NL2030351B1

NL2030351B1 - Photocatalyst and preparation method and use thereof

Info

Publication number: NL2030351B1
Application number: NL2030351A
Authority: NL
Inventors: Zhu Yang; Li Siwen; Zhang Daihua; Liu Gen; Lin Yingzi; Li Yang
Original assignee: Univ Jilin Jianzhu
Priority date: 2021-10-29
Filing date: 2021-12-29
Publication date: 2023-10-30
Also published as: CN114054008A; NL2030351A

Abstract

The present disclosure provides a photocatalyst and a preparation method and use thereof, and belongs to the technical field of photocatalyst preparation. The preparation method 5 of a photocatalyst provided in the present disclosure includes the following steps: soaking peanut shells in a hydrochloric acid solution to obtain acid-treated peanut shells; subjecting the acid-treated peanut shells to extraction in ammonium hydroxide to obtain pretreated peanut shells; soaking the pretreated peanut shells in a tetra-n-butyl titanate solution to obtain a photocatalyst precursor; and calcining the photocatalyst precursor to 10 obtain the photocatalyst. In the present disclosure, the main components of the peanut shell are lignin; hemicellulose and cellulose. The peanut shell contains a large amount of silicon dioxide, and after pretreatment, a silicon-carbon network structure can be formed; which serves as a basic skeleton. The photocatalyst is prepared with the peanut shell as a template; and the obtained photocatalyst has a large specific surface area, and has 15 microporous and mesoporous structures, which can improve the adsorptivity and ultimately improve the photocatalytic performance.

Description

PHOTOCATALYST AND PREPARATION METHOD AND USE THEREOF

TECHNICAL FIELD

[01] The present disclosure relates to the technical field of photocatalyst preparation, and in particular, to a photocatalyst and a preparation method and use thereof.

BACKGROUND ART

[02] Biomimetic materials have been extensively studied for their advantages such as unique structure, a wide range of raw materials, low cost, and simple preparation. Bio- inspired by or by mimicking various functions, structures and components of organisms, materials having a micro- or nano-scale structure and inheriting unique morphological structures of original organisms can be designed and developed, which may be applied to the fields of environment, optics, energy and the like. Templates used for biomimetic materials include almost the entire ecosystem, such as plants, animals and microorganisms.

[03] The prior art has disclosed photocatalysts prepared with biological templates, such as a nano-zinc oxide having a hexagonal wurtzite structure prepared with rapeseed pollen as a biological template and zinc nitrate as a zinc source, a mesoporous nano- cerium oxide prepared with chitosan as a biological template, and a modified straw-Fe; Os composite prepared with modified straw as a biological template. Unfortunately, the resulting photocatalysts are small in specific surface area and poor in photocatalytic performance.

SUMMARY

[04] In view of above problems, an objective of the present disclosure is to provide a photocatalyst and a preparation method and use thereof. The photocatalyst prepared in the present disclosure is large in specific surface area and high in photocatalytic performance.

[05] To achieve the objective of the present disclosure, the present disclosure provides the following technical solutions.

[06] The present disclosure provides a preparation method of a photocatalyst, including the following steps:

[07] soaking peanut shells in a hydrochloric acid solution to obtain acid-treated peanut shells;

[08] subjecting the acid-treated peanut shells to extraction in ammonium hydroxide to obtain pretreated peanut shells;

[09] soaking the pretreated peanut shells in a tetra-n-butyl titanate solution to obtain a photocatalyst precursor; and

[10] calcining the photocatalyst precursor to obtain the photocatalyst.

[11] Preferably, the hydrochloric acid solution may have a mass concentration of 5%.

[12] Preferably, the ammonium hydroxide may have a mass concentration of 5%.

[13] Preferably, the extraction may be conducted for 3 hours.

[14] Preferably, the calcining may be conducted at a temperature of 550°C held for 4 hours.

[15] Preferably, a room temperature may increase to the temperature for the calcining at a rate of 2°C/min.

[16] The present disclosure further provides a photocatalyst prepared by the preparation method described above, including TiO; particles and BiFeO: covering the

TiO; particles, with a specific surface area of the photocatalyst ranging from 144.36- 153.64 m?/g.

[17] Preferably, a molar ratio of the TiO; particles to the BiFeO: in the photocatalyst may be (0.2-1.5):1.

