Masters Theses

Abstract

"This research study was undertaken to investigate the fundamental sorption and desorption of selected organic pesticides by organic humic acids under laboratory-controlled conditions. Emphasis was placed on the evaluation of both the rate and the equilibrium of adsorption and desorption. Two types of chlorinated hydrocarbon pesticides were employed in this study. These are dieldrin and heptachlor, both of which are commonly used in today's agricultural applications. The adsorbent of organic humic acids was extracted from a coal-like substance called "leonardite," which has a humus content as high as 53 percent by weight. The experimental work of this study was conducted in two steps. The first step was a batch study which was used to evaluate the rate and the equilibrium of sorption and desorption. The second step was a column study by which an aqueous pesticide solution was pumped through several adsorbent columns. In both steps of the study, the adsorbent was composed of either organic humic acids or leonardite; in some tests these two materials were mixed with various amounts of montmorillonite clay in an attempt to evaluate their effects on the clay adsorption for pesticides. Results of this study indicate that the relative rates of pesticide adsorption decrease in the order of: clay > leonardite > humic acids. However, the relative adsorptive capacities of these adsorbents are in the reverse order. Both humic acids and leonardite are able to form a layer of water film around the particle surface because of their hydrophilic nature. Before the water film is developed, a large fraction of the initial quantity of pesticide can be adsorbed directly and rapidly on the particle surface. Thereafter, additional adsorption appears to be gradual because pesticide molecules have to diffuse through the water film before the adsorption takes place on the particle surface. The equilibrial adsorption of dieldrin and heptachlor by humic acids and leonardite is generally in well accord with the Freundlich isotherm. The adsorption is generally irreversible as evidenced by the non-coincidence nature of the adsorption and desorption isotherms. This suggests that the mechanism of pesticide adsorption is accomplished primarily by some strong forces of interactions. From the chemical nature of humic acids and the experimental pesticides, it is believed that the adsorption mechanism may include, but is not limited to, the dipole-dipole or iondipole interactions, and the formation of the hydrogen bonding or some other types of chemical bonding"--Abstract, pages ii-iii.

Advisor(s)

Huang, Ju-Chang, 1941-2018

Committee Member(s)

TerKonda, Purush
Bolter, Ernst

Department(s)

Civil, Architectural and Environmental Engineering

Degree Name

M.S. in Civil Engineering

Sponsor(s)

United States. Office of Water Resources Research

Publisher

University of Missouri--Rolla

Publication Date

1972

Pagination

ix, 110 pages

Rights

© 1972 Fu-Sheng Chien, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Soil absorption and adsorptionSoils -- Pesticide contentHumic acidSewage -- Purification -- Activated sludge process

Thesis Number

T 2708

Print OCLC #

6032394

Electronic OCLC #

883306916

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