| The improper exploitation of mineral energy has caused the destruction of ecology in large area of mining area,which seriously restricts the development of economy.At present,our country is in an important stage of economic development,the demand for coal and other ore energy is still very high,and the contradiction between economic growth and environmental pollution is still outstanding.Adjusting industrial structure and restoring the ecology in mining area have become a matter of urgent attention and solution.For the restoration of mining ecology,exogenous restoration measures such as the guest soil method are mainly adopted.These methods can play an urgent role in the restoration of mining ecology,but in the long run,the mining ecology is still very fragile after using this method,the water and soil loss phenomenon has not been substantially improved,and use this method will have adverse effects on the ecology of the guest land.In this paper,starting from the ecological characteristics of the mining area and taking coal gangue,a common solid waste in the mining area,as the raw material,a kind of porous restoration material is developed and prepared to solve the problems in the ecological restoration of the mining area,as a substitute for the guest soil.The physical and chemical properties of the repair material were studied,its environmental safety was assessed,and the possible changes in the practical application of the material were studied by simulating two natural phenomena in the real freeze-thaw process and leaching process,which provided theoretical and data support for the application of the material.The main research is as follows:(1)Using the process of"cement hydration-aluminum powder foaming",the coal gangue is prepared into porous material(CGEr).The retention water of CGEr was 1.19 g water/g soil,4 times higher than that of natural soil,and its loss rate was 2.74%,about85%lower than that of natural soil.CGEr can effectively reduce water evaporation.The results of plant culture experiment and environmental risk assessment showed that CGEr was universal to different plants such as corn and wheat,and its introduction would not cause secondary pollution to the environment.(2)Under the influence of freeze-thaw process,the loose density of CGEr increased to about 0.6 g/cm~3,which was still lower than that of natural soil(1.0 g/cm~3),indicating that it could still effectively improve the degree of soil porosity.The water retention of CGEr decreased to 0.85 g water/g soil,about 3 times that of natural soil,and the loss rate increased to about 4.25%,about 75%lower than that of natural soil.The p H,mineral facies and chemical composition of CGEr are not affected by freeze-thaw process.The freeze-thaw process can inhibit the leaching of heavy metals,and the environmental safety of CGEr as assessed by sediment quality criteria(SQGs),geological accumulation index(Igeo),environmental Potential Ecological Risk Index(RI),and risk assessment code(RAC)continues to improve.(3)Under the influence of leaching process,the loose density of CGEr increased to about 0.5 g/cm~3,which was still lower than that of natural soil(1.0 g/cm~3),indicating that it could still effectively improve the degree of soil porosity.The water retention of CGEr decreased to 0.50 g water/g soil,which was about twice that of natural soil,and the loss rate increased to about 5.50%,which was about 70%lower than that of natural soil.Leaching process will not affect the p H and mineral phase composition of CGEr,but will promote the reaction and the formation of materials.After 1 d,the leaching of heavy metals was limited to a low level,and the subsequent leaching process had no effect on the leaching of heavy metals.The leaching process significantly improved the environmental safety of CGEr. |
