building blocks in all microstructures.
... The process can be categorized into four main stages, namely, acid digestion, hydrolysis, calcination and post-treatment, which are illustrated in Figure 1. In short, the initial step of the process involves converting the raw material, ilmenite, into [34][35][36]. ...
... The resulting compound is then hydrolysed to yield hydrous titania, TiO2·H2O. Finally, the hydrated form is subjected to calcination to form TiO2 [34][35][36]. ...
... To ensure a 94% efficiency in this step, a 60% excess of 96% concentrated sulphuric acid (H 2 SO 4 ) relative to the TiO 2 content in the raw material is required. The excess acid is added to purified ilmenite, which is then digested at 150 • C [34]. The reaction occurring during the digestion of ilmenite, i.e., FeTiO 3 , is revealed below. ...
Although ilmenite and rutile are extensively used to extract TiO2 at the industrial level, through the sulphate and chloride processes, they can also be recognized to possess the potential to be employed as the raw material to synthesize other titanium compounds as well. The Pulmoddai mineral sand deposit in Sri Lanka is considered as a valuable resource containing pure ilmenite and can be used as a very good source of both titanium and iron. Because of the lower TiO2 content compared to rutile, processes, such as the Becher process, Laporte process and Kataoka process, have been developed to upgrade ilmenite into higher grade synthetic rutile. Additionally, research studies have been carried out to develop methods, such as the hydrochloride process, H3PO4/NH3 process, alkaline roasting process, aluminothermic reduction method, alkaline decomposition method, molten salt electroreduction method and magnesiothermic reduction method, to synthesize TiO2 and other related titanium compounds, such as titanium and iron oxides, composites and alloys, from naturally occurring ilmenite where these methods possess both rewards as well as drawbacks over the others.
... Thus, the treatments of industrial wastewaters containing pharmaceuticals, agrochemicals, personal care products, and organic dyes that are serious menace to the humans and environment have attracted much attention (Calvete et al., 2019;Rajasulochana & Preethy, 2016;Srikanth et al., 2017). To date, various separation (physical and physicochemical) and degradation (chemical and biological) strategies have been developed to address environmental challenges (Adeleye et al., 2016;Ahmed & Haider, 2018;Moreira et al., 2016;Ramos-Delgado et al., 2016;Subramani & Jacangelo, 2015;Sudhaik et al., 2018). However, the efficiency of the commonly used traditional methods such as sedimentation, filtration, flocculation, coagulation, adsorption, reverse osmosis, precipitation, and biological methods is not enough due to disadvantages like low decontamination rates and generation of some other types of potential toxic pollutants (Crini & Lichtfouse, 2019;de Andrade et al., 2018;Gallego-Urrea et al., 2016;Raouf & Maysour, 2019;Pype et al., 2016;Sajid et al., 2018;Singh & Borthakur, 2018;Terry & Summers, 2018). ...
... The utilization of MO compounds for the synthesis of thin films and coatings is generally well established and widely employed in the lab for the development of new thin film synthesis recipes 13,14,36,37 as well as on an industrial scale to produce titania, 38 hafnia, 39 and galliumcontaining compound semiconductors, such as GaAs. 40 However, only little is known about the reaction kinetics of the decomposition processes, in particular about the by-product formation and their role in aiding or hindering the overall reaction. ...
