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Boron resources are abundant in Da Qaidam salt lake of Qaidamu Basin. It has been given great attention for the polyborate species present in brine. In this study, the Raman spectroscopy was applied to investigate the existing-form of boron in brine during evaporation. The prepared solutions of MgO·2B2O3-H2O, MgO·2B2O3-MgCl2 -H2O, and MgO·2B2O3-MgSO4-H2O was also evaporated and recorded to study the influence of boron concentration, pH, and electrolytes on the borate speciation in brine. The mononborates of B(OH)3 and B(OH)4- were found to be the only forms present in the original salt lake brine. Brine evaporation promotes the formation of polyborate anions B3O3(OH)4-, B5O6(OH)4-, and B6O7(OH)62- and also disappearance of the B(OH)4- ion in brine with boron concentration of more than 11 g/L in B2O3. The pentaborate ion of B5O6(OH)4- was sensitive to the solution pH and found to be appeared under the pH value of 8.0. While the hexaborate ion of B6O7(OH)62- was observed more dependent on the electrolyte of magnesium chloride due to its special properties, such as promoting boron accumulation, lowering solution pH, and also the strong af?nity for water molecules, which is beneficial to the polymerization of borate ions in brine. The interaction mechanisms among polyborate anions during evaporation had also been proposed. 相似文献
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Boron resources are abundant in the Da Qaidam Salt Lake of the Qaidamu basin in China,which has generated significant attention due to the presence of polyborate species in brine from this lake. In this study,Raman spectroscopy was used to investigate the existing form of boron in brine during evaporation. MgO·2 B_2 O_3-H_2 O,MgO·2 B_2 O_3-MgCl_2-H_2 O,and MgO·2 B_2 O_3-MgSO_4~-H_2 O solutions were also studied to determine the influence of boron concentration,pH,and electrolytes on the borate speciation from brine. The mononborates B( OH)_3 and B( OH)_4~-were found to be the only forms present in natural salt lake brine. Brine evaporation promoted the formation of the polyborate anions B_3 O_3( OH)_4~-,B_5 O_6( OH)_4~-,and B_6 O_7( OH)_6~(2-)and also promoted the disappearance of the B( OH)_4~-ion from brine at boron concentrations of more than 11 g/L B_2 O_3. The pentaborate ion B_5 O_6( OH)_4~-was sensitive to the solution pH and appeared only at p H values less than 8. 0. Meanwhile,the hexaborate ion B_6 O_7( OH)_6~(2-)was observed to be more dependent on the electrolyte magnesium chloride due to its special properties,such as promoting boron accumulation,lowering solution pH,and also its strong affinity for water molecules,which were all beneficial for the polymerization of borate ions in brine. Interaction mechanisms between polyborate anions during evaporation are also proposed herein. ake; evaporation; polyborate species; interaction mechanism. 相似文献
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