非火山灰土壌非晶質粘土成分の表面活性評価

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A study has been undertaken to evaluate the surface reactivity of noncrystalline constituents in the clays from Brown Forest, Red, Yellow, and Brown Lowland soils. The clays (< 2μm) were treated with dithionite (DCB) and hot acid oxalate (90℃),and phosphate adsorption, specific surface area. and ion exchange capacity (CEC and AEC) of the dissolved fractions were estimated from the differences between the respective values determined before and after the treatments. The results obtained are summarized as follows : The dissolved fractions adsorbed phosphate in large quantities which were incomparable with those adsorbed by the residues of the treatments (crystalline constituents), though the quantities were markedly smaller than those of allophanic soil clays. The quantity of the phosphate adsorbed by the untreated clays exhibited a positive correlation with the total contents of the fractions dissolved by the treatments, particularly with the oxalate-extractable fractions, in the clays. Among the respective oxide extracted (SiO_2, Al_2O_3, Fe_2O_3), the correlation was particularly higher with the oxalate-extractable iron oxides. It was considered thus that the soils of non-ash origin owe their phosphate adsorption largely to the oxalate-extractable, i.e., noncrystalline, iron oxides they contain. So far as the soil samples examined are concerned, the contribution of non-or poorly-crystalline aluminosilicates to phosphate adsorption was not evident, though their adsorption activity was expected. The specific surface area of the extractable fractions was difficult to estimate with precision due to a possible underestimate derived from the assumption involved in the method employed. Nevertheless, it was judged from the results that the specific surface area of the noncrystalline constituents was approximately equal to or a little larger than that of the crystalline counterpart in the same clays. The CEC and AEC values of the extractable fractions carried an underestimate due to the same reason as the above and gave rise to negative values for many samples. Particularly in the case of AEC, interpretation of the values obtained was more complicated due to an overestimate which arose by negative adsorption of anion on the surface of the crystalline counterpart.
社団法人日本土壌肥料学会の論文
1992-10-05

非火山灰土壌非晶質粘土成分の表面活性評価

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