Removal of chromium ion (III) from aqueous solution by manganese oxide and microemulsion modified diatomite

Diatomite modified by microemulsion (DMM) and manganese oxide (MnD) were used for the removal of chromium ion (III) from aqueous solution. The characters and performance of these two types of modified diatomite on chromium ion (III) adsorption were compared to each other. The results indicate that the chromium ion (III) sorption capacities of diatomite were of considerably improved after modified by manganese oxide and microemulsion. The surface area of modified diatomite was increased due to the formation of the manganese oxides on the diatomite surface in MnD and corresponding to the present hydrolyzed aromatic acid in DMM. Because of the stronger surface ionized function, the performance of the sorption of chromium ion (III) in DMM was better than that in MnD. Within the experimental range of pH (pH = 2.2–6.3), the chromium ion (III) removal of DMM (varying from 35% to 70%) was higher than that of MnD (varying from 33% to 59%) owing to the different electrostatic forces between chromium ion (III) and the surfaces of the modified diatomite. The chromium removal in MnD and DMM were improved with the increase of synthetic solution concentration (when the solution volume varies from 0 to 2500mL, both their removals improve from lower than 10% to higher than 90%).