Mesoporous activated carbon was prepared from waste tyres via acid wash and steam activation. The effect of synthetic conditions was studied and the surface texture of the tyre carbon was characterized. The optimally obtained carbon sample presents a surface area of ∼1200 m 2 g −1 and is predominantly mesoporous. Acid wash was found to play an important role in the structural development of carbon. The advantage of the mesoporous carbon was demonstrated by its excellent sorption capacity towards the bulky molecule of a basic dye (methylene blue).  2011

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The use of calcium oxide as a precipitant can achieve a nonammonia enrichment of a rare earth leaching liquor. However, an alkaline rare earth sulfate forms during the precipitation process, thus resulting in excessive SO 4 2− content in the mixed rare earth oxides. Therefore, a stirring washing process for precipitation enrichment, which was obtained from calcium oxide precipitation, was investigated using a sodium hydroxide solution. It was determined that the Gibbs free energy of the stirring washing reaction, which was calculated by a group contribution method, was between −60 and −300 kJ/mol, depending on the different rare earth elements. The above results indicated that the reaction was thermodynamically feasible. The optimum conditions of the washing process were obtained, namely, a feed ratio of 2.85, a liquid−solid ratio of 6.5 mL/g, a stirring washing temperature of 35 °C, and a stirring washing time of 20 min. Under the optimal conditions, the purity and the SO 4 2− content of the mixed rare earth oxides were 94.38% and 3.48%, respectively, and the stirring washing process with the sodium hydroxide solution had good recyclability. Moreover, the washing product was tested using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS), which verified that the stirring washing process with NaOH could effectively remove SO 4 2− from the precipitation enrichment into solution. On this basis, a new extraction process of the ion-adsorption-type rare earth ore by magnesium salt leaching−calcium oxide precipitation−sodium hydroxide stirring washing is proposed. This new process can eliminate the traditional aluminum-removal process and effectively reduces the rare earth loss in the process. It can also solve the problem of the excessive SO 4 2− content in the mixed rare earth oxides caused by the calcium oxide precipitation process. The research in this paper can have great significance for green, efficient extraction of the ion-adsorptiontype rare earth ore and the improvement of resource utilization.

In this study, a CO2 carbonization method is introduced for the preparation of 1D yttrium oxide powders. Using YCl3 as the raw material, sodium hydroxide was initially used to completely precipitate Y3+ into yttrium hydroxide, and then CO2 was introduced into the yttrium hydroxide slurry for homogenization-like carbonization to obtain yttrium carbonate precipitation. Then, by studying the effects of carbonization conditions, such as the temperature, CO2 flow rate, and stirring speed, on the morphology and phases of yttrium carbonate, the temperature was observed to exert a greater effect than the other experimental parameters on the morphology and structure of the carbonized products. Finally, Y2(CO3)3·2H2O nanoneedles were obtained at optimal conditions. The carbonized crystals of the acicular yttrium carbonate precipitate because of the solution supersaturation and then quickly complete their crystal growth process through the oriented attachment (OA) and Ostwald ripening (OR) mechanisms. After heat treatment, yttrium carbonate retained a good crystal morphology and produced Y2O3 nanoneedles with a length of 1–2 μm and a width of 20–30 nm.

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