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Decanting ALL elemental impurities from an ionic solution at 1G?
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Alan Nanders
Decanting ALL elemental impurities from an ionic solution at 1G?
To "decanting elemental particles out is a valid way to get rid of 100% of them provided that the elemental impurities are less dense than the solution," the answer is: No.
Only some particles will settle out (depending, mostly, on their size / surface to volume ratio and density).
The smaller the particles, the more unlikely they are to settle, and the more likely they are to exist as colloids in solution. Typically, elemental particles will tend to sediment when denser than the solution and bigger than ~1 mcm. (1)
As for why smaller particles are more likely to exist as colloids in solution, this had been answered, in the following terms, by Abhik Bose: Particles in colloid absorb either positive or negative ion preferentially from solution depending on their surface. This develops a potential on colloid surface called Zeta potential. Due to this potential colloid particles repel each other and can't coagulate.
Particle size also play a major role. With decreasing size surface to volume and hence surface to weigh ratio increases. So, same volume of colloid particles have higher surface area than suspension. (2)
An important factor to influence sedimentation rate seems to be the temperature at which the solution is left to decant. Sedimentation rate seems to increase exponentially with temperature up to a certain point. The trend seems to break by virtue of increased probability that said elements will react and subsequently dissolve at higher temperatures (as carbonates for instance, or oxides; which may be hindered by proper de-gasing of the solution prior to decantation, and covering with inert gas). Though not made on elemental particles but carbonates, a study on the effect of temperature on their sedimentation rate showed, for instance, a twofold increase in sedimentation rate with every ~20C increase in temperature. (3)
As for estimating sedimentation rate from solvent and particle properties, a good reference (as a rule of thumb), might be Stoke's Law:
(4)
Sources:
(1) Shaw, D J (1992). Introduction to Colloids and Surface Chemistry, 4th ed. Butterworth-Heinemann Ltd, Jordan.
To "decanting elemental particles out is a valid way to get rid of 100% of them provided that the elemental impurities are less dense than the solution," the answer is: No.Only some particles will settle out (depending, mostly, on their size / surface to volume ratio and density).
The smaller the particles, the more unlikely they are to settle, and the more likely they are to exist as colloids in solution. Typically, elemental particles will tend to sediment when denser than the solution and bigger than ~1 mcm. (1)
As for why smaller particles are more likely to exist as colloids in solution, this had been answered, in the following terms, by Abhik Bose: Particles in colloid absorb either positive or negative ion preferentially from solution depending on their surface. This develops a potential on colloid surface called Zeta potential. Due to this potential colloid particles repel each other and can't coagulate.Particle size also play a major role. With decreasing size surface to volume and hence surface to weigh ratio increases. So, same volume of colloid particles have higher surface area than suspension. (2)
An important factor to influence sedimentation rate seems to be the temperature at which the solution is left to decant. Sedimentation rate seems to increase exponentially with temperature up to a certain point. The trend seems to break by virtue of increased probability that said elements will react and subsequently dissolve at higher temperatures (as carbonates for instance, or oxides; which may be hindered by proper de-gasing of the solution prior to decantation, and covering with inert gas). Though not made on elemental particles but carbonates, a study on the effect of temperature on their sedimentation rate showed, for instance, a twofold increase in sedimentation rate with every ~20C increase in temperature. (3)
As for estimating sedimentation rate from solvent and particle properties, a good reference (as a rule of thumb), might be Stoke's Law:(4)
Sources:
(1) Shaw, D J (1992). Introduction to Colloids and Surface Chemistry, 4th ed. Butterworth-Heinemann Ltd, Jordan.
To "decanting elemental particles out is a valid way to get rid of 100% of them provided that the elemental impurities are less dense than the solution," the answer is: No. Only some particles will settle out (depending, mostly, on their size / surface to volume ratio and density).
The smaller the particles, the more unlikely they are to settle, and the more likely they are to exist as colloids in solution. Typically, elemental particles will tend to sediment when denser than the solution and bigger than ~1 mcm. (1)
As for why smaller particles are more likely to exist as colloids in solution, this had been answered, in the following terms, by Abhik Bose: Particles in colloid absorb either positive or negative ion preferentially from solution depending on their surface. This develops a potential on colloid surface called Zeta potential. Due to this potential colloid particles repel each other and can't coagulate. Particle size also play a major role. With decreasing size surface to volume and hence surface to weigh ratio increases. So, same volume of colloid particles have higher surface area than suspension. (2)
An important factor to influence sedimentation rate seems to be the temperature at which the solution is left to decant. Sedimentation rate seems to increase exponentially with temperature up to a certain point. The trend seems to break by virtue of increased probability that said elements will react and subsequently dissolve at higher temperatures (as carbonates for instance, or oxides; which may be hindered by proper de-gasing of the solution prior to decantation, and covering with inert gas). Though not made on elemental particles but carbonates, a study on the effect of temperature on their sedimentation rate showed, for instance, a twofold increase in sedimentation rate with every ~20C increase in temperature. (3)
As for estimating sedimentation rate from solvent and particle properties, a good reference (as a rule of thumb), might be Stoke's Law:
(4)
Sources:
(1) Shaw, D J (1992). Introduction to Colloids and Surface Chemistry, 4th ed. Butterworth-Heinemann Ltd, Jordan.
(2) Why don't particles of a colloid settle?
(3) Mkpenie, V (2007). Studies on the effect of temperature on the sedimentation of insoluble metal carbonates.
(4) Wikepedia Page for Stoke's Law
To "decanting elemental particles out is a valid way to get rid of 100% of them provided that the elemental impurities are less dense than the solution," the answer is: No.Only some particles will settle out (depending, mostly, on their size / surface to volume ratio and density).
The smaller the particles, the more unlikely they are to settle, and the more likely they are to exist as colloids in solution. Typically, elemental particles will tend to sediment when denser than the solution and bigger than ~1 mcm. (1)
As for why smaller particles are more likely to exist as colloids in solution, this had been answered, in the following terms, by Abhik Bose: Particles in colloid absorb either positive or negative ion preferentially from solution depending on their surface. This develops a potential on colloid surface called Zeta potential. Due to this potential colloid particles repel each other and can't coagulate.Particle size also play a major role. With decreasing size surface to volume and hence surface to weigh ratio increases. So, same volume of colloid particles have higher surface area than suspension. (2)
An important factor to influence sedimentation rate seems to be the temperature at which the solution is left to decant. Sedimentation rate seems to increase exponentially with temperature up to a certain point. The trend seems to break by virtue of increased probability that said elements will react and subsequently dissolve at higher temperatures (as carbonates for instance, or oxides; which may be hindered by proper de-gasing of the solution prior to decantation, and covering with inert gas). Though not made on elemental particles but carbonates, a study on the effect of temperature on their sedimentation rate showed, for instance, a twofold increase in sedimentation rate with every ~20C increase in temperature. (3)
As for estimating sedimentation rate from solvent and particle properties, a good reference (as a rule of thumb), might be Stoke's Law:
(4)
Sources:
(1) Shaw, D J (1992). Introduction to Colloids and Surface Chemistry, 4th ed. Butterworth-Heinemann Ltd, Jordan.
(2) Why don't particles of a colloid settle?
(3) Mkpenie, V (2007). Studies on the effect of temperature on the sedimentation of insoluble metal carbonates.
(4) Wikepedia Page for Stoke's Law
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