To identify the mineral phases in soils, the clay fractions of selected soil samples were sieved, where
the contaminant metals are more likely concentrated [22]. This metal-rich fraction was then characterized
using X-ray diffraction (XRD, Ultima IV, Rigaku) with Cu Kα radiation (40kv, 40mA) and PDXL2
software with ICDD (2012). Samples were scanned at room temperature by using start angle 10º, end
angle 45º, step size 0.02º with a scanning speed 2º m-1. Selected soil clay was also observed using a
scanning electron microscopy (SEM, JSM-6510LV).