Remediation of a historically Pb contaminated soil using a model natural Mn oxide waste

Abstract

A natural Mn oxide (NMO) waste was assessed as an in situ remediation amendment for Pb contaminated sites. The viability of this was investigated using a 10 month lysimeter trial, wherein a historically Pb contaminated soil was amended with a 10% by weight model NMO. The model NMO was found to have a large Pb adsorption capacity (qmax 346±14 mg g(-1)). However, due to the heterogeneous nature of the Pb contamination in the soils (3650.54-9299.79 mg kg(-1)), no treatment related difference in Pb via geochemistry could be detected. To overcome difficulties in traditional geochemical techniques due to pollutant heterogeneity we present a new method for unequivocally proving metal sorption to in situ remediation amendments. The method combines two spectroscopic techniques; namely electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). Using this we showed Pb immobilisation on NMO, which were Pb free prior to their addition to the soils. Amendment of the soil with exogenous Mn oxide had no effect on microbial functioning, nor did it perturb the composition of the dominant phyla. We conclude that NMOs show excellent potential as remediation amendments.

In situ arsenic oxidation and sorption by a Fe-Mn binary oxide waste in soil

“…At present, there are no studies on the use of Fe-Mn binary oxide by-products to remediate historically As-contaminated soils. This is despite the fact that waste supplies of have been identified from water treatment plants and are available nationally [28]. This water industry by-product may provide an inexpensive and sustainable option for remediation, which synthetic sources cannot.…”

“…The Fe-Mn binary oxide waste used in this study was obtained from a Northumbrian Water Ltd. water treatment works (Co. Durham, UK, 54°51'03.9"N 1°54'00.5"W ) and has been previously described in detail [28]. Briefly, the binary oxide consists of ferrihydrite (total Fe: 20,000 mg kg -1 ) and birnessite (total Mn : 90,000 mg kg -1 ) [29].…”

“…The effect of pH on As sorption was investigated at pH 5.5, 6.5 and 7.5 were maintained with either 1 M NaOH or 1 M HCl using l0 g l 1 binary oxide waste concentration unsieved. Experiments investigating the effect of Pb on As sorption were carried out as above but included Pb at a total concentration of 50 mg l -1 as per [28]. All solutions from experiments were analyzed for As(III), As(V), Mn(II) and Pb using a JY Ultima 2C ICP-OES and sorption data was fitted to the Langmuir isotherm [31].…”

“…Batch sorption experiments were conducted as in [28] using a 10 g l 1 binary oxide waste concentration (<90 m particle size) at a pH of 7. The effect of pH on As sorption was investigated at pH 5.5, 6.5 and 7.5 were maintained with either 1 M NaOH or 1 M HCl using l0 g l 1 binary oxide waste concentration unsieved.…”

“…In addition, as the soil in this study is known to be co-contaminated with lead (Pb) [28], the effect of this competing cation on As sorption was also investigated. This is the first study, to our knowledge, that investigates a waste source of binary oxide for remediation using realistic remediation conditions.…”