Preparation And Modification Of Ultrafine Silica By Acid Dissolution Of Olivine Mineral

The technology of traditional preparation method of ultrafine silica is complicated,and its raw material is expensive,which greatly restricts its application.The new preparation method of ultrafine silica with low cost and good quality has attracted much attention.Analyzed by laser particle analyzer,XRD,SEM and other analytical testing methods,the dissolution conditions of olivine in sulfuric acid under atmospheric pressure,dissolution reaction kinetics,influencing factors of preparation of ultrafine silica and the modification of ultrafine silica were studied.The investigation can provide theoretical and technical support for preparation of ultrafine silica by olivine acid dissolution directly.Experiments of olivine sulfuric acid dissolution show that increasing the leaching temperature,sulfuric acid concentration,the stirring speed and the liquid-to-solid ratio,extending leaching time,and reducing the size of olivine are conducive to the acid dissolution of olivine;The optimum experimental conditions of the dissolution of olivine in sulfuric acid under the atmospheric conditions are:leaching temperature 90?,sulfuric acid concentration 4mol/L,leaching time 180min,stirring speed 500r/min,olivine particle size-0.074mm,liquid-to-solid ratio 20mL/g.The leaching rate of Mg2+from olivine can reach 99.05%under the conditions.The results of olivine dissolution kinetics show that the leaching temperature has the most significant effect on the leaching rate of Mg2+from olivine.The calculated apparent activation energy of the reaction is 52.89kJ/mol by the equivalent leaching rate method,which indicates that the dissolution is controlled by surface chemical reaction,and the reaction order is 0.62.The factors affected the preparation of ultrafine silica were investigated and showed that the dispersion effect of PEG-6000 was obvious.Adding 15%non-ionic surfactant PEG-6000 can produce ultrafine silica with an average particle size of 10.08?.High sulfuric acid concentration and the presence of metal cations(Na+)can lead to the agglomeration of silica.Increasing liquid-to-solid ratio,ultrasonic dispersion,increasing aging time and the calcination temperature can reduce the agglomeration of silica,which are conducive to the preparation of ultrafine silica.The modification test of ultrafine silica shows that using silane coupling agent KH-550 as the modifier,the hydroxyl number on the surface of ultrafine silica can be reduced to 2.08b1020 units/g,the grafting rate is 8.35%,and the contact angle is 101.520 under the condition of modification time 5h,the modifier dosage 6mL/g,and the modification temperature 75?,which improvs the hydrophobicity of ultrafine silica.Using non-metallic mineral olivine as silicon source to produce ultrafine silica by acid dissolution directly,the technology is simple and the raw material is cheap and easy obtained which can greatly reduce the cost of preparing ultrafine silica and has a broad market prospect.It opens up a new way for the deep processing and comprehensive utilization of silicate minerals,and also provides reference for the high value-added comprehensive utilization of tailings comprised of silicate minerals mainly.Figure 63;Table 10;Reference 80...