[18] Preferably, the molar ratio of the TiO; particles to the BiFeOs in the photocatalyst may be 0.2:1, 0.5:1, 0.8:1, 1:1, or 1.5:1.

[19] The present disclosure further provides use of the photocatalyst described above in degrading triclosan.

[20] The preparation method of a photocatalyst provided in the present disclosure includes the following steps: soaking peanut shells in a hydrochloric acid solution to obtain acid-treated peanut shells; subjecting the acid-treated peanut shells to extraction in ammonium hydroxide to obtain pretreated peanut shells; soaking the pretreated peanut shells in a tetra-n-butyl titanate solution to obtain a photocatalyst precursor; and calcining the photocatalyst precursor to obtain the photocatalyst. In the present disclosure, the main components of the peanut shell are lignin, hemicellulose and cellulose. The peanut shell contains a large amount of silicon dioxide, and after pretreatment (including acid treatment and extraction in ammonium hydroxide), a silicon-carbon network structure can be formed, which serves as a basic skeleton. The photocatalyst is prepared with the peanut shell as a biological template, and the obtained photocatalyst has a large specific surface area, and has microporous and mesoporous structures, which can improve the adsorptivity and ultimately improve the photocatalytic performance.

[21] The present disclosure further provides a photocatalyst prepared by the preparation method described above, including TiO: particles and BiFeO; covering the

TiO; particles. In the present disclosure, such means as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption (by Brunauer-

Emmett-Teller (BET) method), ultraviolet-visible diffuse reflectance spectroscopy (UV- vis DRS), photoluminescence spectroscopy (PL) are used to characterize samples, and the results show that the bio-morphology genetic photocatalyst (TiO2/BiFeQs) prepared with a biological template has a hierarchical porous structure. Under the condition of light irradiation with a Xenon lamp for 2.5 hours, the maximal removal rate of triclosan as a target contaminant may be 86.2%.

BRIEF DESCRIPTION OF THE DRAWINGS

[22] FIG. 1 shows XRD spectra of photocatalysts with different doping amounts;

[23] FIG. 2 shows SEM images of 1-T102/BiFeO: at different magnifications;

[24] FIG. 3 shows TEM images of 1-T102/BiFeO: at different magnifications;

[25] FIG. 4 shows XPS spectra of 1-TiO»/BiFeOs, with (A) being a total spectrum, (B) a spectrum of Ti 2p, (C) a spectrum of Fe 2P, (D) a spectrum of Bi 4f, and (E) a spectrum of O IS;

[26] FIG. 5 shows N; adsorption-desorption isotherms and a pore size distribution of

S1-TiO2/BiFeOs, where (A) illustrates Nz adsorption-desorption isotherms, and (B) illustrates a pore size distribution;

[27] FIG. 6 shows UV-Vis DRS spectra of TiO, BiFeOs, and TiO2/BiFeO: in different doping ratios;

[28] FIG. 7 shows photoluminescence spectra of BiFeO: and 1-TiO2/BiFeOs;

[29] FIG. 8 shows triclosan degradation effect curves of TiO, BiFeOs;, and 1-

TiO2/BiFeO: photocatalysts;

[30] FIG. 9 shows triclosan degradation effect curves of TiO»/BiFeO; photocatalysts with different doping ratios;

[31] FIG. 10 shows the influence of the concentration of triclosan on degradation capability,

[32] FIG. 11 shows a changing trend of total organic carbon concentration in 1-

TiO2/BiFeOs solution for degrading triclosan with reaction time; and

[33] FIG. 12 shows trapping results of active species in 1-TiO2/BiFeOs solution for degrading triclosan.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[34] The present disclosure provides a preparation method of a photocatalyst, including the following steps.

[35] Peanut shells are soaked in a hydrochloric acid solution to obtain acid-treated peanut shells.

[36] The acid-treated peanut shells are subjected to extraction in ammonium hydroxide to obtain pretreated peanut shells.

[37] The pretreated peanut shells are soaked in a tetra-n-butyl titanate solution to obtain a photocatalyst precursor.

[38] The photocatalyst precursor is calcined to obtain the photocatalyst.

[39] Inthe present disclosure, peanut shells are soaked in a hydrochloric acid solution to obtain acid-treated peanut shells.

[40] Inthe present disclosure, before use, the peanut shells are preferably washed with clear water for 3 times to remove impurities on the surface.

