scholarly journals Dissolution and solubility of the arsenate - phosphate hydroxylapatite solid solution [Ca5(PxAs1 - xO4)3(OH)] at 25°C

2011 ◽  
Vol 8 (2) ◽  
pp. 133 ◽  
Author(s):  
Xuehong Zhang ◽  
Yinian Zhu ◽  
Honghu Zeng ◽  
Dunqiu Wang ◽  
Jie Liu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
Steady State ◽  
Mole Fraction ◽  
Large Family ◽  
Batch Experiments ◽  
Aqueous Environments ◽  
Phosphate Species ◽  
Peak Value

Environmental contextApatites form a large family of minerals and compounds that can incorporate a variety of ions, including arsenate that can substitute for phosphate. Apatites may therefore control the concentration of arsenic in some aqueous environments. This manuscript describes the synthesis and characterisation of the arsenate–phosphate hydroxylapatite solid solution and the solid solution–aqueous solution interaction. Abstract Nine different members of the arsenate–phosphate hydroxylapatite solid solution [Ca5(PxAs1–xO4)3(OH)] were prepared and characterised by various techniques, and then dissolution of the synthetic solids was studied at 25°C and pH 2 in a series of batch experiments. The concentrations of aqueous arsenate species increased rapidly at the beginning of the dissolution and reached a steady-state after 480 h. The concentrations of aqueous phosphate species increased very fast initially and reached a peak value within the first hour of dissolution and then declined slowly with time and remained constant after 240–360 h. The solubility of the Ca5(PxAs1–xO4)3(OH) solid solution increased and its stability decreased with an increase in the mole fraction of Ca5(AsO4)3(OH). The dissolution followed or slightly overshot the Lippmann solutus curve, then approached the solutus curve. The Ca5(AsO4)3(OH)-poor solid solution was in equilibrium with the arsenate-rich aqueous solution.

The chemical stability of mimetite and distribution coefficients for pyromorphite–mimetite solid-solutions

1989 ◽  
Vol 53 (371) ◽  
pp. 363-371 ◽  
Author(s):  
Adedayo I. Inegbenebor ◽  
John H. Thomas ◽  
Peter A. Williams
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
Solid Phase ◽  
Distribution Coefficients ◽  
Solid Solution Series ◽  
Solution Series ◽  
Ph Values ◽  
Naturally Occurring ◽  
Phosphate Species ◽  
End Members

AbstractThe equilibrium solubility of mimetite has been determined in aqueous solution at 298.2K. For the reaction Pb5(ASO4)3Cl(s,mimetite)+6H+(aq)⇌5Pb2+(aq)+3H2AsO4−(aq)+Cl−(aq) at this temperature log KH+, extrapolated to zero ionic strength, is equal to −27.9(4). This value is equal, within experimental error, to that corresponding to pyromorphite, Pb5(PO4)3Cl, derived from the literature, and redetermined here under analogous conditions. Distribution coefficients in terms of both HXO42− and H2XO4−(aq) ions (X = P,As) have also been determined for solid phases of the pyromorphite-mimetite solid solution series containing from 5 to 95 mol. % mimetite. Although the two end-members are isostructural without being strictly isomorphous, the solid solution series behaves ideally over the whole compositional range; that is, the composition of the solid phase reflects the ratio of arsenate to phosphate species in aqueous solution at pH values corresponding to naturally-occurring aqueous solutions generally associated with the oxidized zones of base metal orebodies. Some relationships between mimetite and other secondary lead(II) and copper(II) arsenate minerals have been explored.

scholarly journals Dissolution and Solubility of the (BaxSr1-x)HAsO4·H2O Solid Solution in Aqueous Solution at 25°C and pH 2

2014 ◽  
Vol 2014 ◽  
pp. 1-11
Author(s):  
Xuehong Zhang ◽  
Yinian Zhu ◽  
Caichun Wei ◽  
Zongqiang Zhu ◽  
Zongning Li
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
Solubility Product ◽  
Enthalpy Of Mixing ◽  
Saturation Curve ◽  
Free Energies ◽  
Batch Experiments ◽  
Dissolution Experiment ◽  
Barium Concentration ◽  
Solubility Products

