Research On The Occurrence Form Of Impurities In The Sapphire Grinding Waste And The Process Of Impurities Removal

With the development of technology,Sapphire is widely used in LED illumination and consumer electronics industry field.Therefore,the demand of boron carbide as grinding material of sapphire wafer sustained growth.The resulting grinding waste is also increasing.After using period of time,the boron carbide grinding material cannot be used due to interfusion of a large quantity of impurity.Smelting boron carbide process needs is high temperature and high energy consumption.Therefore,leaving grinding waste is pollution environment and wasting resources.Hence,removal impurity from grinding waste and recycle of boron carbide is urgently required,which is remarkable economic,environmental and social benefits.In this paper,research contents and results are as follows:(1)The research on the properties of the grinding waste.The results show that the main component of grinding waste is boron carbide with alumina and iron as main impurities.The contents of alumina in the J240 grinding waste and W5 gringding waste are 5.505%and 11.088%,respectively.(2)The investigation on thermodynamic analysis and pre-experiment.The thermodynamic analysis testified that the leaching of alumina is feasible.While the sapphire is a-Al2O3 with stable structure,which is hard to be removed easily.The leaching ratio of alumina in J240 waste with conventional leaching and ultrasound-assisted leaching are only 23.56%and 33.1%,respectively.While the leaching ratio of alumina in W5 waste with conventional leaching and ultrasound-assisted leaching are only 19.56%and 31.45%,respectively.(3)The alumina can be removed efficiently with microwave-assisted alkali leaching method.The optimum conditions for the alumina removal of J240 grinding waste are 40%NaOH,220? leaching temperature,75 min leaching time and 5:1g/mL liquid-solid ratio.Under these conditions,the content of alumina in the J240 waste reduces from 5.505%to 0.27%with 95.02%leaching ratio.The optimum conditions for the alumina removal of W5 waste are 40%NaOH,250?leaching temperature,125 min leaching time and 5:1g/mL liquid-solid ratio.Under these conditions,the content of alumina in the W5 waste reduces from 11.088%to 1.25%with 88.66%leaching ratio.(4)The study on the alumina removal with microwave-assisted acid leaching method.The optimum conditions for the alumina removal of J240 waste are 30%H2SO4,190?leaching temperature,75 min leaching time and 5:1g/mL liquid-solid ratio.Under these conditions,the content of alumina in the J240 waste reduces from 5.505%to 0.25%with 95.33%leaching ratio.The optimum conditions for the alumina removal of W5 waste are 35%H2SO4,250?leaching temperature,110 min leaching time and 6:1g/mL liquid-solid ratio.Under these conditions,the content of alumina in the W5 grinding waste reduces from 11.088%to 0.73%with 93.38%leaching ratio.(5)Kinetic analysis of alumina removal with microwave-assisted leaching method.Through discussion of kinetics,it has been confirmed that the leaching process of alumina from J240 and W5 grinding material all fit diffusion-controlled shrinking core model.(6)The comparison between alkali leaching method and acid leaching method with the assistance of microwave.The acid leaching method can remove alumina and also but iron impurity at the same time.While alkali leaching method can only remove alumina but with iron residued.The result shows that the acid leaching is superior than that of alkali leaching.The purity of boron carbide already meets the enterprise standard of boron carbide grinding material after microwave-assisted acid leaching.(7)The brief introduction of the treatmen process of waste-water and waste-residue.The solid waste was firstly removaed by filter press to seprarte the waste-water and waste-residue.Then the pH of wastewater is adjusted to neutral,which is finally discharged into the municipal pipe network.