Comparison of removal of chromium (III) from aqueous solution by two kinds of modified diatomite: manganese-oxide-modified diatomite and microemulsion-modified diatomite

Crude Diatomites Modified by Microemulsion (DMM) and manganese oxide (MnD) arc tested for the removal of chromium (III) in this study. The results indicate that zero point of charge (pHZPC) of DMM is 4.7 and that of MnD is 4.6. Both DMM and MnD show remarkable increase in the sorption capacity of chromium (III) when compared with untreated diatomite, and the removal of chromium (III) by DMM is higher than that by MnD. In the case of pH on the heavy metal removal rate, both maximum percentage removal by MnD and DMM take place at nearly pH = 4, and decline when pH > 4. In addition, the increment in chromium synthetic solution concentration results in the improvement of the sorption capacity by both MnD and DMM. 36 h for MnD and 24 h for DMM are optimal equilibrium time for maximum removal.