The metal-organic (MO) compound titanium(IV)-isopropoxide (Ti(OiPr)4, TTIP) has tremendous technological relevance for thin film growth and coating technologies, offering a low-temperature deposition route for titania and titanium-oxide-based compounds. Thermal decomposition via the release of organic ligands, a key process in any TTIP-based synthesis approach, is commonly assumed to take place only via the beta-hydride elimination process. Here, we present reactive force field molecular dynamics (ReaxFF-MD) and metadynamics simulations that challenge this conventionally assumed scenario by revealing different, energetically preferred reaction pathways. The complete reaction scheme for the TTIP thermolysis, along with the statistics for the different ligand liberation steps and the associated reaction barriers for the bond dissociation events is presented. ReaxFF-MD simulations performed in the dilute limit realistically capture typical thin film deposition conditions, which in combination with metadynamics data, which produces free energies, constitutes a very powerful tool to quantitatively analyze the reaction dynamics of MO-based thin film growth processes and provide an atomic-scale understanding of how the remaining organic ligands detach from different titanium-containing MO fragments. The approach presented here allows for effective and straightforward identification of the undesirable temperature biasing effects in ReaxFF-MD and represents a predictive framework to identify chemical reaction pathways relevant to film growth processes at the atomic scale under realistic, experimentally relevant conditions. It enables computationally informed engineering of MO molecules with tailored decomposition and reaction pathways, and thus rapid and cost-effective advancements in MO molecule design for existing and future applications of thin film deposition and coating processes.
... Some of the common water treatment methods include adsorption (Subramani and Jacangelo, 2015), reverse osmosis (Dickhout et al., 2017), precipitation (Adeleye et al., 2016), ion exchange (Charles et al., 2016), etc. However, conventional methods have their own disadvantages: high operating costs, greater energy consumption, and low efficiency (Ramos-Delgado et al., 2016). Besides these methods, biological processes utilizing microorganisms like bacteria, fungi, and algae for degrading dyes have also been explored. ...
Concerns over the availability of clean water and the quality of treated wastewater are significant problems that call for an appropriate solution to improve the water quality. The present work emphasized the synthesis of novel SnS2 quantum dots (QDs) deposited on chitosan via a facile green precipitation method involving neem (Azadirachta Indica) leaf extract and investigating its photocatalytic performance for the degradation of Crystal violet (CV) dye under varying reaction parameters, other organic and inorganic salts and water matrices. The crystal structure, surface morphology, and elemental composition of the prepared SnS2 (QDs)/Ch composite were evaluated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and energy dispersive X-ray analysis (EDAX) techniques. The average size of SnS2/Chitosan nanoparticles was calculated to be 8.8 nm using XRD, with the average diameter of SnS2 QDs to be 3.3 nm from TEM. UV-visible spectroscopy was used to investigate its optical properties. The direct band gap of SnS2/Chitosan estimated from Tauc’s plot came to be 2.5 eV. The prepared novel SnS2/Ch composite showed outstanding photocatalytic activity for the degradation of CV through the Advanced Oxidation Process (AOP). The fabricated photocatalyst caused 98.60 ± 1.34% degradation of CV within a short period of 70 min under optimum conditions.
The photodegradation reaction followed pseudo-first-order rate kinetics with a rate constant of 0.0815 min⁻¹. Furthermore, the photocatalyst showed high stability and was reusable for up to four cycles. The present work fulfils the aim of designing a novel, green, and efficient visible light-active nano-photocatalyst.
... INTRODUCTION Nanostructured (NS) titanium dioxides, TiO 2 , have been, and remain, of significant research interest due to their unique physical and chemical properties, as well as their potential application in a wide range of fields including paint pigment, catalysis, photocatalysis, photoluminescence, gas sensors, and solar and fuel cells, among many others. [1][2][3][4][5][6][7][8][9][10][11] One dimensional (1D) and two-dimensional (2D) materials possess characteristics and properties that their three-dimensional (3D) counterparts do not. Arguably the most important difference is in their much higher surface areas. ...
We recently reported on the synthesis of one-dimensional (1D) TiO2-based nanofilaments, (NFs) by reacting water insoluble, earth abundant, and non-toxic Ti-containing precursors, such as TiC, TiB2, and TiSi2, among others, with quaternary ammonium hydroxides, mostly tetramethylammonium hydroxide at near-ambient conditions. From selected area diffraction, X-ray diffraction, and Raman spectroscopy, we previously concluded that the NF's structure was anatase-based. Herein, using high-resolution scanning transmission electron microscopy, Raman spectroscopy, obtained using low laser power, and density functional theory modeling, we conclude that the actual structure is 1D titania lepidocrocite-based structure with minimal cross sections of ≈ 5 × 5 Ų. The NFs grow along [100] with a and c lattice parameters of 3.78 ± 0.01 Å and 3.04 ± 0.06 Å. They tend to self-assemble/stack in two directions, viz. along the b and c axes. And while in-plane and out-of-plane interfilamentous distances are functions of the nature of the cations surrounding the NFs, the band gap, at ≈ 4 eV, is not.