[41] In the present disclosure, the hydrochloric acid solution preferably has a mass concentration of 5%.

[42] In the present disclosure, the soaking is conducted for preferably 3 hours. In the present disclosure, the soaking plays a role in removing impurities.

[43] In the present disclosure, after the completion of the soaking, the resulting acid soaking product is preferably washed with distilled water until it is neutral.

[44] In the present disclosure, after the acid-treated peanut shells are obtained, the acid-treated peanut shells are subjected to extraction in ammonium hydroxide to obtain pretreated peanut shells.

[45] In the present disclosure, the ammonium hydroxide preferably has a mass concentration of 5%.

[46] In the present disclosure, the extraction is conducted for preferably 3 hours. In the present disclosure, the extraction plays a role in increasing the surface area of the peanut shells, thereby improving the adsorptivity.

[47] In the present disclosure, after the completion of the soaking, the resulting extraction product is preferably washed with distilled water until it is neutral, and then dried. In the present disclosure, the drying is conducted at preferably 60°C. The present 5 disclosure has no particular time limitation on the drying as long as the water can be completely removed. In a specific example of the present disclosure, the drying is conducted in a drying oven.

[48] In the present disclosure, after the pretreated peanut shells are obtained, the pretreated peanut shells are soaked in a tetra-n-butyl titanate solution to obtain a photocatalyst precursor.

[49] In the present disclosure, the solvent of the tetra-n-butyl titanate solution is preferably absolute ethanol. The present disclosure has no particular limitation on the concentration of the tetra-n-butyl titanate solution and the usage amounts of the pretreated peanut shells and the tetra-n-butyl titanate solution as long as the molar ratio of TiO; particles to BiFeOs in the photocatalyst is preferably (0.2-1):1.

[50] In the present disclosure, the soaking is conducted for preferably 48 hours.

[51] In the present disclosure, after the completion of the soaking, the resulting solid product from the soaking is preferably washed with distilled water until no color is present, and then dried in the drying oven at 60°C.

[52] In the present disclosure, after the photocatalyst precursor is obtained, the photocatalyst precursor is calcined to obtain the photocatalyst.

[53] Inthe present disclosure, the calcining is conducted at a temperature of preferably 550°C preferably held for 4 hours. In the present disclosure, the calcining is preferably conducted in a muffle furnace.

[54] Inthe present disclosure, a room temperature increases to the temperature for the calcining at a rate of 2°C/min.

[55] The present disclosure further provides a photocatalyst prepared by the preparation method described above, including TiO: particles and BiFeOs covering the

TiO; particles, with a specific surface area of the photocatalyst ranging from 144.36- 153.64 mg.

[56] In the present disclosure, a molar ratio of the TiO; particles to the BiFeO: in the photocatalyst is (0.2-1):1, more preferably 0.2:1, 0.5:1, 0.8:1, 1:1, or 1.5:1.

[57] The present disclosure further provides use of the photocatalyst described above in degrading triclosan.

[58] In the present disclosure, the use is preferably for degrading triclosan in wastewater, and the concentration of triclosan in the wastewater is preferably 5-20 ppm.

[59] To further explain the present disclosure, the photocatalyst and the preparation method and use thereof provided in the present disclosure will be described in detail below in conjunction with examples which, however, should not be interpreted as limitations to the protection scope of the present disclosure.

[60] Example 1

[61] Pretreatment of peanut shells: peanut shells were washed with clear water for 3 times, soaked in Swt% hydrochloric acid for 3 hours, and then washed with distilled water until the peanut shells were neutral. After the completion of the soaking in the hydrochloric acid, the resulting peanut shells were subjected to extraction in 5wt% dilute ammonium hydroxide for 3 hours, washed with distilled water until the peanut shells were neutral, and dried in a drying oven at 60°C to obtain pretreated peanut shells.

[62] Soaking of the pretreated peanut shells: 200 mL of tetra-n-butyl titanate solution was dissolved in 600 mL of absolute ethanol solvent to form a homogeneous mixed solution. The pretreated peanut shells were completely soaked in the homogeneous mixed solution for 48 hours, washed with distilled water until no color was present after the completion of the soaking, and dried in the drying oven at 60°C to obtain a photocatalyst precursor.

