PHOTOCATALYSIS AND DEVICE IMPLEMENTING SAME

Abstract

A method and apparatus for photodegradation of pollutants using a modular baffled wastewater purification tank. Baffle surfaces are lined with a photocatalyst film and arrange in such a way to provide liquid turbulence and increased time for the photodegradation processes to occur. For certain embodiments, after water treatment, the baffle walls may be washed, regenerated, and re-introduced in the water treatment tank. The water treatment tank includes a series of UV lamps placed on the top of the photocatalytic chamber. Because of the modular design of the baffled purification system, the water treatment and the change of baffle pads can take place singly or simultaneously.

Claims

1. A flow photocatalytic reactor for degrading pollutants from a liquid in a batch or a continuous process comprising: a plurality of UV sources for photocatalysis; a reaction chamber to photodegrade the pollutants; a plurality of photocatalyst baffles.

2. The apparatus of claim 1 further comprising a number of baffle pads arranged at an angle to each other and to the base.

3. The apparatus of claim 1 further comprising a number of baffle pads arranged in at least two rows.

4. The apparatus of claim 1 further comprising a number of baffle pads arranged in two rows, the baffles in the first row having a length larger than the second row.

5. The apparatus of claim 1 wherein the baffle surface and walls are coated with a porous film containing at least one photocatalytic component.

6. The apparatus of claim 1 wherein the porous photocatalytic film is nanostructured.

7. The apparatus of claim 1 wherein the porous photocatalytic film is attached to the baffler.

8. The apparatus of claim 1 wherein the porous photocatalytic bafflers can be removed, reconditioned and replaced.

9. The apparatus of claim 1 wherein treating the liquid takes place in the photocatalytic chamber where the bafflers creates agitation and recirculation of the passing liquid.

10. The apparatus of claim 1 wherein the transparent walls of the photocatalytic chamber allow for visible light photocatalysis.

11. The apparatus of claim 1, wherein the UV light sources are hung from the ceiling of the chamber and braced by supports.

12. The apparatus of claim 1 wherein the fluid inlet is positioned below the outlet of the fluid from the photocatalytic chamber.

13. The apparatus of claim 1 wherein at least one UV light source located on top of the photocatalytic chamber is positioned in the same direction with the baffler rows.

14. The apparatus of claim 1 wherein the UV light sources are positioned in the proximity of the surface of the catalyst.

15. The apparatus of claim 1 wherein the treatment of water takes place by passing the liquid through the reaction chamber, allowing the necessary time for the pollutant to react with the photocatalyst.

16. The apparatus of claim 1 wherein the photocatalytic reactor has a modular design, wherein the water treatment process taking place simultaneously in multiple photocatalytic reactor.

17. The apparatus of claim 1 wherein the photocatalytic reactor has a modular design, wherein the water treatment process taking place in several stages in a succession of multiple photocatalytic reactor at the same time or at a time.

18. The apparatus of claim 1 wherein the reaction tank has a modular design, wherein the change of the baffle pads occurring individually or simultaneously.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0022] FIG. 1. Lateral view of the photocatalytic reactor.

[0023] FIG. 2. Top view of the photocatalytic chamber.

[0024] FIG. 3. Perspective view of the photocatalytic chamber showing the baffler arrangement.

[0025] FIG. 4. Side view of the photocatalytic chamber along with the cross-section views A-A and B-B.

[0026] FIG. 5. Top view of the photocatalytic chamber showing the direction of the liquid flow.

[0027] FIG. 6. Perspective view of the baffler arrangement.

[0028] FIG. 7. Top view of the baffler arrangement in the photocatalytic chamber along with the cross section view E-E.

[0029] FIG. 8. Front view of the baffler arrangement in the photocatalytic chamber along with the cross section view S-S.

[0030] FIG. 9. Top view of the UV light module along with the cross-section M-M.

[0031] FIG. 10. Lateral view of the UV light module along with the cross-section X-X.

[0032] FIG. 11. Efficiency of the photocatalytic degradation of MB at different initial concentration.

[0033] FIG. 12. Efficiency (%) of nano-anatase for MB degradation cycles.

