PEG400 - NaCl/KCl - H2O三元体系298 K溶解度、密度、折光率研究

采用等温溶解平衡法研究了 298 K下三元体系NaCl/KCl - PEG400 - H2O的相平衡关系,绘制了相应的相图、密度-组成图和折光率-组成图。研究发现：298 K下,两个三元体系均无分层现象,只存在固液相平衡关系,其平衡相图由不饱和液相区(L)和一固一液区(S+L)构成。PEG400对NaCl、KCl有一定的盐析作用,随着溶液中PEG400含量不断增加单盐溶解度减小。     

Determination of retardation coefficients of sulfolane and thiolane on soils by Kow–Koc and solubility parameter, batch and column experiments

 Retardation parameters (R_f) for sulfolane and thioalne were estimated using reference values and experimentally as they were mainly observed at an aquifer underneath a waste disposal site near Brisbane, Australia. Three soil aquifer materials e.g. clay, silty clay and sand were used as sorbents. At first, R_f was obtained employing K_oc–K_ow and solubility parameter, respectively, while experimental coefficients were determined from both batch and flow-through column tests. Additionally, R_f was observed at a single- and bi-solute system through the column test. There was not found any significant difference in R_f between K_oc–K_ow and solubility parameters, but the retardation coefficient was significantly dependent on organic carbon content for solubility parameter. In contrast, using K_oc–K_ow, the coefficient correspondingly varied with an amount of clay content contained in each soil. In the same manner, the batch-determined parameters were more subject to clay content. On the other hand, the column-determined parameters can be comparable with the desk-derived values. In a bi-solute system, they did not influence each other concerning retardation coefficients while they flew though the column simultaneously. It was concluded that there was a large discrepancy in retardation coefficient of batch- against both reference-oriented estimation and column-determined values. Received: 20 August 1998 · Accepted: 17 May 1999     

Gypsum: a review of its role in the deterioration of building materials

The deterioration of buildings and monuments by gypsum is the result of crystallization cycles of this salt. Although gypsum can dehydrate to a hemihydrate, the mineral bassanite, and to an anhydrate, the mineral anhydrite, this reaction occurs in nature on a geological time scale and therefore it is unlikely to occur when gypsum is found on and in building materials. The CaSO₄–H₂O system appears deceptively simple, however there are still discrepancies between the experimental and thermodynamically calculated data. The reason for the latter can be attributed to the slow crystallization kinetics of anhydrite. Apart from this, the large numbers of studies carried out on this system have focused on industrially important metastable phases, such as the hemihydrate and soluble anhydrite. The paper presents a review of the studies dealing with the phase equilibria of the CaSO₄–H₂O system as well as the influence of other salts on the solubility of gypsum. It tries to glean out the relevant information that will serve to explain the deterioration observed on building materials by the crystallization of gypsum and thus allows developing improved conservation methods.     

交互四元体系Li+, Mg2+//SO2-4, B4O2-7H2O 288 K

采用等温溶解平衡法研究了288K时Li+, Mg2+//SO2-4, B4O2-7- H2O四元体系的固液相平衡关系,测定了该四元体系在288K时平衡液相的溶解度和密度。依据实验测定的平衡溶解度数据及对应的平衡固相,绘制了该四元体系的平衡相图及密度组成图。研究结果表明：交互四元体系Li+, Mg2+//SO2-4, B4O2-7- H2O 288K时平衡相图中有2个共饱点,5条单变量曲线,4个结晶区对应的平衡固相分别为Li2B4O7·3H2O,Li2SO4·H2O,MgB4O7·9H2O和MgSO4·7H2O。     

Solid-liquid Equilibria for the Quaternary NaCl–Na2SO4–Na2B4O7–H2O System at 348 K

正1 Introduction China has very abundant liquid mineral resources.Especially,the brine resources in the west of Sichuan Basin are pushed into the first place in China,whose K and B contents are unusually high.These rare liquid mineral resources have very good exploitation prospect(Lin,2001;2006).Generally speaking,phase equilibrium     

不同pH值水对碳酸盐侵蚀作用的研究

地下水的ｐＨ值可在３～１０的范围内变化，碳酸盐的溶解受地下水ｐＨ值的影响很大。本文从实验和理论上定量探讨了方解石、菱铁矿、菱镁矿、菱锌矿和重晶石在水中溶解度随ｐＨ的变化规律。笔者从溶度积常数出发，在考虑了金属离子和碳酸根的副反应及其活度系数的基础上，导出了一个计算溶解度的公式，给定不同ｐＨ值，就可用微机计算出该条件下的ｌｇＳ～ｐＨ的溶解度曲线。实验证明：计算与实测溶解度曲线形状相同。     

MgSO4水合物溶解平衡时物相的热力学判别

硫酸镁易于形成水合物,例如前次报道我们获得并讨论的用于六元体系溶解度计算合理的单独电解质Pitzer参数,及四元交互体系Na+,K+//Cl-,NO3--H2O、K+,Mg2+//NO3-,SO24--H2O、K+,Mg2+//NO3-,Cl--H2O混合参数和它们的应用。此次报道对同离子四元体系K+//Cl-,NO3-,SO24--H2O、Mg2+//Cl-,NO3-,SO24--H2O的混合参数的研究及其在体系溶解度预测中的应用。     