[63] Calcination of the peanut shells: the photocatalyst precursor was placed into a muffle furnace and calcined at 550°C for 4 hours, with a rate of temperature increase being 2°C/min. In this way, 4 photocatalysts (T102/BiFeO:samples) were finally prepared.

The molar ratios of TiO2 to BiFeO: in the 4 photocatalysts were 0.5:1, 0.8:1, 1:1, and 1.5:1, denoted by 0.5-Ti02/BiFeO3, 0.8-TiO02/BiFeO3, 1-Ti02/BiFeOs (Ti02/BiFe0s), and 1.5-TiO2/BiFeO;, respectively.

[64] By investigating the bio-morphology genetic TiO2/BiFeOs; photocatalytic materials on microstructure, morphology and photoresponse range, the TiO2/BiFeOs catalyst exhibiting the best degradation effect and the best decoloration effect was selected from the photocatalytic materials with different doping ratios. Such characterization means as XRD, SEM, TEM, XPS, BET, UV-vis DRS and PL were used to further demonstrate that the bio-morphology genetic TiO2/BiFeO; catalyst prepared with the peanut shell as the template had an increased specific surface area and exhibited good adsorptivity and degradation capability.

[65] XRD

[66] XRD characterization was conducted on the photocatalysts prepared in Example

L. From FIG. 1 showing the XRD spectra of photocatalysts with different doping amounts, it could be seen that each photocatalyst was composed of TiO: and BiFeO;, with no characteristic peaks of other substances being shown. Moreover, the crystal structure and the composition of main phases of the photocatalyst could be clearly observed in the figure, where the characteristic diffraction peaks at 29=25.34°, 37.91°, 48.12° and 55.07° could directly correspond to crystal planes (101), (111), (200) and (211), respectively, which might be basically consistent with what JCPDS No.74-0534 TiO, photocatalytic material showed; and the characteristic diffraction peaks at 26=23.15°,32.46°, 45.91° and 57.32° could directly correspond to crystal planes (100), (110), (200) and (211), respectively, which might be basically consistent with what JCPDS No.26-1044 BiFeO; photocatalytic material showed. It was indicated that the peanut shell template was removed after calcination at a high temperature. In addition, doping of TiO: and BiFeO: with each other did not affect their crystal structures. The 1-TiO2/BiFeOsphotocatalyst had a mean grain size of 14.98 nm. With increasing doping amount of BiFeO3, the diffraction peak of TiO, was weakened, and the diffraction peak of the BiFeO:; photocatalyst first increased and then decreased. This was mainly because the BiFeO: photocatalyst was able to cover the TiO; photocatalyst while TiO; inhibited the growth direction of BiFeOs;, and when a certain limit was achieved, superfluous BiFeO; photocatalyst was unable to inhibit the growth direction of the TiO2 photocatalyst and the diffraction peak of BiFeO; was weakened.

[67] SEM

[68] SEM images of 1-TiO2/BiFeO; photocatalyst were obtained at different magnifications, as shown inn FIG. 2. As could be seen from FIG. 2, TiO: had a spherical structure and was closely arranged, and BiFeOs adhered to the surface of the former with a flocculent structure. The BiFeO: photocatalytic material inhibited the growth direction of the TiO: photocatalytic material. It could be clearly observed in (C) and (D) in FIG. 2 that BiFeO; almost completely covered the TiO; photocatalyst to form a heterogeneous structure which could inhibit the growth of BiFeO; nanoparticles and reduce the size to provide more reaction sites for the photocatalyst. By contrast, a bismuth ferrite composite exhibited better triclosan degradation effect than the TiO» photocatalytic material used alone, which might be attributed to the reduced size, increased active sites and improved photocatalytic efficiency of the composite. Incomplete soaking or collapse of the template structure resulted in growth breakage.

[69] TEM

[70] A TEM can be used to not only observe the morphology of the 1-TiO2/BiFeOs catalyst but also deeply observe the interior, may have a higher interior than an SEM.

TEM images of the 1-TiO2/BiFeO: catalyst were obtained at different magnifications, as shown in FIG. 3. From (A) in FIG. 3, the outer contour shape of the 1-T102/BiFeO; catalyst could be further determined. It could be observed in (B) (a partially enlarged image of (A) in FIG. 3) in FIG. 3 that bio-morphology genetic 1-TiO2/BiFeOs was composed of a plurality of 1-Ti02/BiFeO: crystal grains grown along different crystal planes and the formed surface was compact with complete particles. It could be observed more clearly in (C) in FIG. 3 that the TiO2 nanoparticles had smooth surface with good crystallinity. It could be observed clearly in (D) (a partially enlarged image of (C) in FIG. 3) in FIG. 3 that different crystal grains were tightly linked to one another with a large specific surface and a porous structure, demonstrating that the catalyst had certain adsorptivity.

