Adsorption of glycerophosphate on goethite (-FeOOH): A macroscopic and infrared spectroscopic study

摘要

Adsorption, desorption, and precipitation reactions at environmental interfaces govern the bioavailability, mobility, and fate of organic phosphates in terrestrial and aquatic environments. Glycerophosphate (GP) is a common environmental organic phosphate, however, surface adsorption reactions of GP on soil minerals have not been well understood. The adsorption characteristics of GP on goethite were studied using batch adsorption experiments, zeta () potential measurements, and in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). GP exhibited fast initial adsorption kinetics on goethite, followed by a slow adsorption. The maximum adsorption densities of GP on goethite were 2.00, 1.95, and 1.44 mol m(-2) at pH 3, 5, and 7, respectively. Batch experiments showed decreased adsorption of GP with increasing pH from 3 to 10. Zeta potential measurements showed a remarkable decrease in the goethite isoelectric point upon GP adsorption (from 9.2 to 5.5), suggesting the formation of inner-sphere surface complexes. In addition, the ATR-FTIR spectra of GP sorbed on goethite were different from those of free GP at various pH values. These results suggested that GP was bound to goethite through the phosphate group by forming inner-sphere surface complexes.