Evolution characteristics of mesoscopic pore structure of weathered crust elution-deposited rare earth ore under solution seepage

In-situ leaching is extensively used in the mining industry to recover rare earths from weathered crust elution-deposited rare earth ore. In the leaching system, the pore structure of rare earth ore is one of the most important factors that influence the leaching performance. A small column leaching experiment was performed with deionized water as a leaching solution to study the effect of solution seepage on pore structure evolution characteristics in the leaching process of weathering crust eluviation rare earth ore. Micro-computed tomography (micro-CT) was performed on the ore sample before and after leaching, and internal structure images of the sample were obtained. The pore structures of the rare earth ore sample were obtained using the threshold segmentation algorithm. The variation characteristics of pore structure of a rare earth ore sample under the action of solution seepage were then studied, and the effects of solution seepage on sample porosity, pore volume, length, width, azimuthal angle, and other parameters were analyzed. The results show that the pore shape and size of rare earth ore change significantly due to solution seepage, most notably in the contact area of the coarse and fine particles. The solution seepage increases the porosity of rare earth ore, decreases the total number of pores, and increases the total volume of pores. Besides, the number of small and medium-sized pores decreases, while the number of large pores increases due to seepage. The change rate of the number of pores in each size interval increases and then decreases as pore size increases. Compared with the initial state, the distribution of pore aspect ratio is more concentrated after the solution seepage. Moreover, the distribution of pore azimuthal angle is more uniform, and the anisotropy of pore structure is enhanced by solution seepage.