Effect of composite modifier on the physical properties of graphite tailings

In order to solve the problem of poor physical properties of graphite tailings in the process of reclamation, a composite modifier which can improve its air permeability, water retention and structure was developed. Firstly, the effects of corn straw, cow dung and weathered coal on the physical properties of graphite tailings and the range of application amount were investigated through laboratory tests. Secondly, the response surface method (RSM) was used to design the experiment, and the optimal ratio of the composite modifier (corn straw+cow dung+weathered coal) was obtained. Finally, the physical properties of the modified tailings were analyzed in terms of air permeability, water retention and structure, and the effects of the composite modifier on the microstructure were discussed by scanning electron microscopy (SEM).The results showed that when a single modified material was applied, corn straw had the most obvious effect on the permeability of graphite tailings, cow dung had the most significant effect on its water retention, and weathered coal had the strongest effect on its large aggregate content. The optimum ratio of the compound improvers was 4.10% corn straw, 10.49% cow dung and 2.94% weathered coal. At this time, the bulk density, maximum water holding capacity and large aggregate content of graphite tailings were 1.1 g/cm³, 61.71% and 84.51%, respectively. Compared with the graphite tailings before improvement, the total porosity and water-stable macroaggregate content of graphite tailings increased by 17.42% and 14.48%, respectively, and the water holding capacity was also significantly improved. SEM analysis showed that there were obvious cements on the surface of graphite tailings after improvement, and the particles changed from angle-surface contact and edge-surface contact to direct point contact. A large number of particles agglomerated together to form an agglomerated structure. The effect of composite modifier on the physical properties of graphite tailings was verified from the microscopic scale. The results show that the composite modifier has a significant effect on improving the physical properties of graphite tailings, and it is feasible to realize the soil utilization of graphite tailings.