A NOVEL METHOD AND A SAND/WATER REMEDIATION SYSTEM WITH A PHOTOCATALYTIC FUEL CELL

Abstract

The present invention belongs to the sewage treatment and sand remediation technology, it is about a new type of system and method about sand/water remediation with photocatalytic fuel cell. The characteristic photocatalytic fuel cell (PFC) using photons or solar energy to produce highly active electron/holes is introduced into soil remediation system to degrade pollutants. In the constructed Visible light photocatalytic fuel cell sand water remediation system, there was 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 were connected by wires with an external resistance. Using 50 W halogen lamp as the light source, it maintains photocatalysis and electrocatalytic reactions to degrade pollutants in the system. By degrading the pollutants in the overlying water, the pollutants in the sand were also desorbed and degraded, and rapidly decreased to a very low level. Thus in this system water purification treatment and sand remediation take place simultaneously.

Claims

1. A novel system and method of sand/water remediation with photocatalytic fuel cell, wherein: in characteristic photocatalytic fuel cells, photons and/or solar energy are used to excite highly active electron/holes to degrade pollutants; thus, a soil/sand remediation system made of visible light responsive photocatalytic fuel cell was constructed to decontaminate solid sands from pollutions; the system consisted of overlying water above sand in a tubular reactor; the pollutant solution that may reach static adsorption equilibrium was treated; the photocatalytic fuel cell has built-in immersed photocatalytic anode and photoelectric catalytic cathode that are connected by wires; and 50 W halogen lamp was used to simulate the solar light, it maintains photocatalysis and electrocatalytic reaction that degrade pollutants inside the system; by degrading the pollutants in the overlying water, the pollutants in sand was also desorbed and degraded, that decreased the content in sand to a very low level, thus achieved the remediation purpose.

2. The novel system according to the sand/water remediation system described in claim 1, wherein when Mn(III) was produced by dropping-in solution containing KMnO.sub.4 /bisulfate, MnO.sub.4.sup. reacted with HSO.sub.3.sup. and that introduced new active species, that improved photocatalytic degradation of pollutants.

3. The novel system according according to claim 1 about sand/water remediation system and method, wherein cyclodextrin was added to the sand, promoting the mass transfer between sand and water, more pollutants migrated from sand to the overlying water, then being degraded by photoelectrocatalysis, achieved water decontamination and sand remediation.

4. The novel system according to the sand/water remediation system of claim 1, the system and method wherein the anode photocatalyst is Ag/Ag/GO and the cathode photocatalyst is ZnIn.sub.2S.sub.4.

5. The novel system according to the sand/water remediation system of the claim 3, wherein the photocatalytic anode has Ag/Ag/GO and the photocatalytic cathode has ZnIn.sub.2S.sub.4.

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

7. The novel system according to the sand/water remediation system of claim 5, wherein the anode Ag/Ag/GO catalyst was obtained by precipitation-light reduction method, in which silver-ammonia solution was used as a silver source; the photocatalytic cathode ZnIn.sub.2S.sub.4 was synthesized by hydrothermal method; silica sol was 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 was stirred throughly to a gain a homogeneous sol paste; catalytic electrodes were prepared by evenly coating the paste into stainless steel mesh eg with the size of 5 cm*3 cm, then air dried at room temperature; the amount of nanophotocatalyst per square centimeter is 5 mg.

Description

DESCRIPTION OF FIGURES

[0016] 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.

[0017] FIG. 2 shows the decontamination of sand pollution in the remediation system of sodium bisulfite/potassium permanganate. The concentration of pollutants in the sand was obviously reduced.

[0018] FIG. 3 is a comparison diagram of the degradation effect of the pollutants in the overlying water after cyclodextrin was added to the remediation system.

[0019] FIG. 4 shows the distribution of pollutants in water and sand over time in the remediation system.

IMPLEMENTATION CASES

[0020] The following are detailed descriptions of the implementation example of the technical scheme and the attached figures.

Implementation 1: The Degradation of Tetracycline in the Sand/Water Remediation System of Photocatalytic Fuel Cell

[0021] At the bottom of the tubular reactor, 25g of sand was added, and 150 mL of 20 mg/L tetracycline solution was put into the reactor, settled 1d 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 uv-visible 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.

[0022] 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.4and 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.

Implementation 2: The Effect of Cyclodextrin on the Degradation of Tetracycline in the Remediation System

[0023] 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.

[0024] 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.

Implementation 3: The Degradation of RhB in the Sand/Water Remediation System of Photocatalytic Fuel Cell

[0025] 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.

[0026] 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.