Biochar Amendment for the Immobilization of Manganese and Cadmium in the Soils of Abandoned Coal Mining in Jambi, Indonesia

High heavy metal contents in soil of abandoned coal mining pose a risk to the environment. Acidic conditions impose a potential mobilization and availability of toxic heavy metals to water body. The objective of this study was to reduce mobilization of manganese and cadmium in the soil by amending lignite base biochar. The immobilization was investigated in a fixed bed column experiment in which concentrations of the metals in aliquot after the column were compared. Demineralized water adjusted to pH 4.7 to mimic environmental condition was pumped up through the column and the aliquots were collected at empty head space at liquid to solid (L/S) ratios of 1, 2, 5, 8 and 10. The results show that biochar amendment improves fraction of Mn and Cd immobilization in the soil and reduces mobility and availability of the metals. Amendment of 10% biochar could immobilize Mn (30%)and Cd (1%), respectively.