Effect of pH, competitive anions and NOM on the leaching of arsenic from solid residuals

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

Implementation of the new arsenic MCL in 2006 will lead to the generation of an estimated 6 million pounds of arsenic-bearing solid residuals (ABSRs) every year, which will be disposed predominantly in non-hazardous landfills. The Toxicity Characteristic Leaching Procedure (TCLP) is typically used to assess whether a waste is hazardous and most solid residuals pass the TCLP. However, recent research shows the TCLP significantly underestimates arsenic mobilization in landfills. A variety of compositional dissimilarities between landfill leachates and the TCLP extractant solution likely play a role. Among the abiotic factors likely to play a key role in arsenic remobilization/leaching from solid sorbents are pH, and the concentrations of natural organic matter (NOM) and anions like phosphate, bicarbonate, sulfate and silicate. This study evaluates the desorption of arsenic from actual treatment sorbents, activated alumina (AA) and granular ferric hydroxide (GFH), which are representative of those predicted for use in arsenic removal processes, and as a function of the specific range of pH and concentrations of the competitive anions and NOM found in landfills. The influence of pH is much more significant than that of competing anions or NOM. An increase in one unit of pH may increase the fraction of arsenic leached by 3-4 times. NOM and phosphate replace arsenic from sorbent surface sites up to three orders of magnitude more than bicarbonate, sulfate and silicate, on a per mole basis. Effects of anions are neither additive nor purely competitive. Leaching tests, which compare the fraction of arsenic mobilized by the TCLP vis-a-vis an actual or more realistic synthetic landfill leachate, indicate that higher pH, and greater concentrations of anions and NOM are all factors, but of varying significance, in causing higher extraction in landfill and synthetic leachates than the TCLP.

Original languageEnglish (US)
Pages (from-to)46-59
Number of pages14
JournalScience of the Total Environment
Volume363
Issue number1-3
DOIs
StatePublished - May 15 2006

Fingerprint

Arsenic
Biological materials
Leaching
Anions
anion
arsenic
Negative ions
leaching
Land fill
organic matter
Toxicity
toxicity
landfill
Chemical Water Pollutants
Sorbents
Silicates
Bicarbonates
bicarbonate
Sulfates
Phosphates

Keywords

  • Activated alumina
  • Anions
  • Arsenic
  • GFH
  • Leaching
  • NOM
  • pH

ASJC Scopus subject areas

  • Environmental Chemistry
  • Environmental Science(all)

Cite this

Effect of pH, competitive anions and NOM on the leaching of arsenic from solid residuals. / Ghosh, Amlan; Saez, Avelino E; Ela, Wendell P.

In: Science of the Total Environment, Vol. 363, No. 1-3, 15.05.2006, p. 46-59.

Research output: Contribution to journalArticle

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