M.Perez R.Jacobs poster 2015
1
Experimental Sample Preparation Particle Sizes Particles of various sizes were prepared by both hand grinding and ball milling processes. Hand grinding was performed using an agate mortar and pestle. Alternatively, other particle sizes were obtained using a high speed ball mill. Samples were extracted at various times to ensure different particle sizes. Doped TiO 2 Electron doped TiO 2 samples were synthesized using high temperature solid-state reactions. Stoichiometric amounts were mixed, pressed into pellets, and sealed in evacuated quartz tubes. The sealed tubes were placed in high temperature furnaces. 2% Ti 3+ Doped TiO 2 0.98 TiO 2 + 0.01 Ti 2 O 3 900 ºC TiO 1.99 12 hrs 4% Ti 3+ Doped TiO 2 0.96 TiO 2 + 0.02 Ti 2 O 3 900 ºC TiO 1.98 12 hrs TaON Stoichiometric amounts of TaCl 5 , Li 3 N, and Li 2 O were weighed out and pelletized inside an argon chamber, sealed in an evacuated silica tube, and heated in a high temperature furnace. In many reactions, Li ions were not fully removed from the system, so the samples were consequently heated with iodine in a different sealed evacuated tube (Figure 7). TaCl 5 + LiO 2 + Li 3 N TaON + 5LiCl LiTa(O x N 1-x ) 3 + 0.5 I 2 TaON + LiI Analysis Formation and purity of all the products were Photocatalytic Treatment of Organic Wastewater Pollutants References 1. Mezyk, S., et al. ACS Symposium Series 1071: Aquatic Redox Chemistry, 1071, 247, (2011). 2. Scanlon, D.O., et al., Nature Materials 12, 798–801 (2013) Roxanne Jacobs , Minué Perez , JoAnna Milam, Stephen Mezyk, and Shahab Derakhshan Keck Energy Materials Program Department of Chemistry and Biochemistry California State University, Long Beach, CA 90840 Acknowledgements This research was supported by W. M. Keck Foundation through the Keck Energy Materials Program (KEMP) at CSULB. Background and Significance Typically, wastewater treatment employs an adsorptive or transformative process 1 . These processes are effective however not always efficient for large scale projects. Our focus is solid catalysts that can employ UV and visible light energy to degrade wastewater contaminants. TiO 2 -assisted photocatalytic degradation of Methylene Blue (a wastewater contaminant) was investigated using a solar simulator. The degradation as a function of time was monitored by samples being taken at different times throughout the exposure within the solar simulator. The absorbance of each solution was quantified employing a UV-Vis spectrophotometer. In addition, the role of particle size, suspension, and electron doping, in photocatalytic performance of TiO 2 was investigated. To improve the efficiency of the process in visible range of spectrum, effort was devoted for preparation of transition metal oxy- nitrides. A new route to synthesize TaON was developed, without the involvement of ammonia gas, which is typically used in synthesis of such crystalline systems. For this purpose metathesis reaction was employed and the formation of the desired phases in various reaction conditions were monitored by powder X-ray diffraction technique. Solar Experiment The performance of each solid catalyst was examined by placing 30 mg of catalyst in 200 mL of 15.6 x 10 -6 M methylene blue solution. This suspension was stirred in a glass dish with a water bath to maintain constant temperature throughout the experiment (Figure 2). Samples were taken every 8 minutes for spectroscopy analysis (Figure 3). The absorbance of each solution was quantified utilizing a UV-Vis spectrophotometer that monitored the degradation of methylene blue as a function of time. Future Work Diffuse reflectance spectroscopy will be used to determine the wavelength of the energy absorbed, which is technique closely related to UV-Vis spectrophotometry. This will enable us to perform further chemical modifications to tune the desired band gap for semiconducting catalysts. In addition, the surface area of the samples will be analyzed employing BET method. This work will continue by analysing the performance of various mixtures of doped TiO 2 samples within the solar experiment to evaluate their photocatalytic activity. The oxy-nitride synthesis method will continue to be refined with the goal of producing pure product. This new method will be continue to be applied towards Ta x Nb 1-x ON products (0 < x < 1) in order to manipulate the