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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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用等压法研究了LiCl-Li2 B4O7-H2 O体系离子强度范围为 0 1 5 3 0～ 3 0 75 8mol kg-1不同质量摩尔浓度分数的等压平衡浓度 ,水活度 ;计算了LiCl和Li2 B4O7,混合盐溶液的饱和蒸汽压 ,渗透系数等热力学性质。以总硼浓度 0 0 8mol·kg-1为界 ,把所有混合盐的实验数据分为高浓度和低浓度两部分 ,按照不同的物种生成转化反应 ,考虑溶液中H3 BO3 和硼氧配阴离子B(OH) 4 -,B3 O3 (OH) 4 -和B4O5(OH) 4 2 -的存在形式。由实验数据用最小二乘法和迭代法求取了LiB(OH) 4 离子对的缔合平衡常数Km1,B3 O3 ,(OH) 4 离子的生成转化反应的化学计量平衡常数Km2 ,以及Pitzer模型的离子相互作用参数。用该模型计算的渗透系数值与实验结果取得合理的一致。对完善含锂、硼盐湖卤水体系的热力学模型和盐湖资源的综合开发具有重要意义 相似文献
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西藏扎北盐湖位于藏北高原腹地,其卤水类型属硫酸钠亚型,富含Li、K、B等元素。为综合利用该湖的液态矿产资源,于西藏当地对该盐湖富锂卤水进行自然蒸发实验。实验以Na+,Mg2+//Cl-,SO42--H2O四元体系15℃等温相图及K+,Mg2+//SO42--H2O三元体系15℃介稳相图为参考,绘制了扎北盐湖夏季卤水在秋季自然蒸发结晶路线图,研究了卤水在蒸发过程中液相的化学组成变化以及其蒸发析盐规律。结果表明,在蒸发过程早期(成卤率23.9%),锂浓度达1.2 g/L时,锂开始以Na3LiSO4.3H2O等复盐形式大量分散析出;硼在整个蒸发过程中以硼砂(Na2B4O7.10H2O)等形式分散析出难于富集;钾以钾镁矾(K2SO4.MgSO4.6H2O)和钾石盐(KCl)形式蒸发浓缩的后期大量析出。实验为扎北盐湖的盐田工程设计及制卤工艺操作提供了必要的基础数据,也可为我国西藏硫酸钠亚型盐湖卤水的综合利用提供一定参考。 相似文献
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The crystal structure of metal borates has been extensively investigated by X-ray and neutron diffraction,but,the structure of aqueous polyborate solutions are still largely unknown.Over the last decade,our group has focused on studying the structure of complex aqueous polyborate solutions of Li,Na,K,Rb,Cs,and Mg using synchrotron radiation X-ray scattering(XRS),EXAFS,Raman,NMR,and DFT,as well as determining the density,conductivity and pH of such solutions.Polyborate species distributions were calculated using pH measurements,and the main species in the solution have been confirmed by NMR and Raman spectra.For alkali-metal metaborates,the dominant species is always B(OH)-4in a wide range of concentration,while the presence of others species is negligible.For alkali metal tetraborates,when concentration is in the extreme low range,only B(OH)3 and B(OH)-4 are present in these solutions.As the total boron concentration increases,B(OH)3 and B(OH)-4 polycondensated to form more complex oligomers.Of them,while B4O5(OH)2-4 in the tetraborate solutions is the main species,B(OH)3,B(OH)-4,and B3O3(OH)-4 are minor species,and B3O3(OH)2-5 and B5O6OH)-4 are present only in negligible amounts.As solution continues to concentrate,B4O5(OH)2-4 eventually becomes the dominant species,which is consistent with the congruent compound M2B4O7·nH2O(M=Li,Na,K,Rb,Cs) in the system