An EXFAS study of the structures of copper and phosphate sorbed onto goethite

The sorption of single (Cu2+, phosphate) and binary sorbate (Cu2+-phosphate) onto goethite (α-FeOOH) was investigated at 25 °C. It was shown that the amount of Cu2+ sorbed increased with increasing the equilibrium pH, whereas the amount of phosphate sorbed decreased. In the binary Cu2+-phosphate sorption system, the amounts of both Cu2+ and phosphate sorbed were enhanced compared to the single sorbate systems. Such enhanced sorption could be explained on the basis of the structures of the sorbed complexes, which were microscopically analyzed from the extended X-ray absorption fine structure (EXAFS) spectra for Fe and Cu edge of fresh goethite, Cu-goethite, and Cu-phosphate-goethite.