conductance band and valence band at the same time. Results and Discussion Particle Size Dependency Particle size analysis revealed that ball milling process resulted in an increased average particle size, which in turn caused less suspension and reduced surface area and photocatalytic activity of the particles (Figure 4). Comparing the first-order decay of the wastewater contaminant using the hand ground and ball-milled TiO 2 samples, revealed that the former exhibits higher photocatalytic activity (Figure 5). Doped TiO 2 The X-ray data for the doped TiO 2 samples were compared. The peaks shift to the left as Ti 3+ content (electron doping) increases. A selected peak for undoped, 2%, and 4% rutile samples were at 27.450°, 27.440°, and 27.428°, respectively. This is consistent with Bragg’s Law as the d-spacing within the unit cell increases, the θ will decrease. TaON Synthesis of pure TaON product was attempted, however X-ray diffraction results continuously displayed LiTaO 3 as the main product. Synthesis of pure LiTaO 3 was then performed in order to compare X-ray results to previous attempts at TaON synthesis (Figure 6). X-ray analysis indicated that LiTa(O x N 1-x ) 3 was likely present. In past experiments, TaON did not show up in the X-ray results until after the sample was washed to dissolve LiCl and reheated. After washing, LiTaO 3 was still displayed as the main product. In order to drive out the excess lithium, an iodine de-intercalation reaction (Figure 7) was employed, yielding the highest percentage of TaON at 38%. Figure 6: A comparison of LiTaO 3 and an attempt at TaON synthesis. Figure 7: Iodine de-intercalation reaction. Figure 5: The degradation of methylene blue follows a first- order rate decay. The slope of the equations correspond to the rate constant of each catalyst. Figure 1: Schematic representation of photocatalytic removal of organic pollutants. Figure 4: Particle size distribution of the hand ground and ball-milled samples. Figure 2: Experiment set up for photocatalytic reactions. Figure 3: Appearance of samples after being exposed to light at different time intervals
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Transcript of M.Perez R.Jacobs poster 2015
ExperimentalSample PreparationParticle Sizes Particles of various sizes were prepared by both hand grinding and ball milling processes. Hand grinding was performed using an agate mortar and pestle. Alternatively, other particle sizes were obtained using a high speed ball mill. Samples were extracted at various times to ensure different particle sizes.
Doped TiO2 Electron doped TiO2 samples were synthesized using high temperature solid-state reactions. Stoichiometric amounts were mixed, pressed into pellets, and sealed in evacuated quartz tubes. The sealed tubes were placed in high temperature furnaces.
2% Ti3+ Doped TiO2 0.98 TiO2 + 0.01 Ti2O3 900 ºC TiO1.99
12 hrs
4% Ti3+ Doped TiO2
0.96 TiO2 + 0.02 Ti2O3 900 ºC TiO1.98
12 hrsTaONStoichiometric amounts of TaCl5, Li3N, and Li2O were weighed out and pelletized inside an argon chamber, sealed in an evacuated silica tube, and heated in a high temperature furnace. In many reactions, Li ions were not fully removed from the system, so the samples were consequently heated with iodine in a different sealed evacuated tube (Figure 7).
TaCl5 + LiO2 + Li3N TaON + 5LiClLiTa(OxN1-x)3 + 0.5 I2 TaON + LiI
Analysis Formation and purity of all the products were monitored using powder X-ray diffraction, employing a PANalytical Xpert Pro MPD diffractometer, equipped with a linear X’Celerator detector, with Cu Kα1 radiation. The X-ray diffraction data were collected at room temperature in the range of 10° ≤ 2θ ≤ 70° with ~0.008° steps. Each particle size was analyzed using a consistent mass of 80:20 TiO2 and flow rate within the Micromeritics Digisizer.
Photocatalytic Treatment of Organic Wastewater Pollutants
References1. Mezyk, S., et al. ACS Symposium Series 1071: Aquatic Redox Chemistry, 1071, 247,
(2011).2. Scanlon, D.O., et al., Nature Materials 12, 798–801 (2013)
Roxanne Jacobs, Minué Perez, JoAnna Milam, Stephen Mezyk, and Shahab Derakhshan Keck Energy Materials Program
Department of Chemistry and Biochemistry California State University, Long Beach, CA 90840
AcknowledgementsThis research was supported by W. M. Keck Foundation through the Keck Energy Materials Program (KEMP) at CSULB.
