Process for producing black TiO2 by bioengineering

Abstract

This invention presents a novel bioengineered process for producing black TiO2 (B-TiO2) photocatalysts, leveraging the environmentally friendly and efficient properties of biosynthesis. Characteristically, this method uses natural plant extracts as chelating agents, combined with deionized water and titanium(IV) bis / ammonium lactate dihydrate as titanium sources, eliminating the need for additional pH-controlling compounds, catalysts, or vacuum processes. In this process, a precipitate is formed from these components, which is then dried and annealed to produce black TiO2 powder. This innovative approach not only simplifies the synthesis of B-TiO2 under mild conditions but also improves catalytic activity under dark conditions, representing a significant advance in the field of photocatalysis. This bioengineered B-TiO2 demonstrates variability in its band gap and potential for diverse environmental and industrial applications, highlighting its versatility and contribution to sustainable technology as a green synthesis method.

Description

Technical Field

[0001] Field of the Invention The present invention relates to a process for the production of black TiO2 photocatalysts by bioengineering. The present invention further relates to the bioengineering of nanoscale B-TiO2, in which biosynthesis is successfully carried out under mild conditions without adding compounds for pH control, without the presence of a catalyst, or without applying a vacuum during the process.

Background Art

[0002] Background of the Invention Photocatalysts are a family of photoactive materials that are known in the art to generate exciton pairs once irradiated, which in turn generate highly reactive superoxide and / or hydroxyl radicals. These fast chemical reactions are effective for H2O decomposition, decomposition of pollutants in waste H2O, air purification, etc.

[0003] The most popular TiO2-based photocatalysts and equivalents such as CeO2, ZnO, SnO 2、 In addition to WO3, there are also a wide group of VIS photocatalysts based on Bi, C, MoS2, and some new composites such as Ag3PO4.

[0004] The development of titanium dioxide (TiO2) photocatalysts has advanced significantly by various synthesis methods aimed at improving photocatalytic efficiency and expanding the application fields. As one such method, in CN103406135B, a novel N-TiO2@WSe2 photocatalyst is synthesized by a sol-gel process. In this method, a sol is formed through the preparation of a titanium ethanol solution, the addition of a thiourea ethanol solution, the introduction of WSe2, and the controlled addition of acidic ethanol water, and then aged and calcined at high temperature, resulting in the uniform distribution of approximately 50 nm N-TiO2 particles on the surface of WSe2. This photocatalyst has improved photocatalytic activity, especially in the decomposition of wastewater containing antibiotics, showing a 69.7% improvement compared to unmodified TiO2, which is due to its unique dispersibility and the synergistic effect of N-TiO2 and WSe2.

[0005] In contrast, CN106563429A introduces a low-cost, efficient porous black TiO2 photocatalyst that reacts to visible light. This is achieved by etching titanium powder with an aqueous H2O2 solution, representing a new approach that replaces the conventional high-temperature, high-pressure hydrogenation method. The etching process forms porous particles, significantly increasing the specific surface area of ​​the material and consequently improving catalytic efficiency. This method not only simplifies the preparation of black TiO2 but also enhances photocatalytic performance by combining visible light absorption capabilities with a special porous structure.

[0006] Another inventive approach is detailed in CN107138161B, which describes a method for preparing doped black titanium dioxide. This method involves hydrolysis of a titanium dioxide precursor, mixing with a metal nitrate, sulfide, fluoride, or nitride, and calcination in an atmospheric or vacuum furnace. This process is adaptable to doping with various metal cations and anions, offering a wide range of applications, simplicity, and cost-effectiveness. However, a notable difference in these inventions is the absence of the use of natural plant extracts as chelating agents, which is a key feature of our bioengineered black TiO2 synthesis process. This innovative approach leverages the environmentally friendly and efficient properties of biosynthesis, emphasizes the principles of green chemistry, and distinguishes our method by enhancing photocatalytic activity under mild conditions.

