Preparation method of a visible-light-driven CC@SnS.SUB.2./SnO.SUB.2 .composite catalyst, and application thereof

Abstract

The present invention disclosed preparation method of a visible-light-driven CC@SnS.sub.2/SnO.sub.2 composite catalyst, and application thereof, comprising the following steps: preparing CC@SnS.sub.2 composite material in a solvent by using SnCl.sub.4.5H.sub.2O and C.sub.2H.sub.5NS as raw materials and carbon fiber cloth as a supporting material; calcining said CC@SnS.sub.2 composite material to obtain the visible-light-driven CC@SnS.sub.2/SnO.sub.2 composite catalyst. The present invention overcomes defects of the traditional methods of treating chromium-containing wastewater, including chemical precipitation, adsorption, ion exchange resin and electrolysis, and the photocatalytic technology can make full use of solar light source or artificial light source without adding adsorbent or reducing agent. In this case, the use of semiconductor photocatalyst to convert hexavalent chromium in chromium wastewater into less toxic and easily precipitated trivalent chromium greatly reduces the cost and energy consumption.

Claims

1. A preparation method of a visible-light-driven CC@SnS.sub.2/SnO.sub.2 composite catalyst, consisting of the two following steps in a sequential order without any additional steps: 1) preparing CC@SnS.sub.2 composite material in isopropanol by using SnCl.sub.4.5H.sub.2O and C.sub.2H.sub.5NS as raw materials and carbon fiber cloth as a supporting material; 2) calcining said CC@SnS.sub.2 composite material to obtain the visible-light-driven CC@SnS.sub.2/SnO.sub.2 composite catalyst, wherein in step 2), a calcination temperature is 400 C. and a calcination time is 15 minutes.

2. The preparation method of a visible-light-driven CC@SnS.sub.2/SnO.sub.2 composite catalyst according to claim 1, wherein in step 1), the molar ratio of SnCl.sub.4.5H.sub.2O and C.sub.2H.sub.5NS is (1.5 to 2):(5 to 10), a reaction temperature is 150 to 200 C., a reaction time is 12 to 20 h.

3. The preparation method of a visible-light-driven CC@SnS.sub.2/SnO.sub.2 composite catalyst according to claim 1, wherein in step 1), the SnCl.sub.4.5H.sub.2O and C.sub.2H.sub.5NS are stirred and mixed with isopropanol for 10 to 30 min, and then carbon fiber cloth is added for further reaction; cooling to room temperature after a reaction of the SnCl.sub.4.5H.sub.2O and C.sub.2H.sub.5NS is completed, a product of the reaction of the SnCl.sub.4.5H.sub.2O and C.sub.2H.sub.5NS is washed with deionized water and ethanol respectively, and dried to obtain CC@SnS.sub.2 composite material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows SEM images of CC@SnS.sub.2, CC@SnS.sub.2/SnO.sub.2 and CC@SnO.sub.2 in implementation 1 to 6.

(2) FIG. 2 shows XRD of CC@SnS.sub.2, CC@SnS.sub.2/SnO.sub.2 and CC@SnO.sub.2 in implementation 1 to 6.

(3) FIG. 3 shows the degradation of hexavalent chromium in water with CC@SnS.sub.2, CC@SnS.sub.2/SnO.sub.2 and CC@SnO.sub.2 in implementation 1 to 6.

(4) FIG. 4 shows cyclic performance of CC@SnS.sub.2/SnO.sub.2-2 for the reduction of hexavalent chromium in implementation 8.

DETAILED DESCRIPTION OF THE INVENTION

(5) The invention will be further described according to the following specific implementations.

Implementation 1

Synthesis of CC@SnS.SUB.2

(6) 1.6 mmol SnCl.sub.4.5H.sub.2O is added in a reaction kettle including 30 mL isopropanol and stirred till dissolved. Adding 6 mmol C.sub.2H.sub.5NS and stirring for 30 min. After that, a piece of carbon fiber cloth of 22 cm.sup.2 is immersed in the kettle standing against the wall, and the kettle is heated at 180 C. for 24 h in an oven. After cooling to room temperature, the product is collected and rinsed with deionized water and ethanol repeatedly and finally dried in an oven at 60 C.

(7) In order to observe the morphology of the composite material, the product prepared by this implementation is characterized by SEM. FIG. 1 is a SEM image of a visible light-responsive CC@SnS.sub.2 catalyst prepared in this implementation. (a) is CC@SnS.sub.2 catalyst prepared in this implementation.

Implementation 2

Synthesis of CC@SnS.SUB.2./SnO.SUB.2

(8) The prepared product of implementation 1 is placed in a quartz boat and calcined at 400 C. for 15 min in a tube furnace to obtain a CC@SnS.sub.2/SnO.sub.2 composite.

(9) In order to observe the morphology of the composite material, the product prepared by this implementation is characterized by SEM. FIG. 1 is a SEM image of a visible light-responsive CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation. (b) is CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation.

Implementation 3

Synthesis of CC@SnS.SUB.2./SnO.SUB.2

(10) The prepared product of implementation 1 is placed in a quartz boat and calcined at 400 C. for 30 min in a tube furnace to obtain a CC@SnS.sub.2/SnO.sub.2 composite.

(11) In order to observe the morphology of the composite material, the product prepared by this implementation is characterized by SEM. FIG. 1 is a SEM image of a visible light-responsive CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation. (c) is CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation.

