Disclosure of Invention
An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
To achieve these objects and other advantages in accordance with the present invention, there is provided a method for preparing surface-oxidized tin disulfide nanosheets-coated tellurium nanowires for treating radioactive wastewater, comprising the steps of:
step one, stirring TeO2Slowly add to N2H4·H2In O, stirring until TeO2Completely dissolving, then dripping the sodium dodecyl sulfate solution, stirring for 0.5-1.5 h, and then centrifuging at the speed of 7000-9000 rpm for 8-15 min; dispersing the centrifuged product in distilled water to obtain a Te nanowire solution;
step two, sodium dodecyl benzene sulfonate and SnCl4·5H2Adding O and L-cysteine into a mixed solvent of ethylene glycol and distilled water, stirring for 5-15 min, then adding a Te nanowire solution, and stirring for 15-25 min to obtain a reaction solution; and (3) moving the reaction solution into a polytetrafluoroethylene high-pressure reaction kettle, heating at 150-170 ℃ for 8-12 h, cooling the reaction system to room temperature, centrifuging, collecting precipitate, washing with distilled water and absolute ethyl alcohol for 5-8 times, and drying in a vacuum oven at 55-65 ℃ for 8-12 h to obtain the surface oxidized tin disulfide nanosheet-coated tellurium nanowire.
Preferably, in the first step, TeO2And N2H4·H2The mass-to-volume ratio of O is 1g: 400-450 mL; the concentration of the sodium dodecyl sulfate solution is 8-12 mmol/L; the TeO2The mass-volume ratio of the sodium dodecyl sulfate solution to the sodium dodecyl sulfate solution is 1g: 3500-4000 mL.
Preferably, in the second step, sodium dodecyl benzene sulfonate and SnCl4·5H2The mass ratio of O to L-cysteine is 2-3: 1: 2.4-3; the volume ratio of the ethylene glycol to the distilled water is 1: 1; the SnCl4·5H2The mass volume ratio of the O to the mixed solvent of the glycol and the distilled water is 1g: 300-350 mL; the SnCl4·5H2The mass-volume ratio of the O to Te nanowire solution is 1g: 100-120 mL.
Preferably, in the second step, before the reaction liquid is transferred to the high-pressure reaction kettle, an Nd: YAG pulse laser is used for carrying out ultraviolet pulse laser irradiation on the reaction liquid.
Preferably, the irradiation time of the ultraviolet pulse laser is 5-10 min; the wavelength of the ultraviolet pulse laser irradiation is 355nm, the pulse width is 15-25 ns, and the pulse frequency is 20-35 Hz; the single pulse energy is 60-135 mJ.
Preferably, in the second step, the centrifugally collected precipitate is directly put into a supercritical device and soaked in a supercritical acetone-water system with the temperature of 360-370 ℃ and the pressure of 10-18 MPa for 5-10 min; the volume ratio of acetone to water in the supercritical acetone-water system is 2: 1.
The invention provides an application of the surface oxidized tin disulfide nanosheet-coated tellurium nanowire in radioactive wastewater treatment, the surface oxidized tin disulfide nanosheet-coated tellurium nanowire is added into the uranium-containing radioactive wastewater, the uranium-containing radioactive wastewater is stirred for 60min under a dark condition, and then a photocatalytic reaction is carried out under a condition that a xenon lamp simulates sunlight, so that the photocatalytic reduction of hexavalent uranium in the uranium-containing radioactive wastewater is realized.
