Content and form distribution of heavy metals in biogas residues

In this study,CaCl2,EDTA,HOAc extraction and modified BCR sequential extraction method were used to study the speciation of Cu and Zn in six types of biogas residues.The results showed that the concentrations of the heavy metal speciation in the biogas residues varied with the element and the residue type.The single extraction efficiency follows the order: EDTA HOAc CaCl2.The extraction efficiency of EDTA was more than 70%,and HOAc extraction efficiency was between 11% and 62%,while CaCl2 extraction efficiency was less than 0.6%.The mobility of Zn was higher than that of Cu.Plants might absorb excessive Zn if there are high concentrations of Zn in biogas residues.