| As one of the main mineral resources,phosphate rock resources are an important material basis for daily life and a basic guarantee for social development.However,with the large amount of phosphate rock being mined,phosphate resources are increasingly scarce and the situation is not optimistic.At present,due to the backwardness of economic technology,an efficient and feasible method of comprehensive utilization of phosphorus tailings has not been found.The massive accumulation of phosphorus tailings not only occupies cultivated land,wastes resources,but also brings serious harm to the ecological environment.As a"secondary mineral resource",phosphorus tailings contain a large amount of elements that can be recycled and reused,such as magnesium,calcium,phosphorus,and so on.Finding effective ways to recycle these elements can not only solve the environmental pollution problems caused by tailings stacking,but also bring huge economic and social benefits.In this paper,the tailings produced by a process flotation phosphate rock from Hubei Ezhong Ecological Engineering Co.,Ltd.is selected as the research object,and the tailings are treated by cyclic acid leaching.First,the tailings are mixed by using the"quadruple method",and then the tailings are subjected to acid leaching pretreatment using industrial hydrochloric acid to obtain slag and acid leaching liquid.The slag is washed by water,and the calcium chlorophosphate is obtained by mixing the water washing solution with the acid leaching solution.Calcium sulfate dihydrate whiskers with good morphology were obtained by acidizing the acid leaching solution with dilute sulfuric acid and controlling the reaction conditions.A portion of the acidified filtrate is involved in the mixing of the next cycle of sulfuric acid,and another portion of the acidified filtrate is concentrated to obtain the product magnesium chloride hexahydrate.The concentrated filtrate and condensate are returned to the next cycle of acid hydrolysis tailings.The elements such as calcium,magnesium and phosphorus in the phosphorous tailings are effectively utilized in the recycling process.The research conclusions are as follows:1)By means of XRF,XRD,SEM and TG,the preliminary mineralogical study of the experimental phosphorus tailings was carried out.The results show that the phosphorus tailings have a Mg O content of 19.75%,a Ca O content of 57.81%,and a P2O5 content of7.44%.It belongs to low-grade high-magnesium phosphate tailings;the phosphorus tailings are mainly composed of dolomite,quartz and fluoroapatite.The tailings lose crystalline water at 180°C,and it began to decompose magnesium carbonate at 450°C,began to decompose calcium carbonate at 700°C,and constant weight at 820°C,the mass loss rate of the whole process is 46%.2)In order to make full use of the effective elements such as calcium,magnesium and phosphorus in the tailings,from the perspective of benefit-maximizing industrial actual production,using the control variable method to explore the best conditions for the acid hydrolysis of the tailings with industrial hydrochloric acid are as follows:the chemical hydrochloric acid is supplied with 2.02mol H+per 100g of tailings,the industrial hydrochloric acid is added dropwise to the slurry,the reaction temperature is 60?,the stirring speed is 120?150r/min,and the reaction time is 30min.3)Acid leaching liquid is obtained by acid hydrolysis of phosphorus tailings with industrial hydrochloric acid,using the control variable method to explore the optimal conditions for preparing calcium sulfate whiskers are as follows:using a dropping method of dropping an acid leaching into dilute sulfuric acid,the reaction temperature is 75°C,the stirring speed is 150r/min,the concentration of hydrogen ion is 3mol/L,the concentration of magnesium ion is 3.3mol/L,the reaction time is 90min.Under these conditions,the ratio of length to diameter of calcium sulfate whiskers is up to 60.4)By comparing the results of three different process flow diagrams,it was found that the acidified filtrate was used to dilute the sulfuric acid,and the filtrate was concentrated and returned to the next cycle of acid hydrolysis tailings.The maximum aspect ratio of whiskers is about 55.When the system reaches equilibrium,the decomposition rate of phosphorus tailings is stable at about 99%,the quality of silicon slag is about 8g,the mass of calcium sulfate whisker is about 70g,and the mass of solid one is about 2g,and the mass of solid two is fluctuating greatly.However,the condensate is not effectively utilized in the process,and the process still needs to be improved.5)From the point of view of ensuring product quality and saving energy consumption,the optimal technological process is designed.After the system is stabilized,the concentration of hydrogen ion species in the acidified filtrate is 2.65mol/L,and the concentration of hydrogen ion in the condensate is 3.45mol/L.The acid leaching rate of effective elements such as calcium,magnesium and phosphorus in phosphorus tailings is more than 99%,and the quality of silicon slag is about 8.5g;calcium sulfate whisker length to diameter ratio is 60,and the color is white,less impurities,the quality is about 70g;the export of solid one is mainly calcium chlorophosphate,the mass is about 2.5g.The export of solid two are mainly magnesium chloride hexahydrate,and the quality fluctuates greatly.The innovations of this paper are as follows:1)Comparing with sulfuric acid and phosphoric acid,decomposition of tailings with hydrochloric acid will not produce calcium sulfate precipitation,resulting in loss of calcium in tailings and easy separation of products.2)Calcium sulfate dihydrate whiskers with good morphology were prepared by atmospheric acidification method,which saved energy consumption compared with high temperature and high pressure hydrothermal method,and integrated into the whole process of phosphate tailings treatment.3)Design a reasonable process flow.The high-magnesium phosphorus tailings are treated by the cyclic acid leaching method,so that the elements such as calcium,magnesium and phosphorus are effectively recycled,and the export products are stable,and the whole process has no"three wastes"emission.The process has high efficiency in treating tailings and saves energy,which provides a data reference for enterprises to treat high-magnesium phosphorus tailings. |
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