The invention at least comprises the following beneficial effects:
the tellurium nanowires wrapped by the surface-oxidized tin disulfide nanosheets prepared by the method can better treat uranium-containing wastewater, and the introduction of the Te nanowires provides hot electron injection through a plasma effect under the illumination condition; SnS2The surface oxidation of the uranium provides abundant surface hydroxyl groups as the limited domain sites of the uranium, so that the uranium has higher photocatalytic reduction capability on hexavalent uranium.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Description of the drawings:
FIG. 1 shows an embodiment of the invention SnS2The (a) TEM and (b-c) HRTEM images of (a);
FIG. 2 shows Te @ SnS of the present invention2The (a) TEM and (b) HRTEM images of (a);
FIG. 3 is Te @ O-SnS of the present invention2The (a) TEM and (b-c) HRTEM images of (a);
FIG. 4 shows an embodiment of the invention SnS2、Te@SnS2And Te @ O-SnS2XRD spectrum of (1);
FIG. 5 shows the present inventionMing SnS2、Te@SnS2And Te @ O-SnS2XPS total spectrum of (a);
FIG. 6 shows an embodiment of the present invention SnS2、Te@SnS2And Te @ O-SnS2Sn 3d (a) and Te 3dXPS high resolution spectra of (1);
FIG. 7(a) is a graph showing the measurement of Te and SnS by UPS spectroscopy2、Te@SnS2And Te @ O-SnS2The secondary electron cut-off edge of (b) is SnS2、Te@SnS2And Te @ O-SnS2The Zeta potential of (c) is Te or SnS2、Te@SnS2And Te @ O-Sn S2 ultraviolet-visible absorption spectrum;
FIG. 8 shows an embodiment of the present invention SnS2、Te@SnS2And Te @ O-SnS2(ii) an infrared spectrum;
FIG. 9 shows an embodiment of the present invention SnS2、(b)Te@SnS2And (c) Te @ O-SnS2Water contact angle of (c);
FIG. 10(a) shows SnS2、Te@SnS2And Te @ O-SnS2Electroreduction potential for uranium (uranium concentration 80. mu.g/L, NaNO)3The concentration of (a) is 0.5mol/L, the temperature is 293K, and (b) is SnS after the uranium is photocatalytically reduced2、Te@SnS2And Te @ O-SnS2Oxidation potential (NaNO)3The concentration of (3) is 0.5mol/L and the temperature is 293K);
FIG. 11 shows Te @ O-SnS under different pH conditions2The photocatalysis removal effect on U (VI) (the concentration of tannic acid is 1mg/L, the concentration of uranium is 8mg/L, the solid-liquid ratio is 0.25g/L, and the temperature is 293K);
FIG. 12 shows Te @ O-SnS under different solid-to-liquid ratios2The photocatalysis removal effect on U (VI) (the concentration of tannic acid is 1mg/L, the concentration of uranium is 8mg/L, the temperature is 293K, and the pH is 4.8);
FIG. 13 shows Te @ O-SnS at different initial concentrations2The photocatalysis removal effect on U (VI) (the concentration ratio of uranium to tannic acid is 8:1, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8);
FIG. 14 shows SnS2、Te@SnS2And Te @ O-SnS2The photocatalytic removal effect on U (VI) (the concentration of uranium is 8mg/L, the concentration of tannic acid is 1mg/L, the solid-to-liquid ratio is 0.25g/L, and the temperature is 29 DEG)3K, pH 4.8);
FIG. 15 is Te @ O-SnS2The cycle stability of U (VI) (uranium concentration of 8mg/L, tannic acid concentration of 1mg/L, solid-to-liquid ratio of 0.25g/L, temperature of 293K, pH of 4.8);
FIG. 16 shows SnS2、Te@SnS2And Te @ O-SnS2The removal effect on the tannic acid (the concentration of uranium is 8mg/L, the concentration of the tannic acid is 1mg/L, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8);
FIG. 17 is Te @ O-SnS2And 1-Te @ O-SnS2The photocatalysis removal effect on U (VI) (the concentration of uranium is 8mg/L, the concentration of tannic acid is 1mg/L, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8);
FIG. 18 is Te @ O-SnS2And 2-Te @ O-SnS2The photocatalysis removal effect on U (VI) (the concentration of uranium is 8mg/L, the concentration of tannic acid is 1mg/L, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8);
FIG. 19 is Te @ O-SnS2And 3-Te @ O-SnS2The photocatalytic removal effect on U (VI) (the concentration of uranium is 8mg/L, the concentration of tannic acid is 1mg/L, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8).
The specific implementation mode is as follows:
the present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
Example 1:
a preparation method of a tellurium nanowire wrapped by a tin disulfide nanosheet for treating surface oxidation of radioactive wastewater comprises the following steps:
step one, under stirring, 24mg of TeO2Addition to 10mL of N2H4·H2In O, stirring until TeO2The solution is completely dissolved and turns blue, then 90mL of 10mmol/L sodium dodecyl sulfate solution is dropped into the solution, and the solution is stirred for 1h and then is stirred at 8000rpmCentrifuging at high speed for 10 min; dispersing the centrifuged product in distilled water to obtain a Te nanowire solution;
step two, 0.2g of sodium dodecyl benzene sulfonate and 0.09g of SnCl4·5H2Adding O and 0.24g L-cysteine into a mixed solvent of 30mL of ethylene glycol and distilled water (v/v is 1:1), stirring for 10min, then adding 10mL of Te nanowire solution, and stirring for 20min to obtain a reaction solution; transferring the reaction solution into a polytetrafluoroethylene high-pressure reaction kettle, heating at 160 ℃ for 10h, cooling the reaction system to room temperature, centrifugally collecting precipitate, washing with distilled water and absolute ethyl alcohol for 6 times, and drying in a vacuum oven at 60 ℃ for 10h to obtain surface-oxidized tin disulfide nanosheets wrapped with tellurium nanowires, namely Te @ O-SnS2。
Example 2:
a preparation method of a tellurium nanowire wrapped by a tin disulfide nanosheet for treating surface oxidation of radioactive wastewater comprises the following steps:
step one, under stirring, 24mg of TeO2Addition to 10mL of N2H4·H2In O, stirring until TeO2Completely dissolving, wherein the color of the solution is changed into blue, then dripping 90mL of 10mmol/L sodium dodecyl sulfate solution, stirring for 1h, and then centrifuging at 8000rpm for 10 min; dispersing the centrifuged product in distilled water to obtain a Te nanowire solution;
step two, 0.2g of sodium dodecyl benzene sulfonate and 0.09g of SnCl4·5H2Adding O and 0.24g L-cysteine into a mixed solvent of 30mL of ethylene glycol and distilled water (v/v is 1:1), stirring for 10min, then adding 10mL of Te nanowire solution, and stirring for 20min to obtain a reaction solution; performing ultraviolet pulse laser irradiation on the reaction liquid by using an Nd-YAG pulse laser; transferring the reaction solution after irradiation into a polytetrafluoroethylene high-pressure reaction kettle, heating at 160 ℃ for 10h, cooling the reaction system to room temperature, centrifugally collecting precipitate, washing with distilled water and absolute ethyl alcohol for 6 times, and drying in a vacuum oven at 60 ℃ for 10h to obtain surface-oxidized tin disulfide nanosheets wrapped with tellurium nanowires; i.e. 1-Te @ O-SnS2(ii) a The irradiation time of the ultraviolet pulse laser is 5-10 min; the wavelength of the ultraviolet pulse laser irradiation is355nm, the pulse width is 15-25 ns, and the pulse frequency is 20-35 Hz; the single pulse energy is 60-135 mJ;
FIG. 17 is Te @ O-SnS2And 1-Te @ O-SnS2The photocatalysis removal effect on U (VI) (the concentration of uranium is 8mg/L, the concentration of tannic acid is 1mg/L, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8); YAG pulse laser is used for carrying out ultraviolet pulse laser irradiation on reaction liquid, and the surface oxidized tin disulfide nanosheet prepared by coating tellurium nano-wires on the surface has better photocatalysis effect on uranium.
Example 3:
a preparation method of a tellurium nanowire wrapped by a tin disulfide nanosheet for treating surface oxidation of radioactive wastewater comprises the following steps:
step one, under stirring, 24mg of TeO2Addition to 10mL of N2H4·H2In O, stirring until TeO2Completely dissolving, wherein the color of the solution is changed into blue, then dripping 90mL of 10mmol/L sodium dodecyl sulfate solution, stirring for 1h, and then centrifuging at 8000rpm for 10 min; dispersing the centrifuged product in distilled water to obtain a Te nanowire solution;
step two, 0.2g of sodium dodecyl benzene sulfonate and 0.09g of SnCl4·5H2Adding O and 0.24g L-cysteine into a mixed solvent of 30mL of ethylene glycol and distilled water (v/v is 1:1), stirring for 10min, then adding 10mL of Te nanowire solution, and stirring for 20min to obtain a reaction solution; transferring the reaction solution into a polytetrafluoroethylene high-pressure reaction kettle, heating at 160 ℃ for 10h, cooling the reaction system to room temperature, centrifuging, collecting precipitate, directly putting the centrifugally collected precipitate into a supercritical device, and soaking for 6min in a supercritical acetone-water system at 365 ℃ and 15 MPa; then washing the substrate for 6 times by using distilled water and absolute ethyl alcohol, and drying the substrate for 10 hours in a vacuum oven at the temperature of 60 ℃ to obtain surface oxidized tin disulfide nanosheets wrapped with tellurium nanowires; i.e. 2-Te @ O-SnS2(ii) a The volume ratio of acetone to water in the supercritical acetone-water system is 2: 1.
