Arsenic sorption onto natural hematite, magnetite, and goethite.

In this work the sorption of As(III) and As(V) on different natural iron oxides (hematite, magnetite, and goethite) has been studied as a function of different parameters. The sorption kinetics for the three iron oxides shows that equilibrium is reached in less than 2 days and the kinetics of sorption seems to be faster for goethite and magnetite than for hematite. The variation of the arsenic sorbed on the three different sorbents as a function of the equilibrium arsenic concentration in solution has been fitted with a non-competitive Langmuir isotherm. The main trend observed in the variation of the arsenic sorbed with pH is the decrease of the sorption on the three sorbents at alkaline pH values, which agrees with results found in the literature. Highest As(III) sorption was observed on hematite surface in all the pH range compared to goethite and magnetite. Natural minerals studied in this work had similar sorption capacities for arsenic than synthetic sorbents.