Temporal variability of dimethylsulfide and dimethylsulfoniopropionate in the Sargasso Sea

Vertical profiles of dimethylsulfide (DMS) and β-dimethylsulfoniopropionate, particulate (pDMSP) and dissolved (dDMSP), were measured biweekly in the upper 140 m of the Sargasso Sea (32°10′N, 64°30′W) during 1992 and 1993. DMS and pDMSP showed strong, but different, seasonal patterns; no distinct intra-annual pattern was observed for dDMSP. During winter, concentrations of DMS were generally less than 1 nmol l⁻¹ at all depths, dDMSP was less than 3 nmol l⁻¹ and pDMSP was less than 8 nmol l⁻¹. In spring, concentrations of both dDMSP and pDMSP rose, on a few occasions up to 20 nmol l⁻¹ in the dissolved pool and up to 27 nmol l⁻¹ in the particulate pool. These increases, due to blooms of DMSP-containing phytoplankton, resulted in only minor increases in DMS concentrations (up to 4 nmol l⁻¹). Throughout the summer, the concentrations of DMS continued to increase, reaching a maximum in August of 12 nmol l⁻¹ (at 30 m depth). There was no concomitant summer increase in dDMSP or pDMSP. The differences among the seasonal patterns of DMS, dDMSP, and pDMSP suggest that the physical and biological processes involved in the cycling of DMS change with the seasons. There is a correlation between the concentration of DMS and temperature in this data set, as required by some of the climate feedback models that have been suggested for DMS. A full understanding of the underlying processes controlling DMS is required to determine if the temperature-DMS pattern is of significance in the context of global climate change.     

A comparative study on the dissolution and solubility of hydroxylapatite and fluorapatite at 25 °C and 45 °C

Dissolution of the synthetic hydroxylapatite (HAP) and fluorapatite (FAP) in pure water was studied at 25 °C and 45 °C in a series of batch experiments. The XRD, FT-IR and SEM analyses indicated that the synthetic, microcrystalline HAP and FAP with apatite structure used in the experiments were found to have no obvious variation after dissolution except that the existence of OH groups in FT-IR spectra for FAP after 2880 h dissolution was observed. During the HAP dissolution (0–4320 h), the aqueous calcium and phosphate concentrations reached the maxima after 120 h and then decreased slowly with time. For the FAP dissolution in pure water, after a transient time of 1440 h (< 60 d), element concentrations and pH became constant suggesting attainment of a steady-state between the solution and solid. During early stages of the FAP dissolution reaction (< 72–120 h), mineral components were released in non-stoichiometric ratios with reacted solution ratios of dissolved Ca:P, Ca:F and P:F being lower than mineral stoichiometric ratios of Ca₅(PO₄)₃F, i.e., 1.67, 5.0 and 3.0, respectively. This indicated that F were preferentially released compared to Ca from the mineral structure. The mean K_sp values were calculated by using PHREEQC for HAP of 10^− 53.28 (10^− 53.02–10^− 53.51) and for FAP of 10^− 55.71 (10^− 55.18–10^− 56.13) at 25 °C, the free energies of formation ΔG_f^o[HAP] and ΔG_f^o[FAP] were calculated to be − 6282.82 kJ/mol and − 6415.87 kJ/mol, respectively.     

Stability of biological and inorganic hemimorphite: Implications for hemimorphite precipitation in non-sulfide Zn deposits

Hemimorphite, Zn₄Si₂O₇(OH)₂·H₂O, one of the most common minerals in non-sulfide Zn deposits, together with smithsonite and hydrozincite, is one of the most abundant minerals in the “calamine” deposits in SW Sardinia. In spite of their importance for the development of ore genesis models, the stability properties of hemimorphite are poorly known. This paper presents solubility experiments on two different types of hemimorphite: a “geological” hemimorphite from a supergene non-sulfide Zn deposit, of supposed abiotic origin, and a hemimorphite precipitated by bacterial activity. Both specimens were characterized, before and after the experiment, by Synchrotron Radiation X-ray powder diffraction, Scanning Electron Microscopy, and X-ray Absorption Spectroscopy. The calculated solubility product constants (logK_s) are similar for both “geological” and biogenic hemimorphite (30.3 ± 0.4 and 30.5 ± 0.1, respectively). During the solubility experiment, biological hemimorphite undergoes an amorphous to crystalline phase transition, and the distinctive features (mineralized bacterial sheaths and organic filaments), that allowed us to demonstrate its biological origin, are no longer recognizable by Scanning Electron Microscopy.The results of this study may be useful for developing ore genesis models, including evolution in a supergene environment, and in general for performing geochemical speciation and equilibrium calculations. Moreover, our findings open the way for a new interpretation of hemimorphite-forming processes, and suggest the possibility that bacteria may have played a role in the formation of this mineral in ore deposits.