Study On Preparation Of Fine-grain Silica And Co-production Polysilicate Aluminum Ferric Sulfate From Oil Shale Pyrolysis Residue

Oil shale is a kind of high ash sedimentary rock with a high degree of mineralization.During the process of refining shale oil and burning for power generation,a large amount of residues are produced,mainly including·quartz,kaolin,and siderite.The inefficient use of pyrolysis residues causes them to be stacked around mining areas,occupying land and causing damage to the ecological environment.In this paper,the Fushun oil shale pyrolysis residues are used as raw materials to prepare high-performance silica and polysilicate aluminum ferric sulfate.The research on the resource and harmless utilization of pyrolysis residues has significant economic and social benefits for achieving clean and efficient utilization of oil shale residues.In this paper,the pyrolysis residues of oil shale in Fushun West Open-pit Coal Mine are selected as the raw material to analyze some experimental conditions,such as calcination and activation,purifying SiO2 by acid leaching reaction and leaching Al and Fe elements,which are based on the content of SiO2,Al2O3 and Fe2O3 in the pyrolysis residue.It was found that the acid leaching time was the most influential factor on the leaching rate,then the optimal reaction conditions were obtained:calcination temperature 800?,calcination time 180 min,and sulfuric acid concentration 40%,the acid leaching temperature 95?,the acid leaching time 120 min,and the liquid-solid ratio is 8:1(mL/g).The content of SiO2 in the filter residue detected by XRF was 90.30%.The XRD analysis showed that the filter residue was mainly composed of crystalline SiO2.Using acid leaching filter residue as raw material,the alkali dissolution effect of filter residue was studied through alkali dissolution reaction and silicic acid aging.The results showed that the optimal reaction conditions for SiO2 dissolution were:reaction time 60 min,alkali concentration 15%,liquid-solid ratio 12:1(mL/g),the reaction temperature 100?,and this moment the SiO2 dissolution rate is 55.61%.Through analyzing the process of preparing silica,the aging conditions for the highest yield of SiO2 were obtained:Na2SiO3 solution concentration 0.025 g/mL(SiO2 concentration),reaction temperature 50?,aging time 60 min,aging stage pH 8.5.In order to reduce the agglomeration of silica particles and particle size of precipitated silica,the silica particle size is adjusted during the aging reaction process by controlling the pH of the aging stage and the amount of dispersant(EDTA-2Na)to determine the best aging condition:pH 8.0,the amount of dispersant(EDTA-2Na)1.25%.Through laser particle size analysis,TG,SEM,XRD and BET analyze the prepared silica,it is found that the structure of the silica is amorphous,and the product has a small particle size and is evenly distributed in the range of 0.5?2.5 ?m,and the specific surface reaches 189.41 m2/g,the pore diameter is about 10 nm,the pore volume is 0.54 cm3/g,the texture is soft,and it is easy to grind.The filtrate analysis result through ICP is that the content of A1 and Fe are relatively high,both of which are metals that can promote the flocculation effect,and can be used to prepare polysilicate aluminum ferric sulfate.The preparation can ensure the materialized preparation of the entire oil shale pyrolysis residue to realize efficient and harmless hierarchical utilization of the whole process.The optimal reaction conditions of exploring silicic acid polymerization gel are polymerization pH 5.0,sodium silicate concentration 0.025 g/mL,reaction temperature 50?,and the polymerization time of silicic acid is 17 min.The filtrate is added to copolymerize Al3+ and Fe3+,bridging on polysilicic acid to form amorphous polysilicate aluminum ferric sulfate.Through studying the effect of n(Al+Fe):n(Si)on the flocculation effect of the flocculants,it is found that when n(Al+Fe):n(Si)is 2:1,the prepared flocculant has best flocculation effect.And the turbidity removal rates of turbid water with different turbidity are above 90%.FTIR and SEM analysis showed that the metal ions in the prepared polysilicate aluminum ferric sulfate are effectively polymerized,and the harmful substances in the turbid water could be effectively flocculated during the flocculation process.