Investigation on Co-sorption and Desorption of Fluoride and Phosphate in a Red Soil of China

Authors: Zhu, Mao-Xu; Ding, Kui-Ying; Jiang, Xin; Wang, Hai-Hua

Source: Water, Air, and Soil Pollution, Volume 183, Numbers 1-4, July 2007 , pp. 455-465(11)

Publisher: Springer

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Abstract:

Agricultural soils high in both fluoride (F) and phosphate (P) are common due to long-term accumulation of F from multi-sources and extensive application of phosphate fertilizers. Iron (Fe) and aluminum (Al) (hydro)oxides in acidic soils serve as main geochemical sinks of both P and F, influencing their transport and bioavailability. Though sorption of P and F in their single-ion system has been extensively investigated, studies on co-sorption of F and P on soils are very limited. In this study, the batch technique was used to investigate mutual effects of F and P on their co-sorption/desorption in an acidic red soil with high contents of Fe and Al (hydro)oxides. Results indicate that, in F-P coexisting system, a decrease in pH enhances the sorption of both F and P. An increase in F concentration suppresses P sorption due to competitive effect. However, F sorption can be improved in the presence of P due to surface precipitation of (Al,Fe)-F-P. Sorption of F and P follows both the Langmuir and Freundlich isotherms. Different orders of F and P addition into the soil have no appreciable effect on P sorption, but exert significant impact on F sorption. The presence of F has no measurable effect on P desorption, while the stability of F in the presence of P can be significantly diminished in comparison with that in the absence of P, which would lead to an improvement of F mobility.

Keywords: Desorption; Fluoride; Phosphrous; Red soil; Sorption; Surface precipitation

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11270-007-9394-0

Affiliations: 1: Email: zhumaoxu@ouc.edu.cn

Publication date: 2007-07-01