A study on selective leaching of heavy metals vs. iron from fly ash

Sipi Seisko,Heini Elomaa,Jenna Lehtola,Mari Lundström

doi:10.1007/s10163-019-00858-w

Sipi Seisko, Heini Elomaa + Show 2 more

Open Access

https://doi.org/10.1007/s10163-019-00858-w

Copy DOI

Abstract

Incinerator plant waste streams contain underexploited metals originating from households and industrial operators. The objective was to investigate the dissolution behavior of fly ash in: 0.2–7 M HCl, 0.2–7 M H2SO4, 0.5–1 M oxalic acid, 0.5–4 M citric acid, 0.5–7 M acetic acid, water, and ethaline, at 33 °C during 24 h leaching. The capability for high metals’ extraction of Zn, Cu, Ni, Pb, and Fe and management of the heavy metal Pb through leaching or precipitation was investigated. Selective leaching of valuable metals vs. Fe was observed. The target was to find a sustainable leaching method and provide a basis for further development of metal recovery from fly ash. The highest Zn extraction (> 80%) was achieved with 3 M H2SO4 and 7 M HCl, which also dissolved Cu (> 87%) and Ni (> 65%). However, more dilute HCl, 0.2 M, was able to provide Zn, Cu, and Ni extractions of 43, 86, and 18%, respectively. Efficient Pb leaching was achieved in HCl—complete extraction was provided by 3 and 5 M HCl, whereas H2SO4 did not extract Pb due to PbSO4 formation; similarly, in oxalic acid, Pb precipitated as PbC2O4. Ethaline could extract 50% of Pb with high selectivity towards Fe.

Highlights

Incineration is a common way to dispose municipal solid waste (MSW) and simultaneously generate energy [1]
MSW incineration (MSWI) produces two main solid by-products, which are divided into bottom ash (BA) and fly ash (FA) [3, 4]
Fly ash is the finer fraction collected from flue gas by air pollution control (APC) devices such as cyclones, electrostatic precipitators, fabric filters, or scrubbers

Summary

Introduction

Incineration is a common way to dispose municipal solid waste (MSW) and simultaneously generate energy [1]. This waste-to-energy incineration process is being increasingly used and is a viable management strategy for treating the increasing amounts of MSW that are not recyclable [1,2,3]. MSW incineration (MSWI) can reduce the waste mass by 70% and waste volume by 90% [2,3,4]. Fly ash is the finer fraction collected from flue gas by air pollution control (APC) devices such as cyclones, electrostatic precipitators, fabric filters, or scrubbers. Fly ash is considered toxic waste due to the enrichment of heavy

Objectives

Methods

Results