Evaluation of the BCR sequential extraction scheme for trace metal fractionation of alkaline municipal solid waste incineration fly ash

Lizhi Tong, Jinyong He, Feng Wang, Yan Wang, Lei Wang, Daniel C.W. Tsang, Qing Hu, Bin Hu, Yi Tang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

18 Citations (Scopus)

Abstract

The BCR sequential extraction scheme (SES), initially developed for soils and sediments, is frequently adopted to evaluate the environmental risks of municipal solid waste incineration (MSWI) fly ash. Within the procedure, metals are liberated from the matrix hosting them relying on the selectivity of the chosen chemical reagents or operation conditions. However, the effect of the high content of alkaline substances in MSWI fly ash on the selectivity of acetic acid to acid-soluble fraction metals was ignored. In this study, the feasibility of the BCR SES for evaluating MSWI fly ash was assessed by adjusting the acetic acid washing times in the acid-soluble extraction step. The metal fractionation, as well as mineralogy, morphology, and surface chemistry of the residues after three successive acid washing processes, were analyzed. The results reveal that only easily soluble salts, but not hydroxides, are entirely extracted after the first acid washing (pH∼12.0). Importantly, carbonates (generally reported as an indicator of the complete release of acid-soluble metals) are mostly decomposed only after the third acid washing (pH∼3.8). The incomplete dissolution of calcium carbonates in a single-step acid washing may convey misleading results of metal fractionation and underestimates the environmental risk of potentially toxic elements. Therefore, complete removal of carbonates should be employed as the endpoint of the acid-soluble fraction extraction step in the evaluation of MSWI fly ash. This work can help in selecting proper strategies for fly ash management and developing proper sequential extraction schemes for similar high-alkalinity hazardous waste risk assessment.

Original languageEnglish
Article number126115
JournalChemosphere
Volume249
DOIs
Publication statusPublished - Jun 2020

Keywords

  • Chemical fractionation
  • Environmental assessment
  • Hazardous waste management
  • Incinerator fly ash
  • Potentially toxic element

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Health, Toxicology and Mutagenesis

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