Theses and Dissertations

Advisor

Varun, Paul

Committee Member

Skarke, Adam

Committee Member

Padmanava, Dash

Committee Member

Huan, Cui

Date of Degree

5-16-2025

Original embargo terms

Visible MSU Only 6 months

Document Type

Dissertation - Campus Access Only

Major

Earth and Atmospheric Sciences

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Arts and Sciences

Department

Department of Geosciences

Abstract

This research focuses on a three-part study to assess water quality in a coastal system and evaluate the absorption capacity of modified biochar and algae to remediate cadmium (Cd). The first chapter introduces the hypothesis and objectives, and the second chapter provides a detailed literature review. The third chapter focuses on the first study, where surface water samples and water quality data collected from a manned boat and a novel autonomous surface vessel (ASV) in the Western Mississippi Sound (WMS) in the summer of 2021 and 2022 were analyzed and the interrelationship between the nutrient, trace metals, salinity, and chlorophyll-a (chl-a) concentrations were compared to understand the dynamics in water quality. Results show that salinity (2 - 23 PSU) varied temporally due to fresh water in-flow, or the lack thereof, from the freshwater inflow inversely correlating with chl-a, due to nutrients-driven phytoplankton growth. Trace metals were higher in 2022 than 2021, particularly at elevated temperatures, pH, salinity, and chl-a. The second study examined Cd uptake by Chaetoceros sp., identifying optimal biosorption conditions at a temperature of 298K, salinity of 15 PSU, and pH level of 6 and highest bioaccumulation occurred at temperature of 298K, salinity of 25 PSU, pH level of 6, and at 0.4 gL-1 dose, achieving 80% Cd removal via biosorption and 70% via bioaccumulation. The third study evaluated magnetite-modified biochar (magnetite-PCBC) for Cd (II) adsorption. Adsorption experiments were done to optimize capacities across various pH, adsorbent dosages, salinities, mixing rates, and initial Cd (II) concentrations. A pseudo-second-order kinetic model best described the Cd adsorption characteristics of a magnetite-modified biochar and Freundlich better described the adsorption behavior. Comprehensive characterization of the adsorbent indicated that mechanisms such as in situ precipitation, electrostatic attraction, and surface complexation were instrumental in the Cd (II) adsorption. Findings demonstrate that magnetite-PCBC is a favorable, sustainable adsorbent for the effective removal Cd (II) from aqueous environments.

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