M2O-B2O3-H2O(M=Li,Na,K,Rb,Cs).For alkali metal pentaborates,B(OH)3 and B(OH)-4 are the main species at low concentrations.The species distribution,Raman and NMR spectroscopy results verified that the dominant species in concentrated pentaborate solutions with Li and Na is pentaborate B5O6OH)-4,but it is surprising that the main species with K,Rb,and Cs is always the triborate monoanion B3O3(OH)-4.Although all M[B5O6OH)4]·nH2O(M=Li,Na,K,Rb,Cs) are all congruent compounds in the system M2O-B2O3-H2O(M=Li,Na,K,Rb,Cs) ,the main species in aqueous solutions are quite different because of various cation hydration distance(d),hydration number(CN),and configuration,especially charge(Z).For bivalent Mg2+,three borate minerals,namely,Inderite(2MgO·3B2O3·15H2O),Hungchaoite(MgO·2B2O3·9H2O),and Mcallisterite(MgO·3B2O3·7.5H2O),exist in the system MgO-B2O3-H2O at 298K.Inderite is a congruent compound,but Hungchaoite and Mcallisterite are incongruent compounds.The species distribution and Raman spectra demonstrat that the predominant species in all the solutions with magnesium borates is bivalent triborate B3O3(OH)2-5,while the subordinate species are B(OH)-4 at a low B2O3/MgO ratio and B(OH)3at a high B2O3/MgO ratio,and the other anions are negligible,as the high Z of the borate anion must match that of Mg2+.The disappearance of divalent B4O5(OH)2-4 is in agreement with its incongruent nature.The DFT and XRS results showed that tetrahedral Li(H2O)+4(d=0.20 nm,CN=4),octahedral Na(H2O)6+(d=0.236 nm,CN=6),and Mg(H2O)2+6(d=0.210 nm,CN=6) in the first hydration shell belong to Platonic polyhedra.However,K(H2O)+8(d=0.28 nm,CN=8,XRS and DFT),Rb(H2O)+8(d=0.293 nm,CN=7.7-8.2,EXAFS),and Cs(H2O)+8(d=0.320-0.326 nm,CN=7.6-7.9,EXAFS) are inclined Voronoi polyhedra.Therefore,the effects of cation Z and d on the structure of polyborates in aqueous solutions are deterministic,while the effect of hydrated-cation symmetry is secondary.Their hydrolysis order was:Mg＞Li＞Na＞K＞Rb＞Cs,in step with hydration power.Among them,Mg2+ and Li+have a strong tendency towards hydrolysis,but Na+ scarcely hydrolyzes,especially Rb+ and Cs+ have a little protonation.X-ray scattering of aqueous alkaline sodium borohydride solutions confirmed that dihydrogen bonds exist in an aqueous solution.The four distinct features of dihydrogen bonds in aqueous solution-unidirectionality,divaricativity,multicentricity,and multidentativity have been also described here in brief. 相似文献
