AMMONIUM OXALATE EXTRACTION OF IRON TRIAD FROM NATURAL CLAY SAMPLES

Abstract

Acidic ammonium oxalate extraction is used to estimate the amount of amorphous or poorly crystalline iron in soils and sediments. Iron is the one element from the “iron triad” which have similar chemical behaviour. Other two elements are nickel and cobalt. The aim of this study was to evaluate acid ammonium oxalate extraction of all elements from iron triad. The samples of natural clay were used in the investigation. Samples for total amounts of metals were prepared with microwave digestion with HNO3 and HF, and measured by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Ammonium oxalate extraction was done by earlier established procedure in acid medium and with absence of light. Measurements were conducted with atomic absorption spectroscopy with flame atomization (FAAS). For statistical evaluation, maximum, minimum, average, median and correlations were used. The investigated iron triad elements lie in the next sequence: Fe>Ni>Co. The poorly crystalline iron and ammonium oxalate extractable Ni showed higher correlation (r = 0.874) than ammonium oxalate extractable cobalt (r = 0.446), suggesting that iron and nickel are more similar regarding ammonium oxalate extractability.