Dynamic Adsorption Characteristics Of Crushed Gangue To Ions In Coal Mine Underground Reservoirs Under Leaching Condition

In recent years,the contradiction of coal resource exploitation and water resource protection has been increasingly emerging in western China.Coal mine goaf is transformed into underground water reservoirs by constructing dams to connect the boundary coal pillars of goaf.The construction of the underground water reservoirs of coal mines achieves storage,purification and reuse of mine water,which is an effective way to recycle the loss water resource in the environmentally fragile mining areas in western China.In the underground water reservoirs,where water is flowing,pollutants are removed during migration due to precipitation or ion exchange with gangue,which leads to the transformation of polluted mine water to clean water.The flow condition of water,the mineral components of gangue,the pollutant contents and so on are able to greatly affect the purification effect of coal mine underground reservoirs.However,the research on these elements is not sufficient.The research on the adsorptive characteristics of gangue of coal mine underground reservoirs is significant for deepening the knowledge of the water purification function of coal mine underground reservoirs.This thesis focuses on the adaptive characteristics of gangue to high-salinity ions,K⁺、Ca²⁺、Mg²⁺,under leaching condition using a mercury intrusion experiment,X-ray diffraction（XRD）,X-ray fluorescence spectrometry（XRF）,CT scanning imaging,a dynamic leaching experiment,and COMSOL Multiphysics numerical simulation.The physicochemical properties of coal gangue were detected.The accumulation interspace characteristics of gangue blocks were analyzed.The ion migration and dissolution,the flow speed distribution of flow field in the leaching column,and the adsorptive characteristics of gangue to 3 sorts of ions were investigated.Finally,the dynamic adsorption characteristics of gangue to high-salinity ions affected The main obtained conclusions are as follows:（1）Size gradient has a significant effect on the structure of the accumulation interspace（or flow channels）structure of gangue blocks.Along with the decrease of gradient,the critical size to distinguish the cavity（or throat）from the large continuous interspace gradually decreases,and the volume ratio of the large continuous interspace rises.The distribution of the cavity size is of multi peaks,the distribution of the throat size is of a single peak,and the interspace size distribution is of a single peak.The interspace size decreasing,the interspace surface gradually changes from concave to convex.（2）A leaching device was designed independently and the leaching experiments were conducted.The results show that size gradient,ion concentration and ion sorts all have a significant influence on the dynamic adsorptive characteristics of gangue.Under the leaching condition,the gangue column has stronger adsorption to Ca²⁺when the gradient of gangue is smaller.A higher Ca²⁺concentration in the displacement liquid leads to a greater adsorption amount but a lower removal rate.The order of 3 sorts of high-salinity ions as to the adsorption difficulty from easy to difficult is K⁺<Ca²⁺<Mg²⁺.Mg²⁺can obviously promote the dissolution of K⁺and Ca²⁺,and K⁺can obviously promote the dissolution of Mg²⁺,but the promotion of Ca²⁺to the dissolution of Mg²⁺and K⁺is weak.（3）A greater size gradient,a greater inlet flow speed or a higher inlet concentration accelerates the migration speed of ions in the gangue leaching column,but the effect mechanisms of them differ.The flow speed in interspaces in the leaching column packed with larger gangue blocks is higher,which causes the faster migration of ions in interspaces and the uneven concentration front.The flow speed distribution in the leaching column with different inlet flow speeds is almost same,and the concentration fronts under the condition of different inlet flow speeds are almost same.The greater inflow speeds cause a proportional increase in the average velocities of gangue and interspace domains,leading to the faster migration of ions in the leaching column.At a higher inlet concentration,the time for upper gangue to reach saturated adsorption status,in which the residence effect of saturated gangue on ions is weakened,is shortened,thus leading to faster downward migration of ions.（4）A higher inlet concentration or a higher inlet speed leads to an increase in the total adsorption rate of gangue in the leaching column,but the effect mechanisms of them differ.The rise of concentration increases the internal adsorption rate of gangue.However,a higher inlet speed causes a larger contact area between ions and gangue in a short period.A smaller size gradient or a higher inlet concentration leads to an increase in the total saturated adsorption amount of gangue in the leaching column,but the effect mechanisms of them differ.A smaller size gradient leads to a higher volume ratio of gangue in the leaching column.By contrast,a higher concentration increases the internal maximum adsorption amount of gangue.The thesis has 60 figures,8 tables and 118 references.