[0007] Furthermore, since the electrochemical photolysis of H2O to TiO2, titanium dioxide (TiO2) has become one of the most studied semiconductors due to its redox properties, chemical stability, non-toxicity, general versatility, and especially its high UV photocatalytic activity. Under standard conditions, 3.2 eV (anatase), 3.0 eV (rutile) and 3.4 We have shown three major crystallographic phases corresponding to different band gap values ​​of eV (brookite): anatase, rutile, and brookite.

[0008] As supported by extensive literature, TiO2 is currently the overwhelmingly preferred photocatalyst in terms of its multi-sector functionality. However, from a catalytic standpoint, its applications are limited by the low quantum yield due to the fast exciton recombination of charge carriers (e⁺ / h⁺) and the need for prior UV irradiation for photoactivation. The latter has been shown to be overcome by nitrogen "N" doping. Furthermore, a wide variety of organic and inorganic compounds have been investigated as effective dopants or surface modifiers. Among these, noble metal particles have attracted particular attention because they may not only promote the movement of exciton pairs generated by light and extend the lifetime of charge carriers, but also broaden light absorption.

[0009] In fact, some of these exhibit plasmonic properties that expand light absorption in the VIS spectral region. Co-doping with nitrogen has been found to be a promising method for extending the photoactivity of TiO2 to the visible light range, in addition to its intrinsic ultraviolet light response.

[0010] In addition to standard TiO2 phases, high-pressure, high-temperature TiO2 phases, and various TiO2-based nanocomposite materials, there is also black titania called "BTiO2," first reported by Chen et al. in 2011. The synthesis of such low-bandgap TiO2 (~1.54 eV) was verified by hydrogenating TiO2 at around 200°C for 5 days under an H2 pressure of 20 bar. It came to be called "black titania" (B-TiO2) due to its appearance.

[0011] This discovery attracted significant global attention, prompting the scientific community to begin research into applying this material to various photocatalytic applications and encouraging the possibility of alternative synthesis methods. Several approaches for the mass production and synthesis of B-TiO2 have been successfully validated and patented.

[0012] As summarized in Table 1 below, the synthesis of B-TiO2 was demonstrated primarily through seven processes: hydrogenation, chemical reduction (Mg, Al, NaBH4, NaH), chemical oxidation, electrochemical reduction, anodic oxidation annealing, sonication, and laser modification. In addition to these demonstrated physical and chemical approaches, the present invention aims to enhance these established methodologies using and through novel approaches to green bioengineering.

[0013] [Table 1] [Overview of the project]

[0014] According to a first aspect of the present invention, the present invention relates to a process for the bioengineering production of nanoscale B-TiO2 that exhibits significant catalytic activity under dark conditions, the process comprising: To provide a source of titanium cations; To provide a solvent in the form of water; and To provide a chelating agent in the form of a natural plant extract.

[0015] This process further includes obtaining a precipitate, drying it, and annealing the precipitate to obtain a dry black powder.

[0016] In one embodiment, the precipitate was allowed to settle and then dried in an oven at 80°C to 150°C, ideally 100°C, for 30 minutes to 2 hours, ideally 1 hour.

[0017] Furthermore, the precipitate can be annealed under air at various temperatures from 100°C to 600°C for 1 to 3 hours, ideally 2 hours.

[0018] In a preferred embodiment of the present invention, the titanium cation may be in the form of titanium(IV)bis / ammonium lactate dihydrate.

[0019] In a preferred embodiment of the present invention, the water can be in the form of deionized water (dH2O).

[0020] In a preferred embodiment of the present invention, the chelating agent can be in the form of the flower of Hibiscus sabdarifa.

[0021] Furthermore, in an ideal embodiment, the bioengineering of nanoscale B-TiO2 uses natural extracts as effective chelating agents and H2O as a universal solvent, and may succeed in biosynthesis under mild conditions (atmospheric pressure (Patm), room temperature (TRoom temperature) ~ 293K). The novelty and specificity of this contribution are as follows.

