DSpace Community: Chemistry

Study on the reaction kinetics of the chemical oxidation of o-phenylenediamine with ammonium persulfate

Mon, 21 Jan 2008 20:01:19 GMT

Title: Study on the reaction kinetics of the chemical oxidation of o-phenylenediamine with ammonium persulfate

Authors: Hohenstein, Edward G.

Abstract: 2,3-Diaminophenazine (DAP) has been extensively studied at Washington College.9-12 The origins of the interest in DAP lie in an enzyme kinetics experiment used in the General Chemistry Laboratory. In this experiment, DAP is formed due to the oxidation of o-phenylenediamine (OPD) catalyzed by horseradish-peroxidase with hydrogen peroxide. The Journal of Chemical Education article,8 on which this experiment is based, suggests that the kinetics of this reaction can be followed by either a colorimeter or a spectrophotometer. In practice, the results gathered by these two instruments are strikingly different. The origins of these differences have been investigated for several years. This study looks at the oxidation of OPD with a chemical oxidant, ammonium persulfate. Most of the experiments in this study were based on a Journal of Organic Chemistry article.13 This study replicated the synthesis of 3-aminophenazin-2-ol (APO), a second product, along with DAP, of the oxidation of OPD with ammonium persulfate in 1 M HCl, described in this article. The kinetics of this oxidation were followed spectrophotometrically for a variety of conditions. Also, the claim made by Iseminger et al.13 that DAP is hydrolyzed to APO in 1 M HCl was tested. It was determined that the mechanism proposed by Iseminger et al.13 was incorrect. Based on a mechanism for the enzyme catalyzed oxidation of OPD by Xie, Li, et al.2 this study proposes a mechanism for the chemical oxidation of OPD with ammonium persulfate. The Runge-Kutta-Fehlberg method was used to approximate solutions to the system of differential equations describing the mechanism proposed by this study and the mechanism proposed by Iseminger et al.13 Numerical data were fit to the experimental data by varying the rate constants for the steps in the mechanisms. The analysis of the mechanism proposed by Iseminger et al.13 showed that it could not correctly describe the behavior of the oxidation of OPD. The mechanism proposed by this study could, using well chosen rate constants, describe the experimental behavior of this reaction. A unique set of rate constants was not found that could be used to fit the calculated data to all the experimental data, but a set of rate constants could be found which would fit the calculated data to a single kinetics run.

Description: Submitted in partial fulfillment of the requirements for the degree of Bachelor of Science. Department of Chemistry Department of Mathematics and Computer Science. May 2007 Thesis Adviser: James R. Locker, Ph.D., Eugene Hamilton, Ph.D.

Analyzing the cation exchange capacity and soil organic matter in a Maryland Coastal Plain Ultisol after two prescribed burns

Mon, 21 Jan 2008 19:42:36 GMT

Title: Analyzing the cation exchange capacity and soil organic matter in a Maryland Coastal Plain Ultisol after two prescribed burns

Authors: Prior, Chelsea Alexandra

Abstract: Grassland restoration projects are designed to restore native habitats on former agricultural land on the Mid-Atlantic Coastal Plain and other areas with the support of the Conservation Reserve Program (CRP) and the Conservation Reserve Enhancement Program (CREP). Land once farmed for 60 years in Queen Anne’s County, Maryland, was used for a grassland restoration project. The 92-ha of land was drilled-seeded with warm-season grasses, such as little bluestem, big bluestem and eastern gamagrass and sectioned off into 12 representative fields. The Ultisol soils on the Eastern Shore of Maryland are characterized by being low in nutrients, low in organic matter and moderately acidic. Prescribed burning was selected to help aid in maintaining the grassland restoration process. The burns increase productivity of grasses by allowing more available light and allow more nutrients to be released into the soil for plant uptake. Soil core samples, 10 cm in depth, were taken from 9 locations within a 13-ha field 1 day before, 11 days after and 1 year after a first prescribed burn, and 12 days after a third prescribed burn. Total soil organic matter (SOM) content was determined by loss-onignition method and total soil cation exchange capacity (CEC) was determined by the barium compulsive exchange method. Total SOM content increased from pre-burn values in samples taken 12 days after the third burn. These increases could have been due to the fact that a year after the first burn, total SOM content did not fall below pre-burn values, so a small build-up of ash is present after each burn. Total available CEC sites were determined via weight of the soil during the compulsive exchange procedure and by atomic absorption spectrophotometry. The two methods gave different results for CEC, suggesting that the weight method is not as accurate. Overall CEC data shows a decrease v both a year after the first burn and 12 days after the third burn as compared to pre-burn conditions in all three layers. In the bottom layer, the CEC following the third burn was overall lower than a year after the first burn. These decreases after the third burn could have been because of the functional groups believed to exist on the ash were still protonated, which prohibited any cations to bind to those sites. This was likely affected by the decreases in soil pH values found at these times. After the third burn, the relationships between CEC, SOM and extractable cations Ca2+, Mg2+ and K+ were still correlated, although the relationships had changed. Results have shown that annual burns provide increase production in the grassland restoration projects.

