| Ionic rare earth is a precious strategic mineral resource in my country.It is a clay mineral formed by granite or volcanic rock containing rare earth after years of weathering.The rare earth ions adsorbed on clay minerals with hydrated ions or hydroxyl hydrates can be chemically more active cations.Dissociated from clay minerals.Currently,in-situ leaching technology is usually used for mining,and ammonium sulfate is used as the leaching agent,but the use of ammonium sulfate as the leaching agent will cause ammonia nitrogen pollution around the mining area,and the field test of magnesium sulfate as a new leaching agent is currently being carried out Research shows that the ionic strength and pH of the magnesium sulfate leaching solution are the key factors affecting the leaching effect of ionic rare earths.Therefore,only by studying the leaching process of magnesium sulfate solution with different ionic strength and different pH can the magnesium salt leaching system be obtained.The best ionic strength and pH of the leaching solution provide a certain theoretical reference for the green and efficient leaching of ionic rare earths.Therefore,in this paper,by carrying out indoor simulated column immersion experiments,magnesium sulfate solutions with different ionic strengths(molar concentrations of 0.1 mol/L,0.2 mol/L,0.3 mol/L,0.4 mol/L and 0.5mol/L)were prepared and passed through Dilute sulfuric acid adjusts the pH to 2,2.5,3,3.5,4 and 4.5.The six sets of magnesium sulfate solutions corresponding to the best ionic strength are used as leaching agents,and the ionization of magnesium sulfate solutions of different ionic strength and different pH is studied.The influence law of the rare earth leaching effect,the inversion image of the sample in the transverse and longitudinal directions measured by nuclear magnetic resonance technology,the T2 spectrum of the sample,the pore structure distribution and other parameters are analyzed to obtain different ionic strengths and different pH magnesium sulfate solutions for leaching ore Influence on the microscopic pore structure of soil samples.Through the above research,the following research results are mainly obtained:(1)The column leaching test was carried out with magnesium sulfate solutions of different ionic strengths,and the change rule of the rare earth ion concentration in the leaching solution of the five groups of leaching test groups during the leaching process was gradually increased and then gradually decreased,and the effective time of ion exchange for leaching For 2-2.5 hours,the liquid rate is between 0.24-0.28 ml/min,and the rare earth leaching rate first increases and then decreases with the increase of ionic strength.The rare earth leaching with 0.3 mol/L magnesium sulfate solution The leaching rate is the highest and the leaching effect is the best.(2)Six groups of 0.3mol/L magnesium sulfate solutions with pH 2,2.5,3,3.5,4 and 4.5were adjusted by dilute sulfuric acid to carry out column leaching tests to obtain the concentration of rare earth ions in the leaching mother liquor of the six groups of leaching test groups They all increase first and then decrease.When the acidity increases,the ion exchange reaction rate increases.With the increase of acidity,the rare earth leaching rate first increases and then decreases.When pH=2.5,the rare earth leaching rate is the highest,and the leaching mother liquor is the highest.The liquid rate is 0.3ml/min.Considering the leaching rate of rare earth and the leaching rate of the leaching solution,it is considered that the leaching effect is the best when pH=2.5.(3)The pore distribution of rare earth samples during the leaching process is determined by using a rock and soil microstructure analyzer based on nuclear magnetic resonance(NMR)technology to obtain T2 spectra of the magnesium sulfate leaching process with different ionic strengths to analyze the leaching process The pore distribution of the ore samples of each leaching cycle in the process,and the internal pore distribution and pore evolution of the effective leaching cycle sample are obtained.After the sample is saturated to the end of the third magnesium sulfate leaching cycle,the number of small pores inside the sample rises rapidly,while the number of mesopores,large pores and super-large pores decreases;after 4-6leaching cycles,At this time,the mesopores,macropores and super-large pores increase,and the number of small pores decreases rapidly,mainly due to the change of clay particles caused by the ion exchange reaction inside the sample and the accumulation and migration of fine particles inside the sample.Such internal pores evolve.(4)Magnesium sulfate solutions of different pH have different effects on the pore evolution of the sample during the leaching process.When the pH is less than 2.5,the small pores in the internal pore structure of the sample account for the majority,and the internal pore radius of the sample is within the effective time of ion exchange.The number of small pores and mesopores less than 60 um increases,while the number of large and super-large pores with pore radius greater than 60 um decreases.When pH>2.5,the number of small and mesopores with pore radius less than 60 um inside the sample increases first and then decreases,while the number of large and super-large pores first decreases and then increases.The analysis suggests that increasing the acidity of the leaching solution will cause the thickness of the electric double layer of fine particles to become thinner,which reduces the repulsive force of the electric double layer,and changes the balance between the van der Waals attraction and the repulsive force of the electric double layer between the fine particles and the pore surface.Van der Waals The force plays a leading role,resulting in a larger number of accumulated fine particles,more severe pore clogging,and a smaller proportion of large pores in the sample and a larger proportion of small pores. |
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