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硫酸镁亚型盐湖老卤是MgCl2、MgSO4的饱和溶液体系,富集了Mg、B、Li等元素。本文针对含硼水盐体系热力学难以表达的问题,开展了硼在水盐体系存在形态及其平衡关系的研究。利用易于水解的Mg(BO2)2作为硼源,借助拉曼光谱和X射线衍射(XRD)为检测手段,定量研究Mg(BO2)2在MgSO4-H2O、MgSO4-MgCl2-H2O体系中水解硼物种转化规律。结果表明:(1)Mg(BO2)2在MgSO4溶液中的水解固相为MgB2O(OH)6、MgB4O7·9H2O和Mg(OH)2;在MgSO4-MgCl2-H2O溶液中水解固相为Mg2B6O11·15H2O、MgB4O7·9H2O、Mg2Cl(OH)3·4H2O。(2)Mg(BO2)2在MgSO4溶液中水解,液相硼物种主要有B3O3(OH)-4、B3O3(OH)52-、B(OH)-4、B4O5(OH)42-、H3BO3,其分布受MgSO4浓度影响很大,MgSO4浓度从0增加至饱和,B3O3(OH)-4始终占总硼量的50.07%以上,B3O3(OH)52-占液相总硼从4.77%上升至37.16%为第2化学物种。(3)在MgSO4-MgCl2-H2O溶液中,硼物种的主要形态有B3O3(OH)-4、B3O3(OH)52-、B(OH)-4,其分布 随[Cl22-]/([Cl22-]+[SO42-])变化很大,在MgCl2和MgSO4的共饱溶液中,分别占液相总硼量的58.91%,14.62%和12.81%。(4)液相硼物种之间平衡关系的活度商lnQ,不仅与溶液pH、水活度有关,还与MgSO4、MgCl2摩尔浓度呈二元线性关系,这样就可将硼在H3BO3-NaOH体系物种分布关系的lnQ扩展到 (MgSO4,MgCl2,MgSO4-MgCl2)水溶液的多元体系。由此获得硼物种的量化关系,可为推算硼在水盐体系的物种分布,进而计算含硼电解质溶液热力学性质提供依据。 相似文献
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用合成的水合四硼酸钾和偏硼酸钾晶体,配制一系列溶液,研究了pH与浓度变化的关系,并计算硼酸根离子的摩尔分数-浓度(δ-c)关系图。用拉曼光谱方法研究四硼酸钾和偏硼酸钾溶液,给出其拉曼光谱图,并对各峰进行了归属。研究表明,四硼酸钾溶液中存在的物种主要有[B4O5(OH)4]2-、[B3O3(OH)4]-和[B(OH)4]-,而其它物种所占摩尔分数很小;在偏硼酸钾水溶液中,[B(OH)4]-占绝大多数,有很少量H3BO3、[B4O5(OH)4]2-和[B3O3(OH)4]3-。硼酸盐离子浓度越低,越容易水解为聚合度较低的简单物种。 相似文献
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大柴旦盐湖夏季组成卤水的天然蒸发（含硼海水型盐湖卤水的天然蒸发） 总被引：2，自引：2，他引：2
在进行大集里盐湖夏季组成卤水的天然蒸发实验中确定，该卤水的蒸发结晶路线不是按照Ｎａ＋、Ｋ＋、Ｍｇ（２＋）／／Ｃ１－、ＳＯ４（２－）──Ｈ２Ｏ体系２５℃平衡溶解度相图，而是按照该体系的介稳相图预示的亚稳过程进行。从天然蒸发过程中盐卤的浓缩倍数与浓缩卤水中硼富集倍数的一致性认为，盐卤在天然蒸发浓缩业折过程中硼酸盐一般地并不以固体业形式析出，而是赋存于浓缩卤水中。 相似文献
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采用物种分布图和核磁共振实验研究了五硼酸钾溶液中含硼物种的类型、含量和溶液浓度间关系。研究表明五硼酸钾在稀溶液中几乎全部水解为B(OH)3和B(OH)4-;在较浓溶液中主要物种为B3O3(OH)4-和B(OH)3,而B5O6(OH)4-和[B4O5(OH)42-]的含量较小。核磁共振实验研究给出了B(OH)4-, B3O3(OH)4-和B5O6(OH)4-的生成常数K1, K3, K5,研究得出B5O6(OH)4-含量很少的原因是其解聚为其它类型硼酸根离子。外加离子促进五硼酸根离子的生成,而高温条件促进B5O6(OH)4-发生解聚反应。 相似文献
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在Pitzer电解质溶液理论的基础上采用两种模型计算了KCl-K2SO4-KBO2-H2O体系及其子体系的溶解度。模型I假设溶液中只有一种硼物种B(OH)4-,模型II假设溶液中有4种硼物种,分别对应于B(OH)3、B(OH)4-、B3O3(OH)4-和B4O5(OH)42-。模型I与模型II的溶解度计算结果接近,且与实验值吻合较好。采用模型II计算了上述体系溶液中的硼物种和OH-的浓度。各硼物种的浓度主要受溶液中总硼浓度的影响,而很少受KCl和K2SO4的影响。计算结果说明在计算偏硼酸钾溶液体系溶解度时,可近似认为溶液中硼物种只有B(OH)4-。模型II可用于计算含偏硼酸钾体系的pH值。本文的计算结果可为复杂偏硼酸钾体系模型的构建提供理论基础。 相似文献
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系统地总结和讨论了固体硼氧酸盐１１ＢＭＡＳＮＭＲ和硼氧酸盐水溶液１１ＢＮＭＲ波谱学研究结果。对于固体硼氧酸盐１１ＢＭＡＳＮＭＲ谱．虽然可以从中定量计算ＢＯ３与ＢＯ４比值，但因为１１Ｂ化学位移变化小，很难将配位多面体与它们的配位环境相联系，用其作为表征固体硼氧酸盐尚缺少特征性。而对于硼氧酸盐水溶液１１ＢＮＭＲ谱，由于在ＮＭＲ谱仪时间规模下一些硼氧酸盐阴离子中不同化学位置上Ｂ核交换速率影响，在１１ＢＮＭＲ波谱上没有观察到信号。实践证明，溶液１１ＢＮＭＲ波谱与Ｒａｍａｎ光谱的联合使用，将是研究水溶液中硼氧酸盐阴离子结合最直接和有力的手段。 相似文献