Preliminary Study on Additives for Controlling As, Se, B, and F Leaching from Coal Fly Ash

Farrah Hanum,Yukio Hayakawa,Erda Desfitri,Shinji Kambara

doi:10.3390/min8110493

Abstract

The application of paper sludge ash as an additive in controlling the leaching of trace elements has been satisfactorily effective to date. Previous studies have found that paper sludge ash has a promising effect in controlling the leaching of arsenic, selenium and boron. The content of calcium oxide in paper sludge ash is believed to be one of the important factors in decreasing the concentration of trace elements in leachate. Therefore, this study aimed to verify the effect of paper sludge ash in the leaching process and to propose an effective and applicable suppressing material that can control the leaching of As, Se, B and F simultaneously. In light of this aim, Ca(OH)2, PS ash 8 and blast furnace cement (BF cement) were tested as single and mixed additives in two different coal fly ashes (FA C and FA H). The results indicate that the application of a mixture of additives is necessary to control the leaching of trace elements. A mixture of PS ash 8, Ca(OH)2 and blast furnace cement (BF cement) was proposed to be an applicable and suitable additive that could suppress arsenic, selenium, boron, and fluorine leaching simultaneously.

Highlights

As reported by the World Energy Council, even though coal production growth was decreasing in 2014, the first decline since the 1990s, almost 40% of the world’s electricity was still provided by coal [1]
Calcium hydroxide (Ca(OH)2 ), paper sludge ash number 8 (PS Ash 8), and blast furnace cement (BF cement) were each added to both coal fly ash samples
The effect of single and mixed additives on the As, Se, B and F leaching concentrations of both of the coal fly ashes is explained in the discussion below

Summary

Introduction

As reported by the World Energy Council, even though coal production growth was decreasing in 2014, the first decline since the 1990s, almost 40% of the world’s electricity was still provided by coal [1]. The study of coal fly ash, especially related to the content of trace metals, such as As, B, Se, Pb, Cd, Cr, Cu, Zn and F in this waste, remains a concern for the few years. The leaching behaviour of some heavy metals from various types of coal fly ashes has been discussed by some researchers [3,4,5,6,7]. These studies indicated that the leaching characteristics of each metal are different and that the alkalinity of the leaching solution plays an important role.

Objectives

Methods

Results

Conclusion