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Aluminosilicate phases during initial clay formation: H + ‐Al 3+ –oxalic acid–silicic acid–Na + system
Author(s) -
BILINSKI H.,
HORVÁTH L.,
INGRI N.,
SJÖBERG S.
Publication year - 1990
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1990.tb00050.x
Subject(s) - allophane , oxalic acid , aluminosilicate , silicic acid , chemistry , silicate , imogolite , inorganic chemistry , precipitation , phase (matter) , podzol , tetramethylammonium , mineralogy , clay minerals , geology , soil water , ion , biochemistry , physics , organic chemistry , meteorology , soil science , catalysis
SUMMARY The solid phases and the precipitation boundary characterizing the system H + ‐Al 3+ ‐oxalic acid‐silicic acid‐Na + are discussed. Model experiments have been used to throw more light on two environmental problems: the formation of sparingly soluble aluminium silicates in oceans and alkaline lakes, which could be determining aluminium and silicate concentrations in pore waters of sediments, and the validity of inorganic and organic mechanisms of podzolization and their significance for soil science. pH and Tyndallometric measurements were performed at constant ionic strength of 0.6 M NaCl at 25°C. Three phases Al(OH) 4 , H 4 SiO 4 (phase Vi a ), Al 2 , (OH) 6 .H 4 SiO 4 (phase VI b ) and NaAl(OH) 4 .(H 4 SiO 4 ), (phase VIII) determine the precipitation boundary. Phase NaAl(OH) 4 .H 4 SiO 4 (phase VII precipitates at 0.4pH units above NaAl(OH) 4 .(H 4 SiO 4 ) 2 . Using a set of previously determined binary and ternary complexes, and phases of the subsystems, the following formation constants were deduced:Phases VI a and VI b are described as end‐members of the allophane series with Si: Al ratios of 1:1 and 1.2. Phase VI b was identified with protoimogolite allophane. These two phases are good model clays for podzolic soils and are extremely soluble at pH < 4. Sodium phases could be hydrous feldspathoids. These phases are possible in sediments of seawater or saline lakes. It is suggested that organic and inorganic mechanisms of podzolization operate sequentially and that neither of them alone can completely describe the process.