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Characterizing trace metal adsorption on kaolinite
Author(s) -
SPARK K.M.,
WELLS J.D.,
JOHNSON B.B.
Publication year - 1995
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.1995.tb01359.x
Subject(s) - adsorption , kaolinite , chemistry , metal , electrolyte , inorganic chemistry , mineralogy , organic chemistry , electrode
Summary Adsorption of Cu(II), Zn(II), Co(II) and Cd(II) on kaolinite has been investigated at 25°C as a function of pH, concentration of the substrate, and the nature and concentration of the supporting electrolyte. The adsorption edges for three metals (Zn(II), Co(II) and Cd(II)) showed clear evidence of two distinct adsorption processes. As the pH was increased adsorption began at pH 4.5 for all metals, but the fraction of metal adsorbed at the completion of the first stage differed, the order being Zn(II)>Co(II)∼Cd(II). The second stage of adsorption had characteristics similar to those for adsorption of the metals on alumina and silica. Type 1 adsorption (the first stage) probably occurs on the permanent negatively charged kaolinite faces, while Type 2 (the second stage) is associated with the variable‐charge surfaces. Increasing the concentration of supporting electrolyte (KNO 3 or NaCl) dramatically reduced the extent of Type 1 adsorption: at 0.1 m no evidence of this process existed. At intermediate concentrations electrolytes containing K + suppressed Type 1 adsorption more than those containing Na + .