Study On The Separation And Enrichment Of Lithium And The Preparation Of Lithium Phosphate From Aluminous Rock In Guizhou

In this paper,taking the lithium-bearing aluminous rock in Guizhou as the research object,study on the properties of aluminous rock,the leaching methods of lithium,the purifying of leaching liquid and the preparation of lithium phosphate was carried out.As a result,the better conditions of separating and enriching lithium and the technological process of preparing lithium phosphate were determined to obtain a relatively pure lithium phosphate product.By chemical analysis,XRD analysis,microscopic analysis,SEM-EDX analysis,the properties of aluminous rock were studied.The results shows that Si O₂ and Al₂O₃ are the main chemical composition of raw ore,its total content reaches as high as 80.60%,followed by Ti O₂and Fe₂O₃,but Ca O and Mg O content are relatively low.Li₂O grade is 0.199%,which has a comprehensive utilization value.In addition,the raw ore is mainly composed of diaspore and kaolinite,with a small amount of anatase,hematite,chlorite and carbonate minerals,also has a simple mineral composition and fine dissemination size.By using the mixed acid of sulphoric acid and phosphoric acid,the leaching verification test was conducted.The results show that it can be applied to the leaching of lithium in the aluminum rock,the lithium leaching rate is high,and under the conditions of temperature 100℃,leaching time 3h,solid-liquid ratio 1:4,stirring intensity 300r·min^-1,the lithium leaching rate is 96.67%,the aluminum leaching rate is 88.35%.Next,HF was used to the leaching trying tests and the leaching condition tests.The results show that HF has a better leaching effect,and kaolinite which is the most important lithium-bearing mineral is selectively dissolved by HF,the most of lithium adsorbed in kaolinite is released,so the lithium leaching rate is high,while the aluminum leaching rate is low.Under the better conditions of room temperature 25℃,solid-liquid ratio 1:8,HF concentration 17%,reaction time 15min,stirring intensity 300r·min^-1,the lithium leaching rate is83.80%,the aluminum leaching rate is 36.01%.In addition,a comparative analysis of the two methods was conducted.It reveals that the lithium leaching rate of the two methods are higher,but because the hydrofluoric acid is toxic,it limits its application greatly,while the mixed acid leaching of sulphoric acid and phosphoric acid is easy to operate and widely applicable,so it is adopted.By using the methods of chemical precipitation and solvent extraction,the purifying tests of leaching liquor were conducted.Finally the chemical precipitation was selected to remove impurity.The results show that the loss of lithium is bigger,but the aluminium deposition rate is high.Under the better conditions of the leaching liquor neither dilution or enrichment,temperature45℃,stirring speed 300 r·min^-1,hydrogen peroxide concentration 30%,hydrogen peroxide dosage5%,ammonia concentration 6 mol·L^-1,p H5.5,and filling water with a same volume of leaching liquid（45℃）,the lithium loss rate is 28.22%,the aluminium deposition rate is 99.99%.Moreover,it is reliable and easy to operate with the capability of recovering the by-products such as aluminum hydroxide,ammonium sulfate and ammonium dihydrogen phosphate and so on comprehensively.By using sodium carbonate,the preparation test of lithium phosphate and the preparation trying test of lithium carbonate were conducted.The results show that lithium phosphate can be directly obtained from the mother liquor containing lithium by using sodium carbonate,and under the conditions of temperature 90℃,solid feeding way,p H8,reaction time 30min,the lithium phosphate is a relatively pure product,and doesn’t contain water of crystallization.Before the preparation of lithium carbonate by using sodium carbonate,the mother liquor containing lithium need to remove phosphorus,the precipitation method of magnesium ammonium phosphate have a high efficiency to remove phosphorus,the phosphorus precipitation rate is 93.32%,while the lithium loss rate is only 7.14%,with less loss of lithium,but because the content of lithium in the mother liquid is low,thus after removing phosphorus,a relatively pure lithium carbonate product isn’t obtained from the filtrate by using sodium carbonate.