[0034] FIG. 13. SEM images of the formation of TiO.sub.2 on the surface of Ti sheets (a) and (b) before photocatalytic activity. The TiO.sub.2 was obtained from Ti sheets by contact with a mixture of 0.1 N NaOH and acetone for 72 hours under ambient conditions.

[0035] FIG. 14. Ultraviolet-visible spectra for methylene blue solutions as a function of the irradiation time. Conditions: 1 sheet of TiO.sub.2/Ti was used in the presence of 0.1 mg/L methylene blue.

[0036] FIG. 15. Effect of the contact time upon the photocatalytic degradation of methylene blue for concentrations of 0.01, 0.05, 0.1, 0.2, and 0.3 mg/L. Conditions: 2 sheets of TiO.sub.2/Ti were used to treat 100 mL of methylene blue solution using contact times of 15, 30, 45, 60, 90, and 120 min.

[0037] FIG. 16. Pseudo-first-order kinetic plot for the degradation of methylene blue by TiO.sub.2/Ti at initial methylene blue concentrations of 0.01, 0.05, 0.1, 0.2, and 0.3 mg/L. Conditions: 2 sheets of TiO.sub.2/Ti were used to treat 100 mL of methylene blue solution for contact times up to 120 min.

[0038] FIG. 17. Variation of the pseudo first-order rate constant, k.sub.1, as a function of dye concentration.

[0039] FIG. 18. SEM images of the TiO.sub.2 nanoparticles embedded into PLA electrospun nanofibers at various magnifications.

DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail.

[0041] FIG. 1-2 show the lateral and the top views of the photocatalytic reactor 100 consisting of multiple UV lamps 102 and photocatalytic chamber 104. The UV lamps 102 are placed on top of the photocatalytic chamber 104 and hold in place by support elements 108. The photocatalytic chamber contains bafflers 106 coated with a photocatalytic layer. The bafflers 106 may have attached a thin layer of photocatalytic material. FIG. 3 shows a perspective view of the photocatalytic chamber viewing the baffler arrangement through the transparent walls of the chamber. FIG. 4 shows the side view of the photocatalytic chamber along with the cross-section views A-A and B-B. The position of the inlet to the chamber is below the outlet to allow for recirculation of the fluid. FIG. 5 shows the top view of the photocatalytic chamber, where the arrows point the direction of the liquid flow. The flow rate is established so the liquid remains at least 10-60 min in the photocatalytic chamber depending on the pollutants to be degraded. A pump is pushing the liquid through the inlet into the chamber at a constant flow rate.

[0042] FIG. 6 shows a perspective view of the baffler arrangement in the photocatalytic chamber. The buffers are fixed to the base of the chamber at an angle and arranged in two rows. Buffers in one row are different in width from the bafflers in the other row. FIG. 7 shows a top view of the baffler arrangement in the photocatalytic chamber along with the cross section view E-E. FIG. 8 shows a front view of the baffler arrangement in the photocatalytic chamber along with the cross section view S-S.

[0043] FIG. 9 shows the top view of the UV light module along with the cross-section M-M and FIG. 10 shows the lateral view of the UV light module along with the cross-section X-X. Here there are only 3 UV lights in a module, but more UV lights can be used. Because the photocatalytic chamber has transparent walls, other light sources can be used such as visible light.

[0044] On the surface exposed to light source, baffles are coated with photocatalytic material. A number of processes may be used to coat the surface of baffles, including, but not limited to physical deposition, chemical deposition, metallurgical, electrochemical deposition, or combination thereof. On the surface exposed to light source, photocatalytic film can be attached to the surface of baffles. A number of processes may be used to attach catalytic material to baffles, including, but not limited to mechanical, chemical, metallurgical, electrochemical, or combination thereof.

[0045] In still other embodiments of the present disclosure, a catalytic material comprising a plurality of catalytic nanoparticles supported on a structured support is provided. For example, the structured support may comprise a nanostructured surface such as etched Ti surface, nanofiber non-woven mat, foam etc.