Background and SignificanceTypically, wastewater treatment employs an adsorptive or transformative process1. These processes are effective however not always efficient for large scale projects. Our focus is solid catalysts that can employ UV and visible light energy to degrade wastewater contaminants. TiO2-assisted photocatalytic degradation of Methylene Blue (a wastewater contaminant) was investigated using a solar simulator. The degradation as a function of time was monitored by samples being taken at different times throughout the exposure within the solar simulator. The absorbance of each solution was quantified employing a UV-Vis spectrophotometer. In addition, the role of particle size, suspension, and electron doping, in photocatalytic performance of TiO2 was investigated. To improve the efficiency of the process in visible range of spectrum, effort was devoted for preparation of transition metal oxy-nitrides. A new route to synthesize TaON was developed, without the involvement of ammonia gas, which is typically used in synthesis of such crystalline systems. For this purpose metathesis reaction was employed and the formation of the desired phases in various reaction conditions were monitored by powder X-ray diffraction technique.
Solar Experiment The performance of each solid catalyst was examined by placing 30 mg of catalyst in 200 mL of 15.6 x 10-6 M methylene blue solution. This suspension was stirred in a glass dish with a water bath to maintain constant temperature throughout the experiment (Figure 2). Samples were taken every 8 minutes for spectroscopy analysis (Figure 3). The absorbance of each solution was quantified utilizing a UV-Vis spectrophotometer that monitored the degradation of methylene blue as a function of time.
Future WorkDiffuse reflectance spectroscopy will be used to determine the wavelength of the energy absorbed, which is technique closely related to UV-Vis spectrophotometry. This will enable us to perform further chemical modifications to tune the desired band gap for semiconducting catalysts. In addition, the surface area of the samples will be analyzed employing BET method.
This work will continue by analysing the performance of various mixtures of doped TiO2 samples within the solar experiment to evaluate their photocatalytic activity. The oxy-nitride synthesis method will continue to be refined with the goal of producing pure product. This new method will be continue to be applied towards TaxNb1-xON products (0 < x < 1) in order to manipulate the conductance band and valence band at the same time.
Results and DiscussionParticle Size Dependency Particle size analysis revealed that ball milling process resulted in an increased average particle size, which in turn caused less suspension and reduced surface area and photocatalytic activity of the particles (Figure 4). Comparing the first-order decay of the wastewater contaminant using the hand ground and ball-milled TiO2 samples, revealed that the former exhibits higher photocatalytic activity (Figure 5).
Doped TiO2 The X-ray data for the doped TiO2 samples were compared. The peaks shift to the left as Ti3+ content (electron doping) increases. A selected peak for undoped, 2%, and 4% rutile samples were at 27.450°, 27.440°, and 27.428°, respectively. This is consistent with Bragg’s Law as the d-spacing within the unit cell increases, the θ will decrease.
TaONSynthesis of pure TaON product was attempted, however X-ray diffraction results continuously displayed LiTaO3 as the main product. Synthesis of pure LiTaO3 was then performed in order to compare X-ray results to previous attempts at TaON synthesis (Figure 6). X-ray analysis indicated that LiTa(OxN1-x)3 was likely present. In past experiments, TaON did not show up in the X-ray results until after the sample was washed to dissolve LiCl and reheated. After washing, LiTaO3 was still displayed as the main product. In order to drive out the excess lithium, an iodine de-intercalation reaction (Figure 7) was employed, yielding the highest percentage of TaON at 38%.
Figure 6: A comparison of LiTaO3 and an attempt at TaON synthesis.Figure 7: Iodine de-intercalation reaction.
Figure 5: The degradation of methylene blue follows a first-order
rate decay. The slope of the equations correspond to the rate
constant of each catalyst.
Figure 1: Schematic representation of photocatalytic removal of organic
pollutants.
Figure 4: Particle size distribution of the hand ground and ball-milled samples.
Figure 2: Experiment set up for photocatalytic reactions.
Figure 3: Appearance of samples after being exposed to light at
different time intervals
