| Red mud is an alkaline solid residue produced in the process of refining alumina from bauxite.Due to its strong alkalinity and a large amount of heavy metal elements,it cannot be used for large-scale resource utilization,resulting in a large number of storage and a series of environmental problems such as soil and groundwater pollution.In this paper,phosphogypsum and vinegar residue are selected as red mud dealkalization modifiers,and the physicochemical properties of red mud,phosphogypsum and vinegar residue are analyzed and studied;through the experiment of phosphogypsum-vinegar residue dealkalization modification of red mud,the mechanism of dealkalization modification was explored,and the effect of adding phosphogypsum and vinegar residue on the physical and chemical properties of red mud was analyzed;through pot experiment and leaching experiment,the growth status of plants and the environmental safety of modified red mud were tested and analyzed,and the feasibility of red mud soilization was verified.The main research contents and conclusions are as follows:(1)Through the study on the physical and chemical characteristics of red mud,it is known that red mud is strongly alkaline(p H value is about 11.08),low conductivity(EC is about 0.23m S/cm),strong moisture absorption(moisture content is about 20.2%),fine particle size(the range of 0.01～0.1μm is about 44.6%)and the content of Cr in heavy metal elements is beyond the range of soil pollution risk control value of agricultural land;phosphogypsum is weakly acidic(p H value is about 6.71),high moisture content(moisture content is about 13%),high conductivity(EC is about 2 m S/cm),high Ca content(Ca content is about 19100 mg/kg),the content of heavy metal elements As,Pb and Cr is low the range of soil pollution in paddy fields;the vinegar residue is acidic(p H value is about 4.67),high moisture content(moisture content is about 42%),low conductivity(conductivity is about 0.61 m S/cm),large particles(particle size is in the range of 3～6 mm)and rich in nutrients(organic matter is about 636×10~3mg/kg,hydrolyzable nitrogen is about 2.86×10~3 mg/kg,and the available phosphorus is about1.73×10~3 mg/kg),the content of heavy metal elements As,Pb and Cr is low the range of soil pollution in paddy fields.Through the analysis of the three,it can be found that phosphogypsum can achieve the purpose of effective dealkalization of red mud,and vinegar residue can achieve the purpose of increasing the content of nutrients in red mud.(2)It can be seen from the experiment of phosphogypsum-vinegar residue dealkalization modified red mud that the addition of phosphogypsum can effectively achieve stable dealkalization of red mud in a short time,and reduce the p H value of red mud from about11.08 to about 9.00,the addition of vinegar residue can further reduce the p H of red mud to around 8.00;the addition of phosphogypsum can promote the formation of large-size aggregates of red mud and increase pore size,and the addition of vinegar residue further promotes the formation of large-size aggregates of red mud,increases the content of large particle size aggregates,enhances the agglomerate stability,reduces the bulk density of red mud and increases the porosity of red mud,which is beneficial to the soilization of red mud;the addition of phosphogypsum provides a large amount of Ca for plant growth,which is beneficial to the subsequent red mud soilization.(3)Through the pot experiment,it can be seen that the germination rate of plants in the20%and 60%vinegar residue modified group is 85%～90%,which is close to that of horticultural soil,and the germination rate is good;when the addition amount of vinegar residue is 20%,the plant height is lower,which is 13.3 cm;when the vinegar residue addition is 40%and 60%,the plant height is about 15 cm,the fresh weight is between 0.6～0.7 g,and the dry weight is between 0.1～0.15 g,which is close to horticultural soiland grew well;the chlorophyll concentration of the 40%vinegar residue modified group and the 60%vinegar residue modified group is between 45～55 mg/L,which is close to the horticultural soil,and the plant growth condition is good;after the pot experiment,the soil p H value decreased and the soil catalase content increased,indicating that the physicochemical properties of red mud after pot planting were significantly improved,and the soilization effect of modified red mud was good.Through the environmental safety analysis of the modified red mud with the addition of 40%vinegar residue,it can be seen that the contents of heavy metals As,Pb and Cr are all lower than the screening value of agricultural land pollution risk,and the soil pollution risk of agricultural land is small;compared with the red mud,the red mud modified by phosphogypsum-vinegar residue has a lower impact on the environment。... |
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