Flotation Performances And Mechanisms Of Aluminum And Silicate Minerals Using Propyl Gallate As Collector

With the rapid development of aluminum industry,China’s demand for bauxite is increasing.However,the diasporic bauxite is the main type of bauxite in China with high aluminum,high silicon and low A/S,it is difficult to meet the requirement of producing alumina by bayer method.Therefore,how to realize desilication of bauxite is a hot topic.Flotation is a common method to improve teh quality of bauxite,in which collector plays an important role.In view of this,a new collector,propyl gallate(PG),compared with common collector sodium oleate(Na OL)was used in this work to study the flotation behaviors of diaspore and kaolinite,and interaction mechanisms of collectors with diaspore.The main research approaches are physical property characteristics of minerals,mineral flotation,adsorption experiment,surface property chanding analysis and AFM testings.The main contents of this work are as follows.Firstly,the mineral composition,surface wettability and surface electricity of diaspore and kaolinite were studied.The results show that the distribution of surface element compositions surface wetting ability and of diaspore and kaolinite is similar.In addition,the surface electricity of diaspore and kaolinite is positively charged under acidic conditions and negatively charged under alkaline conditions.The similar surface properities make it difficult to separate two minerals.Flotation experiment results illustrate that:the optimum flotation conditions are as follows:the stirring speed 1600 r/min,inflating volume 60 m L/min,solution p H 9,colletor dosage 60mg/L,and flotation time 6 min.Under the optimum conditions,the flotation recovery of diaspore is 87.28%.Under the same conditions,no matter what kind of collector is used,the recovery rates of diaspore and kaolinite were found to be above80%,while the recoveries of kaolinite were 23.35%and 43.58%using PG and Na OL as collectors,respectively,indicating that the collector PG with better selectivity for diaspore than Na OL.Secondly,adsorption experiments indicate that:the appropriate p H can increase the adsorption amount of PG on the diaspore.The optimum adsorption amount of PG on diaspore at p H 9 is 2.94 mg/m~2,while that of kaolinite at p H 3 is 1.45 mg/m~2.According to the adsorption isotherm results,the Freundlich model and the Langmuir model are better fitting the adsorption behavior of PG on diaspore and kaolinite respectively.The monolayer adsorption of PG on kaolinite was occurred,while multilayer adsorption for the condition of diaspore was happended.Based on the adsorption thermodynamics results,the adsorption process of PG onto the two minerals is spontaneous and endothermic.At the same time,△H of diaspora is greater than that of kaolinite,which indicates that the binding force between diaspore and PG is greater than that between kaolinite and PG.What’s more,the effects of collector PG on the surface properties of two minerals showes that the contact angle of diaspore after interaction with Na OL and PG was above 89°.The contact angle of kaolinite after interaction with Na OL and PG was increasing 3°and decreasing 6.25°respectively.The zeta potential of two mineral after interaction with PG extends to a more negative direction than that of Na OL.The above results confirme that PG have better selectivity for diaspore than Na OL.The zeta potential testing,FTIR and XPS characterization indicate that PG was chemically adsorbed on the diaspore surface.Finally,the interaction behavior between the particles of monohydrite and kaolinite in aqueous medium,Na OL solution and PG solution was investigated by EDLVO calculation and AFM test.In addition,the interaction between Na OL or PG and kaolinite/diaspore was investigated by AFM test.The results show that the total potential energy of minerals in the aqueous medium inder the acid condition was dominated by gravitation and under the alkaline condition was dominated by repulsion.The total potential energy of minerals after interation with collectors,the repulsion was enhanced,which is beneficial to the dispersion of mineral particles.AFM tests verified that PG had a weak interation with kaolinite and a strong interation with diaspore.