（1） Roadbed materials made from red mud[1]
Red mud can be used as roadbed material instead of lime soil in the plain area because of its high bearing strength and durability. Besides red mud, several solid wastes from industry, such as fly ash, boiler slag and carbide slag was use in the Roadbed materials.
（2） Silicate cement made from red mud[2]
The red mud which is generated by alumina sintering, containing a large number of the calcium silicate mineral composition of cement, can be used to produce cement. Silicate cement produced from red mud is strong, sulphate and frost-resistant, and inexpensive.
（3） Silicate fertilizer made from red mud[1]
Silicate fertilizer made from red mud is very suitable to acid red soil, yellow soil and rice soil in south China because it contains many trace elements, and is especially high in potassium and phosphate. Silicate fertilizer contains elements of a weak acid soluble, which can improve soil and increase crop yields.
（4） ceramics materials made from red mud[3]
The chemical and the mineralogical investigations indicated that major constituents of the red mud were hematite and sodium aluminium silicate hydrate. The production of the porcelain, vitreous (sanitary ware glazes), tile and electroporcelain glazes was done using the red mud. The glazes, which contain different compositions and properties, were examined. It was found that the addition of up to 37 wt% of the red mud waste was possible in the production of the glazes.
（5） Removal of arsenate from water with the modified red mud[4]
The modified red mud with FeCl3 could be used for the removal of arsenate from water. The modification of red mud was carried out as follows: red mud was sieved and the particles below 177μm were used for modification. Ten gram of powder was added to 1 L water and pH of the solution was about 13. The mixture was stirred at 60 rpm and 0.5M FeCl3·6H2O was added dropwise to the mixture until the pH reached 5. The resulting solution was aged for 1 day and the mixture was centrifuged. The obtained solid was washed with deionized water for three times and dried at 105 ◦C. The red mud was then sieved again, and particles below 177μm obtained were used as adsorbent for the experiments. They believed that the solution pH significantly affected the adsorption, and the adsorption capacity increased with the decrease in pH. Adsorption capacity of modified red mud was 68.5 mg/g, 50.6 mg/g and 23.2 mg/g at pH 6, 7 and 9 respectively. NO3− had little effect on the adsorption. Ca2+enhanced the adsorption, while HCO3− decreased the adsorption. The modified red mud could be regenerated with the NaOH, and the regeneration efficiency reached 92.1% when the concentration of NaOH was 0.2mol/L.
（6） Recycling alumina and iron from red mud[5]
The transport fluxes of Al, Fe and Na ions from red mud through charged heterogeneous and Neosepta CMB and CMX cation exchange membranes has been studied as a function of H+ ion concentration in stripping phase. In this process, the feed solutions is initially red mud aqueous solution or half-diluted solution which
contains Al, Fe, Ti and Na ions and other side is HCl solutions at different concentrations (0.05, 1.0 M).It was shown that the fluxes and recovery factor value of metal ions were enhanced with increasing concentration in feed phase and H+ ion concentration in stripping phase.
（7） Recovery rare earth elements from red mud[6]
A chromatographic method has been developed for separation and determination of scandium (Sc) and rare earth elements (REEs) in samples from a red mud utilization process. By use of this method Sc, which is the most expensive of the elements investigated and occurs in economically interesting concentrations in red mud, could be separated not only from co-existing Fe but also from Y/Dy, Yb, Er, Ho,
Gd, Eu, Sm, Nd, Pr, Ce and La. All the elements investigated were individually recovered. Their recoveries were found to be nearly quantitative.
References
[1] Yongshuang Zhang, Yongxin Qu, Shuren Wu. Engineering geological properties and comprehensive utilization of the solid waste (red mud) in aluminium industry. Environmental Geology,2001,12(41):3~4
[2] Eke Kalian. Utilization of red mud as a stabilization material for the preparation of clay liners. Engineering Geology, 2006, 87(3-4),220 ~ 229
[3] Nevis Yale õn, Vahdettin Sevinc.Utilization of bauxite waste in ceramic glazes. Ceramics international,2000,26:485~493
[4] Zhang SW, Liu CJ, Luan ZK, Peng XJ, Ren HJ, Wang J. Arsenate removal from aqueous solutions using modified red mud. 2008,152: 486~492
[5] Yunus Cengeloglu, Esengul Kir, Mustafa Ersoz .Recovery and concentration of metals from red mud by Donnan dialysis. Colloids and Surfaces A.2003,223:95~101
[6] Investigation of the separation of scandium and rare earth elements from red mud by use of reversed-phase HPLC. Analytical and Bioanalytical Chemistry,2004,378:796~802