FIG. 18 is Te @ O-SnS2And 2-Te @ O-SnS2Photocatalytic removal of U (VI) (concentration of uranium)8mg/L, the concentration of tannic acid is 1mg/L, the solid-to-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8); as can be seen from the figure, the photocatalytic effect of the tellurium nano-wires wrapped by the tin disulfide nano-sheets with oxidized surfaces on uranium is better through soaking and precipitating in a supercritical acetone-water system.
Example 4:
a preparation method of a tellurium nanowire wrapped by a tin disulfide nanosheet for treating surface oxidation of radioactive wastewater comprises the following steps:
a preparation method of a tellurium nanowire wrapped by a tin disulfide nanosheet for treating surface oxidation of radioactive wastewater comprises the following steps:
step one, under stirring, 24mg of TeO2Addition to 10mL of N2H4·H2In O, stirring until TeO2Completely dissolving, wherein the color of the solution is changed into blue, then dripping 90mL of 10mmol/L sodium dodecyl sulfate solution, stirring for 1h, and then centrifuging at 8000rpm for 10 min; dispersing the centrifuged product in distilled water to obtain a Te nanowire solution;
step two, 0.2g of sodium dodecyl benzene sulfonate and 0.09g of SnCl4·5H2Adding O and 0.24g L-cysteine into a mixed solvent of 30mL of ethylene glycol and distilled water (v/v is 1:1), stirring for 10min, then adding 10mL of Te nanowire solution, and stirring for 20min to obtain a reaction solution; performing ultraviolet pulse laser irradiation on the reaction liquid by using an Nd-YAG pulse laser; transferring the irradiated reaction solution into a polytetrafluoroethylene high-pressure reaction kettle, heating at 160 ℃ for 10h, cooling the reaction system to room temperature, centrifugally collecting precipitates, directly putting the centrifugally collected precipitates into a supercritical device, and soaking for 6min in a supercritical acetone-water system at 365 ℃ and 15 MPa; then washing the substrate for 6 times by using distilled water and absolute ethyl alcohol, and drying the substrate for 10 hours in a vacuum oven at the temperature of 60 ℃ to obtain surface oxidized tin disulfide nanosheets wrapped with tellurium nanowires; i.e. 3-Te @ O-SnS2(ii) a The volume ratio of acetone to water in the supercritical acetone-water system is 2: 1; the irradiation time of the ultraviolet pulse laser is 5-10 min; the wavelength of ultraviolet pulse laser irradiation is 355nm, the pulse width is 15-25 ns, and the pulse frequency isIs 20 to 35 Hz; the single pulse energy is 60-135 mJ.
FIG. 19 is Te @ O-SnS2And 3-Te @ O-SnS2The photocatalytic removal effect on U (VI) (the concentration of uranium is 8mg/L, the concentration of tannic acid is 1mg/L, the solid-liquid ratio is 0.25g/L, the temperature is 293K, and the pH is 4.8).