... Thus, the treatments of industrial wastewaters containing pharmaceuticals, agrochemicals, personal care products, and organic dyes that are serious menace to the humans and environment have attracted much attention (Calvete et al., 2019;Rajasulochana & Preethy, 2016;Srikanth et al., 2017). To date, various separation (physical and physicochemical) and degradation (chemical and biological) strategies have been developed to address environmental challenges (Adeleye et al., 2016;Ahmed & Haider, 2018;Moreira et al., 2016;Ramos-Delgado et al., 2016;Subramani & Jacangelo, 2015;Sudhaik et al., 2018). However, the efficiency of the commonly used traditional methods such as sedimentation, filtration, flocculation, coagulation, adsorption, reverse osmosis, precipitation, and biological methods is not enough due to disadvantages like low decontamination rates and generation of some other types of potential toxic pollutants (Crini & Lichtfouse, 2019;de Andrade et al., 2018;Gallego-Urrea et al., 2016;Raouf & Maysour, 2019;Pype et al., 2016;Sajid et al., 2018;Singh & Borthakur, 2018;Terry & Summers, 2018). ...
... Among the different techniques that are being used to produce nanoparticles, flame synthesis has received considerable attention because it allows large-scale production at low-cost of nanoparticles, with properties that may be controlled by suitably selecting flow configurations, flame structures and operating conditions [1][2][3]. The case of titanium dioxide synthesis is considered in the present article because it is generic, raises fundamental issues and has practical importance [4,5]. Although flame synthesis only covers a small part of the worldwide market for pigmentary TiO 2 [6], it represents a promising alternative for the industrial production of nanoparticles with specific properties, possibly leading to the creation of new materials with interesting characteristics. ...
... • TiCl 4 hydrolysis into Ti(OH) 4 via the chemical pathways identified by Wang et al. [49]. ...
... • The bimolecular collision of two Ti(OH) 4 molecules into TiO 2 , based on the model of Lindberg et al. [50] for TTIP flames. Concerning TiCl 4 hydrolysis into Ti(OH) 4 , in order to dispose of a kinetic mechanism, the reaction rates = ˜ [cm 3 mol −1 s −1 ] need to be expressed in the form of an Arrhenius law: ...
The description of TiO2 synthesis in TiCl4-seeded flames is most often based on phenomenological models that qualitatively reproduce experimental trends in terms of final production but they do not provide chemical insights into the actual kinetic pathways. Alternatively, thermodynamically-consistent detailed TiCl4 oxidation kinetics are available. However, since they have been developed under dry conditions they still need to be challenged and validated when employed for flame synthesis where the presence of water molecules may potentially activate TiCl4 hydrolysis. To derive accurate chemical descriptions for TiO2 flame synthesis, it is essential to evaluate the possible contribution of TiCl4 hydrolysis. For this, numerical simulations of TiO2 flame synthesis in laminar flames are carried out in this article using different chemical descriptions for TiCl4 conversion into TiO2. Detailed oxidation kinetics neglecting hydrolysis are shown to predict an extremely slow formation of TiO2 particles in flames when the O2 concentration is small. As a consequence, a significant underestimation of the conversion yield is observed compared to experimental evidences and to trends deduced from phenomenological models. To correct this behavior, a new scheme is proposed by combining a detailed oxidation kinetics with a five-reaction mechanism describing the first steps of TiCl4 hydrolysis. Conversion of TiCl4 is found to be faster and more efficient with this new combined scheme, leading to log-normal particle size distributions in agreement with the experimental data for nanoparticles flame synthesis.