By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then incr...By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.展开更多
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 ...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)4^- in 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)4^2- in the tetraborate solutions is the main species,B(OH)3 ,B(OH)4^-,and B3O3(OH)4^- are minor species,and B3O3 (OH)5^2- and B5O6 OH)4^- are present only in negligible amounts.As solution continues to concentrate,B4O5(OH)4^2- 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 B5O6 OH)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[B5O6 OH)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 Mg^2+,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 B 3O3(OH)5^2-,while the subordinate species are B(OH)4^- at a low B2O3 /MgO ratio and B(OH)3 at a high B2O3 /MgO ratio,and the other anions are negligible,as the high Z of the borate anion must match that of Mg 2+.The disappearance of divalent B4O5(OH)4^2- 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)6^2+(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,Mg^2+ 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.展开更多
Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radi...Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function（RDF）. The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function（DRDF）. The calculation of the geometric model shows that octahedrally six-coordinated Mg（H2O）62＋, with an Mg2＋…OW bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair（CIP） in the more concentrated solution（1：18, H2O/salt molar ratio） with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42– ion happens in the solution. The S…OW bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.展开更多
The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optim...The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optimization and energy calculation of nickel sulfate hydrated clusters of the molecular formula [NiSO4(H2O)n ]^0 (n=1-12) were determined via DFT using the B3LYP method.Several possible initial structures were considered for clusters of each size to locate the equilibrium geometry.Based on the DFT calculation,the favorable structure of Ni^2+ includes the six-coordinated form of [NiSO4(H2O)n ]^0 clusters.The results of hydration energy calculation suggest that the six-coordinated contact ion pair (CIP) is the stable configuration for small hydration clusters (n≤5),while the solvent-shared ion pair (SSIP) represents the favorable structure for medium hydration clusters (6≤n≤10).The solvent is separated by x water molecules (xSIP,x≥2 is the number of water molecule between Ni^2+ and SO4^2-) in larger hydration clusters (n≥11).The EXAFS analysis of the NiSO 4 aqueous solutions and NiSO4 ·6H2O solid established that Ni^2+ was surrounded by six water molecules tightly forming an octahedral structure in the first hydration shell,and no CIP was found from 0.70 mol/L to 2.22 mol/L (near saturation).The Ni-O distance and coordinated number were 2.040±0.020 and 6.0±1.0,respectively.These results are consistent with the DFT calculations for [NiSO4(H2O)n ]^0 clusters.DFT and EXAFS are powerful techniques that can be used to enhance the resolution of NiSO 4 solution microstructure.展开更多
In order to greet the 36th International Conference on Solution Chemistry (36th ICSC) held in Xining, Qinghai, and organized by Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, the special issue on Soluti...In order to greet the 36th International Conference on Solution Chemistry (36th ICSC) held in Xining, Qinghai, and organized by Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, the special issue on Solution Chemistry was applied for and approved by the National Publication Administration of China. I’d like to start this afterword by thanking the editorial office for giving me the opportunity to read such 10 excellent papers involved in the special issue. The papers cover the abundant content, including many branches of solution chemistry, such as stable and metastable phase equilibria in the multicomponent salt-water system, solution structure,applied solution chemistry and so on. The first two papers of themare special contributing manuscripts as the “Study Highlights” section of the issue. In my view, this issue reflects many of the significant progresses and the latest results that have taken place in the solution chemistry field in the last decade.In particular, the Li salt sequences for 20 brines in the hexa-component system Li^+, Na^+, K^+, Mg^2+/Cl -, SO4^2-,-H2O during the isothermal evaporation at 298 K have been predicted by a thermodynamic model proposed in 2003. The predicted results indicate that the first crystallized Li salt will be varied with composition;Li2SO4 ·H2O will firstly appears in the brines of magnesium sulfate subtype, while Li2SO4 ·K2SO4 or 2Li2SO4Na2SO4 ·K2SO4 will emerge in sodium sulfate subtype and magnesium sulfate subtype with lower Mg/Li composition. These information extend our knowledge of Li chemistry and will provide some helpful suggests to solar pond technology of Li-brine process.展开更多
文摘By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.
