Table 1: BET surface areas and removal capacity of different kinds of adsorbent samples.

Adsorbent samples BET surface area (m2·g−1) Adsorption capacity for Cr(VI) (mg·g−1) Fe2O3-Mn3O4 (1 : 0)* 187 22.9 Fe2O3-Mn3O4 (1 : 2.5)* 213 21.3 Fe2O3-Mn3O4 (1 : 5)* 222 21.2 Fe2O3-Mn3O4 (1 : 10)* 264 24.6 Fe2O3-Mn3O4 (1 : 15)* 268 26.3 Mn3O4 61 11.6 -Fe2O3 [15] 178 19.4 Fe3O4 198 21.0 MnFe2O4(MnO2 and Fe2O3) [14] 208 31.3

Different ratio of MnCl2 to KCl in the preparation.