XAS Technique in Copper Binding in Medium Textured Soil

Abstract

Copper binding in soil using X-ray Absorption Spectroscopy (XAS) technique was studied in Ustalfs soil suborder. The studied soil is clay loam texture with medium level of organic matter and slightly acidity. Soil was spiked-contaminated with 300 mg copper kg^-1. K-edge spectrum were carried out in fluorescence mode using a 13-channel array germanium detector in which XANES and EXAFS spectrum were recorded in a photon energy region of 8,879 to 9,179 eV and 8,779 to 9,837 eV, respectively. A Ge (220) double crystal monochromator was employed for photon energy scanning. XANES structure was analyze by Linear Combination Fit (LCF) using weighted combination of spectrum from 5 standards Spectrum of chemical models of Cu(OH)₂, CuPO₄, Cu(NO₃)₂, Cu(CH₃COO)₂, CuSO₄. The result showed that the phase atomic fraction of copper was 53.9 % and 46.1 % of Cu(CH₃COO)₂ and CuSO₄, respectively. EXAFS structure was fitted with chemical model copper acetate (CuH₆(CO2)₄) revealed that copper was surrounded in the first shell with six oxygen atoms at 5.99±0.27 Å and in the second shell with 3 carbon atoms at 2.97±0.76 Å. It could be concluded that XAS study provide more information in molecular structure of atom apart from a relative portion from chemical extraction method.