Preparation Of Iron Tailings Glass-ceramics By Sol-gel Method

In order to protect the environment,achieve the goal of sustainable development,improve the comprehensive recovery and utilization of industrial solid waste has been widely discussed and studied by the society,and the amount of tailings generated by smelting steel has been very large.Taking iron tailings as raw materials for the preparation of glass-ceramics is a common waste recycling method.In the past,glass-ceramics were usually prepared by sintering and melting method with iron tailings added as raw materials.However,both methods have high temperature and high energy consumption.Sol-gel method is rarely used,mainly because this method requires high purity of raw materials for basic glass,and there are many kinds of impurities in iron tailings,which are inconsistent with the requirements of sol-gel method.Therefore,the useful elements in iron ore tailings were extracted in this experiment,and the tailings were purified so that they could be used in the sol-gel method.Si element in tailings was prepared by thermal-alkali reaction and iron element was prepared by acid reaction.Si element in iron tailings was used as the silicon source of sol,FeCl3 was used as the nucleating agent,supplemented by other raw materials for the preparation of multi-sol and gel,and then after heat treatment,the glass-ceramics of CaO-SiO2-MgO-Al2O3 system were obtained.The microcrystalline glass is compact in structure,but the gel cracks and shrinks during drying and aging.In order to prevent the formation of this adverse factor,commonly used dry crack control agent.In this experiment,the basic glass was ground into powder to deal with this phenomenon.In this experiment,as one of the raw materials,iron tailings were used to prepare CaO-SiO2-MgO-Al2O3 microcrystalline glass with diopside as the main crystalline phase by sol-gel method.In order to reduce the preparation cycle,save economy and energy,this paper studied the extraction of iron tailings heavy elements,the preparation of gels and sols,the preheating treatment of dry gels,the heat treatment system and technology,and the use of the nucleating agent FeCl3.In the process of extracting iron tailings,Fe is mainly extracted to react with acid.By comparing the advantages and disadvantages of various acids,hydrochloric acid was finally selected as the reaction reagent.The main reason is that hydrochloric acid can react with iron at room temperature without introducing new impurities.In the process of extracting Si elements,it mainly reacts with strong base.In the experiment,through the following conditions can make Si dissolution rate is relatively high,will react with HCl after iron tailings powder mixed with caustic soda fully,at 500? in the muffle furnace heating around 50 min,take out into the water(water to the amount of NaOH concentration is 5%),under the 70? heating and stirring the mixture for 30 min,silicon dissolution rate was 40%after the filtration of sodium silicate solution.In order to shorten the cycle of sol-gel process,uniform and good gel can be prepared in a relatively short time,the factors of gel time(H2O amount,C2H5OH amount,pH and temperature)are tested.The preparation process of the gel was determined as follows:normal temperature reaction was used.The amount of water added was based on the mass percentage of SiO2 in Na2SiO3 solution of 5%,with pH=8 and Na2SiO3:EtOH=1:5 to prepare the gel.Found in heat treatment experiment,the dry gel preheat treatment 1 h under 120?,gel in the organic solvent and water of crystallization can be volatile,is advantageous to the material density increases.In the optimization test of heat treatment system,the crystallization heat preservation time and nucleation heat preservation time are both significant with the density of glass-ceramics as the reference,but the crystallization time is more significant.The heat treatment scheme was determined as follows:nucleation heat preservation for 1h and crystallization heat preservation for 2h.Too long heat treatment will result in uneven crystallization of materials and too short crystallization will result in incomplete crystallization.The average size of crystal particle size calculated by XRD curve also verified this idea.FeCl3 was obviously helpful for material crystallization when it was added as nucleating agent,mainly by reducing the activation energy required for crystallization.By extracting the corresponding elements of iron tailings,the gel of basic glass can be prepared.After heat treatment,the microcrystalline glass that can be used in buildings can be prepared.The research content of this topic is completed.