Improving Hold And Release Capacities Toward Phosphate Of Reclaimed Soil Through Activation Of Coal Gangue In Coal Mining Area

In coal mining areas,the use of coal gangue for coal mining collapsed land filling reclamation is a more common way,not only can restore the use value of sunken land,but also can effectively deal with digestion of coal gangue,reduce the rate of land occupation caused by the accumulation of coal gangue,to achieve the recycling of coal gangue and reduce the waste of resources.However,the original coal gangue filling,inter-particle pore space,low capillary porosity,water and fertilizer retention capacity is insufficient,direct application will cause the reclaimed mine soil structure loose,and restrict soil function,topsoil nutrients easy to lose,affecting the release and circulation of nutrients,resulting in low nutrient content of reclaimed topsoil.Therefore,the modification of coal gangue into a material with high adsorption of soil nutrients and further investigation of the adsorption and desorption capacity of modified coal gangue on soil phosphorus solution on this basis are of great significance to achieve resource conservation and environmental protection.In this study,the coal gangue from Yanzhou mine in Jining city,Shandong province was used as the research object,and the two best activation paths were selected through different activation treatments,combining characterization experiments,static adsorption and desorption,dynamic leaching and desorption,and simulated gangue-filled reclamation of small rape pot planting test,and the seedling rate and The effect of different activation gangue filling on reclamation was analyzed and evaluated through simulated gangue filling reclamation pot planting test,and the effect of activation gangue filling on the soil reclamation of mine area in terms of effective phosphorus sequestration and release capacity was investigated,and the main research results are as follows:（1）Under the conditions of different particle sizes of activated gangue,AS-FCG had the best activation effect,and its maximum phosphate adsorption was 11.796 mg/g,which was 4.41,8.16 and 73.73 times that of AS-MCG,AS-LCG and RCG,respectively;the adsorption penetration time of AS-FCG filled column was longer than that of other samples,and its adsorption performance was related to C-S-H and AFt generation.In addition,when the phosphate-loaded AS-FCG-filled column was desorbed with distilled water,the phosphate concentration in the filtrate was low and rapidly tended to 0 mg/L,while the concentration continued to be high when desorbed with NaHCO₃ solution.（2）Among the different pH activated coal gangue,Al-CG had better adsorption and desorption effects on phosphate,and the adsorption process was more consistent with the secondary kinetic model and Langmuir isothermal adsorption model,in which Al-CG had the highest Langmuir maximum adsorption capacity（3.599 mg/g）;the good or bad adsorption performance of Al-CG was also affected by the C-S-H and AFt generation The adsorption performance of Al-CG was also influenced by C-S-H and AFt generation.When the Al-CG samples were desorbed with distilled water after phosphate adsorption,the lowest phosphate desorption capacity was observed,while the highest desorption capacity was observed when NaHCO₃ solution was used for desorption.（3）The activated coal gangue prepared under different exciter type conditions showed better adsorption and desorption of phosphate.The maximum theoretical phosphate adsorption amount of ACG-2 was 53.217 mg/g,which was 183.51 and 4.51 times higher than that of RCG and ACG-1,respectively.In addition,the ACG-2 filled column showed complete adsorption capacity of phosphate at the early stage of adsorption,and at 12 h.The ACG-2filled column showed complete adsorption of phosphate at the beginning of adsorption and still had good phosphate adsorption capacity after reaching a stable state at about 12 h.In terms of desorption capacity,the desorption curves of the ACG-2 filled column differed greatly,and the desorption process was slow and long-lasting when using Na HCO₃solution for desorption,and reached a stable state at about 25 h.At this time,the phosphate desorption amount was 10 mg/L.（4）Through the above test to screen out two comprehensive effect of activation of gangue to simulate gangue-filled reclamation of small oilseed rape pot test.The pot test showed that when ACG-1 and ACG-2 were used for filling,the seedling rate and growth status of Brassica napus were significantly improved,especially when ACG-2 was used for filling,the full seedling time of Brassica napus was 6 days earlier than the control group,and the fresh weight and dry weight were 1.33 times and 1.30 times higher than the control group,and the average plant height,stem length and root length were higher than the control group,which indicated that ACG-2 This indicates that the soil under the reclamation of ACG-2 is more favorable to the growth of Brassica napus.In summary,activation treatment can improve the retention and release ability of coal gangue to reclaimed soil in mining area,effectively solve the soil nutrient loss caused by undisturbed coal gangue filling and reclamation,and promote the growth of planted crops.The research results will provide data support and technical guidance for optimizing the improvement method of coal gangue,improving the reclamation effect of coal gangue filling and improving the safety utilization performance of coal gangue.