Abstract
A release of phosphorus from calcium phosphate, iron(III) phosphate, and aluminum phosphate owing to the complex formation of their metals with fulvic acid was examined. Fulvic acid was extracted from lake sediments and treated with Amberlite XAD-8 resin. The non-adsorbed fraction of fulvic acid on the resin, which has highly Cu2+-complexing capacity, was used in this study, because the adsorbed fraction has only little Cu2+-complexing capacity as reported in our previous paper.
The non-adsorbed fraction was able to release phosphorus from calcium phosphate, but not from iron(III) phosphate, and aluminum phosphate. The application of X-ray analysis to the calcium phosphate indicated that the major component is hydroxyapatite. The stability constant of the Cu2+-fractionated fulvic acid was determined to be 2×105 (log K=5.3) and the average molecular weight of the fulvic acid was 1,026.
