Study On Preparation Of Layered Crystalline Sodium Disilicate Using Nickel Residue

The annual emissions of iron and silicon containing waste slag represented by water-quenched nickel slag is over 10 million tons.However,the utilization rate in China is low and a large amount of nickel slag is deposited on the slag yard,which not only causes waste of resources but also pollutes the environment.At present,the main researches at home and abroad focus at the recovery of iron from the fire method process.However,the process is difficult and it requires high temperature.Therefore,this study proposes a new method for the comprehensive utilization of nickel slag,namely preparing layered crystalline sodium disilicate using silicon components in nickel slag.This can make full use of nickel slag and minimize environmental pollution.At the same time,raw material costs could be reduced.The main conclusions of this study are as follows:（1）Nickel slag was treated with high-temperature oxidation,studying the influence of various factors and the oxidation mechanism.The parameters for the high temperature oxidation of nickel slag were:oxidation temperature 800℃,oxidation time5 h,the oxidation rate of nickel slag with fine grain size was higher than that of coarse grain nickel slag,and the highest oxidation rate was 97.1%.The characterization analysis showed that the main phase of the nickel slag was fayalite.Fayalite densely packed together,the surface was smooth and there were a few block crystals.The fayalite decomposed into hematite and quartz after oxidation.（2）The alkaline leaching was used to treat the oxided nickel slag.The influence of various factors and dissolution mechanism was studied.The optimal parameters of alkaline dissolution of SiO₂ in nickel slag were:oxidation temperature 800℃,solid-liquid ratio 1:5,alkali concentration 250 g/L,dissolution temperature 160℃,dissolution time 80 min,Al₂O₃ would reduce SiO₂ concentration.The best SiO₂dissolution rate is 85.4%of fine particles and 83.2%of coarse particles.The characterization analysis showed that the characteristic peak of quartz in the nickel slag disappeared after alkali dissolution,and the hematite did not change.Additionally,many pores formed and the nickel slag particles became smaller.（3）The layered crystalline sodium disilicate was prepared using the alkali solution containing SiO₂.It’s properties were determined,and its microscopic characteristics were explored through characterization analysis.The preparation process of the layered crystalline sodium disilicate were:adjusting the mold,drying and calcination,and the process parameters were:the modulus is 2.0,the additive KCl added n（K）:n（Si）=0.0015,the shaking reaction temperature and time were 35℃and 2 h.The drying temperature and time were 160℃and 2.5 h.The calcination temperature and time were 700℃and30 min.The characterization analysis showed that theδphase of the prepared layered crystalline sodium disilicate is main phase,and has a high degree of crystallinity.It is lamellar and flaked and is an irregular layered crystal.The calcium and magnesium exchange capacities were 366 mg/g and 404 mg/g,which were higher than the national standard.It’s performance is stable and compared to the products on the market.What’s more,It does not contain secondary pollution.In this study,making use of silicon components in nickel slag to produce layered crystalline sodium disilicate,which reduced the cost of raw materials and provided a way for the comprehensive utilization of nickel slag.The treatment process is simple and easily operate.The prepared layered crystals sodium disilicate has good calcium and magnesium exchange capacity and application prospect is very broad.