Research On Recovery Of Boron Carbide From Sapphire Grinding Waste

In the case of increasingly serious global shortage of resources,LED is widely used in the lighting market because of its low energy consumption and long life characteristics.Currently sapphire is used as raw material in the most of the world's LED companies and boron carbide is the main abrasive to grind sapphire.With the continuous development of LED and sapphire industry,the demand of boron carbide is increasing,at the same time,the amount of grinding waste is also increasing,which contains a lot of boron carbide.If the waste cannot get effective treatment,it would be lost.From the aspects of preparation,the traditional preparation method of boron carbide is complex and high energy consumption.From the aspects of application,boron carbide is widely used in ceramics,abrasive,nuclear industrial materials,military protective materials,coating and other fields.If the boron carbide can be recycled from the waste,it can not only realize the secondary utilization of resources,reduce pollution,but also reduce the production cost,which has high economic benefits.The purpose of this paper is to explore a recycling processing route of boron carbide from sapphire grinding waste,in order to realize the recycling of boron carbide.Using boron carbide grinding waste provided by the Yunnan lanjing technology limited company as the research object,the main research contents and results are as follows:(1)Study of the properties of boron carbide grinding waste.Analysis test results of pretreated waste,type W5 and J240,show that type W5 contents iron impurity 0.97%and aluminum oxide 8.45%;3.78%and 8.20%respectively in type J240.(2)Study of the removal of iron oxide in the grinding waste.The optimized conditions of iron oxide removal were determined by the single factor experiments.Under the conditions of sulfuric acid volume fraction 20%,the temperature 50?,reaction time 40min,the liquid-solid ratio 6:1,stirring speed 400r/min,the iron oxide removal effect of W5 waste is good,and its content can be reduced to 0.156%;Under the conditions of sulfuric acid volume fraction 15%,temperature 50?,reaction time 20min,liquid-solid ratio 4:1,stirring speed 400r/min,the iron oxide content can be reduced to 0.095%in the waste of J240.(3)Study of dynamics analysis of removal of iron oxide in the grinding waste.The dynamics analysis shows that the processes of W5 and J240 scrap iron oxide reacting in sulfuric acid conform to shrinking core model.The former is mainly controlled by the solid product layer diffusion and its the apparent activation energy is 25.94 kJ/mol;the latter is controlled by the main chemical reaction,and its apparent activation energy is 35.09kJ/mol.(4)Study of the alumina removal in the grinding waste.Through investigating the factors such as temperature,concentration,liquid-solid ratio and time,the optimized conditions of the influence of ultrasonic acid leaching and microwave acid leaching have been obtained respectively.(5)The comparison of acid leaching results.Through comparing the results of conventional acid leaching,ultrasonic acid leaching and microwave acid leaching,the optimized condition of purification process is determined.The optimized condition of W5 waste is using microwave acid leaching under the conditions of volume fraction of sulfuric acid 30%,liquid-solid ratio 6:1,temperature 150?,time 50min.Under this condition,the alumina content and the iron oxide content can be reduced to 1.948%and 0.098%respectively in type of W5.The optimized condition of J240 waste is using microwave acid leaching under the conditions of volume fraction of sulfuric acid 30%,liquid-solid ratio 6:1,temperature 150?,time 70min.Under this condition,the alumina content and the iron oxide content can be reduced to 1.981%and 0.038%respectively in type of J240.The effect of acid leaching can be certified intuitively by XRD,SEM/EDS detections.