[71] XPS

[72] XPS was used to analyze the valence of the photocatalytic material. The total

XPS spectrum of 1-Ti02/BiFeO; was as shown in (A) in FIG. 4, where among the major elements Ti, Fe, Bi, O and C, C was from two aspects: C pollution in air, and carbon source pollution caused by calibration with 248.8 eV peak as a reference peak. The XPS spectrum of Ti 2p of 1-T102/BiFeO: was shown in (B) in FIG. 4, where the binding energy peak values of Ti 2p3/2 and Ti 2p1/2 were 458.4 eV and 464.8 eV, respectively, indicating that the valence of Ti was positive tetravalent. The XPS spectrum of Fe 2p of 1-

TiO2/BiFeOs; was shown in (C) in FIG. 4, where the binding energy peak values of Fe 2p3/2 and Fe 2p1/2 were 710.9 eV and 724.5 eV, respectively, indicating that the valence of Fe was positive trivalent. The XPS spectrum of Bi 4f of 1-TiO2/BiFeO; was shown in (D) in FIG. 4, where the binding energy peak values of Bi 4f7/2 and Bi 4f5/2 were 159.0 eV and 164.3 eV, respectively, indicating that the valence of Bi was positive trivalent. The

O 1s spectrum of 1-T102/BiFeO: was shown in (E) in FIG. 4. Lorentzian-Gaussian in

Xpseak4.1 program was used to perform peak-differentiating and imitating on O 1s with background removed. The O Is spectrum of 1-TiO2/BiFeOs could be divided into two peaks at 529.8 eV and 531.5 eV. Ti-O bond was formed at the binding energy of 529.8 eV, and the peak at the binding energy of 531.5 eV was related to an oxide absorbed on the photocatalyst. By the above analysis, it was shown that TiO; was successfully loaded on

BiFeO: according to the solutions of the present disclosure to obtain 1-TiO2/BiFeOs without causing damage to the electronic structure of BiFeQOs.

[73] NN: adsorption-desorption (by BET method)

[74] Na: adsorption-desorption analysis was performed. Nz adsorption-desorption isotherms of 1-Ti02/BiFeO: were shown in (A) in FIG. 5, and a BJH pore size distribution curve of 1-T102/BiFeO; was shown in (B). According to the major categories divided by

International Union of Pure and Applied Chemistry (IUPAC), it could be clearly observed that the adsorption curve of 1-T102/BiFeO; was V type H3 hysteresis loop, indicating that 1-Ti02/BiFeO; had microporous and mesoporous structures. The BJH pore size distribution curve showed a major pore size distribution range of 1 to 20 nm, with a specific surface area of 153.64 m?/g. By combining the SEM and TEM images, it would be seen that TiO; having the spherical structure prepared with the peanut shell as the biological template inhibited the growth size of BiFeO: and the flocculent structure of 1-

TiO2/BiFeOs was conducive to the response to visible light and the photocatalytic activity.

[75] UV-vis DRS

[76] UV-Vis DRS was used to analyze the photocatalyst. The UV-Vis DRS spectra of

TiO, BiFeO;, and TiO2/BiFeO: in different doping ratios were shown in FIG. 6. As shown, TiO: exhibited the light absorption characteristic only in the ultraviolet region, with the absorption edge at 378 nm. The absorption edge of BiFeOs; was expanded by 25 nm to 410 nm, indicating that excellent light absorption performance would be exhibited in the visible light region. The absorption edge of TiO2/BiFeO; was expanded by 70 nm to 450 nm, indicating that compared with the pure phase materials, the composite exhibited stronger response to light. This might be attributed to the doping of C from the biological template peanut shell or the formed heterogeneous structure. By calculation, the forbidden bandwidths of the pure phases TiO; and BiFeQOs, and the TiO2/BiFeOs photocatalysts with different doping ratios (0.5-TiO2/BiFeOs, 0.8-TiO2/BiFeOs, 1-

Ti02/BiFeO: (TiO2/BiFe0s), and 1.5-TiO2/BiFe0s) were sequentially 3.26 eV, 2.23 eV, 2.57 eV, 2.37 eV, 1.92 eV, and 2.49eV, and the photocatalyst with the smallest forbidden bandwidth was 1-T102/B1FeO: photocatalyst.