Six different members of the (BaxSr1-x)HAsO4·H2O solid solution were prepared and characterized, and then dissolution of the synthetic solids was studied at 25°C and pH 2 in a series of batch experiments for 4320 h. With the increase in the Ba/(Ba+Sr) mole fraction of the solids, the aqueous pH decreased and the aqueous barium concentration increased. The aqueous strontium and arsenic concentrations had the highest values atBa/(Ba+Sr)=0.21. The solubility products for BaHAsO4·H2O and SrHAsO4·H2O were calculated to be10-5.52and10-4.62, respectively. The corresponding free energies of formation were determined to be −1543.99±0.18 kJ/mol and −1537.94±0.02 kJ/mol. The solid solution had a minimum solubility product of10-5.61atBa/(Ba+Sr)=0.82. The Guggenheim coefficients were determined to beao=1.55anda1=-4.35. The Lippmann diagram was a typical Lippmann diagram for a nonideal solid solution with a negative enthalpy of mixing. The system shows an “alyotropic” minimum at the aqueousBa/(Ba+Sr)activity fraction of 0.87 where thesolutusandsoliduscurves meet. At the end of the dissolution experiment, the dissolution followed the saturation curve for the pure endmember BaHAsO4·H2O and approached the intersection with the minimum stoichiometric saturation curve on the Lippmann diagram.

scholarly journals Removal of Chromium from Aqueous Solution Using Modified Pomegranate Peel:Mechanistic and Thermodynamic Studies

2009 ◽  
Vol 6 (s1) ◽  
pp. S153-S158 ◽  
Author(s):  
Tariq S. Najim ◽  
Suhad A. Yassin
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Aqueous Solution ◽  
Adsorption Process ◽  
Batch Process ◽  
The Other ◽  
Water Molecules ◽  
Pomegranate Peel ◽  
Solution Interface ◽  
Adsorbent Surface

Modified pomegranate peel (MPGP) and formaldehyde modified pomegranate peel (FMPGP) were prepared and used as adsorbent for removal of Cr(VI) ions from aqueous solution using batch process. The temperature variation study of adsorption on both adsorbents revealed that the adsorption process is endothermic, from the positive values of ∆H˚. These values lie in the range of physisorption. The negative values of ∆G˚ show the adsorption is favorable and spontaneous. On the other hand, these negative values increases with increase in temperature on both adsorbents, which indicate that the adsorption is preferable at higher temperatures. ∆S˚ values showed that the process is accompanied by increase in disorder and randomness at the solid solution interface due to the reorientation of water molecules and Cr(VI) ions around the adsorbent surface. The endothermic nature of the adsorption was also confirmed from the positive values of activation energy, Ea, the low values of Ea confirm the physisorption mechanism of adsorption. The sticking probability, S*, of Cr(VI) ion on surface of both adsorbents showed that the adsorption is preferable due to low values of S*(0< S*< 1 ), but S*values are lower for FMPGP indicating that the adsorption on FMPGP is more preferable .

scholarly journals Coumarin 153 Dynamics in Ethylammonium Nitrate: The Effects of Dilution with Methanol

2021 ◽  
Vol 2 (4) ◽  
pp. 778-795
Author(s):  
Mark P. Heitz ◽  
Tyler J. Sabo ◽  
Stephanie M. Robillard
Keyword(s):  
Steady State ◽  
Mole Fraction ◽  
Marked Change ◽  
Hydrodynamic Theory ◽  
Binary Solvent ◽  
Magic Angle ◽  
Anionic Dyes ◽  
Model Framework ◽  
Coumarin 153 ◽  
Ethylammonium Nitrate

Magic angle intensity decay and dynamic fluorescence anisotropy measurements were made on the binary solvent system composed of ethylammonium nitrate ([N2,0,0,0+][NO3−], EAN) + methanol (MeOH) across the complete EAN mole fraction range (xIL = 0–1) using the neutral dipolar solute coumarin 153 (C153) at 295 K. Stokes–Einstein–Debye (SED) hydrodynamic theory was used as a model framework to assess the C153 rotational reorientation dynamics. Departure from stick SED prediction was observed (in contrast to literature reports that used cationic or anionic dyes) and indicated a significant influence of domain nanoheterogeneity on probe dynamics. Steady-state spectroscopy indicated minimal changes in spectral peak and width with mole fraction, except at xIL = 0.3 where absorption widths decreased by ~170 cm−1, signaling that C153 sensed a change in solution heterogeneity. Magic angle intensity decays corroborated the steady-state observation and the excited-state lifetimes showed a marked change from xIL = 0.2–0.4 where EAN-EAN interactions became notably more significant. C153 average rotation times (⟨τrot⟩) showed significant solvent decoupling with increased EAN. The rotational data were fit to a power law dependence, ⟨τrot⟩ ∝ (ηT)p, where p = 0.82, demonstrating the presence of dynamic heterogeneity in the EAN/MeOH solutions. With increased EAN, rotation times showed that the heterogeneity became increasingly more significant since the rotation times systematically decreased away from the hydrodynamic stick limit.

