Effect of Additive Material on Controlling Chromium (Cr) Leaching from Coal Fly Ash

Erda Rahmilaila Desfitri,Shinji Kambara,Yukio Hayakawa,Ulung Muhammad Sutopo

doi:10.3390/min10060563

Abstract

Coal fly ash contains a considerable number of toxic elements that can be leached into the environment, such as chromium (Cr), thereby quickly leading to severe contaminations. In this research, the leaching behaviors of Cr were analyzed from 14 kinds of coal fly ash samples collected from the electrostatic precipitators of coal-fired thermal power plants in Japan. The level of Cr concentration found in the samples varied from 0.00 to 82.93 μg/L. However, Cr toxicity depends on its valence state; Cr6+ is more toxic than Cr3+. Additive materials containing high calcium content were used to control the leaching concentration of Cr, such as Ca(OH)2, paper sludge ash, and blast furnace cement. This research used several instruments. An X-ray fluorescence was adopted to measure the major chemical composition of the fly ash samples and the additive materials. A thermogravimetric analyzer was used to examine the calcium compounds in the additive materials. Inductively coupled plasma was used to determine the Cr leaching concentrations from the fly ash samples. Findings showed that the three-additive mixture had a promising effect on controlling the Cr leaching concentrations. These results were also supported by FactSage 7.2 simulation.

Highlights

The International Energy Agency predicts that coal will still be the largest source of power supply worldwide (35%) in 2024 [1]
The combustion produces coal fly ash, which contains toxic elements. These elements, once in landfills, leach into water environments after coming into contact with rain. This condition affects the concentration of toxic elements in water environments in that toxic elements could leach from lignite fly ash into aquatic environments when it comes into contact with water [2]
Ca(OH)2 and CaCO3 were used as standards in analyzing the calcium compounds in the PS ash 8 and BF cement

Summary

Introduction

The International Energy Agency predicts that coal will still be the largest source of power supply worldwide (35%) in 2024 [1]. The combustion produces coal fly ash, which contains toxic elements. These elements, once in landfills, leach into water environments after coming into contact with rain. This condition affects the concentration of toxic elements in water environments in that toxic elements could leach from lignite fly ash into aquatic environments when it comes into contact with water [2] Concentrations of these toxic elements will increase continuously. One of the toxic elements in coal fly ash is chromium (Cr). The Environmental Protection Agency tested coal ash leachate by obtaining waste from numerous operating power plants and found that many ashes and sludge produce Cr-rich leachate [3]. Permissible limit (for the protection of human health) of chromium set by the Ministry of the Environment of the government of Japan is 50 μg/L

Methods

Results

Conclusion