Preparation And Application Of Zeolite Ceramsite From Rare Earth Tailings

The rare earth reservesare huge in Inner Mongolia,and a large amount of rare earth tailings are produced in the exploitation process.The resource utilization of rare earth tailings concerns the resource-saving and environment-friendly society construction of Inner Mongolia.Thus,it is urgent to develop recycling methods for rare earth tailings.In this study,construction and demolition(C&D)waste and rare earth tailings were tested as the major raw material for the preparation of ceramsite.The obtained ceramsite was treated in hydrothermal condition for zeolite synthesis and surface modification.The main aims were:(1)relieving environmental impacts of C&D waste and rare earth tailings;(2)developing an eco-material from C&D waste and rare earth tailings.The main researches were as follows:(1)Adding rare earth tailings cound significantly reduce the sintering temperature of C&D waste ceramsite,especially while the tailings addition was less than 1/10.There was no more obviously reduction of sintering temperature when talings addition exceeded 1/5.Considering the current environmental requirements and resource recycling policy,C&D waste and rare earth tailings are potential materials for ceramsite production.(2)As the rare earth tailings is rich in Fe oxides,it cound create gases in the sintering process.On the one hand,it would promote the formation of porous structure.On the other hand,it would result in phenomenon like hollow and cracks with an excessive tailings addition.according to experimental results,the optimized addition of rare earth tailings is 1/10,and the corresponding optimized sintering temperature is 1140℃.The main factors which influence the product of hydrothermal reaction include rare earth tailings addition,hydrothermal temperature,NaOHconcentration and hydrothermal reaction time.A high rare earth tailings addition is disadvantageous to the synthesis of zeolite structure.Faujasite was produced under the condition with reaction temperature of 180℃,NaOH solution concentration of 4mol/Land reaction time of 10 h.The rankinites and zeolite P are intermediate products of alkaline hydrothermal reaction.Through hydrothermal reaction,the specific surface area of the ceramsite increases from 1.03 m2/g to 32.56 m2/g.The zeolitic ceramsite has a greater specific surface area and a good disposal effect forPb2+in wastewater.The adsorption isotherm conformed to Langmuir isotherm model(R2 is 0.989).Adsorption reaches equilibrium when adsorption time was 4 h,and the maximum absorptive capacity could be up to 95.2381 mg/g.With rare earth elements loaded on surface,the zeolitic ceramsite has a good disposal effect on anionic phosphate.The adsorption isotherm conformed to Langmuir isotherm model(R2 is 0.989).Adsorption reaches equilibrium when adsorption time was 6h,and the maximum absorptive capacity couldbe up to 8.5470 mg/g.