Phase Interactions--Definitions
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- bacterial floc
- Aggregated bacterial particles--these flocs remove a substantial portion of the organic
carbon from wastewater
- bridging compounds
- Compounds which bridge between two colloidal particles, binding them together in a
larger mass, a floc
- cation exchange capacity (CEC)
- The quantity of cationic material which can be sorbed by a given quantity of
solid. It is generally expressed in milliequivalents per 100 g of solid. This varies with
pH and salt concentration.
- coagulation
- Coalescence of colloidal particles, brought about by the reduction of the surface
charges on the particles, thus overcoming the interparticle repulsion
- colloidal surface charge
- Colloids will collect ions on their surfaces, leading to a charged double layer. For
instance, in an acid solution, an oxide particle will sorb H+ ions, and have a positive
charge. At high pH, H+ ions are lost, and a negatively charged colloid results. The point
at which the charge changes from positive to negative, is the zero point of charge.
- double layer
- A colloidal particles generally has a surface charge which attracts a second layer of
ions of opposite charge, producing a charged surface. This electrical double layer
prevents particles from adhering to each other until it is disrupted.
- double layer compression
- Ions in the solution neutralize the surface double layer and allow the particles to
adhere to each other. This is a particularly important mechanism for the production of
river deltas. Colloidal particles travel down the river, and are coagulated and deposited
on contact with seawater.
- exchangeable cations
- Cations which can be exchanged between a solid surface and the surrounding solution.
- flocculation
- Coalescence of colloidal particles by bridging compounds which join the particles
together.
- Henry's law
- The solubility of a gas in a liquid can be calculated by Henry's law which states that
the solubility of the gas is proportional to the partial pressure of the gas in contact
with the liquid.
- Henry's law constant
- The constant in Henry's law which depends on the solvent, the gas being dissolved and
the temperature.
- hydrophobic colloid
- A colloid which does not interact strongly with water, and which is stabilized by
formation of an ionic double layer
- hydrophyllic colloid
- A colloid, usually a macromolecule, which interacts strongly with water and is less apt
to coagulate when salts are added to the solution. Proteins and some synthetic polymers
form hydrophobic colloids.
- hydrous mica
- A clay mineral of the formula KAl2(OH)2(AlSi3)O10
- interstitial gases
- Gases dissolved in pore water. The pore gases are usually different from the gases
dissolved in the overlying water.
- interstitial water or pore water
- This is the water which exists between the particles of sediments
- kaolinite
- A clay mineral of the formula Al2(OH)4Si2O5
- micelle
- A colloidal particle composed of a group of surfactant molecules. In water the inside of
the micelle holds the hydrophobic, oily ends of the molecules, while the outer surface is
covered with the hydrophyllic groups at the other ends of the molecules. Micelles enable
the solublization of hydrophobic compounds in water.
- montmorillonite
- A clay mineral of the formula Al2(OH)2Si4O10
- nontronite
- A clay mineral of the formula Fe2(OH)2Si4O10
- polyelectrolyte
- A high molecular weight polymeric molecule with ionizable functional groups, which can
act as a bridging compound and cause flocculation. Often these have anionic functional
groups, and negatively charged colloids can be joined by bridging through metal
ions.
- sediment
- Soild particles which have settled out of suspension in water
- sedimentary rock
- Rock formed from the coagulation and precipitation of colloidal particles and dissolved
minerals from water
- solubility product
- The equilibrium constant for the solution process, solid -> ions
- zero point of charge (ZPC)
- Condition of pH where the colloidal particles have a neutral surface charge and can
readily coagulate.
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