Description: Submitted in partial fulfillment of the requirements for the degree of Bachelor of Science. May 2007 Thesis advisor: Leslie A. Sherman, Ph.D.

A periodic analysis of grassland soil chemistry 11 days and 6 months after a prescribed burn

Mon, 21 Jan 2008 19:37:04 GMT

Title: A periodic analysis of grassland soil chemistry 11 days and 6 months after a prescribed burn

Authors: McDevitt, Kelly Arielle

Abstract: Prescribed burning is a widespread management practice utilized across many grassland restoration projects in the United States. Unfortunately many of these grassland restoration projects are not located in the Mid-Atlantic Coastal Plain. Due to this fact, there has been limited research conducted to determine the effects of prescribed burning on the soil chemistry of Mid-Atlantic Ultisols. Core soil samples were collected on November 19, 2006 (6-months after the 3rd burn/pre 4th burn, PY3B) and December 3, 2006 (11-days post the 4th burn, P4B) and divided into 5 different layers intervals to be analyzed for pH, organic matter, and extractable Ca and Mg. Overall soil pH, organic matter, and extractable Ca and Mg were lower in samples 6 months after the 3rd burn/pre 4th burn than in preburn samples obtained on April 3, 2003; suggesting that preburn samples were still affected by liming that occurred 3 years prior. Overall soil pH, organic matter, and extractable Ca and Mg were lower on samples 6 months after the 3rd burn/pre 4th burn when compared to third burn samples obtained on March 13, 2006 (12-days post 3rd burn). This evidence suggests that the overall initial spike in values, caused by the prescribed burn, are only short-term. On the other hand, some statistical evidence from the lower layers supports the theory that a gradual build up of organic matter and extractable cations is occurring in the bottom layers of the soil. Overall soil pH, organic matter, and extractable Ca and Mg were higher in 4th burn samples in comparison to 6 months after the 3rd burn/pre 4th burn samples. Once again this supports the theory that prescribed burning has an immediate impact on the soil chemistry; namely pH, organic matter, and extractable Ca and Mg. In addition a comparative analysis of two analytical instruments (AA and ICP-OES) was obtained to evaluate the instrumental differences in v the values obtained for Ca and Mg concentration for samples 6 months after the 3rd burn/pre 4th burn. It was found that the instruments differed greatly, with the AA returning readings that were much higher than that of the ICP-OES. It is not yet understood why this is occurring. Two reasons have been proposed: human error, and differences in matrices. Further studies will need to be done in order to provide conclusive evidence to support either theory.

Description: Accepted in partial fulfillment of the requirements for the degree of Bachelor of Science. May 3, 2007 Thesis Advisor: Leslie A. Sherman, Ph.D.

Chemical analysis of contaminated groundwater in proximity of gas stations

Tue, 04 Dec 2007 15:10:00 GMT

Title: Chemical analysis of contaminated groundwater in proximity of gas stations

Authors: Huba, Zachary J.

Abstract: The Chester River Association (CRA) found that Horsey Lane Creek, located just off of Maple Avenue in Chestertown, Maryland might be contaminated with volatile organic compounds (VOCs) and other harmful chemicals. The possible contamination source of VOCs was suspected to be one of the gas stations located on Maple Avenue upstream of Horsey Lane Creek. Gas chromatography coupled with mass spectrometry was used to quantify the amount of VOCs in the creek and spectrophotometry was used to quantify the concentrations of iron, nitrates, orthophosphates, cadmium, aluminum, copper, and phenols. The results of the VOC analysis showed non alarming levels of methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) which are both gasoline additives. The water quality analysis showed levels of iron and orthophosphates that were above the maximum contaminant levels (MCL) set by the EPA. This study gave more insight about the presence of gas stations as possible sources of MTBE and TAME contamination in Horsey Lane Creek. The sources of the high concentrations of iron and orthophosphates need to be investigated further.

Description: Accepted in partial fulfillment of the requirements for the degree of Bachelor of Science Anne E. Marteel-Parrish, Ph.D., Thesis Adviser