Effect of time on the sorption and distribution of phosphorus in treated soil with minerals and nanoparticles

Effect of time on the sorption and distribution of phosphorus (P) in a sandy soil was investigated in the presence of minerals (i.e., bentonite, calcite, kaolinite and zeolite) and nanoparticles (NPs) (TiO2, Al2O3 and Fe3O4). Compared with control soil, treated soils with 10 % of mineral adsorbents and 3 % of NPs had the highest adsorption capacity. The sorption isotherm of P by treated soils with different adsorbents was well described by the Freundlich and Langmuir models. Among used adsorbents, the highest percentage of P retention was produced by treated soil with 3 % TiO2 while the lowest percentage of P retention was in treated soil with 5 % bentonite. Results showed that with increasing time, the amount of P adsorbed by the control and treated soils with adsorbents (expect treated soil with TiO2 and TiO2-chitosan) increased. After 1 day and 8 weeks of incubation, P in control and treated soils were fractionated by a sequential extraction procedure. The highest percentage of P in the control and treated soils has been observed in Ca-bound (HCl-P) and residual (Res-P) fractions. The results showed that application of adsorbents leads to transfer of P from HCl-P fraction to Res-P and Fe-and Al bound (NaOH-P) fractions which indicate that over time, the availability of P in the soil has decreased.