[77] PL analysis

[78] PL was mainly used in comparative analysis of the photon-generated carrier recombination rates in the photocatalytic materials. Photoluminescence spectra of BiFeO: and 1-T10:2/BiFeO; were shown in FIG. 7. By contrast, 1-T102/BiFeO; showed lower PL spectrum emission intensity than the pure phase BiFeO3 photocatalyst, indicating a relatively low photon-generated carrier recombination rate in 1-TiQ»/BiFeOs. This might be attributed to that the tight binding of BiFeO; and TiO: caused translocation of the photon-generated carrier at the interface and that the electrons generated on the BiFeOs conduction band were transferred rapidly through TiO», resulting in reduced recombination of photon-generated electrons and holes and hence improved photocatalytic degradation activity.

[79] Photocatalytic comparison test

[80] TiO. BiFeOs, and TiO2/BiFeOs (doped with each other in different ratios of 0.5 mol/mol, 0.8 mol/mol, 1 mol/mol, and 1.5 mol/mol) photocatalysts were selected to degrade triclosan. As could be seen from FIG. 8, the degradation rates of TiO, BiFeO: and I-TiO2/BiFeOs to triclosan were 38.7%, 49.3%, and 77.8%, respectively.

[81] Comparison of photocatalysts with different doping ratios

[82] The photocatalysts with the doping ratios of 0.5 mol/mol, 0.8 mol/mol, 1 mol/mol, and 1.5 mol/mol were selected and tested on photocatalytic performance, with the degradation results being shown in FIG. 9. With increasing doping ratio, the photocatalytic performance first improved and then declined. The degradation rates were 67.8%, 68.5%, 81.2%, and 74.9%, which were related to the specific surface area. It could be seen that the best degradation effect was achieved when the doping ratio was 1 mol/mol.

The hierarchical porous TiOz was able to effectively inhibit the size of BiFeQs, limit its growth, increase active sites, excite more electrons and holes, and suppress size increase, with no agglomeration and enhanced photocatalyst performance.

[83] Concentration of triclosan

[84] The influence of the initial concentration of triclosan on the degradation rate was studied. Four initial concentrations of triclosan were chosen: 5 ppm, 10 ppm, 15 ppm, and 20 ppm, with degradation results being shown in FIG. 10. When the other conditions were constant, with increasing initial concentration, the degradation rates of triclosan were 81.2%, 86.2%, 83.1%, and 82.2%, respectively. It was shown that when the initial concentration of triclosan was 5 ppm, active sites on the surface of the photocatalyst did not reach a dynamic equilibrium, and when the initial concentration was increased to 10 ppm, the active sites reached a dynamic equilibrium point. When the initial concentration was further increased, the active sites on the surface of the photocatalyst increased, leading to reduced hydroxyl radical and superoxide radicals adsorbed on the surface of the photocatalyst and hence decreased degradation rates.

[85] Study on the mechanism of photocatalysis

[86] A changing trend of total organic carbon concentration in 1-T102/BiFeO: solution for degrading triclosan with reaction time (mineralization dynamics) was shown in FIG. 11. As could be seen from FIG. 11, after triclosan at the initial concentration of 10 mg/L was degraded with 0.5 g/L of 1-T102/BiFeO3 under simulated sunlight for 3 hours, its

IO mineralization rate was 58.9%.

[87] Trapping results of active species in 1-T10;/BiFeO; solution for degrading triclosan were shown in FIG. 12. In the trapping experiment of active species, sodium oxalate was used as h” inhibiting trapping agent, while isopropanol as OH inhibiting trapping agent, sodium thiosulfate as e° inhibiting trapping agent, and p-benzoquinone as

O% inhibiting trapping agent. The sodium oxalate, the isopropanol, the sodium thiosulfate and the p-benzoquinone were separately added to the solution, each in an amount of 0.1 mmol, to determine the active substances degrading triclosan.

