A comparative study on recovery of chromium from tannery wastewater as nano magnesium chromite
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Central Metallurgical Research & Development Institute (CMRDI), P.O. Box 87 Helwan, Cairo, Egypt
Ain Shams University, Faculty of Science, Khalifa El-Maamon street, 11566 Cairo, Egypt
Publication date: 2016-06-01
Corresponding author
F. E. Farghaly   

Central Metallurgical Research and Development Institute (CMRDI), elflezat street - eltabbin - Helwan - Cairo - Egypt, P.O Box 87 Helwan 11421 - Cairo, Egypt
Physicochem. Probl. Miner. Process. 2016;52(2):821-834
In this paper, two different precipitation routes involving NaOH and MgO were investigated to remove chromium from tannery wastewater. It was found that the optimum pH for precipitation of chromium using NaOH or MgO was from 8.0 to 8.5 to give total chromium removal of 99.1 and 99.7%, respectively. The MgO route showed less sludge and shorter settling time (3h) compared with NaOH route. Furthermore, MgO enhanced dewatering of the sludge and the total chromium removal. Consequently, the chromium in the formed sludge was recovered as magnesium chromite (MgCr2O4) by calcination of the sludge in the temperature range of 550-650 °C for 6 h. The formed magnesium chromite was characterized with the help of XRD, FE-SEM, FT-IR, TEM and thermal analyses (TGA and DSC). XRD analysis revealed the formation of cubic nano crystalline magnesium chromite powder at a temperature of 550-650 °C for 6 h. TEM images show that the obtained powders exhibited nanospheres with particle a size less than 40 nm. Such formed materials were a good candidate in various applications such as refractory material and catalytic support.
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