Study On The Activated Mechanism Of Silicon By Roasting Processing With Sodium Carbonate From Electrolytic Manganese Residue

Electrolytic manganese residue?EMR?is a kind of solid waste generated along with the production of electrolytic manganese from electrolytic manganese industry.With the increase in the demand for electrolytic manganese and the decrease in the quality of manganese ore,the total amount of manganese residue in China has exceeded 50 million tons in 2016,with an increase of 10 million each year after.Most companies directly store manganese residue in open air for a long time,which will not only waste land resources,but also seriously pollute the surrounding environment.Therefore,rational use of resources to reduce the disposal of manganese slag has important practical significance.Over 50%of arable land in China is lack of effective silicon,and the demand for effective silicon in soil is increasing daily.It is impossible to maintain the balance of effective silicon in the soil because of the natural weathering of soil silicon and the return of crops to the field.Manganese residue is an important source of silicon.Using it as a raw material to activate silicon can not only solve the problem of serious shortage of effective silicon,but also be an effective way to reduce the treatment of manganese residue.In this dissertation,the author systematically studied the activation conditions and the roasting process theory of roasting silicon from manganese residue sodium salt.The specific contents and conclusions are as follows:?1?Study on the basic properties of manganese residueThrough the analysis of the chemical composition and mineral composition of the manganese residue of Guangxi CITIC Damn Company,the elemental composition of EMR is Si,Ca,S,Fe,Al,Mn,etc.,and its corresponding oxidation state content is:SiO₂?24.14%?,CaO?14.96%?,SO₃?27.58%?,Fe₂O₃?8.57%?,Al₂O₃?2.46%?,MnO?1.24%?,and effective silicon content was only 0.13%.Si mainly occurs in quartz,rhodopsite,hectorite,orthoclase,feldspar,and muscovite,and quartz is mostly produced as a monolithic mineral.?2?Comparative study of silicon activation conditionsBy comparing the activation effects of three different activation methods:muffle furnace roasting activation,mechanical ball milling and roasting activation in microwave sintering furnace,results show that the mechanical force alone can only reduce the size of the material particles and increase their specific surface area.The improvement of the effective silicon content is not obvious.Only under the conditions of addition of roasting,the effective silicon content in the EMR can be significantly increased.Among the three activation methods,roasting activation in microwave sintering furnace is the best.Under the premise of mechanical milling,the optimal roasting process conditions optimized by the response surface method are:milling time is 80 min,calcination temperature is 854°C,roasting time is 43 min,microwave power is 2608 W,EMR/Na₂CO₃=1/0.55,active silicon up to 18.16%.?3?Study on the mechanism of roasting activationBy using thermodynamic calculation software to add sodium carbonate to the manganese residue,the chemical reactions that can occur with various substances were analyzed,and the reaction between silica and sodium carbonate and the ease of formation of silicate were determined.According to the roasting kinetics equation of sodium salt roasting EMR,the apparent activation energy controlled by chemical reaction is 87.77 kJ·mol^-1,and the apparent activation energy of diffusion control is45.33 kJ·mol^-1.The activation energy controlled by the chemical reaction is higher than the apparent activation energy of the diffusion control.Therefore,the chemical reaction control is the key factor affecting the content of f effective silicon during sodium salt roasting process.The results of XRD and FTIR analysis show that the direct high-temperature roasting of electrolytic manganese residue cannot activate the silicon.Only with roasting,SiO₂ in manganese residue can be converted to soluble silicon.The SEM micro-morphology analysis shows that the main forms of manganese slag include columnar,strip and irregular substances,and some irregular granular materials exist in the gap,some smaller particles stick together,forming a stacked structure.The manganese residue roasted by the sodium salt has an amorphous structure and a porous bentonite on the surface of the particles.This structure can increase the permeability of the soil,laying the foundation for the electrolytic manganese residue as an effective silicon resource in the soil.