Evaluation of Hexavalent Chromium Extraction Method EPA Method 3060A for Soils Using XANES Spectroscopy

Abstract

Hexavalent chromium (Cr(VI)) occurrence in soils is generally determined using an extraction step to transfer it to the liquid phase where it is more easily detected and quantified. In this work, the performance of the most common extraction procedure (EPA Method 3060A) using NaOH–Na2CO3 solutions is evaluated using X-ray absorption near edge structure spectroscopy (XANES), which enables the quantification of Cr(VI) directly in the solid state. Results obtained with both methods were compared for three solid samples with different matrices: a soil containing chromite ore processing residue (COPR), a loamy soil, and a paint sludge. Results showed that Cr(VI) contents determined by the two methods differ significantly, and that the EPA Method 3060A procedure underestimated the Cr(VI) content in all studied samples. The underestimation is particularly pronounced for COPR. Low extraction yield for EPA Method 3060A was found to be the main reason. The Cr(VI) present in COPR was found to be more concentrated in magnetic phases. This work provides new XANES analyses of SRM 2701 and its extraction residues for the purpose of benchmarking EPA 3060A performance

Biogenic nano-magnetite and nano-zero valent iron treatment of alkaline Cr(VI) leachate and chromite ore processing residue

“…However, the Cr K edge XANES results, discussed in detail later, when subjected to linear combination fitting suggested that the samples contained 26% Cr(VI). Recent studies have highlighted underestimation of bulk Cr(VI) content by alkaline extraction of COPR due to the recalcitrance of a fraction of Cr(VI) to dissolution ( Malherbe et al, 2011 ). The Cr K edge XANES is therefore assumed to represent a more robust method for bulk Cr(VI) determination.…”

Quantification of Cr(VI) in soil samples from a contaminated area in northern Italy by isotope dilution mass spectrometry

“…Therefore, there is no soil contamination in this region, nor any correlation among the polluted water diffusion and the Cr(VI) concentrations in the soil samples. Nevertheless, previous work using XANES spectroscopy (Malherbe et al 2011) demonstrated that Cr(VI) can strongly bind to the soil matrix, and the application of conventional extraction procedures may not ensure complete extraction of Cr(VI) from the soil sample.…”

Speciation of Chromium in Alkaline Soil Extracts by an Ion-Pair Reversed Phase HPLC-ICP MS Method

“…Exchangeable (mobile) forms of Cr(VI) were extracted with KH 2 PO 4 -K 2 HPO 4 and K 2 HPO 4 buffers [13,15,16]. Soluble (Na 2 CrO 4 ) and sparingly soluble chromates (CaCrO 4 , BaCrO 4 , PbCrO 4 ) were most often extracted with alkaline media, such as Na 2 CO 3 [17], Na 2 CO 3 -NaOH solutions [18], Na 2 CO 3 and NaOH with MgCl 2 and phosphate buffer (EPA method 3060A) [19,20,21,22]. Some chelating agents (EDTA, DPTA) [12,23,24] were also proposed for Cr(VI) extraction.…”