Comparative example 1:
step one, under stirring, 24mg of TeO2Addition to 10mL of N2H4·H2In O, stirring until TeO2Completely dissolving, wherein the color of the solution is changed into blue, then dripping 90mL of 10mmol/L sodium dodecyl sulfate solution, stirring for 1h, and then centrifuging at 8000rpm for 10 min; dispersing the centrifuged product in distilled water to obtain a Te nanowire solution;
step two, 0.2g of sodium dodecyl benzene sulfonate and 0.09g of SnCl4·5H2Adding O and 0.24g L-cysteine into 30mL of distilled water, stirring for 10min, then adding 10mL of Te nanowire solution, and stirring for 20min to obtain a reaction solution; transferring the reaction solution into a polytetrafluoroethylene high-pressure reaction kettle, heating at 160 ℃ for 10h, cooling the reaction system to room temperature, centrifugally collecting precipitate, washing with distilled water and absolute ethyl alcohol for 6 times, and drying in a vacuum oven at 60 ℃ for 10h to obtain Te @ -SnS2。
Comparative example 2:
mixing 0.2g sodium dodecylbenzenesulfonate and 0.09g SnCl4·5H2Adding O and 0.24g L-cysteine into 30mL of distilled water, and stirring for 10min to obtain a reaction solution; transferring the reaction solution into a polytetrafluoroethylene high-pressure reaction kettle, heating at 160 ℃ for 10h, cooling the reaction system to room temperature, centrifuging, collecting precipitate, washing with distilled water and absolute ethyl alcohol for 6 times, and drying in a vacuum oven at 60 ℃ for 10h to obtain SnS2。
FIG. 1 shows an embodiment of the invention SnS
2The (a) TEM and (b-c) HRTEM images of (a); FIG. 2 shows Te @ SnS of the present invention
2The (a) TEM and (b) HRTEM images of (a); FIG. 3 is Te @ O-SnS of the present invention
2The (a) TEM and (b-c) HRTEM images of (a); TEM image display Te @ O-SnS
2And Te @ SnS
2A typical 1D-2D hybrid structure is presented. On the (101) face of the Te nanowire, a plane pitch of
The lattice fringes of (2). At Te @ SnS
2Similar results were also observed in the samples. Te @ O-SnS
2The HRTEM images of (g) show that in the nanoplatelet region most of the phases exhibit two closest lattice fringes with an orientation angle of 60 ° and a face-to-face spacing of
This corresponds to a hexagonal SnS
2The (100) and (010) planes of (1). Another set of the plane spacing is
And
the orthogonal lattice stripes of (A) respectively correspond to square SnO
2The (110) plane and the (002) plane of (A), verified that SnS
2And oxidizing the surface of the nano sheet. Furthermore, SnS
2Leads to a variety of defects including dislocations and faults.
FIG. 4 shows an embodiment of the invention SnS2、Te@SnS2And Te @ O-SnS2XRD spectrum of (1); from XRD of the material, Te @ O-SnS2And Te @ SnS2SnS with two hexagons2And the characteristic peak of the Te nanowire proves that Te @ O-SnS2The successful synthesis of the compound.
X-ray photoelectron Spectroscopy (XPS) analysis was performed using a Kratos Axis Ultra photoelectron Spectroscopy (Thermo escalab 250Xi, Thermo Fisher, USA) using monochromatic AlKαAs an X-ray source. FIG. 5 shows an embodiment of the invention2、Te@SnS2And Te @ O-SnS2XPS total spectrum of (a); FIG. 6 shows an embodiment of the present invention SnS2、Te@SnS2And Te @ O-SnS2Sn 3d (a) and Te 3dXPS high resolution spectra of (1); in XPS spectra, all SnS2The main elements of the substrate are S and Sn, and Te @ SnS2And Te @ O-SnS2Showing an additional Te element, Te @ O-SnS2Additional O elements are shown. Further, the positions of the Sn 3d peak and Te 3d peak correspond to the oxidationSn of state4+And Te0And is at Te @ O-SnS2Is dominant.
