Preparation Of Ferrous Sulfate Heptahydrate And Polysilicate Ferric Sulfate From Hematite Slag

FeSO₄?7H₂O is a commonly used chemical raw material and is widely used in various fields such as electronic appliances,automobile parts,machinery and equipment,housewares,pesticides,and medicine.Among them,in industry,it is a raw material for the preparation of various iron salts,iron pigments,polyferric sulfate,inks and other products.Polysilicon ferric sulfate?PFSS?as a new inorganic polymer flocculant is widely used in the purification process of alcoohol,chemical,electroplating,mineral processing,printing and dyeing,pharmaceutical,coking and other industrial sewage as well as drinking water and so on.As a kind of solid waste in the production process,hematite slag contains some valuable metal ions and also contains heavy metal ions.Arbitrarily burying or depositing on the one hand will pollute the environment,on the other hand,it will waste resources.Comprehensive utilization of the hematite slag can realize turning waste into treasure,increase the utilization rate of the enterprise's products,reduce the cost,and have the environmental,social,and economic benefits of the exploration goal.The subject first used hematite slag as raw material to prepare FeSO₄?7H₂O,and then used FeSO₄?7H₂O as raw material to prepare PFSS.Through the combination of single factor and response surface experiments,the process conditions of the two products were respectively explored to obtain the optimal conditions and the products prepared under the optimal conditions were characterized by ICP-AES,XRD,TG-DSC,SEM and FTIR.The specific work is as follows:?1?In the process of preparing high-purity ferrous sulfate heptahydrate using hematite slag as a raw material,a single factor and response surface experiment were both used and the influences of leaching temperature,sulfuric acid concentration,leaching time,liquid-solid ratio and stirring speed on the iron leaching rate in the acid leaching experiment were studied respectively;the effects of reduction reaction temperature,reaction time,iron powder excess coefficient on the reduction rate were investigated.The optimum conditions for obtaining the acid leaching experiment were:leaching temperature 100?,sulfuric acid concentration 50%,leaching time 2.5 h,liquid-solid ratio 4:1,stirring speed 300 r/min;the optimal conditions for the reduction experiments were:reaction temperature 80?,reaction time 2 h,iron powder excess coefficient 1.2.?2?When the ferrous sulfate solution was crystallized,ethanol was added to the solution at a ratio of V_ethanol:V_H2O=1:1 for recrystallization reaction.The final FeSO₄?7H₂O was characterized by ICP-AES,XRD,TG-DSC,and SEM and the results showed that the FeSO4?7H2O product meets the requirements of GB/T 664-2011chemical reagentAR ferrous sulfate heptahydrate.?3?Using FeSO4?7H2O as the raw material to prepare the PFSS by the blended oxidation method,the single factor and response surface experiments were combined to explore the optimal conditions for the preparation of PFS and PS respectively.In the PFS synthesis experiment,the results of the PFS total iron content,density,and salt base degree were measured by chemical analysis.The optimal conditions for the synthesis of PFS were:4.70 g of concentrated sulfuric acid,reaction temperature of30?,aging temperature of 20?,and aging time of 9 h.The basicity of PFS prepared under optimal conditions was 14.21%,and the stability was high,which meets GB/T 14591-2016 water treatment agent-fist grade requirements of polymeric ferric sulfate.?4?The factors affecting the stability of PS were explored through the combination of single factor experiments and response surface experiments.The optimal conditions were:SiO₂ content 3%,activation temperature 30?,and pH 3after activation.?5?The PFS and PS were blended and the turbidity was taken as the index through the single factor experiment,which got the optimal conditions:Fe/Si ratio1,the aging time 2 h,the activation time 30 min.The PFSS prepared under the optimal conditions was characterized by XRD,FTIR,SEM,and compared with the corresponding characterization of PFS.The results showed that the product PFSS is a new type of high molecular polymer.