低品位胶磷矿经强化离心重选抛尾后得到了部分合格精矿，但其重选中矿的量仍然较大、品位仍然较高。为更充分地回收磷矿，基于对重选中矿的元素组成、矿物组成和嵌布情况分析，进行了浮选试验，并通过FTIR分析了反浮选的机理，最后将强化离心重选与浮选研究结果加以整合，确定采用重浮联合工艺。研究结果表明：重选中矿的P₂O₅品位为17.12%，主要矿物为磷灰石、白云石和石英，其细粒级解离相对较充分，但粗粒级（> 0.074 mm）仍有部分未解离。对重选中矿进行磨矿后浮选，正浮选中随着碳酸钠用量的增加，精矿品位逐渐上升、产率逐渐下降，随着捕收剂ZF-1用量的增加，精矿产率不断上升、品位不断下降，两者最佳用量分别为3.0，1.5 kg/t，此时精矿产率和品位分别为67.81%和21.41%；反浮选中随着硫酸用量的增加，精矿产率不断下降，品位则先升高而后趋于稳定，随着捕收剂ZF-2用量的增加，精矿产率不断下降，但下降速度逐渐减小，精矿品位则先升高而后趋于平稳，两者最佳用量分别为5，0.9 kg/t，此时精矿产率和品位分别为60.49%和26.97%。FTIR测试发现，最佳试验条件下ZF-2与胶磷矿未发生明显吸附，而在白云石表面则发生了化学吸附，并对白云石本身的${mathrm{CO}}_3^{2-} $起到了良好的遮蔽效果，因而起到了反浮选脱除碳酸盐类矿物的目的。将重选与浮选整合，得到重浮联合的最终精矿和最终尾矿，产率和品位分别为39.06%和25.12%，60.94%和8.51%，整体效果良好。

With the use of enhanced gravity separation method to separate out tailings from low-grade collophanite, only part of up-to-standard concentrate is obtained, and lots of middlings still with a higher grade are produced during the separation process. In order to get a higher recovery of concentrate, test on flotation of the middling is conducted based on result of analysis of its elementary and mineralogical compositions and dissemination of minerals. Through FTIR analysis of mechanism of reverse flotation process, a gravity separation + flotation combined process is developed based on the results of study on enhanced centrifugal gravity separation and flotation processes. As indicated by study results, the grade of P₂O₅ of gravity separated middling is 17.12%; the middling contains predominately apatite, dolomite and quartz; the finer sizes of the middling can get comparatively a better dissociation while some of the > 0.074 mm coarser particles still remain undissociated; in direct flotation of milled middling, the concentrate tends to gradually rise in grade and drop in yield with the increase of dosage of sodium carbonate, and the contrary is the case with the increase of dosage of collector ZF-1; the optimum dosages of sodium carbonate and ZF-1 are 3.0 kg/t and 1.5 kg/t, respectively, and in this case the yield and grade of concentrate are 67.81% and 21.41%, respectively; in reverse flotation of the middling, with the increase of dosage of sulfuric acid, the yield of concentrate tends to gradually decrease with its grade first going up and then maintaining stabilized; with the increase of dosage of collector ZF-2, the yield of concentrate gradually drops yet with a gradually declining rate while the grade of concentrate tends to first rise and then keep stabilized; in this case, the optimum dosages of the sulfuric acid and ZF-2 are 5 kg/t and 0.9 kg/t, respectively, with the yield and grade of concentrate being 60.49% and 26.97%, respectively. FTIR analysis shows that no obvious adsorption effect can be observed between ZF-2 and collophanite under optimal testing conditions, and the ZF-2 is seen to only adsorb onto surface of dolomite forming a good barrier for the ${mathrm{CO}}_3^{2-} $ of the dolomite itself, which can help achieve the objective of getting rid of carbonate minerals through reverse flotation process. Through the use of the gravity separation + flotation combined process, the yield and grades of final concentrate and tailing product are 39.06% and 25.12%, 60.94% and 8.51%, respectively, well demonstrating the effectiveness of the process.