| 1. |
- Bao, Ningzhong, et al.
(författare)
-
Thermodynamic modeling and experimental verification for ion-exchange synthesis of K2O·6TiO2 and TiO2 fibers from K2O·4TiO2
- 2002
-
Ingår i: Fluid Phase Equilibria. - 0378-3812 .- 1879-0224. ; 193, s. 229-243
-
Tidskriftsartikel (refereegranskat)abstract
- A thermodynamic model was established to determine ion-exchange conditions for the synthesis of potassium hexatitanate (K2O·6TiO2) and titanium dioxide (TiO2) from potassium tetratitanate (K2O·4TiO2) fiber. In the proposed model equilibrium species in the solid phase and corresponding ion-exchange equilibrium constants at 298.15 K were determined from the experimental data of Sasaki et al. [Inorg. Chem. 24 (1985) 2265]. In order to verify the proposed model, prediction results were compared with experimental data determined in literature and those measured in this work. The comparison shows a good agreement. Based on this, the proposed model was also used to predict more extensive suitable conditions for the synthesis of K2O·6TiO2 and TiO2.
|
|
| 2. |
- He, Ming, et al.
(författare)
-
A controllable approach for the synthesis of titanate derivatives of potassium tetratitanate fiber
- 2004
-
Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 39, s. 3745-3750
-
Tidskriftsartikel (refereegranskat)abstract
- Three types titanate derivatives, K2Ti6O13 fiber, K2Ti8O17 fiber and anatase TiO2 fiber, were synthesized by ion-exchange reaction from potassium tetratitanate fiber (K2Ti4O9) based on the hydrate conditions predicted by a thermodynamic model. These products were formed by a heat treatment of the corresponding hydrate intermediates K1.33H0.67Ti4O9·H2O, KHTi4O9·0.5H2O and H2Ti4O9·1.2H2O which were quantitatively obtained by controlling the pH value and the equilibrium concentration of potassium ion. The mole ratio of Ti/K in solid phase (R) of the target products was taken as the controlling aim in the hydrate process. The temperature for heat treatment of hydrate intermediates was determined by thermogravimetry (TG) and differential scanning calorimetry (DSC). All products retained fibrous morphology similar to that of K2Ti4O9 used as the starting material.
|
|
| 3. |
|
|
| 4. |
- Ji, Xiaoyan, et al.
(författare)
-
A generalized method for the solid-liquid equilibrium stage and its application in process simulation
- 2002
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 41, s. 2040-2046
-
Tidskriftsartikel (refereegranskat)abstract
- For the important need of simulations of the crystallization process in aqueous electrolyte solutions, a generalized method is proposed in this paper for predicting the solid-liquid equilibrium stage by identifying the number of phases and their identities automatically. The proposed method is also used to generate phase diagrams and crystallization paths and to provide an example of the software that can be used to design, simulate, and optimize the related process. Several cases are studied to demonstrate the capability of the proposed method for systems with hydrate, multi-ion, and complex salts.
|
|
| 5. |
- Ji, Xiaoyan, et al.
(författare)
-
Activity coefficients of HCl in the HCl + NH4Cl + H2O systems at 298.15 and 313.15 K
- 2000
-
Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 45:1, s. 29-33
-
Tidskriftsartikel (refereegranskat)abstract
- Using the ion-selective electrode method with a concentrated electrolyte solution added continuously, the mean activity coefficients of HCl in the HCl + NH4Cl + H2O system were experimentally measured at 298.15 and 313.15 K and at five molality fractions of NH4Cl (y2 = mNH4Cl/(mHCl + mNH4Cl) from 0.1 to 0.9. The measurements were made by an electrochemical cell using a H glass ion-selective electrode and a chloride solid-state ion-selective electrode. It was found that the influence of NH4+ on the H glass ion-selective electrode could be neglected up to 1.3 molkg-1, and this pair of ion-selective electrodes was suitable for determining the activity coefficients of HCl in the system. A new set of Pitzer mixing parameters, correlated from the experimental results, was used to calculate the activity coefficients for HCl in the system from 293.15 to 313.15 K up to 3.0 molkg-1.
|
|
| 6. |
- Ji, Xiaoyan, et al.
(författare)
-
Determination of dissolution kinetics of K2SO4 crystal with ion selective electrode
- 2001
-
Ingår i: Chemical Engineering Science. - 0009-2509 .- 1873-4405. ; 56, s. 7017-7024
-
Tidskriftsartikel (refereegranskat)abstract
- The dissolution kinetics of potassium sulfate crystals was studied and the effects of hydrodynamic situation and temperature on the dissolution were investigated. The dissolution was determined by measuring the change of electromotive force (E) with the potassium ion selective electrode. From the values of E, the concentration of K+ was calculated combined with an activity coefficient model. The results are accurate and rapid, the maximum deviation is less than 2%. Theory, developed for constant bulk concentration in a rotating disk system, was modified in order to analyze the general grain dissolution process. Normal distribution was introduced in calculating the area of crystals in order to obtain reliable dissolution rate. Using the modified theory diffusion rate constant, equilibrium exchange rate constant and thickness of diffusion layer were obtained. It is found that the diffusion rate constants increase while the thickness of diffusion layer decreases with the increase of temperature and stirring speed; the equilibrium exchange rate is dependent on bulk concentration.
|
|
| 7. |
- Ji, Xiaoyan, et al.
(författare)
-
Determination of the activity coefficients of NaCl in the system NaCl-NH4Cl-H2O
- 2001
-
Ingår i: Journal of Solution Chemistry. - 0095-9782 .- 1572-8927. ; 30, s. 463-473
-
Tidskriftsartikel (refereegranskat)abstract
- Using ion-selective electrode(s) (ISE) the activity coefficients of NaCl in the system NaCl-NH4Cl-H2O at 10, 25, and 40°C were measured by a computer-controlled automatic titration system. The ionic strength fractions of NH4Cl were 0.2, 0.4, 0.6, and 0.8, respectively. It was found that the influence of the NH4+ cation on the Na glass ISE was small enough to be neglected up to 3.0 mol-kg-1. The Pitzer equation was adopted to calculate the activity coefficients of NaCl in this system and compared with the experimental data. Comparison of results indicates that the Pitzer parameters correlated from solubility data are suitable for calculating the activity coefficients for this system within the saturated solutions.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Ji, Xiaoyan, et al.
(författare)
-
Mean activity coefficients of NaCl in (sodium chloride + sodium bicarbonate + water) fromT = (293.15 to 308.15) K
- 2001
-
Ingår i: Journal of Chemical Thermodynamics. - : Elsevier BV. - 0021-9614 .- 1096-3626. ; 33, s. 1107-1119
-
Tidskriftsartikel (refereegranskat)abstract
- The mean activity coefficients of NaCl in (sodium chloride + sodium bicarbonate + water) were determined experimentally in the temperature range 293.15 K to 308.15 K at four NaHCO3 molality fractions (0.1, 0.3, 0.5, and 0.7). The measurements were made with an electrochemical cell, using a Na+ glass ion-selective electrode and a Cl- solid-state ion-selective electrode. The experimental values reported by Butler and Huston are found to be higher than those calculated from the Pitzer equation using the existing parameters while the experimental results of this work are close to the calculated values, up to an NaHCO3 molality fraction of 0.5. At the NaHCO3 molality fraction of 0.7, the experimental data are much lower than the calculated values, implying that the interference of HCO3- on the Na+ glass ion-selective electrode can only be neglected up to a molality fraction of NaHCO3 of 0.5, an observation which is consistent with that of Butler and Huston.
|
|
