Sorption of inositol hexaphosphate on desert soils

Sorption of inositol hexaphosphate (IP6) on desert soils was studied to evaluate their use as a novel low-cost sorbent material for organic P removal in water treatment. The kinetics of IP6 sorption, pH effects, and sorption isotherms were examined in batch experiments on four desert saline-sodic soils: Antofagasta (AN), Mejillones (ME), Aguas Blancas I (ABI), and Aguas Blancas II (ABB). The sorption kinetics of inositol hexaphosphate expressed as P (P-IP6) on these soils were described by the Elovich equation and the initial sorption velocities ranked in the order: ABII > ABI > ME > AN. In addition, P-IP6 sorption capacity in AN, ME, and ABI was strongly influenced by the solution pH, but in ABII it was not pH-dependent. Whereas the experimental data of P-IP6 sorption on ME, ABI, and ABII were better fitted by the Langmuir equation (implying a homogenous distribution of active sorption sites), for AN the best fit was obtained with the Freundlich model (implying heterogeneous, multi-layered sorption surfaces). The maximum P-IP6 sorption capacities ranked: ABII > ME > AN > ABI. Based on the results of our study, ABII soil is recommended for P-IP6 removal. In this soil, P-IP6 sorption did not depend on solution pH, and the precipitation and sorption of IP6 were associated with Ca2+, Mg2+, and minerals such as montmorillonite and vermiculite. (C) 2014 Elsevier B.V. All rights reserved.