Sand/water remediation method with a photocatalytic fuel cell

Abstract

A method in sand/water remediation by using photocatalytic fuel cell is related to the sewage treatment and sand/soil remediation field. The characteristic photocatalytic fuel cell uses photons or solar energy to produce highly active electron/holes is introduced to degrade pollutants. In the constructed visible light photocatalytic fuel cell, there is overlying water above polluted sands in a tubular reactor. Allowing static adsorption equilibrium to buildup, in the built photocatalytic fuel cell, the photocatalytic anode and photoelectric catalytic cathode are connected by wires with an external resistance. Using 50 W halogen lamp as the light source, it maintains photocatalysis and electro-catalytic reactions to degrade pollutants in the method. By degrading the pollutants in the overlying water, the pollutants in the sand are also desorbed and degraded, and rapidly decreased to a very low level. Thus in this method water purification treatment and sand remediation take place simultaneously.

Claims

1. A method for sand/water remediation by using a photocatalytic fuel cell, wherein the photocatalytic fuel cells apply photons and/or solar energy to excite highly active electron/holes to degrade pollutants; and the photocatalytic fuel cells are visible light responsive; the method comprising the steps of: overlying water over sand in a tubular reactor; treating pollutant solution with the pollutants that may reach static adsorption equilibrium; establishing the photocatalytic fuel cells with immersed photocatalytic anode and photoelectric catalytic cathode that are connected by wires; and providing 50 W halogen lamp for photocatalysis and electro-catalytic reactions to degrade the pollutants in the tubular reactor; wherein by degrading the pollutants in the overlying water, the pollutants in sand is desorbed and degraded, to decrease the pollutants in sand and achieve the remediation.

2. The method according to claim 1, wherein Mn(III) is produced by dropping-in solution containing KMnO.sub.4/bisulfate, MnO.sub.4.sup. reacted with HSO.sub.3.sup. to improve photocatalytic degradation of the pollutants.

3. The method according to claim 1, further comprising adding cyclodextrin to the sand to promote the pollutant migrating from the sand to the overlying water, and degrading the pollutants by the photocatalysis and electro-catalytic reactions to achieve the water decontamination and sand remediation.

4. The method according to claim 1, wherein the photocatalytic anode is Ag/Ag/GO and the photocatalytic cathode is ZnIn.sub.2S.sub.4.

5. The method according to claim 3, wherein the photocatalytic anode is Ag/Ag/GO and the photocatalytic cathode is ZnIn.sub.2S.sub.4.

6. The method according to claim 4, wherein the photocatalytic anode is Ag/Ag/GO and prepared by precipitation-light reduction method, in which silver-ammonia solution is used as a silver source; the photocatalytic cathode is ZnIn.sub.2S.sub.4 and synthesized by a hydrothermal method; silica sol is prepared by stirring the mixture of ethyl ortho-silicate, anhydrous ethanol, deionized water and concentrated hydrochloric acid, at a volume ratio of 4.5:10:9:2.45; after adding photo-catalysts into the silica sol, the sol is stirred thoroughly to a gain a uniform sol-paste; catalytic electrodes are prepared by evenly coating the sol-paste onto a stainless steel mesh sized at 5 cm*3 cm, then dried at room temperature; the amount of nano-photocatalyst per square centimeter is 5 mg.

7. The method according to claim 5, wherein the photocatalytic anode is Ag/Ag/GO and obtained by precipitation-light reduction method, in which silver-ammonia solution is used as a silver source; the photocatalytic cathode is ZnIn.sub.2S.sub.4 and synthesized by hydrothermal method; silica sol is prepared by stirring a mixture with ethyl orthosilicate, anhydrous ethanol, deionized water and concentrated hydrochloric acid at a volume ratio of 4.5:10:9:2.45; after adding catalysts into silica sol, the sol is stirred thoroughly to a gain a homogeneous sol paste; catalytic electrodes are prepared by evenly coating the paste into stainless steel mesh with the size of 5 cm*3 cm, then air dried at room temperature; the amount of nano-photocatalyst per square centimeter is 5 mg.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a comparison diagram of the degradation effect of the pollutants in the overlying water before and after the addition of sodium bisulfite/potassium permanganate in the process of sand/water remediation in photocatalytic fuel cells.

(2) FIG. 2 shows the decontamination of sand pollution in the remediation method of sodium bisulfite/potassium permanganate. The concentration of pollutants in the sand was obviously reduced.

