Monazite ((Ce, La)PO₄) 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 recovery 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 1s 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.

独居石 ((Ce, La)PO ₄) 是轻稀土元素的主要类型之一，可从中经济地提取轻稀土元素铈 (Ce) 和镧 (La)。浮选广泛用于回收细粒独居石。油酸钠（NaOL）被认为是独居石浮选捕收能力强的捕收剂。然而，这项研究表明，它的收集能力仍然有限。在本文中，膦酸壬烷-1,1-双膦酸 (C9-BPA) 被用作代替 NaOL 的新型捕收剂。浮选实验表明，即使 C9-BPA 用量小于 NaOL 用量的五分之一，使用 C9-BPA 作为捕收剂的独居石回收率也比使用 NaOL 高出约 22 wt%。使用 zeta 电位研究了 C9-BPA 吸附在独居石上的机理，红外 (IR) 光谱和 X 射线光电子能谱 (XPS) 测量以及第一性原理计算。Zeta 电位测量显示，与添加 NaOL 后相比，添加 C9-BPA 后独居石的 zeta 电位下降更显着。对于C9-BPA处理的独居石，在IR和C 1s XPS光谱中观察到C9-BPA的特征峰，而对于NaOL处理的独居石，没有观察到NaOL的特征峰。实验结果表明，CP-BPA 在独居石表面的吸附能（-204.22 kJ/mol）高于 NaOL（-48.48 kJ/mol），证实了 C9-BPA 对独居石表面的亲和力比 NaOL 更强。