基金the National Natural Science Foundation of China (21573268,U1607106,Y21503251,21373251,Y41503061,20873172,11079047)the Ministry of Science and Technology,China (2008CB617612)+1 种基金Chinese Academy of Sciences (KZCX2-EW-307,YWSA,YIPA2017467 WKFCASY510071017)the Natural Science Foundation of Qinghai (No.2015-ZJ-938Q,2019-ZJ 7037,2019-ZJ-7001)
文摘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)4^- in 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)4^2- in the tetraborate solutions is the main species,B(OH)3 ,B(OH)4^-,and B3O3(OH)4^- are minor species,and B3O3 (OH)5^2- and B5O6 OH)4^- are present only in negligible amounts.As solution continues to concentrate,B4O5(OH)4^2- 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 B5O6 OH)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[B5O6 OH)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 Mg^2+,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 B 3O3(OH)5^2-,while the subordinate species are B(OH)4^- at a low B2O3 /MgO ratio and B(OH)3 at a high B2O3 /MgO ratio,and the other anions are negligible,as the high Z of the borate anion must match that of Mg 2+.The disappearance of divalent B4O5(OH)4^2- 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)6^2+(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,Mg^2+ 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.
基金Supported by the Key Program of the National Natural Science Foundation of China(Nos.20836009 and 20873172)
文摘Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function（RDF）. The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function（DRDF）. The calculation of the geometric model shows that octahedrally six-coordinated Mg（H2O）62＋, with an Mg2＋…OW bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair（CIP） in the more concentrated solution（1：18, H2O/salt molar ratio） with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42– ion happens in the solution. The S…OW bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.
基金Nature Science Foundation of Qinghai Province(2018-ZJ-945Q)NSFC(21573268)+1 种基金Joint Foundation of Salt Lake Chemical(U1607106)Instrument function development and technology innovation project of Chinese academy of sciences(2018g108)
文摘The microhydration structure of nickel sulfate aqueous solution has been determined via density functional theory (DFT) calculation and extended X-ray absorption fine structure (EXAFS) spectroscopy.The geometric optimization and energy calculation of nickel sulfate hydrated clusters of the molecular formula [NiSO4(H2O)n ]^0 (n=1-12) were determined via DFT using the B3LYP method.Several possible initial structures were considered for clusters of each size to locate the equilibrium geometry.Based on the DFT calculation,the favorable structure of Ni^2+ includes the six-coordinated form of [NiSO4(H2O)n ]^0 clusters.The results of hydration energy calculation suggest that the six-coordinated contact ion pair (CIP) is the stable configuration for small hydration clusters (n≤5),while the solvent-shared ion pair (SSIP) represents the favorable structure for medium hydration clusters (6≤n≤10).The solvent is separated by x water molecules (xSIP,x≥2 is the number of water molecule between Ni^2+ and SO4^2-) in larger hydration clusters (n≥11).The EXAFS analysis of the NiSO 4 aqueous solutions and NiSO4 ·6H2O solid established that Ni^2+ was surrounded by six water molecules tightly forming an octahedral structure in the first hydration shell,and no CIP was found from 0.70 mol/L to 2.22 mol/L (near saturation).The Ni-O distance and coordinated number were 2.040±0.020 and 6.0±1.0,respectively.These results are consistent with the DFT calculations for [NiSO4(H2O)n ]^0 clusters.DFT and EXAFS are powerful techniques that can be used to enhance the resolution of NiSO 4 solution microstructure.
文摘In order to greet the 36th International Conference on Solution Chemistry (36th ICSC) held in Xining, Qinghai, and organized by Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, the special issue on Solution Chemistry was applied for and approved by the National Publication Administration of China. I’d like to start this afterword by thanking the editorial office for giving me the opportunity to read such 10 excellent papers involved in the special issue. The papers cover the abundant content, including many branches of solution chemistry, such as stable and metastable phase equilibria in the multicomponent salt-water system, solution structure,applied solution chemistry and so on. The first two papers of themare special contributing manuscripts as the “Study Highlights” section of the issue. In my view, this issue reflects many of the significant progresses and the latest results that have taken place in the solution chemistry field in the last decade.In particular, the Li salt sequences for 20 brines in the hexa-component system Li^+, Na^+, K^+, Mg^2+/Cl -, SO4^2-,-H2O during the isothermal evaporation at 298 K have been predicted by a thermodynamic model proposed in 2003. The predicted results indicate that the first crystallized Li salt will be varied with composition;Li2SO4 ·H2O will firstly appears in the brines of magnesium sulfate subtype, while Li2SO4 ·K2SO4 or 2Li2SO4Na2SO4 ·K2SO4 will emerge in sodium sulfate subtype and magnesium sulfate subtype with lower Mg/Li composition. These information extend our knowledge of Li chemistry and will provide some helpful suggests to solar pond technology of Li-brine process.
