Effect of pH and Complex Formation on Mercury (II) Adsorption by Bentonite1
- D. W. Newton,
- R. Ellis and
- G. M. Paulsen2
Reactions of Hg with bentonite clay were studied to determine behavior of the metal in aquatic ecosystems. Mercury (II) adsorption by bentonite as a function of pH and complex formation was investigated using a radioisotopic technique. Maximum Hg(II) adsorption in 0.01M Ca(NO3)2 systems occurred in the pH range 4.5–5.5. Varying the Ca(NO3)2 concentration only slightly influenced adsorption or the pH of maximum adsorption.
Chloride ions sharply reduced Hg(II) adsorption, especially at low pH's. At pH 6 or lower, increasing CaCl2 concentration from 10−5 to 10−4M depressed adsorption; higher CaCl2 levels were required to decrease adsorption at pH 7. At a given Cl− concentration, maximum observed Hg(II) adsorption occurred near the calculated pH where HgClOH occurred as a transition complex between HgCl2 and Hg(OH)2.
Chloride salts (0.01M CaCl2, NaCl, and KCl) were more effective desorbers of Hg(II) than was 0.01M Ca(NO3)2 or various 0.01N acids. HCl (0.01N) removed the most adsorbed Hg(II).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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