Fundamental Study On The Hydrolysis Separation Of Coal Gangue Acid By Pure Material Simulation

Coal gangue is a kind of solid waste generated in coal mining and coal dressing.The stockpiling of coal gangue will bring serious environmental pollution and waste of resources.According to the chemical composition of coal gangue to develop environment-friendly technology and improve the resourceful comprehensive utilization of coal gangue have great significance.In order to solve the problem of fine particle size,poor filterability,difficulty in,washing high water content of cake in the research of coal gangue polymetallic extraction,aluminum hydroxide was synthesized by one-pot precipitation method using sodium carbonate(Na2CO3)and aluminum sulfate(Al2(SO4)3·18H2O)as precipitator and precipitate precursor agents respectively.The effects of pH,temperature,concentration and crystal seed on the filtration properties,phase and morphology of the product were studied.Simultaneously,the growth mechanism was investigated by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),thermo gravimetric analysis(TGA)and scanning electron microscopy(SEM).The study provides a theoretical basis for the hydrolysis mechanism of the separation of aluminum and iron from acid leaching solution of coal gangue.Meanwhile,the effect of crystal seed on the filtration performance of the simulated system and the real product of acid leaching of coal gangue was studied.The results showed that,(1)When pH was less than 3,Al3+ kept a stable state as[Al(OH2)6]3+.With the gradual increase of pH,[Al(OH)4(OH2)2]-was generated hydrolyzed from[Al(OH2)6]3+and subsequently dehydrated-condensed into[Al2(OH)8(OH2)2]2-under the effect of hydration.Then[Al2(OH)8(OH2)2]2-transformed into[Al2O(OH)6]2-with the increase of alkalinity.Finally,aluminum hydroxide was generated.Aggregated and amorphous aluminum hydroxide could be obtained.(2)When pH was 3,5 and 7 at 75℃;under the pH of 9 and 11,amorphous aluminum hydroxide transformed into crystalline state of boehmite[γ-AlOOH]and a little bayerite[α-Al(OH)3].Meanwhile,the greater the pH,the better the filtration.(3)The temperature was less than or equal to 96℃,aluminum hydroxide is unstable,and pore size distribution is not uniform.There is a redissolution re-precipitation process when the hydrothermal temperature at 120℃.Then,amorphous aluminum hydroxide hydrothermally crystallized and transformed into NaAl3(SO4)2(OH)6.Under the hydrothermal temperature of 180℃,the hydrothermal products of aluminum sulfate transformed into NaAl3(SO4)2(OH)6 and the preferred direction is(1 1 3).Furthermore,the hydrothermal products pore distribution is narrow and uniform.(4)Hollow urchin like boehmite[γ-AlOOH],solid spherical aluminum hydroxide,cubic gibbsite[Al(OH)3]as seeds can improve the filtration of Al3+,Fe2+,Ti4+ hydrolysis hydrolysis products,improve the phase and morphology of hydrolysate.(5)Cubic gibbsite[Al(OH)3]as seed added to acid leaching solution of coal gangue can improve the filtration performance of the hydrolysate,and the hydrolysis products have a massive structure and crystalline form when pH was 4.5 and temperature was less 75℃.