[0046] In certain exemplary embodiments, nanofibers may be combined with microfibers to form an inhomogeneous mixture of fibers. In other exemplary embodiments, a combination of nano and micrometer fibers may be formed as an overlayer on an underlayer comprising the non-woven fibrous web support layer. A number of processes may be used to produce and deposit nanoparticles and nanofibers, including, but not limited to melt blowing, melt spinning, electrospinning, gas jet fibrillation, or combination thereof.

IMPLEMENTATIONS AND EXAMPLES OF THE INVENTION

[0047] Without intent to limit the scope of the invention, exemplary methods and their related results according to the embodiments of the present invention are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the invention. Moreover, certain theories are proposed and disclosed herein; however, in no way they, whether they are right or wrong, should limit the scope of the invention so long as the invention is practiced according to the invention without regard for any particular theory or scheme of action.

Example 1

[0048] According to the present invention, the photocatalytic degradation of methylene blue (MB) by TiO.sub.2 nanopowder is presented. In this exemplary embodiment, about 5 mL of titanium tetra iso-propoxide (Ti(OCH(CH.sub.3).sub.2].sub.4, Sigma-Aldrich, 97%) was added to a mixture of 5 mL acetic acid (CH.sub.3COOH, Sigma-Aldrich) and 50 mL ethanol (C.sub.2H.sub.5OH, Sigma-Aldrich). The mixture was continuous stirred for 30 min; dilute ammonia aqueous solution (1N NH.sub.3, Sigma-Aldrich) was then added to reach the pH 10. The precipitate was washed thoroughly with distilled water and ethanol before dried at 100° C. The powder was calcined at 550° C. for 1 h to improve the crystallinity of the nano-anatase. The photocatalytic activity of nano-anatase was measured based on the reaction rate of the photocatalytic degradation of MB. The results show that the MB efficiency increases with the irradiation time, demonstrating the photocatalytic degradation of MB. FIG. 11, shows that MB efficiency decreases from 99.72 to 78% with increasing the concentrations from 0.5 to 8 mg/L during the 60 min irradiation time. To confirm the photocatalytic stability of the nano-anatase on the degradation of MB, the experiments where repeated tree times consecutively reusing the nano-anatase powder. The stability of the powder was assessed after three cycles of photocatalytic degradation of MB. FIG. 12 shows that the photocatalytic degradation of MB by nano-anatase depends on the contact time. In the first cycle, the photocatalytic degradation of MB increases from 43 to 89% with increasing the contact time from 15 to 60 min, but it drops below 39% in the third cycle at 60 min irradiation time.

Example 2

[0049] According to the present invention, the photocatalytic degradation of methylene blue (MB) by TiO.sub.2 nanopowder is presented. In this exemplary embodiment, Ti sheets with 2 cm diameter and 3 mm thickness were used. In a typical synthesis, the Ti sheets were chemically polished and treated by sonication with distilled water for 30 minutes to obtain a clean and homogeneous surface. The Ti sheets were subsequently left for 72 hours in a solution of 0.1 N NaOH and acetone at room temperature. The nanostructured Ti sheets were washed with distilled water and dried. X-ray diffraction (XRD) analysis has demonstrated the formation of TiO.sub.2 on Ti sheet. The SEM images presented in FIG. 13 show the formation of TiO.sub.2 on the edges of the pores structure that has an average size distribution from 36 to 356 nm. Photocatalytic activity pf the nanostructured porous surface was investigated on the degradation of methylene blue under four fluorescent tubes served as the source for ultraviolet light with vertical irradiation. Photocatalytic experiments were performed on the degradation of 100 mL aqueous solution of methylene blue using various TiO.sub.2/Ti sheets with different amounts of TiO.sub.2 nanostructures. Prior to irradiation, in order to allow the system to reach equilibrium, the TiO.sub.2/Ti sheets were magnetically stirred for 30 min in the dark and exposed to ultraviolet light. During the irradiation, 5 mL of solution was collected at regular time intervals. The photocatalytic degradation of the MB dye was monitored using an ultraviolet-visible spectrophotometer at 665 nm wavelength. The degradation of the methylene blue solution was evaluated using the following equation:

% Dye Efficiency=(C.sub.o−C)/C.sub.o×100   (1)

where C is the concentration of methylene blue at a given time (mg/L) and C.sub.o is the initial concentration of methylene blue (mg/L).

