Experimental Study On Dust Suppression Of Microbial And Urease Mineralized Cemented Red Mud

Alumina is one of the important raw materials for the development and construction of the country.The continuous production of alumina has led to an increase in the stock of its by-product red mud,and the area of red mud storage yard has continued to expand.Due to the fine particle size of red mud,the long-term outdoor storage of red mud is affected by environmental weathering and transportation,resulting in the formation of red mud dust,which expands the pollution area and poses a threat to ecology and human health.At present,the prevention and control measures have problems such as secondary pollution,high cost,and poor effectiveness,and the practical application of dust treatment in large storage yards is relatively difficult.Therefore,timely conducting experimental research on new measures for controlling red mud dust has important theoretical significance and engineering application value.Microbial mineralization technology(MICP)and urease mineralization technology(EICP)cementation of loose soil particles has the advantages of environmental protection,durability and good cohesiveness.Therefore,this paper proposes to use microorganisms and urease mineralization to cement red mud for dust suppression.Analyze the effects of various factors on the mineralization and cementation of red mud particles by microorganisms and urease,and test the dust suppression effect of the cementation sample.Chitosan and Biomineralization technology were introduced to cement red mud.The main research results of this article are as follows:(1)Study the strength performance of microbial and urease mineralized red mud.Under various influencing factors,soil fixation tests of microorganism and urease were carried out respectively.The results showed that both microorganism and urease could overcome the characteristics of red mud,such as strong alkalinity and small particle size.A hard shell layer could be formed on the surface of red mud by using the surface spraying solidification process.The spraying interval of 12 h was enough to enable Biomineralization to fully react in the red mud layer.When the total amount of cementitious liquid sprayed remains unchanged,one-time spraying is more conducive to fully exerting urease activity and generating a large amount of cementitious calcium carbonate than multiple spraying.As the amount of bacterial solution,urease solution,and binder increases,the micro penetration resistance and calcium carbonate production continue to show a positive increase,while the disintegration rate and strength loss rate of the sample gradually decrease.The higher the number of spraying rounds and the concentration of the binder,the greater the calcium carbonate production and micro penetration resistance of the solidified red mud sample by microorganisms and urease,and the smaller the disintegration rate and strength loss rate of the sample.The sample with better water stability has a smaller disintegration rate and a smaller strength loss rate.(2)Study the dust suppression effect of microbial and urease mineralization cemented red mud separately.The micro penetration resistance,calcium carbonate production,and dust suppression effect of microbial and urease soil fixation were measured under various factors.The results showed that the micro penetration resistance,calcium carbonate production,and dust suppression effect of MICP were greater than those of EICP,while the disintegration rate and strength loss rate of MICP were lower than those of EICP.The wind resistance of the red mud soil layer after mineralization by microorganisms and urease is significantly improved.The critical failure wind speed of the red mud sample cemented by microorganisms and urease mineralization increases with the increase of the number of spraying rounds and the concentration of the binder.The wind erosion rate of the red mud sample decreases with the increase of the concentration of the binder and the number of spraying rounds,gradually increases with the increase of the sample slope,and gradually increases with the increase of wind speed and blowing erosion time.(3)The effect of red mud cementation by chitosan and Biomineralization technology was studied.The experiment was conducted with the addition of chitosan as the key parameter,and the results showed that chitosan as a green and economical additive can effectively improve mineralization efficiency.The introduction of chitosan can increase the production of calcium carbonate during microbial and urease mineralization.At the same time,the micro penetration resistance and calcium carbonate production of the cemented sample increase with the increase of the concentration of the binder.The effect of microbial mineralization and cementation is better than that of urease mineralization and cementation.With the increase of chitosan incorporation,the gap between the micro penetration resistance and calcium carbonate production gradually decreases,the viscosity of chitosan urease solution and chitosan microbial solution is significantly improved,and the solution is easier to adhere to the red mud particles to extend the mineralization time.Chitosan adhesion between red mud particles strengthened the cementation of microbial mineralization and urease mineralization on red mud hard shell layer,and optimized the single cementation mode of calcium carbonate precipitation cementation soil mass during Biomineralization reaction.(4)By studying the microscopic characteristics of red mud after cementation through scanning electron microscopy,and comprehensively analyzing the dust suppression performance of microbial and urease mineralization cementation red mud,the results show that the cementation strength of red mud samples mainly comes from the cementation filling effect of calcium carbonate.From scanning electron microscopy,calcium carbonate crystals are mostly polygonal plate-like or rhombic crystals,and calcium carbonate crystals are continuously stacked into clusters.Calcium carbonate,which plays a bonding and bridging role,is the main source of soil cementation performance.The introduction of chitosan gives calcium carbonate crystals an irregular block like structure,making the spatial structure of mineral precipitation more compact and promoting crystal aggregation and binding.There is a synergistic mineralization effect between polysaccharides and bacteria.The research results of this paper enrich the engineering application fields of microbial and urease mineralization technology,and provide new solutions for the prevention and control of red mud dust.