Fig. 4

Structural and compositional characterization of attapulgite (ATP), oyster shell (OS), and their composites (ATP–OS) pre- and post-heavy metal adsorption. (a) FT-IR spectra, (b) XRD patterns, and (c) XPS survey spectra before and after Cd(II)/Pb(II) adsorption. High-resolution (d) C 1s and (e) O 1s XPS spectra.