[0050] To characterize the mechanism of photocatalytic degradation of methylene blue using TiO.sub.2/Ti, experimental kinetic measurements were performed by first order kinetics:

1n C/C.sub.o=−k.sub.1t   (2)

where C.sub.o represents the initial the initial concentration of methylene blue (mg/L), C is the concentration of methylene blue at time t (min), and k.sub.1 is the pseudo-first-order rate constant (min.sup.−1) and second order kinetics:

1/C−1/C.sub.o=k.sub.2t   (3)

where k.sub.2 is the pseudo-second-order rate constant. By plotting (1/C−1/C.sub.o) vs t, the pseudo-second-order rate constant (k.sub.2) can be obtained from the slope. The photocatalytic degradation of methylene blue by TiO.sub.2/Ti from the synthetic wastewater solution was evaluated using ultraviolet-visible spectroscopy for a contact time of 8 hours (FIG. 14). The results show that with increasing irradiation time, the absorbed MB at 665 nm decreased, which indicates that the presence of TiO.sub.2/Ti has induced the degradation of the dye. The photocatalytic activity of TiO.sub.2/Ti film was studied by monitoring the degradation of methylene blue by ultraviolet light. To understand the influence of the initial methylene blue concentration on the degradation rate, wastewater solutions containing 0.01, 0.05, 0.1, 0.2, and 0.3 mg/L methylene blue were used for two sheets of TiO.sub.2/Ti. The results show that the highest efficiency was obtained at 99.12% for an initial methylene blue concentration of 0.01 mg/L in the first 15 min irradiation time. With an increase in the methylene blue concentration from 0.01 to 0.3 mg/L, the efficiency decreased from 99.24% to 22.56% at 60 min irradiation time (FIG. 15).

[0051] FIG. 16 shows that the photocatalytic degradation of methylene blue follows the pseudo first-order kinetics, which indicates than an increase in dye concentration results in a linear decrease in reaction rate (FIG. 17). The pseudo-first-order kinetic model provided a better fit than pseudo-second-order kinetics for the photocatalytic degradation of methylene blue by the TiO.sub.2/Ti catalyst. The highest value of k.sub.1 was 0.02560 min.sup.−1.

Example 3

[0052] According to another embodiment of the present invention, electrospinning techniques may be used to form nanofibrous non-woven mats to coat the baffler surface exposed to light according to the various embodiments of the present invention as described above. Electrospinning is a method of choice to produce fibers, which uses electric force to draw charged threads of polymer solutions or polymer melts up to fiber diameters in the order of nanometers. The process does not require coagulation or high temperatures to produce solid threads from solution. This makes the process particularly suited to the production of fibers using large and complex molecules. Electrospinning ensures that no solvent can be carried over into the final product. Depending on the size of the collector, large areas of membranes can be obtained. When a sufficiently high voltage is applied to a liquid droplet, the body of the liquid becomes charged, and electrostatic repulsion counteracts the surface tension and the droplet is stretched; at a critical point a stream of liquid erupts from the surface. This point of eruption is known as the Taylor cone. If the molecular cohesion of the liquid is sufficiently high, a charged liquid jet is formed. The size of an electrospun fiber can be in the nano scale and the fibers may possess nano scale surface texture, leading to different modes of interaction with other materials compared with macroscale materials. In addition to this, the ultra-fine fibers produced by electrospinning are expected to have two main properties, a very high surface to volume ratio, and a relatively defect free structure at the molecular level. This first property makes electrospun material suitable for activities requiring a high degree of physical contact, such as providing sites for chemical reactions, or the capture of small sized particulate material by physical entanglement—filtration. The second property should allow electrospun fibers to approach the theoretical maximum strength of the spun material, opening up the possibility of making high mechanical performance composite materials. FIG.18 shows a few SEM images at different magnification as examples of the TiO.sub.2 nanoparticles embedded into a Poly(L-lactide) (PLA) nanofiber non-woven mesh. The PLA nanofibers were obtained from PLA solution obtained by dissolving 10 wt. % in a solvent mixture of 90 wt. % chloroform and 10 wt. % dimethylformamide.