A refractory phosphate ore obtained from Guizhou, China, contains high amounts of detrimental metal impurities (e.g., Fe, Al, and Mg) which affect the deep wet processing of phosphorus products before use. In this study, mineralogy parameters of the ore such as mineral composition, disseminated particle size, mineral liberation degree, and intergrowth relationship were investigated using X-ray fluorescence spectrometer (XRF), X-ray powder diffractometer (XRD), and advanced mineral identification and characterization system (AMICS). The mechanism for flotation separation was also discussed. The results showed that the ore was a fine-grained calcareous-siliceous collophanite with high P₂O₅ grade. The gangue minerals such as quartz, sericite (muscovite), pyrite, and dolomite were finely disseminated and encapsulated by fluoroapatite particles in a rather complex relationship. A double reverse flotation process was carried out based on the separation principle of less flotation and more inhibition. A phosphorous concentrate with a P₂O₅ grade of 35.53%, SiO₂ content of 5.88%, MgO content of 0.91%, sesquioxide (Fe₂O₃ + Al₂O₃) content of 1.98%, MER value of 8.13%, and phosphorus recovery of 75.04% was obtained. Based on the flotation test results and the analysis of process mineralogy parameters, we concluded that the main causes of difficulty in separation of collophanite are fine disseminated particle size, poor mineral liberation degree, and serious argillization. The selection of foam-controlled collectors, efficient dispersing inhibitors and classified desliming process will be necessary for improving flotation index. These results provide a technical reference for subsequent development and utilization of collophanite resources.

The separation of ultrafine apatite from quartz through reverse flotation is a challenge due to its low mass and high specific surface area. In this work, xanthan gum–Fe³⁺ (XG–Fe³⁺) was explored as a novel and efficient depressant–flocculant for the selective flotation separation of apatite and quartz. The flotation performance and separation selectivity of XG–Fe³⁺ were systematically assessed using micro-flotation tests. The mechanisms were revealed through turbidity analysis, microscopic observation, contact angle measurement, zeta potential, and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Flotation results illustrated that XG-Fe³⁺ strongly depressed the flotation of apatite, while it hardly affected the flotation of quartz. Turbidity analysis and microscopic observation indicated the flocculation of fine apatite in the presence of XG-Fe³⁺, while no flocculation was found for quartz. Contact angle, zeta potential and FTIR results indicated that XG-Fe³⁺ was chemically adsorbed onto the apatite surface, hindering the adsorption of dodecylamine (DDA) and maintaining the hydrophilicity of apatite. XG-Fe³⁺ enhanced the flotation separation of ultrafine apatite from quartz by maintaining the hydrophilicity of ultrafine apatite while simultaneously reducing its entrainment into the froth via selective flocculation.

To satisfy the industrial standards for phosphate products, phosphate ore must undergo beneficiation for the removal of gangue minerals such as carbonate minerals, silicate minerals, and clay minerals. Reverse flotation is commonly used to remove carbonate minerals from apatite. However, reverse flotation removes carbonate gangue minerals but fails to eliminate silicate and clay minerals. The use of pre-concentration (such as dense-medium cyclones and photoelectric sorting) in phosphate ore beneficiation enables the early rejection of gangue before the ore enters the fine-grinding and complex flotation circuits, thereby providing a range of technical and economic benefits. In addition, pre-concentration holds the potential to reject silicate and clay minerals in the beneficiation of phosphate ore. The phosphate ore investigated in this study was obtained from Hubei, China. It is characterized by well-defined gangue banding, which facilitates the liberation of some gangue minerals at relatively coarse comminution sizes (−15 + 0.5 mm). Based on these characteristics, photoelectric separation and dense-medium cyclone separation were employed as pre-concentration methods prior to reverse flotation, with the aim of achieving economically viable recoveries and marketable product grades. The results indicate that the combined dense-medium cyclone separation–reverse flotation process was the most effective for this phosphate ore, producing a final concentrate with a P₂O₅ grade of 31.08% and a recovery of 81.91%. Comparative evaluation reveals notable differences in gangue removal efficiency among the tested processes. While both reverse flotation and the combined photoelectric separation–reverse flotation process effectively removed dolomite, the dense-medium cyclone separation–reverse flotation process demonstrated superior overall performance by enabling the simultaneous removal of both silicate and dolomite impurities.