Variscite dissolution rates in aqueous solution: does variscite control the availability of phosphate in acidic natural waters?

2008 ◽  
Vol 72 (1) ◽  
pp. 349-351 ◽  
Author(s):  
T. Roncal-Herrero ◽  
E. H. Oelkers
Keyword(s):  
Aqueous Solution ◽  
Natural Waters ◽  
Free Solution ◽  
Pore Fluids ◽  
Mixed Flow ◽  
Dissolution Rates ◽  
Near Surface ◽  
Flow Through ◽  
Solubility Products ◽  
Time Required

AbstractThe dissolution rates of natural well-crystallized variscite (AlPO4.2H2O) were measured from the evolution of aqueous Al and P concentrations in closed and mixed-flow through reactors at 25°C and from 1.5 to 9 pH. Measured dissolution rates decrease with increasing pH from 5.05x10-16 mol/cm2/s at pH = 1.51 to 4.92x10-17 mol/cm2/s at pH = 5.89 and then increase with increasing pH to 1.64x10-17 mol/cm2/s at pH = 8.99. Estimates of the time required to equilibrate a mildly acidic, initially Al- and P-free solution with variscite based on measured dissolution rates and solubility products suggests it takes no more than several weeks to equilibrate this mineral with soil pore fluids. This result suggests that variscite can buffer aqueous phosphate concentrations in a significant number of near surface environments.

scholarly journals Faecal Pellets in Deep Marine Soft Clay Crusts: Implications for Hot-Oil Pipeline Design

2011 ◽  
Author(s):  
Matthew Y-H. Kuo ◽  
Malcolm D. Bolton
Keyword(s):  
Soft Clay ◽  
Faecal Pellet ◽  
Major Constituent ◽  
Biological Origin ◽  
Near Surface ◽  
Faecal Pellets ◽  
Oil Pipeline ◽  
Average Grain Size ◽  
Time Required ◽  
Pipeline Design

In recent years, the presence of crusts within near surface sediments found in deep water locations off the west coast of Angola has been of interest to hot-oil pipeline designers. The origin for these crusts is considered to be of biological origin, based on the observation of thousands of faecal pellets in natural crust core samples. This paper presents the results of laboratory tests undertaken on natural and faecal pellet-only samples. These tests investigate the role faecal pellets play in modifying the gemechanical behaviour of clayey sediments. It is found that faecal pellets are able to significantly alter both the strength and the average grain-size of natural sediments, and therefore, influence the permeability and stiffness. Hot-oil pipelines self-embed into and subsequent shear on crusts containing faecal pellets. Being able to predict the time required for installed pipelines to consolidate the underlying sediment and thus, how soon after pipe-laying, the interface strength will develop is of great interest to pipeline designers. It is concluded from wet-sieving samples before and after oedometer tests, that the process of pipe laying is unlikely to destroy pellets. They will therefore, be a major constituent of the sediment subject to soil-pipeline shearing behaviour during axial pipe-walking and lateral buckling. Based on the presented results, a discussion highlighting the key implications for pipeline design is therefore provided.

Preparation of crosslinked chitosan magnetic membrane for cations sorption from aqueous solution

2017 ◽  
Vol 75 (9) ◽  
pp. 2034-2046 ◽  
Author(s):  
Adnan Khan ◽  
Samina Begum ◽  
Nauman Ali ◽  
Sabir Khan ◽  
Sajjad Hussain ◽  
...  
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Adsorption Capacity ◽  
Magnetic Particles ◽  
Isotherm Models ◽  
Chitosan Membrane ◽  
Dilute Aqueous Solution ◽  
Chitosan Membranes ◽  
The Fourier Transform ◽  
Time Required