[88] According to the experimental results shown in FIG. 12, the sodium oxalate and the isopropanol exhibited an inhibitory effect, resulting in a decrease in the degradation rate; and the sodium thiosulfate and the p-benzoquinone exhibited no significant inhibitory effect but a slight promoting effect, resulting in that the degradation rate was basically consistent with that when no trapping agent was added. It was indicated that h” and OH were the active substances for degrading triclosan. Relatively speaking, OH exhibited a more significant inhibiting effect for triclosan and was the principal active oxidizing substance.

[89] By analyzing the results of the trapping experiment, it could be seen that the mechanism of triclosan degradation by 1-T102/B1FeO: was probably as follows: when the energy of the irradiation light was greater than the forbidden bandwidth of the BiFeO3, electrons would be excited from the valence band and transferred to the conduction band, and h* would be generated around the valence band. The electrons were transferred to the

TiO: photocatalyst, and oxygen molecules were trapped to generate O”. The h* oxidized water molecules in the valence band would generate OH. Triclosan molecules adsorbed on the surface of BiFeO; were oxidized by OH and 0%, and finally, most of triclosan molecules were oxidized. Since the peanut shell used as the biological template had the mesoporous structure, the specific surface area of TiO; was increased, leading to increased active sites and enhanced photocatalytic activity. In addition, TiO: and BiFeO: formed the heterogeneous structure, and the existence of the heterogeneous structure could be well confirmed by such characterization means as TEM and XPS. The heterogeneous structure could effectively reduce the electron-hole recombination rate, thus improving the photocatalytic activity. BiFeO; had the forbidden bandwidth of 2.23 eV and could be easily excited to generate electron-hole pairs. The TiO; had the forbidden bandwidth of 3.26 eV and was not easy to excite. When the two materials were doped with each other, the forbidden bandwidth would be 1.92 eV and uniform lattice fringes were formed. Under irradiation of light emitted by a xenon lamp, the electrons would move from BiFeO3 to the conduction band of TiO, thus inhibiting electron-hole recombination and improving the photocatalytic performance.

[90] The mechanism of triclosan photodegradation by the 1-TiO2/BiFeO; photocatalyst might be expressed as the following process:

[91] BiFeOs+hv—BiFeO3(e +h’)

[92] BiFeOs(e)+1i0,—BiFeQs+Ti0O:(e)

[93] 7iO:e) +0: Ti02+ Or

[94] BiFeQs(h')+H.O— OH+H'

[95] -OH+TCS-—degradation product ~~ CO:++H:0

[96] h++TCS—degradation product ...........CO2+H20

[97] The foregoing are merely descriptions of the preferred examples of the present disclosure, and are not meant to limit the present disclosure in any form. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should be deemed as falling within the protection scope of the present disclosure.

Claims

Conclusions l. Preparation method of a photocatalyst, which includes the following steps: soaking peanut shells in a hydrochloric acid solution to obtain acid-treated peanut shells; subjecting the acid-treated peanut shells to extraction in ammonium hydroxide to obtain pretreated peanut shells; soaking the pretreated peanut shells in a tetra-n-butyl titanate solution to obtain a photocatalyst precursor; and calcining the photocatalyst precursor to obtain the photocatalyst.

Preparation method according to claim 1, wherein the hydrochloric acid solution has a mass concentration of 5%.

Preparation method according to claim 1 or 2, wherein the ammonium hydroxide has a mass concentration of 5%.

The preparation method according to claim 1, wherein the extraction is carried out for 3 hours.

Preparation method according to claim 1, wherein the calcination is carried out at a temperature of 550°C which is maintained for 4 hours.

The preparation method according to claim 1 or 5, wherein a room temperature rises to the calcining temperature at a rate of 2°C/min.

A photocatalyst prepared by the preparation method according to any one of claims 1 - 6, comprising TiO2 particles and BiFeO: covering the T1O2 particles, with a specific surface area of the photocatalyst ranging from 144.36 - 153, 64 m?/g.

A photocatalyst according to claim 7, wherein a molar ratio of the TiO:-

particles to the BiFeO: in the photocatalyst (0.2 — 1.5):1 1s.

9. Photocatalyst according to claim 7 or 8, wherein the molar ratio of the TiO» particles to the BiFeO: in the photocatalyst is 0.2:1, 0.5:1, 0.8:1, 1:1 or 1.5:1.

Use of the photocatalyst according to any one of claims 7 to 9 in degrading triclosan.