The charge change of the surface of the material is analyzed by a Zeta potentiometer (zetaPALS); ultraviolet photoelectron spectroscopy was performed on an X-ray photoelectron spectrometer (UPS, Thermo escalab 250Xi, Thermo Fisher, US) with a monochromatic He I source (21.22 eV). To verify Te @ O-SnS2We analyzed the UPS spectrum and zeta potential of the sample. FIG. 7(a) is a graph showing the measurement of Te and SnS by UPS spectroscopy2、Te@SnS2And Te @ O-SnS2The secondary electron cut-off edge of (b) is SnS2、Te@SnS2And Te @ O-SnS2The Zeta potential of (c) is Te or SnS2、Te@SnS2And Te @ O-Sn S2 ultraviolet-visible absorption spectrum; as shown, Te nanowire, SnS2Nanosheet, Te @ SnS2And Te @ O-SnS2Respectively 15.87eV, 18.69eV, 18.79eV and 19.19eV, corresponding to work functions of 5.35eV, 2.53eV, 2.43eV and 2.03eV, respectively. SnS2The lower work function of the base sample relative to the Te nanowire is due to SnS2The delocalized electrons caused by the surface defects of the nanosheets. In particular, Te @ O-SnS is due to the abundance of free electrons and oxidation-induced surface defects in conductive Te nanowires2Has the lowest work function. The result shows that Te @ O-SnS2Tends to transfer electrons outward, which may facilitate the reduction of u (vi). Likewise, Te @ O-SnS2Zeta potential ratio SnS2And Te @ SnS2The zeta potential of (a) is more negative, which is also a defect due to integration of free electrons provided by the Te nanowires and surface oxidation. Thus, the introduction of Te nanowires and surface oxidation increases SnS2The negative surface charge of the nano sheet enhances the positive valence UO2 2+Coulomb interaction of ions. The plasmon effect of Te prompted us to further explore SnS caused by the injection of thermal electrons under light irradiation2The electrons at the nanosheet surface accumulate. FIG. 7c shows Te nanowire, SnS2、Te@SnS2And Te @ O-SnS2Ultraviolet-visible spectrum of (a). Plasma adsorption of Te nanowire to ensure Te @ SnS2And Te @ O-SnS2Light response range extension ofUp to the visible/near infrared region.
To verify SnS2Surface oxidation of (2), we studied O-SnS2Functional groups present on the surface. FIG. 8 shows an embodiment of the present invention SnS2、Te@SnS2And Te @ O-SnS2(ii) an infrared spectrum; FIG. 9 shows an embodiment of the present invention SnS2、(b)Te@SnS2And (c) Te @ O-SnS2Water contact angle of (c); as shown, 3436cm-1And 1631cm-1The adsorption bands are respectively related to the stretching vibration and the bending vibration of isolated hydroxyl groups. Te @ O-SnS2Is stronger than SnS2And Te @ SnS2Indicating that surface oxidation results in the formation of-OH groups. The water contact angle of the material is shown in FIG. 9, SnS2Has a water contact angle of 81 degrees, Te @ SnS2The water contact angle of the film is 77 degrees, Te @ O-SnS2Has a water contact angle of 68 DEG, Te @ O-SnS2The lower water contact angle further validates this result. The above results show that the surface oxidation of the added-OH groups provides additional confinement sites for U (VI).
Electrochemical characterization of the materials prepared in the examples and comparative examples was done on a chi760d workstation, with Ag/AgCl (3.5M KCl) and Pt wire as reference and counter electrodes, respectively. The working electrode was prepared as follows: first, 3mg of catalyst powder (materials prepared in example 1 and comparative examples 1 to 2) was mixed with 9mg of carbon black, 30. mu.L of Nafion solution (0.5 wt%), and 2mL of ethanol to obtain a carbon-based catalyst ink. Then, carbon-based catalyst ink was uniformly brushed on 1 × 2cm of carbon paper. At 80. mu.g/LU (VI) +0.5M NaNO3In the electrolyte of (2 mV s)-1Speed of U (VI) reduction LSV curve test, potential window from 0V to-1.6V vs Ag/AgCl. For oxidation of U (IV), at 0.5MNaNO3In solution at 2mV s-1LSV measurements were performed with a potential window of-1.6V to 0V vs Ag/AgCl.
The increase in negative charge and-OH groups is associated with an increase in U (VI) binding strength. FIG. 10(a) shows SnS2、Te@SnS2And Te @ O-SnS2Electroreduction potential for uranium (uranium concentration 80. mu.g/L, NaNO)3At a concentration of 0.5mol/L and a temperature of 293K), and FIG. 10(b) shows SnS after photocatalytic reduction of uranium2、Te@SnS2And Te @ O-SnS2Oxidation potential (NaNO)3At a concentration of 0.5mol/L and at a temperature of 293K). Two peaks appear at-0.36 to-0.44V (vs Ag/AgCl) and-0.88 to-1.13V (vs Ag/AgCl), respectively the peak for U (VI) to U (V) and the peak for U (V) to U (IV). Te @ O-SnS2Peak position ratio SnS2And Te @ SnS2The peak position of (A) is more negative, indicating that Te @ O-SnS2Is the easiest to reduce U (VI) in the three samples. In addition, we have also investigated the SnS after U (VI) reduction deposition2LSV curve of u (iv) oxidation of base material (fig. 10 b). Of the three samples, Te @ O-SnS2The upper deposited u (iv) exhibits the most positive potential. The results demonstrate that Te incorporation and surface oxidation increase uranium in SnS2The binding strength on the surface, which is attributed to the negative charge and the enhanced uranium confinement effect of the surface-OH groups.
