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Effect of pH and Complex Formation on Mercury (II) Adsorption by Bentonite
Author(s) -
Newton D. W.,
Ellis R.,
Paulsen G. M.
Publication year - 1976
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1976.00472425000500030007x
Subject(s) - adsorption , chemistry , bentonite , mercury (programming language) , chloride , inorganic chemistry , metal , mercure , nuclear chemistry , environmental chemistry , analytical chemistry (journal) , organic chemistry , computer science , programming language , paleontology , biology
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 0.01 M Ca(NO 3 ) 2 systems occurred in the pH range 4.5–5.5. Varying the Ca(NO 3 ) 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 CaCl 2 concentration from 10 −5 to 10 −4 M depressed adsorption; higher CaCl 2 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 HgCl 2 and Hg(OH) 2 . Chloride salts (0.01 M CaCl 2 , NaCl, and KCl) were more effective desorbers of Hg(II) than was 0.01 M Ca(NO 3 ) 2 or various 0.01 N acids. HCl (0.01 N ) removed the most adsorbed Hg(II).