Implementation 4

Synthesis of CC@SnS.SUB.2./SnO.SUB.2

(12) The prepared product of implementation 1 is placed in a quartz boat and calcined at 400 C. for 45 min in a tube furnace to obtain a CC@SnS.sub.2/SnO.sub.2 composite.

(13) In order to observe the morphology of the composite material, the product prepared by this implementation is characterized by SEM. FIG. 1 is a SEM image of a visible light-responsive CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation. (d) is CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation.

Implementation 5

Synthesis of CC@SnS.SUB.2./SnO.SUB.2

(14) The prepared product of implementation 1 is placed in a quartz boat and calcined at 400 C. for 60 min in a tube furnace to obtain a CC@SnS.sub.2/SnO.sub.2 composite.

(15) In order to observe the morphology of the composite material, the product prepared by this implementation is characterized by SEM. FIG. 1 is a SEM image of a visible light-responsive CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation. (e) is CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation.

Implementation 6

Synthesis of CC@SnO.SUB.2

(16) The prepared product of implementation 1 is placed in a quartz boat and calcined at 400 C. for 90 min in a tube furnace to obtain a CC@SnO.sub.2 composite.

(17) In order to observe the morphology of the composite material, the product prepared by this implementation is characterized by SEM. FIG. 1 is a SEM image of a visible light-responsive CC@SnO.sub.2 catalyst prepared in this implementation. (f) is CC@SnS.sub.2/SnO.sub.2 catalyst prepared in this implementation.

(18) Based on the above, it can be seen from FIG. 1 (a) that the sheets of the CC@SnS.sub.2 catalyst are composed of hexagonal SnS.sub.2 sheets. When starting calcination, the SnO.sub.2 particles appear on the CC@SnS.sub.2 catalyst to form CC@SnS.sub.2/SnO.sub.2 composite catalyst. It is found from FIG. 1 (b) to (e) that with the oxidation time increases, the amount of the SnO.sub.2 particles increases and start to aggregate. Therefore, when the calcination time reaches 90 min, the SnO.sub.2 nanosheets composed of SnO.sub.2 nanoparticles are formed. Moreover, the retention of the nanosheet structure during calcination can be attributed to the stable support of CC and the slow oxidation rate at lower temperatures.

(19) FIG. 2 shows the XRD pattern of CC@SnS.sub.2, CC@SnS.sub.2/SnO.sub.2 and CC@SnO.sub.2, where (a) to (d) represent the products of implementation 2 to 5, respectively. It is clear that the increasing calcination time led to an increase in the peak intensity of the SnO.sub.2 phase at the expense of decreasing the peak intensity of SnS.sub.2, demonstrating that SnS.sub.2 on carbon cloth gradually becomes SnO.sub.2. Meanwhile, it is worth noting that no unassigned diffraction peaks are present for any sample, which illustrates the high purity of the catalysts.

Implementation 7

Photocatalytic Reduction of Hexavalent Chromium (Cr(VI)) by CC@SnS.SUB.2., CC@SnS.SUB.2./SnO.SUB.2 .and CC@SnO.SUB.2

(20) 120 mg photocatalysts obtained in implementation 1 to 6 is added into 50 mL of Cr(VI) solution at a concentration of 10 mg/L. The samples are treated in the dark for 60 min at room temperature to achieve adsorption-desorption equilibrium. After that, the system is illuminated under a 300 W xenon lamp. At each 20 min interval, 3 mL of solution is extracted and analyzed by recording the variations in the absorption band maximum (540 nm) of Cr(VI) using a UV-Vis spectrometer. FIG. 3 shows the photocatalytic reduction of Cr(VI) solution (10 mg/L) in the presence of 120 mg of CC@SnS.sub.2, CC@SnS.sub.2/SnO.sub.2-(a-d), and CC@SnO.sub.2, under visible light irradiation. It can be seen that the photocatalytic activities of CC@SnS.sub.2/SnO.sub.2-(a) and CC@SnS.sub.2/SnO.sub.2-(b) are higher than that of CC@SnS.sub.2. However, CC@SnS.sub.2/SnO.sub.2-(c) and CC@SnS.sub.2/SnO.sub.2-(d) exhibited lower photocatalytic activity. The CC@SnS.sub.2/SnO.sub.2-(b) displayed the highest photocatalytic activity. When irradiated for 60 min with CC@SnS.sub.2/SnO.sub.2-(b), Cr(VI) in aqueous solution almost completely reduced. In this experiment, the reduction of Cr(VI) in water by CC@SnS.sub.2/SnO.sub.2-(b) is greatly improved because of inhibiting the recombination of electrons and holes.

Implementation 8

Cycling Photocatalytic Reduction of Hexavalent Chromium (Cr(VI)) by CC@SnS.SUB.2./SnO.SUB.2

(21) The composite material CC@SnS.sub.2/SnO.sub.2-(b) recollected after 60 minutes of illumination in implementation 7 is washed with water and ethanol, dried and placed in 50 mL hexavalent chromium solution (10 mg/L). The xenon lamp is used to simulate sunlight for 60 min, and 3 mL is extracted as sample every 20 minutes. The absorbance at 540 nm of the water sample is measured using an UV-vis spectrophotometer. According to the above steps, repeat 3 times, test and record the data.

(22) It can be seen from FIG. 4 that the composites maintain excellent photocatalytic performance after three cycles and the final removal efficiency of hexavalent chromium in solution is more than 90%. Therefore, the catalyst can be reused with good stability.