Unravelling heavy metals (HMs) speciation route during vermiremediation employing a novel approach based on spectroscopic interpretations

Abstract

The present study was designed to understand the speciation route of 7 heavy metals (Cu, Fe, Mn, Zn, Ni, Co, and Cr) during the vermicomposting of food industry sludge through a novel approach achieved through combining vibrational and electronic transitions employing spectroscopic interpretations. Earthworm species Eisenia fetida was utilized in the experiment conducted for the duration of 60 days. The results revealed that the addition of earthworms and the participation of microorganisms appearing during various stages of vermicomposting have accelerated the waste mineralization process. The concentrations of heavy metals have shown a significant decline upon vermicomposting as the HMs speciation route was triggered through the generation of metal ions. The spectroscopic interpretations revealed that the production of heavy metal intermediates coupled with oxides, sulphates, chlorides, and amines contributes to the bio-transformations of HMs achieving their successful immobilization in the vermicomposting system. Furthermore, the intermediate compounds found in the vermicompost are reported to have the potential to promote plant growth establishing vermicomposting as a superior management strategy for industrial organic wastes.