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Photocatalytic oxidation of carbonyl sulfide in the presence of CO
ABSTRACTS
In my opinion, this was the most successful of the three environmental workshops we have presented, and the cost was minimal. The Texas Water Commission and Texas A & M University provided speakers at no cost other than a little help with travel expenses. Lamar University provided the facilities and faculty services, and through this grant we were able to provide teaching materials, food, lecturers, and transportation. As a representative of the Museum and the Lamar History Department, I thank the EPA and GCHSRC for the financial support that made this very successful program possible. We have reached approximately 700 students over the past year as a result of this funded workshop.
P H O T O C A T A L Y T I C OXIDATION OF C A R B O N Y L S U L F I D E IN THE P R E S E N C E O F CO Ali T-Raissi Florida Solar Energy Center, 3300 State Road 401, Cape Canaveral, Florida 32920, U.S.A.
Chlorination of titanium oxide ore, in the presence of coke, is the most widely used process for manufacturing high quality, pigment-grade TiO2: TIO2+2C+2CI2 2CO+TiCI4, followed by high temperature oxidation of TiCl4 to TiO2. Sulfur in coke is the source of COS emissions from the chloride process, at 500-5000 ppmv levels. In addition, the gaseous emissions contain 1-5% by volume carbon monoxide. Pigment TiO2 synthesis accounts for approximately 1/3 of all abiogenic COS emissions into the atmosphere. Carbonyl sulfide ranks 37th on the U.S. EPA 1991 Toxic Release Inventory list. As a stable photocatalyst, TiO2 has been used extensively to oxidize a large number of organic contaminants in both water and air. The anatase form of titania has a bandgap of 3.0 eV and is readily activated upon exposure to light at near ultraviolet wavelengths. Since COS itself is known to be photochemically active, it appears plausible that titania may be used to catalyze photooxidation reactions involving trace COS in the process vent gases. Moreover, titania produced from the chloride process may prove potentially useful in catalyzing destruction reactions leading to COS and CO removal.
359
At the Florida Solar Energy Center (FSEC), we have developed semiconductor particle based detoxification processes which employ special immobilization techniques in conjunction with the UV excitation to treat hazardous organic contaminants (e.g., U.S. Patent No. 5,246,737). FSEC process was used to study the treatability of carbonyl sulfide in process vent gases that mimic those found in the chloride process. The main objective of this work was to evaluate, via an exploratory research, the effectiveness of FSEC-developed process for treating gaseous streams containing 1-5% of CO and 5005000 ppm of COS in an approximately 50/50 mixture of CO2 and N2. Several continuous flow photoreactors that employ low-pressure mercury lamps as the light source have been designed and fabricated. COS, CO and their photooxidation byproducts have been analyzed using GC-MS (COS, CS2, H2S), GC (CO, CO2), and spectrophotometric (SO2, SO3) techniques. Results, to date, indicate that COS photocatalytic oxidation can be accomplished with destruction and removal efficiencies exceeding 97%. The reaction products of COS photooxidation, detected, were CO, CO2, SO2, and SO3. However, in the presence of TiO2, photooxidation of COS yielded, mostly, products of deep oxidation, i.e. CO2 and SO3. In the absence of catalyst, SO and SO2 were the main photoreaction byproducts. In addition, our data indicated that COS can be selectively oxidized in the presence of carbon monoxide and CO2. L E A C H A B I L I T Y AND
B I O D E G R A D A T I O N OF HIGH C O N C E N T R A T I O N S O F P H E N O L AND O-CHLOROPHENOL C. Vipulanandan, Deborah Roberts, and Dennis Clifford Department of Civil and Environmental Engineering, University of Houston, 4800 Cullen Blvd., Houston, Texas 77204-4791, U.S.A.
