Study On The Harmless Treatment Of Harmful Ions Of Phosphorus Tailings Filling Body By Additives And Its Mechanism

Tailings filling has the functions of controlling ground pressure,preventing collapse and improving recovery rate.However,the infiltration of harmful substances in the filling slurry and the dissolution of harmful substances in the later stage pollute groundwater.It is of great significance to prevent the backfill of phosphorus tailings from polluting groundwater resources to realize the safety,environmental protection and efficient mining of mines.In this paper,the physicochemical characteristics of the filling raw materials,such as phosphorus tailings,fly ash and cement,and the characteristics of the filling slurry are analyzed.Through the bleeding test,the changes of harmful substances in the bleeding water,the flow performance of the slurry and the compressive strength after adding the additive are investigated,and the types and dosage of the additive are determined.The leaching test device was designed and prepared to explore the influence of p H,temperature and pressure changes in the filling environment on the release of harmful substances from the backfill and analyze the mechanism of action of additives on harmful substances.?1?The main mineral composition of phosphate tailings is dolomite,fluorapatite and quartz,the main chemical components are Ca O,Mg O and P₂O₅;the main mineral composition of fly ash is quartz,gypsum and hematite,the main chemical components are Si O₂,Al₂O₃ and Fe₂O₃;The main minerals of cement are tricalcium silicate,dicalcium silicate and tricalcium aluminate,the main chemical components in cement are Ca O and Si O₂;dissolution of dolomite and fluorapatite in phosphate tailings releases total hardness,fluoride and total phosphorus And other harmful elements.?2?The measured total hardness,sulfate,fluoride,and total phosphorus concentrations in raw material slurry are 1728.80mg/L,2189.70mg/L,6.20mg/L,0.25mg/L.The total hardness,sulfate,and fluoride are Groundwater quality standard?,total phosphorus belongs to surface water quality standard?,The concentration of harmful substances is high,and there is a risk of polluting groundwater.?3?In order to reduce the pollution to groundwater after filling,a test study on the harmless disposal of additives was carried out.Based on the screening effect of the additives on harmful substances and considering the slurry characteristics and the compressive strength of the filling body,0.01%PSAF is recommended Mining with long conveying distance,simple geological conditions,low compressive strength requirements,stable ore body and surrounding rock.Adding 0.003%CMC+0.01%PSAF,the total hardness,sulfate,fluoride,and total phosphorus concentration in the secretion drops to 796.30mg/L,868.50mg/L,0.81mg/L,0.01mg/L,and they respectively decrease by 53.90%,60.30%,91.80%,96.00%,the fluoride concentration reaches the groundwater quality class I,the total phosphorus concentration reaches the surface water quality standard class I,it is recommended to use it in higher environmental water quality requirements,longer slurry transportation distance,ore body Relatively stable mine filling and mining.0.003%PSAF+0.2%SAP can be used for filling and mining in mines with high requirements on environmental water quality and filling compressive strength and short slurry transportation distance.?4?it was found that within the test range,the increase of acidity,temperature and pressure all promoted the dissolution of calcium-magnesium minerals,sulfate minerals and fluorine apatite in backfill,which increased the concentration of total hardness,sulfate,fluoride and total phosphorus in the leaching solution,and the pollution increased.After adding?0.003%PSAF+0.2%SAP?,the total hardness,sulfate,fluoride and total phosphorus in the backfill leach solution were relatively low,and the pollution was reduced.?5?The additive did not change the composition of the main substances after backfill hardening,but the microstructure changed and the porosity decreased.The additive reduced the exudation of harmful substances by means of flocculation adsorption and changing the microstructure of backfill.