Effect of Photolytic Oxalate Treatment on Soil Hydroxy-Interlayered Vermiculites

Sampath S. Iyengar1, Lucian W. Zelazny and David C. Martens
Agronomy Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
1 Present address: D'Appolonia Consulting Engineers, Inc., Pittsburgh, Pennsylvania 15235.

Abstract: The effects of Na-citrate-dithionite (NaCD), ammonium oxalate in the dark (NH4Ox-D), and photolytic reaction under ultraviolet radiation (NH4Ox-P) on the mineralogy of <2-µm fractions of selected soils from Virginia were investigated. The NH4Ox-D treatment removed the smallest amounts of Al (<0.22%) and Fe (<0.50%) from all soils, indicating low levels of noncrystalline material in these materials. From the six soils examined, NH4Ox-P treatment extracted 5–62% more Fe and 12–300% more Al than the NaCD treatment. The NH4Ox-D and NaCD treatments revealed no X-ray diffraction detectable alterations to mineral phases present in <2-µm fractions of these soils. The NH4Ox-P treatment, on the other hand, produced considerable degradation of hydroxy-interlayered vermiculites in these soils, as evidenced by a shift of the 14-Å X-ray diffraction maxima to lower spacings with heat treatment of the sample. The NH4Ox-P treatment removed variable amounts of hydroxy-Al material from the interlayers of 2:1 layer silicates, depending on their stability and degree of development.

Key Words: Hydroxy-interlayer • Iron oxide • Noncrystalline • Oxalate extraction • Photolytic reaction • Soil • Vermiculite

Clays and Clay Minerals; December 1981 v. 29; no. 6; p. 429-434; DOI: 10.1346/CCMN.1981.0290603
© 1981, The Clay Minerals Society
Clay Minerals Society (www.clays.org)