ARS | Publication request: BORON SORPTION AND RELEASE BY ALLOPHANE

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 8, 1996
Publication Date: N/A

Interpretive Summary: Interaction of B with soil materials is important because there is a narrow range between the levels of B required by and toxic to plants. Boron sorption, with, and after, precipitation of a poorly crystlized aluminosilicate was studied to evaluate the effects of precipitation conditions on the B sorption and to investigate leachability of sorbed B from allophane. This study showed that more B was removed when B was present during precipitation as compared to reaction of the B solution after precipitation. Based on spectroscopy studies, adsorbed B was identified as both trigonally and tetrahedrally coordinated, with the former being predominant. Only tetrahedrally coordinated B was observed for the coprecipitated B. The coprecipitated B is expected to be more resistant to release from minerals than the adsorbed B. The results of this study are related to prediction of long term B release from soils under irrigation.

Technical Abstract: Boron was found to be removed via adsorption and coprecipitation mechanisms. Based on FTIR studies, adsorbed B was identified as both trigonally and tetrahedrally coordinated, with the former being predominant. Most initially sorbed B with allophane precipitation was held onto the surface of precipitates rather than within the structure. Only tetrahedrally coordinated B was observed for the coprecipitated B. Coprecipitation presumably occurs when B substitutes for Si in the tetrahedral layer of allophane. The coprecipitated B is expected to be more resistant to release than the adsorbed B by repeated washing.