Leaching Kinetics of As, Mo, and Se from Acidic Coal Fly Ash Samples

Abstract

Annually, coal-fired electric power plants produce large volumes of potentially hazardous coal combustion products (CCPs) including fly ash. Since majority of the coal fly ash and other CCPs deposited in dry land fills or wet lagoons, they pose risk of contamination to local environment. In this study, we present results of leaching kinetics for As, Mo, and Se from three acidic fly ash samples collected from coal-fired power plants in the southeastern United States. This study shows that the leachate concentrations of As, Mo, and Se increase over time. Three kinetics equations, pseudo-second order, Elovich, and power-function, are able to adequately describe the experimental leaching kinetics data. Experimental leaching data and modeling results indicate that the rate limiting leaching of As, Mo, and Se is controlled by the diffusional process responsible for transferring these elements from interior to the surface of the particles as well as the dissolution of the fly ash particles. Therefore, it is important to adopt effective containment/treatment schemes to avoid potential and persistent dispersion of trace elements from ash disposal facilities to surrounding environment for a long time.

Influence of Blending High-Calcium Additive on Environmental Safety of B, F, and Se: A Case Study from Thermodynamic Calculation

“…Coal power plants generate millions of tons of coal combustion products (CCPs) each year, such as flue gas desulfurization materials, bottom ash, coal fly ash, boiler slag, and pollutant gases. Coal fly ash (CFA) is the most hazardous coal combustion product, as it contains hazardous leachable trace elements (TEs), such as As, Mo, and Se [1], in quantities sufficient to cause environmental damage. In coal fly ash, the concentration of trace elements is over 50 mg/kg, though the exact concentration depends on the composition of the original coal [2][3][4].…”

An Experimental and Thermodynamic Equilibrium Analysis on the Leaching Process of Arsenic (As) from Coal Fly Ash

“…Coal power plants generate large volumes of coal combustion products such as flue gas emissions, bottom ash, fly ash. Fly ash is the most hazardous coal combustion product because it contains environmentally significant quantities of hazardous leachable trace elements such as As, Mo, and Se 1) . During the combustion process, the organic matter in coal was destroyed, and as a result, the concentration of trace elements in fly ash enhanced relatively according to their contains in the feedstock coal 2) .…”