Molecular study of concentrated copper pollutant with a compost

Humic substance in compost contains various organic functional groups that can sorb metal ions through ionic force. This study used thermal treatment technology to concentrate copper in the heated residues while destroying the humic substance of copper-sorbed kitchen compost. Scanning electron microscopy (SEM) results show that copper clusters were formed in the heated residues. Information from both X-ray diffraction (XRD) patterns and Cu K-edge X-ray absorption spectroscopy (XAS) spectrum indicates that about 30% of the doped Cu(II) was chemically reduced to Cu(I) and Cu(0) when the sample was heated at 500 and 900 °C for 2 h. The XAS results indicate that after 500 °C thermal treatment, the loaded Cu(NO3)2 was transformed into CuO (ca. 54%), Cu (ca. 18%), Cu(OH)2 (ca. 15%), and Cu2O (ca.13%). Heating at 900 °C caused more transformation into elemental Cu probably due to more release of oxygen.