Experimental Study On Separation Of Silicon And Calcium From Coal Gangue Acid Leaching Residue

Coal gangue is the solid waste which is produced in the process of coal mining and washing,and the accumulation of a large amount of coal gangue not only takes up a lot of land,but also pollutes the environment,and even threatens the life and property safety of the residents in the mining area.Therefore,the study of the comprehensive utilization of coal gangue has both environmental and economic benefits,which has important practical and long-term significance.Comprehensive utilization of coal gangue is a more feasible method to extract aluminum,iron and titanium with acid leaching method,coal gangue in most of aluminum,iron and titanium will generate the corresponding salt into the solution,silicon oxide and most other acid insoluble in acid leaching residue is present in the form of solid phase separation.The sulfate can be used to produce aluminum,iron and titanium products.The main component of solid acid residue is silicon dioxide,and has good reactivity,can be used to produce water glass or white carbon black and other chemical products.In the water glass carbon thermal method during the preparation of calcium sulfate acid in the slag is reduced into calcium oxide and sulfide,further into calcium metasilicate and sodium metasilicate,eventually forming a eutectic mixture,will cause the loss of sodium and silicon,so how to remove the acid leaching residue of coal gangue calcium,as acid residue dry preparation of water glass is the key problem of economic feasible.In this paper,the acid leaching residue of coal gangue in a pilot plant in Guizhou,Panxian was studied,and the separation of calcium and silicon in acid leaching residue of coal gangue was studied by increasing the solubility of CaSO4 and flotation:(1)Acid leaching residue analysis shows that silicon is mainly in the form of silica,the content is about 55.6%,and the calcium is mainly calcium sulfate,the content of CaO is about 5.75%,the particle size is mainly concentrated in the range from 5 to 15 m.(2)By single factor and orthogonal experiment to examine the dissolution time,hydrochloric acid,sulfuric acid concentration,the influence factors of different inorganic salts NaCl,MgCl2 concentration and solution temperature on acid leaching of CaS04 dissolved in the slag,the separation of coal gangue acid leaching slag calcium dissolution method,optimum conditions were:the concentration of HC1 lOg/100mL the concentration of NaCl,15g/100mL,MgCl2,15g/100mL concentration of dissolved temperature 40 C,calcium sulfate solubility is 1.33g/100mL,the condition is not enough to meet the production process.(3)Investigated by single factor test and orthogonal test collector,foaming agent,modifier and other factors on the direct reverse flotation,the optimum conditions were:the collector of twelve sodium dodecyl sulfate concentration of 400mg/L foaming agent,methyl isobutyl carbinol concentration of 100mg/L,concentration of 0.4mol/L,inhibitor of water glass slurry pH value 4,SiO2 grade 98.6%,the recovery rate of SiO296.71%,it’s suitable water glass production.(4)For the experimental study of Zeta mineral surface potential the isoelectric point of SiO2 was 2.3,and the isoelectric point of calcium sulfate was about 5.7;the collector after adding silica and calcium sulfate zeta potential decreased;the addition of Mg2+ makes CaSO4 a positively charged electric capacity,the value of 10～12 becomes positive in pH;calcium sulfate increase of dynamic potential than in deionized water with after joining Al3+,CaSO4 potential with the increase of the pH value decreased first and then increased finally gradually decreased.