Quantum Chemical Calculation And Experimental Study On Flotation Separation Of Bastnaesite And Fluorite

Rare earth is an important strategic mineral resource in China,and bastnaesite is an important rare earth fluorocarbonate mineral.Flotation is a common beneficiation method for industrial separation of bastnaesite from gangue minerals.The surface properties and floatability of bastnaesite and calcium-containing minerals such as fluorite are similar,which causes their separation difficult.Study on the flotation reagents and its mechanism on bastnaesite and fluorite has important guiding significance for improving the separation efficiency of rare earth ore.In this paper,the structural models of the flotation reagents octylhydroxime（OHA）,oleic acid（OA）,ethylenediaminetetraacetic acid（EDTA）,and their corresponding Ca/Ce ion complexes were established using Gaussian software.The electronic structure parameters such as geometry optimization,charge distribution,front-line molecular orbital composition,were calculated based on Density Functional Theory（DFT）,with B3LYP functional and SDD pseudopotential basis,and the gibbs free energy for complexing dissolving transformation of Ca/Ce-OHA by EDTA were calculated.Finally,the Quantum Chemical Calculation results were verified by tests of Ca/Ce-OHA precipitation and their dissolving by EDTA,infrared spectroscopy and flotation.Quantum Chemical Calculation and Ca/Ce-OHA dissolving transformation test results showed that compared with OA anion,OHA anion had stronger electron donor capacity and reactivity,the order of binding energies between OA/OHA and Ca²⁺/Ce³⁺ions is OHA-Ce>OA-Ce>OA-Ca>OHA-Ca,it can be determined that OHA was easier to form a stable five-element cyclochelation structure with metal ions.The reaction products of OHA with Ce³⁺and Ca²⁺ions existed mainly in the form of complexes Ce（OHA）（OH）₂ and Ca（OHA）（OH）respectively,and the stability of Ce（OHA）（OH）₂ complex was greater than that of Ca（OHA）（OH）;Compared with Ce³⁺,Ca²⁺had a better coordination ability with EDTA,the structure of complexing product Ca（EDTA）^2-was more stable,and EDTA could react with Ca（OHA）（OH）preferentially to form soluble Ca（EDTA）^2-.Flotation test reulsts showed that OHA had a high collecting capacity and selectivity for bastnaesite flotation,while EDTA had a significant selective inhibition effect on fluorite flotation and had little effect on bastnaesite flotation.the separation index between bastnaesite and fluorite increased from 1.18 to 12.66 with the increase of EDTA concentration from 0 to 2×10^-3 mol/L,indicating that EDTA had a strong selective inhibition effect on fluorite,the separation efficiency was good,which was consistent with the results of quantum chemistry calculation.The combination of Quantum Chemical Calculation methods and experiment can not only improve the efficiency and shorten the cycle of research and development,on new rare earth mineral flotation reagents,but also can be used to compare and evaluate the flotation performance of rare earth minerals by different reagents for the future research and thus providing a new metod for the development of new rare earth flotation reagents.