scholarly journals BIOSORPTION OF METHYLENE BLUE BY WASTE APRICOT SHELLS FROM FOOD INDUSTRY

2018 ◽  
Vol 4 (7) ◽  
Author(s):  
Tatjana Šoštarić ◽  
Marija Petrović ◽  
Jelena Milojković ◽  
Jelena Petrović ◽  
Marija Stanojević ◽  
...  
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Methylene Blue ◽  
Food Industry ◽  
Fruit Juice ◽  
Waste Waters ◽  
Batch Experiments ◽  
Biosorption Capacity ◽  
Biosorption Process ◽  
Monolayer Adsorption

In this paper, the removal of methylene blue (MB) from aqueous solution by biosorption ontoapricot shellshas been investigated through batch experiments. Apricot shells were chosen as alocally available and abundant waste from fruit juice industry. Methylene blue is common pollutantof waste waters from textile industry.The influence of initial MB concentration on biosorption process has been studied. Theexperimental data have been analysed using Langmuir and Freundlichisotherm models. TheLangmuir model better fits to experimental data, which explain monolayer adsorption. Maximumbiosorption capacity is 24,31 mg/g. A comparison of the biosorption capacity of waste apricot shellswith biosorption capacities of similar adsorbents previously investigated indicates that apricotshells could be a promising biosorbent for removal of MB from aqueous solution.

scholarly journals Synthesis Fe3O4/Talc nanocomposite by coprecipition-ultrasonication method and advances in hexavalent chromium removal from aqueous solution

2020 ◽  
Vol 38 (9-10) ◽  
pp. 483-501
Author(s):  
Nguyen Thi Huong ◽  
Nguyen Ngoc Son ◽  
Vo Hoang Phuong ◽  
Cong Tien Dung ◽  
Pham Thi Mai Huong ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Adsorption Process ◽  
Low Cost ◽  
Batch Experiments ◽  
X Ray Diffraction ◽  
Order Model ◽  
X Ray ◽  
Pseudo Second Order ◽  
Ft Ir ◽  
Langmuir And Freundlich Equations

The Fe3O4/Talc nanocomposite was synthesized by the coprecipitation-ultrasonication method. The reaction was carried out under a inert gas environment. The nanoparticles were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), fourier-transform infrared spectroscopy (FT-IR) and vibrating sample magnetometry techniques (VSM), the surface area of the nanoparticles was determined to be 77.92 m2/g by Brunauer-Emmett-Teller method (BET). The kinetic data showed that the adsorption process fitted with the pseudo-second order model. Batch experiments were carried out to determine the adsorption kinetics and mechanisms of Cr(VI) by Fe3O4/Talc nanocomposite. The adsorption process was found to be highly pH-dependent, which made the material selectively adsorb these metals from aqueous solution. The isotherms of adsorption were also studied using Langmuir and Freundlich equations in linear forms. It is found that the Langmuir equation showed better linear correlation with the experimental data than the Freundlich. The thermodynamics of Cr(VI) adsorption onto the Fe3O4/Talc nanocomposite indicated that the adsorption was exothermic. The reusability study has proven that Fe3O4/Talc nanocomposite can be employed as a low-cost and easy to separate.

Ionizing Irradiation Property of L(+)-Alpha-Phenylglycine in Acid Aqueous Solution

2011 ◽  
Vol 343-344 ◽  
pp. 469-475
Author(s):  
Wen Yan Shi ◽  
Jian Zhong Gu ◽  
Zheng Jiao ◽  
Wen Jing Wu ◽  
Gang Xu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Steady State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Transient Species ◽  
Ionizing Irradiation ◽  
Steady State Analysis ◽  
Applied Dose ◽  
Acid Aqueous Solution

(+)-alpha-phenylglycine are significant contaminants at pharmaceutical intermediates production. To study processes for the destruction of contaminant L(+)-alpha-phenylglycine in acid aqueous solution we have investigated the transient species using both laser flash photolysis. The OH· reaction with L(+)-alpha-phenylglycine process was investigated and formed polymer. Furthermore, the results of steady-state analysis suggested that L(+)-alpha-phenylglycine removal was found to be more efficient with increasing applied dose. L(+)-alpha-phenylglycine, decreased by 44.50%, using a dose of 14kGy.

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