Research Of Utilizing Alunite Comprehensively From Zijin Copper Tailings

Mineral resources are of non-renewable resources and relate to human existence and development.Tailings,as a kind of products after beneficiation technology,increase a lot along with the rapid development of industry and the increasing demand for mineral resources.In addition,tailings would occupy a lot of land and environmental pollution.In the other hand,tailings contain a lot of valuable resources and the potential of comprehensive recovery is enormous.Zijingshan Copper Mine is one of the large low grade copper mines in our country.The ore quantity of Copper mines with grade over 0.4%processed by flotation process is about 125 million tons and the tailings mineral rate is 90%.So the quantity of Zijingshan Copper Mine tailings will reach 100 million tons,and alunite of the tailings is about 13%,which has the very high value of utilization.Alunite,as a kind of alkali type aluminum potassium sulfate minerals,is a multielement mineral resources with comprehensive utilization value.The traditional techniques of extracting potassium and aluminum from alunite is "roasting and leaching" technical route.It's not only has complex technics flow,high cost and serious environmental pollution but also just has a single,low value-added products.Therefore,the traditional techniques always have the problem of high cost and wide industrialization.In conclusion,the alunite which floated from the tailings of Zijin copper ore was processed by non-roasting pressure acid-leaching firstly in our paper.The directly pressure acid leaching method has the following characteristics:firstly,the alunite is processed by directly pressure acid leaching without high-temperature calcined.It makes roasting,flue gas dust collecting,gas sulphuric acid and solvent leaching process achieved in the autoclave directly with simple process,low investment and low energy consumption.Secondly,the excessive added sulfuric during the acid leaching process can recover by recycling the mother liquor after crystallization.The actual consumption of sulfuric in the acid leaching process can be close to the theory of consumption,which has low raw material consumption;Finally,the potassium alum after crystallization is further processed to produce potassium sulphate,aluminium hydroxide and by-product gypsum.Moreover,The main ingredients of leaching slag is silica,which can be used in building materials industry.In the whole process of extraction,the elements of alunite,like potassium,aluminium,sulfur and silicon can be utilized comprehensively.First of all,The analysis approaches were used for the mineralogy analysis of the alunite,which floated from the tailings of Zijin copper ore.Then,the directly pressure leaching process of alunite in a sulfuric acid medium was studied by single-factor experiments.And the optimum leaching conditions were determined to be:leaching temperature of 220?,acid to ore ratio(g/g)of 3:1,initial acid concentration of 25%,leaching time of 120 min and stirring rate of 600 rpm.Under the optimized leaching condition,the leaching rate of Al was 98.54%,and the leaching rates of K was 95.73%.Moreover,the process of separation K and A1 in leaching solution by alum crystallization were studied.The results indicated that the optimum operating temperature of crystallization process was 5?.The recovery of K and Al would reach 74.36%?62.56%respectively when the K+/A13+ molar ratio of the leaching solution was 0.50,and the recovery of Al could increase with the addition of NH4+.After alum crystallization and filtration.The alum solid was treated with lime and water,the study on size mixing experiment indicated that the optimal conditions which are pH 6-7,the ratio of liquid to solid 5:1,mixing time 20 min,mixing temperature 70?.After separating,the gypsum residue which obtained aluminum could manufacture aluminum hydroxide by Bayer process,and the solution of potassium sulphate can produce potassium sulfate through further condensing crystallizing.Through the experimental results and analysis,The directly pressure acid leaching method not only have simpler technological route,low cost and higher efficiency of utilization,but also have less investment in equipment and pollution.It makes it possible to achieve the massive industrialization development and utilization of alunite,and provides a new way to comprehensive utilization of similar tailing.