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Characteristics and Mechanisms of Pb(II) Sorption onto Fe-rich waste Water Treatment Residue (WTR): A potential sustainable Pb immobilisation technology for soils

DOI: 10.1016/j.jhazmat.2020.123433 DOI Help

Authors: Nina C. Findlay (Durham University) , Caroline L. Peacock (University of Leeds) , Karen A. Hudson-edwards (University of Exeter) , Karen L. Johnson (Durham University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Hazardous Materials

State: Published (Approved)
Published: July 2020
Diamond Proposal Number(s): 4133

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 modelling 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 LIII-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.

Journal Keywords: Water treatment residue (WTR);lead sorption; ferrihydrite; EXAFS

Subject Areas: Chemistry, Environment, Earth Science

Instruments: I20-Scanning-X-ray spectroscopy (XAS/XES)