The treatability of phenol and o-chlorophenol by solidification/stabilization and phenol by biodegradation was investigated. The effect of two concentrations, 0.1 and 2% of contaminant in cement (equivalent to 2,000 and 40,000 ppm in water) on the setting and solidification process of Type 1 Portland cement was studied. Leachability of these phenolic compounds from the solidified cement matrix, cured up to 180 days was evaluated using the U.S. EPA recommended Toxicity Characteristic Leaching Procedure (TCLP) and the American Nu-
In my opinion, this was the most successful of the three environmental workshops we have presented, and the cost was minimal. The Texas Water Commission and Texas A & M University provided speakers at no cost other than a little help with travel expenses. Lamar University provided the facilities and faculty services, and through this grant we were able to provide teaching materials, food, lecturers, and transportation. As a representative of the Museum and the Lamar History Department, I thank the EPA and GCHSRC for the financial support that made this very successful program possible. We have reached approximately 700 students over the past year as a result of this funded workshop.
P H O T O C A T A L Y T I C OXIDATION OF C A R B O N Y L S U L F I D E IN THE P R E S E N C E O F CO Ali T-Raissi Florida Solar Energy Center, 3300 State Road 401, Cape Canaveral, Florida 32920, U.S.A.
Chlorination of titanium oxide ore, in the presence of coke, is the most widely used process for manufacturing high quality, pigment-grade TiO2: TIO2+2C+2CI2 2CO+TiCI4, followed by high temperature oxidation of TiCl4 to TiO2. Sulfur in coke is the source of COS emissions from the chloride process, at 500-5000 ppmv levels. In addition, the gaseous emissions contain 1-5% by volume carbon monoxide. Pigment TiO2 synthesis accounts for approximately 1/3 of all abiogenic COS emissions into the atmosphere. Carbonyl sulfide ranks 37th on the U.S. EPA 1991 Toxic Release Inventory list. As a stable photocatalyst, TiO2 has been used extensively to oxidize a large number of organic contaminants in both water and air. The anatase form of titania has a bandgap of 3.0 eV and is readily activated upon exposure to light at near ultraviolet wavelengths. Since COS itself is known to be photochemically active, it appears plausible that titania may be used to catalyze photooxidation reactions involving trace COS in the process vent gases. Moreover, titania produced from the chloride process may prove potentially useful in catalyzing destruction reactions leading to COS and CO removal.
359
At the Florida Solar Energy Center (FSEC), we have developed semiconductor particle based detoxification processes which employ special immobilization techniques in conjunction with the UV excitation to treat hazardous organic contaminants (e.g., U.S. Patent No. 5,246,737). FSEC process was used to study the treatability of carbonyl sulfide in process vent gases that mimic those found in the chloride process. The main objective of this work was to evaluate, via an exploratory research, the effectiveness of FSEC-developed process for treating gaseous streams containing 1-5% of CO and 5005000 ppm of COS in an approximately 50/50 mixture of CO2 and N2. Several continuous flow photoreactors that employ low-pressure mercury lamps as the light source have been designed and fabricated. COS, CO and their photooxidation byproducts have been analyzed using GC-MS (COS, CS2, H2S), GC (CO, CO2), and spectrophotometric (SO2, SO3) techniques. Results, to date, indicate that COS photocatalytic oxidation can be accomplished with destruction and removal efficiencies exceeding 97%. The reaction products of COS photooxidation, detected, were CO, CO2, SO2, and SO3. However, in the presence of TiO2, photooxidation of COS yielded, mostly, products of deep oxidation, i.e. CO2 and SO3. In the absence of catalyst, SO and SO2 were the main photoreaction byproducts. In addition, our data indicated that COS can be selectively oxidized in the presence of carbon monoxide and CO2. L E A C H A B I L I T Y AND
B I O D E G R A D A T I O N OF HIGH C O N C E N T R A T I O N S O F P H E N O L AND O-CHLOROPHENOL C. Vipulanandan, Deborah Roberts, and Dennis Clifford Department of Civil and Environmental Engineering, University of Houston, 4800 Cullen Blvd., Houston, Texas 77204-4791, U.S.A.
The treatability of phenol and o-chlorophenol by solidification/stabilization and phenol by biodegradation was investigated. The effect of two concentrations, 0.1 and 2% of contaminant in cement (equivalent to 2,000 and 40,000 ppm in water) on the setting and solidification process of Type 1 Portland cement was studied. Leachability of these phenolic compounds from the solidified cement matrix, cured up to 180 days was evaluated using the U.S. EPA recommended Toxicity Characteristic Leaching Procedure (TCLP) and the American Nu-