[0022] Furthermore, the present invention provides an effective process without adding a compound for pH control.

[0023] In addition, the process of the present invention is effective without the presence of any catalyst and without a vacuum.

[0024] Next, a process for producing a black TiO2 photocatalyst by bioengineering according to the present invention will be described by the following non-limiting examples while referring to the accompanying drawings.

Brief Description of the Drawings

[0025] [Figure 1] Figure 1 summarizes (a) the main oxide and sulfide photocatalysts, and (b) the main multifaceted applications of nanoscale TiO2. [Figure 2] Figure 2 shows the standard room temperature / atmospheric pressure stable crystal structure of TiO2. [Figure 3] Figure 3 is a schematic diagram of Hibiscus sabdarifa, its main phytocompounds (plant compounds), and its powder. [Figure 4] Figure 4 shows pelletized titania nanoparticles biosynthesized through various annealing stages. The sample labeled "Reference" corresponds to powder obtained by centrifugation and pelletization without annealing. After annealing under standard air pressure conditions, pelletized samples annealed up to 400°C were all black in color and amorphous in their X-ray diffraction patterns. When annealed at temperatures above 400°C, the pelletized samples showed a significant color change from dark black to yellowish-white and then to white. This color change is thought to be related to crystallographic phase changes, as reflected in the diffraction patterns (amorphous to anatase (450-600°C), and further to rutile (above 700°C)). [Figure 5] Figure 5 is a typical transmission electron microscope image of B-TiO2 annealed at 400°C. It shows nanoscale particles with clear crystalline anisotropy. The nanoparticles are not spherical but rather nanoplatelets. The average base dimension of the nanoscale platelets is approximately 9 x 7 nm². [Figure 6] Figure 6 shows a typical scanning electron spectroscopy (EDS) profile of bioengineered nanoscale B-TiO2 annealed at 400 °C. Eight major peaks are observed, three of which are attributed to Ti. In the low-energy channels, peaks for O and C were identified. O is attributed to the TiO2 matrix, while C is related to the C coating used in the EDS study. In addition, there are three peaks corresponding to Mg, Na, and K. These are generally considered to be contaminants derived from natural extracts. These contaminants are systematically detected in the bioengineering processes of nanomaterials. C originates from the coating used in the EDS. [Figure 7]Figure 7 shows the corresponding room-temperature X-ray diffraction profile of nanoscale B-TiO2 annealed at 450°C by bioengineering. Several Bragg peaks are observed, consistent with the anatase crystal structure with lattice constants (a) = (b) = 3.782 Å, (c) = 9.502 Å, and α = β = γ = 90°. Compared to bulk anatase, (a) = (b) = 3.796 Å, (c) = 9.444 Å, and a = b = g = 90°. Compared to bulk anatase, nanoscale B-TiO2 annealed at 450°C by bioengineering is strained a priori in the (c) direction. [Figure 8] Figure 8 reports the room-temperature Raman spectra of bioengineered B-TiO2 annealed at 400°C and standard reference white anatase B-TiO2 in the spectral range of 100–800 cm⁻¹. They are centered at 150, 400, 525, and 650 cm⁻¹ for white TiO2, but at 150, 400, 525, and 650 cm⁻¹ for B-TiO2. However, there are significant differences in intensity as well as spectral position, and the observed vibrational modes are attributed to the Eg, B1g, A1g, and Eg modes in both samples. Therefore, we conclude that bioengineered B-TiO2 annealed at 450°C has an anatase crystal structure with a priori defect surface. [Figure 9] Figure 9 shows the ESR spectrum of bioengineered B-TiO2 annealed at 400°C and the ESR spectrum of standard white anatase W-TiO2 used as a reference. The ESR signal of standard white TiO2 is quasi-flat over a scanning magnetic field of 3400–3650 Gauss, while the spectrum of bioengineered B-TiO2 annealed at 400°C showed a relatively symmetric signal centered at approximately 3525 Gauss. Such broad ESR signals have been reported in the literature and are attributed to Ti3+ (3d1) ions in TiO2, electrons localized in oxygen vacancies, or both (Ti3+ and O-). [Figure 10] Figure 10 shows the diffuse reflectance over the spectral range of 250–1100 nm for various pelletized bioTiO2 samples (annealed at various temperatures as reported in the insert). A priori, two types of samples can be distinguished: these are labeled as defective TiO2-d (low temperature, ≤400°C, black in color) and anatase / rutile TiO2 (relatively high temperature, >400°C, yellowish-white, white). This latter class exhibits diffuse reflectance spectra similar to those of standard anatase and rutile. [Figure 11] Figure 11 shows the lumo (LUMO) and homo (HOMO) supercells of Ti33O66 and oxygen-deficient Ti33O65, along with their corresponding electron density functions. It can be seen that the band gap of Ti33O65 is significantly reduced from 2.141 eV to 0.039 eV due to the surface oxygen vacancies. [Figure 12] Figure 12 shows (a) the color of B-TiO2 in MB-contaminated H2O samples at 0 min, 30 min, and 120 min, and (b) the corresponding optical absorbance "A" in the spectral region of 250–800 nm. [Figure 13] Figure 13 illustrates a key finding of this innovation, showing the standard change of ln(A / A0) over time under complete dark conditions. A net, regular decrease in ln(A / A0) over time is observed, which can be approximated as linear. This trend supports the remarkable decomposition of MB under complete dark conditions and the unique catalytic activity of bioengineered nanoscale B-TiO2. [Modes for carrying out the invention]

