Distributed 13 days in advance due to GSSO oversight.

School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

Ion Exchange for the Capture of Aqueous Selenium Oxyanions

By Zhuoyi Zeng

Advisor:

Dr. Sotira Yiacoumi (CEE)

Committee Members: 

Dr. Costas Tsouris (CEE/Oak Ridge National Lab), Dr. Yongsheng Chen (CEE), Dr. Xing Xie (CEE), Dr. Radu Custelcean (Oak Ridge National Lab)

Date and Time:  Tuesday, May 5th, 2026.  10 am EST

Location: 

Room 4222, Price Gilbert Memorial Library or https://gatech.zoom.us/j/99747481518  

ABSTRACT
Selenium (Se) is an essential micronutrient but becomes toxic at elevated concentrations, posing significant risks to aquatic ecosystems and human health. Coal-fired power plant wastewaters are a primary source of Se contamination, and the U.S. Environmental Protection Agency has set a stringent discharge limit of 5 μg/L for freshwater systems. Removing Se from these wastewaters is technically challenging because Se exists at trace concentrations alongside extreme competing sulfate concentrations. Ion exchange using commercially available strong-base anion-exchange resins offers a promising approach, yet its deployment is hindered by fundamental knowledge gaps and practical challenges, including insufficient mechanistic understanding, limited evaluation under real industrial conditions, and the absence of effective regeneration protocols for complex matrices.In this context, the dissertation presented here develops and evaluates an ion-exchange-based process using the commercial resin AmberLite IRA-900 for effective and sustainable Se removal from aqueous solutions. The work progresses through three interconnected tasks. The first task establishes a comprehensive understanding of Se oxyanion equilibrium, kinetics, and competitive interactions on IRA-900, supported by the mechanistic equilibrium and kinetic models that describe the ion-exchange behavior. The second task advances the evaluation to continuous-flow fixed-bed operations across increasingly complex aqueous matrices, from simulated wastewaters to real industrial leachate, and explores an integrated treatment strategy combining crystallization pretreatment with ion exchange polishing. The third task addresses resin regeneration, developing and validating a novel two-step protocol that overcomes the limitations of conventional approaches in complex industrial matrices. Together, these tasks establish a comprehensive scientific framework that bridges fundamental ion-exchange principles with practical process development, advancing the knowledge base needed for the effective treatment of Se-contaminated industrial wastewaters.