In the photocatalytic process, 5mg of the prepared photocatalyst (materials prepared in examples 1 to 4 and comparative examples 1 to 2) was dispersed in 20mL of a dispersion having various concentrations (C)U(VI)Concentrations of 8ppm, 50ppm, 100ppm, 150ppm and 200ppm, respectively, CTA1ppm) in u (vi) solution. The pH was then adjusted with 0.1mol/L NaOH and HCl solution. Before the reaction, the photocatalyst was added under protection from light and stirred for 60 minutes to ensure adsorption-desorption equilibrium. Then, a 300W xenon lamp (BL-GHX-V, China) with an am1.5G filter was used as a light source. The concentrations of U (VI) and TA were determined in a UV spectrophotometer at 651.8nm and 273nm, respectively, over time. After each u (vi) photocatalytic cycle, the photocatalyst was further treated with 0.1M HCl solution under ultrasonic conditions for 4h, washed twice with ultrapure water and twice with alcohol, respectively, to remove uranium. The removal rates (Ads,%) for u (vi) and TA were calculated by the following formula:
Ads=(C0-Ct)/C0×100%;
the enhancement of the u (vi) binding strength prompted us to study the photocatalytic reduction of u (vi) under am1.5g filter xenon lamp conditions (simulated sunlight). TA is used as a sacrificial agent as an organic substance commonly present in real radioactive wastewater. FIG. 14 shows SnS in a solution of 1mg/L TA in 8mg/L U (VI)2、Te@SnS2And Te @ O-SnS2Plots are removed for U (VI) as a function of reaction time. In the absence of illumination, Te @ O-SnS2The removal rate of (2) is 13% which is higher than that of SnS2(19.8%) and Te @ SnS2(25%). After the introduction of the simulated sunlight, Te @ SnS2And Te @ O-SnS2The removal rate of U (VI) is obviously improved, and the removal rate in 60min is 82.3 percent and 97.3 percent respectively. Furthermore, Te @ O-SnS2U (VI) was almost completely removed within 90min, with a removal of 98.6%. At the same time, Te @ O-SnS2Degradation ratio of TA to SnS2And Te @ SnS2Respectively 1.66 times and 1.04 times higher (fig. 16).
As an important factor for evaluating the utility of the photocatalyst, we further evaluated Te @ O-SnS by repeating the photoreduction U (VI) 5 times2Reusability of (2). As shown in FIG. 15, Te @ O-SnS2After 5 cycles, the U (VI) removal rate is kept above 92.4 percent, which means the feasibility of applying the U (VI) extraction in industrial wastewater.
The pH stability is another important index for evaluating the photocatalytic reduction U (VI) performance of the material. Therefore, we studied Te @ O-SnS2The removal rate of U (VI) when the pH of the solution is 2.8-9.8. Te @ O-SnS2Over 88.4% removal was maintained over a wide pH range, with Te @ O-SnS2 reaching 98.6% removal of U (VI) at pH 4.8 (FIG. 11). FIG. 12 is Te @ O-SnS2The removal rate of U (VI) and U (VI) is reduced under different solid-to-liquid ratios of 0.10g/L to 0.40 g/L. When the solid-liquid ratio is more than 0.25g/L, the removal rate can reach more than 98.6 percent. We further tested the initial concentration pair Te @ O-SnS2Influence of photocatalytic reduction of U (VI). Te @ O-SnS at an initial concentration of between 8mg/L and 200mg/L2Both showed higher u (vi) removal (fig. 13). At an initial concentration of 200mg/L, Te @ O-SnS2The extraction of U (VI) reaches 704.8 mg/g. These results show that Te @ O-SnS2Has good application prospect in the complex uranium-bearing actual wastewater treatment environment.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.