[0026] Detailed description of the invention (i) Preparation of hibiscus extract Hibiscus subdulfa Dried Hibiscus sabdarifa flowers were gently and thoroughly washed several times with running tap water to remove dust particles. After this preliminary washing, they were washed with dH2O and then dried in the sun. The dried flowers were finely chopped. In a typical experiment, about 10g of dried, chopped Hibiscus sabdarifa flowers were directly poured into a round-bottom flask containing about 400mL of dH2O. The mixture was infused at room temperature for about 24 hours. The red solution was filtered using Whatman filter paper with a pore size of 2.5 μm. The natural extract thus filtered can be used as a chelating agent without the addition of bases, acids, catalysts, or any special treatment.

[0027] (ii) Preparation of TiO2-NPs In a typical biosynthesis, 10 mL of titanium(IV) bis / ammonium lactate dihydrate is mixed with 350 mL of a pre-extracted hibiscus solution. The prepared solution is stirred for 2 hours at ambient temperature using a magnetic stirrer to uniformly disperse the nanoparticles at a pH equivalent to 2.97, with the final solution pH recorded in the range of 3.91. The resulting precipitate is allowed to set and dried in a 100°C oven for 1 hour. Generally, the original precipitate from biosynthesis is amorphous, so the resulting dried black powder was annealed in air at various temperatures from 100°C to 600°C for 2 hours.

[0028] The inventors of this invention were the first to propose the possibility of biosynthesis of TiO2, thereby verifying the reduction of the optical band gap of TiO2 and demonstrating that biosynthesized B-TiO2 is active in the effective degradation of methylene blue (MB) under dark conditions.

[0029] It should be further emphasized that this invention does not use additional compounds for pH control, as is standard practice in conventional processes.

[0030] Furthermore, this invention does not use a catalyst and does not require a vacuum during the process.

[0031] Finally, the initial stages of bioengineering are carried out under mild conditions (atmospheric pressure (Patm), room temperature (TRoom Temperature) ~293 K).

Claims

1. A process for manufacturing a photocatalyst, wherein the photocatalyst is titanium dioxide (TiO 2 ) is a photocatalyst based on the TiO 2 This process does not require additional compounds for pH control and does not require a vacuum during the manufacturing process to produce nanoscale black titanium dioxide (B-TiO2). 2 A process characterized by being formed by bioengineering.