A chitosan magnetic membrane was prepared in order to confer magnetic properties to the membrane, which could be used for the removal of cations from aqueous solution. The crosslinked magnetic membrane was compared with pristine chitosan membrane in term of stability, morphology and cation adsorption capacity. The fabricated magnetic materials are thermally stable as shown by thermogravimetric curves. The membrane containing nickel magnetic particles (CHNiF-G) shows high thermal stability compared to the other membranes. The Fourier transform infrared spectroscopy showed successful preparation of chitosan magnetic membrane. Scanning electron microscopy micrographs showed the rough surface of the membrane with increased porosity. The prepared chitosan membranes were applied to cations of copper, nickel and lead in dilute aqueous solution. The chitosan membrane showed the following adsorption order for metallic cations: Cu2+ > Ni2+ > Pb2+, while CHNiF-G showed higher capacity, 3.51 mmol g−1 for copper, reflecting the improvement in adsorption capacity, since the amount of copper on pristine chitosan gave 1.40 mmol g−1. The time required for adsorption to reach to the equilibrium was 6 h for the selected cations using different chitosan membranes. The kinetic study showed that adsorption followed pseudo-second order kinetics. The most commonly used isotherm models, Freundlich, Langmuir and Temkin, were applied to experimental data using linear regression technique. However, The Temkin model fits better to experimental data.

Movement of Aldolase From Excised Rat Diaphragm

1956 ◽  
Vol 185 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Kenneth L. Zierler
Keyword(s):  
Aqueous Solution ◽  
Cell Membrane ◽  
Potassium Concentration ◽  
Fiber Surface ◽  
Rat Diaphragm ◽  
High Potassium ◽  
Flow Through ◽  
High Potassium Concentration

A protein, aldolase, flows from excised rat diaphragm incubated in a variety of media. The rate of outflow of aldolase is increased by anoxia and by a high potassium concentration in the medium, and it is decreased by a reduction in temperature and by addition of glucose. When diaphragm is transferred to fresh media and reincubated the rate of outflow of aldolase is also accelerated. From measurements of rates of outflow of aldolase, estimates have been made of the area of the membrane required for aldolase to flow through the cell membrane as though it were flowing simply through an aqueous solution. This area is about 10–7–10–8 of the estimated total fiber surface. The estimated area for diffusion of aldolase is modified 16-fold by factors which alter the metabolism of diaphragm.

Performance Study of a Mixed Flow Impeller Covering an Unsteady Flow Field

1992 ◽  
Vol 206 (2) ◽  
pp. 83-93 ◽  
Author(s):  
S Sarkar
Keyword(s):  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Performance Study ◽  
Mixed Flow ◽  
Pump Impeller ◽  
Wide Range ◽  
Reversal Flow ◽  
Flow Through ◽  
Flow Pump

The results presented here are part of a detailed programme measuring the aerodynamics of a high specific speed mixed flow pump impeller over a wide range of operating conditions, including its behaviour in the unsteady stalled regime. The aim is to elucidate the physics of the flow through such an impeller. The noticeable features are the formation of part-span rotating stall cells having no periodicity and organized structure at reduced flow and also the shifting positions of reversal flow pockets as the flowrate changes. Measurements of loss and its variation with span-wise positions and flowrates enable the variation of local efficiency to be determined. The overall flow picture is similar to that expected in an axial flow impeller, though the present impeller displays a narrow stall hysteresis loop almost right through its operating range.

scholarly journals Chapter 16 Geohazards caused by gypsum and anhydrite in the UK: including dissolution, subsidence, sinkholes and heave

2020 ◽  
Vol 29 (1) ◽  
pp. 403-423 ◽  
Author(s):  
Anthony H. Cooper
Keyword(s):  
Time Scale ◽  
Geological Hazards ◽  
Dissolution Rates ◽  
Near Surface ◽  
The Uk

AbstractGypsum and anhydrite are both soluble minerals that form rocks that can dissolve at the surface and underground, producing sulphate karst and causing geological hazards, especially subsidence and sinkholes. The dissolution rates of these minerals are rapid and cavities/caves can enlarge and collapse on a human time scale. In addition, the hydration and recrystallization of anhydrite to gypsum can cause considerable expansion and pressures capable of causing uplift and heave. Sulphate-rich water associated with the deposits can react with concrete and be problematic for construction. This paper reviews the occurrence of gypsum and anhydrite in the near surface of the UK and looks at methods for mitigating, avoiding and planning for the problems associated with these rocks.

