Structure and Mn2+ adsorption properties of boron-doped goethite

Abstract Two kinds of boron-doped goethites were synthesized, one was called ad-B-goethite prepared by reacting the original goethite with borax solution and the other called oc-B-goethite prepared in the presence of boric acid solution. The goethites were characterized by IR and XRD. The IR bands of Fe OH Fe in-plane bending and free OH of the boron-doped goethites were weak compared with the original goethite. The IR bands of bending modes of trigonal and tetrahedral B were found in ad-B-goethite (420 cm − 1 ) and oc-B-goethite (527 cm − 1 and 476 cm − 1 ). These results suggest that some hydroxyl groups were replaced by the introduced boron. Analysis of XRD patterns indicated ad-B-goethite remained the characteristic of α-FeOOH, while oc-B-goethite did not. The specific surface areas of these goethites using BET method were 108 m 2 /g, 89 m 2 /g and 120 m 2 /g for the original goethite, ad-B-goethite and oc-B-goethite, respectively. The relatively large surface area of oc-B-goethite indicated the likelihood of higher activity than the original goethite, which was supported by evidence of the higher Mn 2+ adsorption ability of oc-B-goethite. The amount of adsorbed Mn 2+ increased with pH by the geothites and the order of Mn 2+ adsorption capability was oc-B-goethite > ad-B-goethite > the original goethite. It was suggested that boron in soils not only serves as a plant nutrient, but can also decreases the Mn 2+ toxicity through the function of enhancing Mn 2+ adsorption in acidic soils.