2. The process according to claim 1, wherein the titanium dioxide photocatalyst is known to be activated by ultraviolet (UV) light to generate reactive oxygen species for environmental purification, and the bioengineered B-TiO 2 It showed significant catalytic activity under dark conditions and beyond UV light dependence. 2 A process characterized by extending the usefulness of the base photocatalyst.

3. A process according to claim 1 or 2, comprising the use of a titanium cation source, a solvent, and a chelating agent for the synthesis of a photocatalyst, wherein the titanium cation source is titanium(IV)bis / ammonium lactate dihydrate, the solvent is deionized water, and the chelating agent is a natural plant extract from the flowers of Hibiscus sabdariffa.

4. A process according to any of the preceding claims, wherein the photocatalyst is conventionally synthesized under conditions requiring strict pH control and catalysts, but the bioengineered process does not require any additional compounds for pH control and does not involve any catalysts, and is synthesized under mild conditions of B-TiO 2 A process characterized by effectively synthesizing [a certain substance].

5. A process according to any of the preceding claims, wherein the production of the photocatalyst comprises obtaining a precipitate and drying and annealing the precipitate, wherein the precipitate is dried in an oven at a temperature between 80°C and 150°C, ideally at 100°C, for a period of 30 minutes to 2 hours, ideally for 1 hour.

6. A process according to any of the preceding claims, characterized in that the precipitate is annealed in air for 1 to 3 hours, ideally 2 hours, at various temperatures in the range of 100°C to 600°C, to obtain a dry black powder.

7. A method for producing a photocatalyst under high temperature and high pressure conditions, comprising B-TiO by bioengineering. 2 A method characterized by synthesizing under atmospheric pressure and room temperature, simplifying the manufacturing process, and being more environmentally friendly.

8. A method according to any of the prior claims, characterized in that conventional photocatalytic synthesis involves the use of harmful chemicals, but employs a green bioengineering approach using natural plant extracts as chelating agents, thereby reducing the environmental impact of the synthesis process.

9. A process for manufacturing a photocatalyst focused on UV photoactive catalysis, the produced B-TiO 2 shows a low band gap of about 1.54 eV, enables activation under dark conditions, and expands the application range of TiO 2 -based photocatalysts.

10. A process according to any of the prior claims, wherein the photocatalytic particles are mainly spherical and are bioengineered by B-TiO 2 A further feature of this method is the use of particles, which have an average base area with dimensions of approximately 9 nanometers in length and 7 nanometers in width, and are clearly nanoplate-like in shape. This unique morphology contributes to the improvement of photocatalytic activity.

11. A process for synthesizing photocatalysts that typically require an external catalyst or additive, and involves bioengineering of B-TiO 2 The synthesis process is characterized by being effective without requiring such external catalysts or additives, thereby simplifying the process and reducing potential contaminants.

12. A process according to any of the prior claims, wherein synthesized B-TiO 2 The process is characterized by nanoparticles exhibiting a crystalline phase that can be adjusted from amorphous to anatase and then to rutile by controlling the annealing temperature, providing flexibility to target specific photocatalytic applications.

13. A bioengineering method for producing photocatalysts that involves complex and energy-intensive methods, characterized by a process that is not only simpler and less energy-intensive, but also yields photocatalysts with unique properties such as adjustable band gap and improved catalytic activity under dark conditions.

14. A process according to any of the prior claims, wherein B-TiO is bioengineered. 2 This process is characterized by the fact that when nanoparticles are annealed at 450°C, they exhibit crystallographic strain in the c-direction, resulting in unique structural properties that can contribute to photocatalytic efficiency.

15. A process for producing photocatalysts, which involves bioengineering synthesis of B-TiO using a green and sustainable approach. 2 This process is characterized by its effectiveness in environmental remediation applications and its manufacturing process, which minimizes environmental impact, thus offering two advantages: efficient catalytic action and environmentally friendly synthesis, leading to photocatalysis.

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