Study On The Preparation Of Sodium Silicate And White Carbon Black From Serpentine Acid Leaching Silicon Slag

The effective utilization rate of serpentine wet acid leaching silicon residue is low,which not only occupies land,pollutes the soil environment,but also causes waste of mineral resources.The serpentine acid-leaching silicon slag has a high content of amorphous silica and only a small amount of metal impurities,which is an ideal raw material for the production of sodium silicate and white carbon black.In this paper,sodium silicate was prepared by leaching serpentine acid leaching silicon residue with Na OH hot alkali,and then the white carbon black product was prepared by the co-current dropwise addition method.Finally,the Ag-loaded white carbon black composite antibacterial material was prepared by impregnation-calcination method with white carbon black as the carrier.The problem of utilization of silicon resources in serpentine is solved,and a new way is provided for the comprehensive development of serpentine wet acid leaching residue.The main research work and achievements are as follows:Using the silica slag obtained by countercurrent leaching of serpentine with sulfuric acid as the raw material,the main influencing factors for the preparation of sodium silicate by alkaline solution of silica slag were determined by single factor experiment:Na OH mass fraction,liquid-solid ratio and reaction temperature.Based on this,according to the Box-Behnken experimental design principle,the response surface method was used to optimize the optimal reaction conditions for preparing sodium silicate,and the interaction between the main factors was studied,and the kinetics of the alkali-dissolution reaction of silicon slag was discussed.The results show that the optimal process parameters for the alkali dissolution of silicon slag are as follows:the mass fraction of Na OH is 10%,the reaction temperature is 70℃,and the liquid-solid ratio is 2.5:1.The influence degree of each factor on Si O₂ dissolution rate and sodium silicate modulus weighted value is Na OH mass fraction>liquid-solid ratio>reaction temperature,and the most significant interaction is Na OH mass fraction and liquid-solid ratio.The Si O₂dissolution rate of the sodium silicate prepared under the optimal reaction conditions was 83.1%,the modulus was 3.27,and the relative error between the actual weighted value and the model predicted value was only 0.24%.The results of kinetic studies show that the alkali dissolution process of silicon slag conforms to the Avrami kinetic equation.According to the Arrhenius formula,the apparent activation energy of the process is 8.62k J/mol.The overall reaction rate of the dissolution process is mainly controlled by diffusion.Using sodium silicate as raw material,the process conditions for preparing white carbon black were studied by the co-current dropwise addition method.The effects of a series of factors such as sodium silicate modulus,Si O₂ mass fraction,reaction temperature,end point p H,H₂SO₄concentration,additive NS concentration,co-current feeding time,stirring speed,aging time on the average particle size and DBP oil absorption value of white carbon black products were discussed respectively,and the optimal reaction conditions were optimized by orthogonal experiment method.The results show that the optimal process parameters for preparing white carbon black are:sodium silicate modulus 2.0,Si O₂ mass fraction 11%,p H=7,reaction temperature 80℃,H₂SO₄ concentration1.5mol/L,additive NS concentration 5%,co-current feeding time 30 min,stirring speed 300r/min,aging time 1.5h,under these conditions,the average particle size of the prepared white carbon black product was6.96μm,and the DBP oil absorption value was 2.85 m L/g.The structure and properties of the prepared white carbon black samples were characterized by XRD,SEM,FT-IR,TG-DTA and other analytical methods.The results show that white carbon black has an amorphous silica structure and is composed of aggregates of primary particles with a size of about 80～100 nm.The specific surface area is 277.2 m²/g.There are free water and crystal water on the surface of the sample,and the thermal decomposition weight loss rate is about 9.16%,the content of Si O₂ is 98.0%,Fe,Mn,Cu element impurity content is less than 30mg/kg,all the main performance indicators meet the product requirements of the HG/T3061-2020 national standard.Using white carbon black and AgNO₃ as raw materials,Ag-loaded white carbon black antibacterial materials were prepared by impregnation-calcination method,and the preparation mechanism was preliminarily analyzed.The effects of silver ion concentration,solid content,reaction time and stirring speed on the silver loading of white carbon black and the effect of calcination temperature and time on the dissolution of silver ions were discussed by single factor experiment,and the optimal process parameters were determined as follows:Ag⁺concentration 0.2mol/L,solid content 10%,reaction time 2h,stirring speed 400r/min,calcination temperature 500℃,calcination time 1.5h.The white carbon black prepared under these conditions has a silver loading of 3.6%and a silver ion dissolution rate of 0.05mg/g.The phase structure,chemical bond composition,morphology,valence and particle size distribution of Ag-loaded white carbon black were characterized by XRD,SEM,FT-IR,XPS and laser particle size analyzer,and the antibacterial properties of the samples were tested by taking Escherichia coli as an example.The results show that the Ag-loaded white carbon black still has an amorphous structure,the Si-O bond infrared absorption peak is slightly shifted,and the average particle size is 9.9μm.Among them,the silver exists in the form of nano-Ag and is uniformly loaded on the white carbon black,the antibacterial rate of white carbon black with Ag loading of 3.6%exceeds 99.3%.