Effect mechanism of nonane-1,1-bisphosphonic acid as an alternative collector in monazite flotation:Experimental and calculational studies

Monazite((Ce,La)PO_(4))is one of the major types of light rare earth minerals from which the light rare earth elements cerium(Ce)and lanthanum(La)are economically extracted.Flotation is extensively used to recover fine-grained monazite.Sodium oleate(NaOL)is considered as the collector with strong collecting ability for monazite flotation.However,this study shows that its collecting ability is still limited.In this paper,a phosphonic acid,nonane-1,1-bisphosphonic acid(C9-BPA),was employed as the novel collector in place of NaOL.Flotation experiments show that even when the C9-BPA dosage is less than one-fifth of the NaOL dosage,the monazite recove ry using C9-BPA as the collector is approximately 22 wt%higher than that using NaOL.The mechanism by which C9-BPA adsorbs on monazite was investigated using zeta potential,infrared(IR)spectroscopy and X-ray photoelectron spectroscopy(XPS)measurements as well as first-principles calculations.Zeta potential measurements show a more significant decrease in the zeta potentials of monazite after the addition of C9-BPA compared to those after the addition of NaOL.For C9-BPA-treated monazite,the characteristic peaks of C9-BPA are observed in the IR and C 1 s XPS spectrum,whereas for monazite treated by NaOL,no characteristic peak of NaOL was observed.Experimental results show that C9-BPA has a stronger affinity towards the monazite surface than NaOL as confirmed by the higher adsorption energy of CP-BPA on the monazite surface(-204.22 kJ/mol)than NaOL(-48.48 kJ/mol).This study demonstrates an extensive application value and prospect of C9-BPA in monazite flotation and helps design novel collectors with strong collecting ability for monazite flotation.