The diffusion of electrolytes in a cation-exchange resin membrane I. Theoretical

1955 ◽  
Vol 232 (1191) ◽  
pp. 498-509 ◽  
Keyword(s):  
Aqueous Solution ◽  
Activity Coefficient ◽  
Cation Exchange ◽  
Exchange Resin ◽  
Volume Fraction ◽  
Cation Exchange Resin ◽  
Physical Nature ◽  
Concentration Difference ◽  
Flow Through ◽  
Resin Membrane

An equation for the flux of electrolyte through a water-swollen cation-exchange resin membrane separating two solutions of the same electrolyte at different concentrations is derived on the basis of several assumptions regarding the physical nature of a swollen resinous exchanger. The complete flux equation contains three terms, one determined by the concentration difference across the membrane, another determined by the variation of the activity coefficient of the electrolyte with concentration in the membrane and a third concerned with the rate of osmotic or hydrostatic flow through the membrane. If ions in the resin are transported entirely in an internal aqueous phase, the mobilities required for the flux equation can be related to mobilities in aqueous solution and to the volume fraction of resin in the swollen membrane. The treatment is readily extended to anion exchangers.

scholarly journals Flow through Guide Vanes of Low Specific Speed Mixed Flow Pumps.

1993 ◽  
Vol 59 (568) ◽  
pp. 3831-3837
Author(s):  
Toshiaki Kanemoto ◽  
Hirotaka Akamatsu ◽  
Shigenori Matsunaga ◽  
Hiroshi Tsukamoto
Keyword(s):  
Mixed Flow ◽  
Guide Vanes ◽  
Flow Through ◽  
Low Specific Speed ◽  
Specific Speed

The effect of aqueous sulphate on basaltic glass dissolution rates

2008 ◽  
Vol 72 (1) ◽  
pp. 39-41 ◽  
Author(s):  
T. K. Flaathen ◽  
E. H. Oelkers ◽  
S. Gislason
Keyword(s):  
Steady State ◽  
Rate Equation ◽  
Rate Increase ◽  
Basaltic Glass ◽  
Mixed Flow ◽  
Dissolution Rates ◽  
Flow Reactors ◽  
Glass Dissolution ◽  
Sulphate Concentration

AbstractSteady-state dissolution rates of basaltic glass were measured in mixed-flow reactors at 50ºC at pH 3 and 4 as a function of aqueous sulphate concentration. Dissolution rates in the presence of 0.1 moles/kg SO42- were found to be ~3 times greater than those in corresponding SO42- free solutions. This rate increase is found to be approximately consistent with that calculated using a rate equation previously proposed by Gislason and Oelkers (2003). These results suggest that the addition of sulphate to injected CO2 may facilitate CO2 sequestration in basalts by accelerating basaltic glass dissolution rates thus more rapidly releasing aqueous Ca and Mg to solution.

Complex formation and solubility of Pu(IV) with malonic and succinic acids

2009 ◽  
Vol 97 (4-5) ◽  
Author(s):  
Takayuki Sasaki ◽  
Taishi Kobayashi ◽  
I. Takagi ◽  
Hirotake Moriyama ◽  
A. Fujiwara ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Solvent Extraction ◽  
Complex Formation ◽  
Extraction Method ◽  
Formation Constants ◽  
Complex Formation Constants ◽  
Solvent Extraction Method ◽  
Experimental Solubility Data ◽  
Experimental Solubility ◽  
Solubility Products

AbstractThe complex formation constants of tetravalent plutonium ion with malonic and succinic acids in aqueous solution were determined by the solvent-extraction method. Also, by taking the known values of the solubility products, the hydrolysis constants and the formation constants, the experimental solubility data of plutonium in the presence of carboxylates were analyzed.

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