Saturday May 5th – Presentations

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Reductive dechlorination of chlorinated compounds by zero-valent iron with Vitamin B12

Nicole Lapeyrouse, Dr. Greg Booth, Dr. Cherie Yestrebsky

University of Central Florida

01:30 PM
Environmental

During the 1970’s chlorinated organic solvents, such as 1,2-dichlorpropane (DCP), were used heavily as degreasers, paint strippers, chemical intermediates, and soil fumigants. Within the last 30 years, use of these solvents has steadily declined due to their adverse health effects and now are primarily used as chemical intermediates. DCP is classified as a probable human carcinogen and has been shown to cause damage to kidneys, blood cells, liver, respiratory and reproductive systems, and prolonged exposure to high concentrations can lead to death.  Due to these hazards and contamination in the environment, DCP has secured a place on the EPA Priority Pollutants List. DCP is a recalcitrant compound and current remediation methods that employ zero-valent iron (ZVI) are unable to remediate it making its elimination urgent and necessary. Researchers at UCF’s Industrial and Environmental Lab have employed a novel method for the remediation of DCP by the utilization ZVI and vitamin B12 as an electron shuttle. Batch reactions were performed in order to determine a kinetic model for this degradation mechanism. In addition, varying concentration of vitamin B12 were tested to determine degradation parameters. Dechlorination byproducts of DCP were confirmed by gas chromatography mass spectrometry (GC-MS) couple to a purge and trap. Experiments were conducted over a 3-week period and more than 95% degradation was observed for DCP. The primary degradation product was propene. Based on these results the proposed mechanism follows a SN2 like reaction with the formation of a cobalt alkyl intermediate yielding the release of a single chloride. In a subsequent step the cobalt complex undergoes an elimination reaction forming propene and releasing the second chloride. Future work aims to utilize this technology to aid in the dechlorination of other recalcitrant organic compounds such as 1,2,3-trichloropropane (TCP) and 1,2-dichloroethane. Preliminary studies have shown the complete degradation of TCP using the same reaction scheme.

Dechlorination comparison of octachlorodibenzofuran with Mg and Mg/C in different solvent systems

Amal Mogharbel and Cherie Yestrebsky

University of Central Florida

02:05 PM
Environmental

 

Polychlorinated dibenzofurans (PCDFs) are a group of nonpolar, chlorinated hydrocarbons that contains 135 individual congeners. These compounds are known to be persistent, highly toxic, and bioaccumulative in the environment. PCDFs have never produced intentionally; however, they are formed as byproducts of industrial activities and combustion processes. Therefore, PCDFs can be found in all compartment of the ecosystem. Due to the harmful effects of these compounds on the environment and health, it is important to develop a safe, effective, and inexpensive method for PCDF degradation in the environment. In this study, four different systems were used to study the degradation of octachlorodibenzofuran (OCDF). OCDF was selected as the compound of interest since it is the fully chlorinated congener of the PCDFs. In the first and second systems, acidified ethanol under ball-milled zero-valent magnesium (ZVMg) and under ZVMg over activated carbon were used, respectively. For the other two systems, ethanol/ethyl lactate co-solvent system over ZVMg and over ZVMg with activated carbon were used. The results of the four systems were compared. However, all the four systems were able to dechlorinate OCDF to less chlorinated furans over time.

Dechlorination comparison of PCB 153 with ball-milled ZVMg with and without activated carbon

Shannon D. Prendergast, Adibah M. Almutairi, Cherie L. Yestrebsky

University of Central Florida

02:25 PM
Environmental

Polychlorinated biphenyls (PCBs) are a class of man-made halogenated organic compounds that were used in many commercial and industrial applications. PCBs are currently a source of contamination due to leaching into surrounding areas. High toxicity and strict regulations create an urgent need to remediate PCBs in an economical way. In this project, our main objective is to dechlorinate PCBs by using ball-milled zero-valent magnesium (ZVMg), with and without activated carbon, in the presence of acidified ethanol and ethyl lactate (EtOH/EL). The completed experiments showed promising results on the degradation of PCB-153. Degradation-rate constants for both systems in EtOH/EL were calculated. There was a significant difference in the rate of reaction containing activated carbon, as opposed to just using ball-milled ZVMg. A detailed study of the byproducts formed in the dechlorination processes and degradation pathway are presented in this work.

Zero-Valent Iron (ZVI) Activation of Persulfate (PS) for Oxidation of 3,5,6-Trichloro-2-Pyridinol

Roaa Mogharbel and Cherie Yestrebsky

University of Central Florida

03:00 PM
Environmental

3,5,6-trichloro-2-pyridinol (TCPy) is the main hydrolytic product of chlorpyrifos, a broad-spectrum organophosphorous insecticide, widely used in agriculture. The USEPA has been listed TCPy as a persistent and mobile pollutant. TCPy is more water soluble than its parent compound, which significantly increases its ability to leach into surface water and groundwater, causing widespread contamination in soils and the aquatic environment. Because of this hazard, the EPA issued a proposal in 2015 recommending that chlorpyrifos use be completely ceased. In this study, the degradation of TCPy by sulfate radicals was evaluated using zero-valent iron (ZVI) activated persulfate (PS) in aqueous media. The reaction kinetics were examined as functions of ZVI concentration, PS dose, and pH. Results show that ZVI-activated persulfate can effectively degrade TCPy in water. Increasing initial concentration of persulfate or ZVI significantly enhances degradation efficiency. ZVI-activated persulfate appeared to be a cost-effective method for treatment of TCPy.

In situ treatment systems for remediation of polychlorinated biphenyl-contaminated building materials

Adibah Almutairi, Charles G. Lewis, Christian Clausen, Cherie Yestrebsky.

University of Central Florida

03:20 PM
Environmental

Poly-Chlorinated Biphenyls (PCBs) are a family of synthetic organohalides comprising 209 congeners which were used historically as additives in paint over a span of many years. Even though the production of PCBs in the USA has been banned since the late 1970s due to their carcinogenic nature, their former prevalence and widespread use means many structures are still coated with PCB-laden paints. This results in an urgent need for development of a cost-effective method to extract and degrade PCBs from contaminated materials. Experiments employing reductive dehalogenation through the use of zero-valent magnesium (ZVMg) ball-milled with activated carbon (AC) in an acidified solvent system have shown that PCBs can be broken down. This research describes the development of two delivery systems for effective deployment of this treatment reaction to field samples. Two treatment systems formulated in this process, the Non-Metal Treatment System (NTMS) and the Activated Metal Treatment System (AMTS), are capable of extracting or extracting and degrading, respectively. In the development of NMTS and AMTS, an acidified dual system of ethanol/ethyl lactate and an acidified 2-BOE were used as solvents while ZVMg over activated carbon is used in the AMTS. After development, applications of the systems extended to laboratory prepared PCB-laden paint as well as field samples received from Seattle. PCBs were degraded significantly below their starting concentrations with removal efficiency greater than 99% for all samples after treatment. The use of acidified 2-BOE and ZVMg permitted the extraction and destruction of PCBs from contaminated building materials in a one-step treatment.