Donglin Huang

Date of Graduation

2010

Document Type

Dissertation/Thesis

Abstract

Although selenium is as essential element for animal and human growth, selenium released from coal mining process and coal combustion residues to surface and groundwater may cause toxicity to aquatic life. There is urgent need for an easy and accurate analytical method to speciate and determine trace selenium concentrations in waters impacted by coal mine drainage, and treatment technique to remove selenium from aqueous solution. The primary objective of present work is to develop a speciation procedure and analytical method for inorganic selenium species (Se0, SeIV, SeVI) with Multimode Sample Introduction System-Inductive Coupled Plasma Optic Emission Spectrometer (MSIS-ICP). Experiments showed that MSIS-ICP had good repeatability and accuracy in determination three selenium species SeVI, SeVI and Se 0 with a detection limit of 0.1 μg L-1. Within the concentration range of 2.5-400 μg Se L-1, interferences from common components of non-acid mine drainage (FeII, Fe III, MnII) up to 5 mg L-1and SO 42- up to 1000 mg L-1 were less than 4%. The system and procedure obtained results comparable to other instrumental methods in a blind, inter-laboratory comparison study. The second objective of this study is to investigate the reaction mechanism between SeIV and ZVI-SW under anoxic environment using wet chemical analysis and microspectroscopic analysis (X-ray photoelectron spectroscopic) techniques. Bench top experiments kinetic data and microspectroscopic analysis identified a two-step removal mechanism. The main removal mechanism was electrochemical reduction by Fe0 in the initial lag stage followed by a faster heterogeneous reduction mediated by FeII bearing hydroxides or Green Rust (GR) The initial pH was the controlling factor for the removal rate in the lag stage, and dissolved FeII concentration was critical for induction of the faster stage. Se0 was the primary reductive product in both stages.

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