Research On Recycling And Purifying Of Sapphire Diamond-wire Cutting Waste

In recent years,with the evolution of scientific technology,Sapphire wafer has been widely applied in the LED and the electronics industry.Sapphire ingot can’t directly be applied to LED field until being sliced into sapphire wafer.The thickness of wafer is approximately 0.2mm,being close to the diameter of diamond wire,which means about 40%～50%sapphire ingot materials are transformed into powder washed away by the cooling liquid.LED industry develops rapidly,which means more and more sapphire wafers are demanded.As a result,more and more sapphire diamond-sawing cutting waste will be produced,the domestic sapphire diamond-wire cutting waste was mostly disposed with accumulation or landfill,which reasonably made no use of the resources and causes great pollution to the environment.Hence,removing impurity from the cutting waste and recycling the α-Al2O3 to reproduce sapphire single crystal are urgently required,which will make remarkable economic and environmental benefits.The purpose of this investigation is to explore a way to recycle and purify the α-Al2O3 for reproducing sapphire single crystal.The diamond-sawing waste was used as raw material which is provided by Yunnan Yuxi Hengyu Technology Co.,Ltd in this paper,the results of the research are as follows:Firstly,the analysis of the cutting waste after washing,drying and sieving shown that the main component of the cutting waste is alpha alumina with nickel and diamond as main impurities,where the contents of impurity nickel and diamond were 0.70%and 0.164%,respectively.Then,the efficient conditions of conventional acid leaching and ultrasound acid leaching of nickel were determined.Under these conditions,the content of nickel reduced from 0.70%to 0.012%and 0.009%with 98.25%and 99.67%leaching ratio,respectively.As can be seen that ultrasound acid leaching is better than conventional acid leaching.Kinetic analysis of ultrasound acid leaching and conventional acid leaching shown that the process of Ni reacting with acid is controlled by chemical reaction.By determining the optimum conditions of extraction and baci-extraction,the recovered solution was evaporated and crystallized to obtain nickel sulfate crystals with a recovery rate of 95.32%.Secondly,the diamond-sawing cutting waste was put into furnace reacting with oxygen after leaching.Under the optimized burning conditions,the contents of diamond in cutting waste were reduced to 0.00062%from 0.164%,the removal rate of diamond was 99.62%.Kinetic analysis of burning process shown that the reaction,diamond burning in the oxygen,fits reaction-controlled shrinking core model.After being purified,the purity of α-Al2O3 in diamond-sawing cutting waste is 99.99%,which basically meet the demand for reproducing sapphire ingot.