Comment on “Removal of Ni²⁺ and Cu²⁺ Ions from Aqueous Solutions on to Lignite-based Carbons”, by S.E. Samra

Recently, Samra (2000) published the paper entitled as above. In the section on kinetic measurements, Samra mentioned that “Coleman et al. (1956) assumed that the adsorption of a divalent metal ion on carbon proceeds via a pseudo-second order mechanism in which adsorption is the rate-limiting step”. In fact, Coleman et al. (1956) reported the formation constants for CuII–peat complexes. The peat–CuII reaction may be written in two ways, in which P refers to the concentration of peat functional groups: