Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Kevin E. O'Shea

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Yong Cai

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Raphael Raptis

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Alexander Mebel

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Wenzhi Li

Fifth Advisor's Committee Title

Committee member

Keywords

Nanoparticles, humic acid, adsorption, water treatment, arsenic, selenium, phosphorous, photocatalysis, magnetite

Date of Defense

6-11-2018

Abstract

The crisis of freshwater has been a big concern worldwide. Water contamination that occurs through the discharge of toxic pollutants from different natural and anthropogenic sources have worsened the situation. Adsorption has emerged as a simple and economical water treatment procedure although the challenge is to find the right adsorbent that can efficiently remove the target contaminant followed by their easy recovery from the reaction vessel. In this dissertation, I have focused on the synthesis, characterizations and applications of environmentally compatible and magnetic humic acid coated magnetite nanoparticles (HA-MNP) as a potential adsorbent for water purification.

Phosphate is an essential nutrient for many plants and organisms in the environment. However, it can also cause water pollution when present in excess amounts. The adsorption experiments showed that the laboratory synthesized nanoparticles (HA-MNP) can remove more than 90% of phosphate from water mainly through the mechanism of chemisorption. The overall removal process is spontaneous, endothermic and favorable.

Water contamination by arsenic is considered one of the biggest natural disasters in human history. In the study, HA-MNP has been applied for the successful trapping and separation of two highly toxic inorganic As species, As(III) and As(V) from water. The removal of As(V) was faster than As(III) for the same initial arsenic concentration and HA-MNP loading. The binding of As species is mainly attributed to three different phases, rapid surface association, intraparticle diffusion and equilibrium adsorption.

Selenium is a micronutrient for humans that can be toxic at modest concentrations. The remediation of toxic selenium species, Se(IV) and Se(VI) by using HA-MNP has been found effective under a variety of environmental conditions except at highly alkaline pH and the presence of sulfate and phosphate in aqueous solution. Selenite or Se(IV) forms strong inner sphere complexes while Se(VI) forms relatively weaker outer sphere complexes with the adsorbent sites.

The oxidation and adsorption of As(III) is explored by using the photocatalytic and adsorptive behavior of HA-MNP. The higher removal efficiency is attained through the reactive oxygen species mediated photo-conversion As(III) to As(V). Combination of oxygen and 350 nm light provides the best results.

Identifier

FIDC006892

ORCID

0000-0003-2920-0770

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Available for download on Saturday, July 20, 2019

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