(3) FIG. 3 is a comparison diagram of the degradation effect of the pollutants in the overlying water after cyclodextrin addition.

(4) FIG. 4 shows the distribution of pollutants in water and sand over time in the remediation method.

DETAILED DESCRIPTION OF THE INVENTION

(5) The following are detailed descriptions of the implementation example of the technical scheme and the attached figures.

Example 1: The Degradation of Tetracycline in the Sand/Water Remediation Method of Photocatalytic Fuel Cell

(6) At the bottom of the tubular reactor, 25 g of sand was added, and 150 mL of 20 mg/L tetracycline solution was put into the reactor, settled Id for adsorption equilibrium. Catalyst Ag/AgCl/GO loaded stainless steel was used as Photocatalytic anode, ZnIn2S4 loaded on stainless steel as photocatalytic cathode, an external 51 resistance was connected, with 50 w halogen lamp placed on the top, the light source was 5 cm from the solution surface. Take samples at intervals for analysis. If Add KMnO.sub.4 and NaHSO.sub.3 at the same time (The concentration of KMnO4 in the solution was 7 mg/L, and NaHSO.sub.3 was 23 mg/L), then water samples and soil samples were taken simultaneously for analysis measurement. The water samples were measured by uvvisible spectrophotometer at 358 nm after filtration of 0.45 um. The soil samples were dried in 50 C. in oven. 3 mL extract was added with the mixture of 0.1 mol/L NaCl, 0.5 mol/L oxalate and ethanol (25/25/50 volume ratio). After fully shaking, followed ultrasound treatment for 15 min, 8000 r/min centrifugation for 10 min. Repeat the above extraction for three times, the extract was determined after filtration.

(7) FIG. 1 shows that as time goes on, the degradation rate of tetracycline in the solution was increasing, more significantly after the addition of KMnO.sub.4 and NaHSO.sub.3. FIG. 2 shows that the content change of tetracycline in sand before and after the addition of KMnO.sub.4 and NaHSO.sub.3. The results showed that the content of tetracycline in the sand was significantly decreased after the addition.

Example 2: The Effect of Cyclodextrin on the Degradation of Tetracycline in the Remediation Method

(8) 25 g of sand was added to the bottom of the tubular reactor. 150 ml 20 mg/L tetracycline solution was put in, also 5 mg cyclodextrins. The tetracycline solution without cyclodextrin was used as the control group, set aside for one day stay for adsorption equilibrium; With 50 w halogen lamp placed above the reactor, catalyst Ag/AgCl/GO was loaded stainless steel for Photocatalytic anode, stainless steel as cathode, 51 external resistance was connected in the circuit, water samples were took at intervals, measured by uv-visible spectrophotometer after filtration of 0.45 um.

(9) FIG. 3 shows that the content of tetracycline in solution decreases gradually, the degradation rate increases with time. After adding cyclodextrin, the degradation rate of tetracycline is increased.

Example 3: The Degradation of RhB in the Sand/Water Remediation Method by Photocatalytic Fuel Cell

(10) 25 g of sand was added to the tubular reactor, 150 mL 20 mg/L RhB solution with 0.1 mol/L Na.sub.2SO.sub.4 was put in. It was set aside for one day, after reaching adsorption equilibrium. Photocatalytic fuel cells was constructed using electrodes inserted in overlying water (using Ag/AgCl/GO loaded photocatalytic anode and ZnIn.sub.2S.sub.4 loaded cathode), 100 external resistance was connected. 50 w halogen lamps were installed on both sides of the catalytic electrodes for vertical illumination, 5 cm away from photocatalytic electrodes. Water samples and soil samples were took at intervals, The water samples were filtered by 0.45 um filter and measured at 553 nm with spectrophotometer. The sand was extracted using ultra pure water. 3 mL water extract was added for extraction each time, then vortex, ultrasonic treatment 15 min, then 8000 r/min centrifugation for 10 min, repeated extraction three times. All extracts were combined after three extractions, then the extract was measured.

(11) FIG. 4 shows the concentration of RhB in overlying water and sand. The concentration of RhB in sand/water gradually decreased over time. It shows that the concentration of RhB in overlying water can influence the distribution of RhB in sand. By degrading and decreasing the content of RhB in the overlying water, the content in sand was also reduced and the remediation was achieved.