Novel low temperature synthesis of spinel nano-magnesium chromites from secondary resources

A novel low temperature method for synthesis of nano-crystalline magnesium chromites from the tannery waste solution was investigated. Magnesium and chromium hydroxides gel was co-precipitated at pH 8.5 using ammonia solution. MgCr2O4 was obtained by heating the gel formed at different temperatures 300-500 degrees C for to 8 h. FT-IR, TG-DTG-DTA, FE-SEM and TEM were used to investigate the produced materials. XRD patterns of the primary oxides revealed the formation of amorphous oxide phase by heating at 300 degrees C. Heating at 400 degrees C produces nano-crystallite magnesium chromites partly having the structure MgCrO4 and mainly MgCr2O4 and traces of Cr2O3+ 500 degrees C MgCrO4 mostly decomposed into MgCr2O4 structure. After 8 h of heating at 500 degrees C, Cr2O3 completely disappeared. A high surface area about 42.6 m(2)/g and mesoporous structure was obtained for the produced sample at 500 degrees C for 8 h. A thermodynamic model has been suggested to explain the findings. (c) 2013 Elsevier B.V. All rights reserved.