Characteristics and mechanisms of Pb(II) sorption onto Fe-rich waste water treatment residue (WTR): A potential sustainable Pb immobilisation technology for soils

Nina C Finlay; Caroline L Peacock; Karen A Hudson-Edwards; Karen L Johnson

doi:10.1016/j.jhazmat.2020.123433

Characteristics and mechanisms of Pb(II) sorption onto Fe-rich waste water treatment residue (WTR): A potential sustainable Pb immobilisation technology for soils

J Hazard Mater. 2021 Jan 15:402:123433. doi: 10.1016/j.jhazmat.2020.123433. Epub 2020 Jul 8.

Authors

Nina C Finlay¹, Caroline L Peacock², Karen A Hudson-Edwards³, Karen L Johnson¹

Affiliations

¹ Department of Engineering, Durham University, Durham DH1 3LE, UK.
² School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
³ Environment & Sustainability Institute and Camborne School of Mines, University of Exeter, Penryn, Cornwall, TR10 9FE, UK. Electronic address: k.hudson-edwards@exeter.ac.uk.

PMID: 32683153
DOI: 10.1016/j.jhazmat.2020.123433

Abstract

Pb contamination of soils is a global problem. This paper discusses the ability of an Fe-rich waste, water treatment residual (WTR), to adsorb Pb(II). This was investigated using batch sorption experiments, X-ray diffraction, electron microprobe microanalysis, PHREEQC modeling and Extended X-ray Absorption Fine Structure (EXAFS) analysis. The WTR is composed of approximately 23 wt. % natural organic matter (NOM), 70 wt. % ferrihydrite and <10 wt. % silicate material. Pb(II) sorption to WTR was dependent on initial Pb(II) load, particle size, time and pH, but not on ionic strength. EXAFS analysis at the Pb L_III-edge confirmed that Pb(II) sorbed to WTR by co-existing bidentate edge-sharing and monodentate or corner-sharing complexes, with 2 O at ∼2.31-2.34 Å, 1 Fe at ∼3.32-3.34 Å, 2 Fe at ∼3.97-3.99 Å and 1 Pb at ∼3.82-3.85 Å. Linear combination showed that the Pb(II)-sorbed spectra were best fit with a ∼0.9 ± 0.1 and 0.1 ± 0.1 contribution from Pb(II)-sorbed ferrihydrite and Pb(II)-sorbed humic acid end members, respectively. Overall, we show that Pb(II) sorbs via strong inner-sphere complexation of Pb(II) to the ferrihydrite component of the WTR, which itself is stable over a wide pH range. Therefore, we suggest that Fe-rich WTR wastes could be used as effective adsorbents in Pb(II)-contaminated soils to help ensure sustainable terrestrial ecosystems.

Keywords: EXAFS; Ferrihydrite; Lead; Sorption; Water treatment residue (WTR).

Publication types

Research Support, Non-U.S. Gov't