13C NMR and EPR Spectroscopic Evaluation of Oil Shale Mined Soil Recuperation

J V Dos Santos,B F Pereira,G Abbt-Braun,T J Bonagamba,E H Novotny,F H Frimmel,C N Pillon,A S Mangrich

doi:10.5935/0103-5053.20130041

J V Dos Santos, B F Pereira + Show 6 more

Open Access

https://doi.org/10.5935/0103-5053.20130041

Copy DOI

Abstract

In this work, native forest soil (NFS) organic matter (SOM) sample and SOM samples from a neighboring forest soil area of an oil shale mine which is being rehabilitated for thirty years (RFS) were analyzed. X-band electron paramagnetic resonance (EPR) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopies were used to evaluate the soil reclamation of the Brazilian oil shale mining process. Two-dimensional heterospectral correlation studies of the results obtained from EPR and 13C NMR were used to obtain information about SOM structures and their interactions with residual paramagnetic metal ion. The signal of the residual metallic oxycation, VO2+ correlated positively with uronic acid-type hydrophilic organic structures, determined from the 13C NMR spectra, and correlated negatively with the organic free radical (OFR) signal associated with oxygen atoms (g = 2.0042). The hydrophobic aromatic structures correlate positively with the EPR OFR signal associated with carbon atoms (g = 2.0022). The data from the two spectroscopic magnetic techniques show that the used recuperation process is effective.

Highlights

Following the US, Brazil is the second most important country in oil shale reserves
The applied characterization techniques revealed that the sample RFS5 and in particular RFS6 showed significant differences in relation to the soil samples from the native forest soil (NFS) area and to the rehabilitated forest soil (RFS) samples of other depths as well
The sample RFS6, which is composed mainly by retorted shale which is used for rebuilding the soil profile in the depth, is the sample in which the largest differences are observed compared to the other samples both of the NFS and the RFS areas

Summary

Introduction

Following the US, Brazil is the second most important country in oil shale reserves. The biggest Brazilian oil shaleJ. In some studies of the soil organic matter (SOM) structure, the metal ions present can affect the results obtained with spectroscopic techniques, such as nuclear magnetic resonance (NMR),[2,3,4,5,6] fluorescence[4,7,8] and electron paramagnetic resonance (EPR)[4,9,10,11] spectroscopy. Spectroscopic correlation studies among the results obtained from EPR and 13C NMR spectroscopy were used to gain information about SOM structure interaction with residual paramagnetic metal ion.[4,11,25]

Results

Conclusion