Brine is a high-concentration solution of salt in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% up to about 26%. Lower levels of concentration are called by different names: fresh water, brackish water, and saline water.
An ion-selective electrode (ISE), also known as a specific ion electrode (SIE), is a transducer that converts the activity of a specific ion dissolved in a solution into an electrical potential. The voltage is theoretically dependent on the logarithm of the ionic activity, according to the Nernst equation. Ion-selective electrodes are used in analytical chemistry and biochemical/biophysical research, where measurements of ionic concentration in an aqueous solution are required.
Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted mopping up calcium ions. Soft water also extends the lifetime of plumbing by reducing or eliminating scale build-up in pipes and fittings. Water softening is usually achieved using lime softening or ion-exchange resins but is increasingly being accomplished using nanofiltration or reverse osmosis membranes.
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic "ion exchangers".
Ion chromatography is a chromatography process that separates ions and polar molecules based on their affinity to the ion exchanger. It works on almost any kind of charged molecule—including large proteins, small nucleotides, and amino acids. However, ion chromatography must be done in conditions that are one unit away from the isoelectric point of a protein.
A counterion is the ion that accompanies an ionic species in order to maintain electric neutrality. In table salt (NaCl), the sodium cation is the counterion for the chlorine anion and vice versa.
Polystyrene sulfonates are polymers derived from polystyrene by the addition of sulfonate functional groups. They are widely used as ion-exchange resins to remove ions such as potassium, calcium, and sodium from solutions in technical or medical applications.
Dishwasher salt is a particular grade of granulated, crystalline sodium chloride intended for regenerating the water softener circuit of household or industrial dishwashers. Analogous to water softener salt, dishwasher salt regenerates ion exchange resins, expelling the therein trapped calcium and magnesium ions that characterize hard water. Dishwater salt granules are larger than those of table salt. The granule size ensures that the salt dissolves slowly, and that fine particles do not block the softener unit.
Synthetic resins are industrially produced resins, typically viscous substances that convert into rigid polymers by the process of curing. In order to undergo curing, resins typically contain reactive end groups, such as acrylates or epoxides. Some synthetic resins have properties similar to natural plant resins, but many do not.
Diethylaminoethyl cellulose (DEAE-C) is a positively charged resin used in ion-exchange chromatography, a type of column chromatography, for the separation and purification of proteins and nucleic acids. Gel matrix beads are derivatized with diethylaminoethanol (DEAE) and lock negatively charged proteins or nucleic acids into the matrix. The proteins are released from the resin by increasing the salt concentration of the solvent or changing the pH of the solution as to change the charge on the protein.
Chelex 100 is a chelating material from Bio-Rad used to purify other compounds via ion exchange. It is noteworthy for its ability to bind transition metal ions.
Chelating resins are a class of ion exchange resins. They are almost always used to bind cations. They utilize chelating agents covalently attached to a polymer matrix. Chelating resins have the same bead form and polymer matrix as usual ion exchangers. Their main use is for preconcentration of metal ions in a dilute solution.
The dealkalization of water refers to the removal of alkalinity ions from water. Chloride cycle anion ion exchange dealkalizers remove alkalinity from water.
Potassium binders are medications that bind potassium ions in the gastrointestinal tract, thereby preventing its intestinal absorption. They consist of polystyrene sulfonate resins attached to a cation and are administered either orally or by retention enema to patients who are at risk of developing hyperkalaemia. Increased serum potassium levels are a condition likely to occur in patients suffering from chronic kidney disease in advanced stages.
Uranyl carbonate, UO2(CO3), is a carbonate of uranium that forms the backbone of several uranyl mineral species such as andersonite, mckelveyite-(Y) and wyartite and most importantly rutherfordine. It is also found in both the mineral and organic fractions of coal and its fly ash and is the main component of uranium in mine tailing seepage water.
Electrodeionization is a water treatment technology that utilizes electricity, ion exchange membranes and resin to deionize water and separate dissolved ions (impurities) from water. It differs from other water purification technologies in that it is done without the use of chemical treatments and is usually a polishing treatment to reverse osmosis (RO). There are also EDI units that are often referred to as continuous electrodeionization (CEDI) since the electric current regenerates the resin mass continuously. CEDI technique can achieve very high purity, with conductivity below 0.1 µS/cm. Recently, Argonne National Laboratory developed a process called Resin-Wafer Electrodeionization
(RW-EDI), which uses a unique porous resin wafer mold made from immobilized loose ion-exchange resin beads. The resin wafer material enhances mass transfer between solid and liquid phases to achieve a high purity, especially when treating impaired or brackish water.
Chromatofocusing is a protein-separation technique that allows resolution of single proteins and other ampholytes from a complex mixture according to differences in their isoelectric point. Chromatofocusing utilizes ion exchange resins and is typically performed on fast protein liquid chromatography (FPLC) or similar equipment capable of producing continuous buffer gradients though this is not a requirement.
In contrast to typical ion exchange chromatography, where bound molecules are eluted from the resin by increasing the ionic strength of the buffer environment, chromatofocusing elutes bound species by altering the pH of the buffer. This changes the net surface charge of bound molecules, altering their avidity for the resin. As the changing pH of the buffer system traverses the pI of a given molecule, that molecule will elute from the resin as it will no longer possess a net surface charge.
Chromatofocusing is a powerful purification technique with respect to proteins as it can resolve very similar species only differing by 0.02 pH units that may not separate well, or at all, using traditional ion exchange strategies.
A major drawback to this technique is that some proteins will aggregate when they are present at relatively high concentrations and carry no net surface charge. This can cause blockage of the resin, which is highly problematic when using sealed columns of ion exchange resin on FPLC equipment, resulting in pressure buildup and possible equipment failure. Apparent aggregation issues can sometimes be overcome by limiting the sample concentration and use of buffer additives that deter aggregate formation.
Anion-exchange chromatography is a process that separates substances based on their charges using an ion-exchange resin containing positively charged groups, such as diethyl-aminoethyl groups (DEAE). In solution, the resin is coated with positively charged counter-ions (cations). Anion exchange resins will bind to negatively charged molecules, displacing the counter-ion. Anion exchange chromatography is commonly used to purify proteins, amino acids, sugars/carbohydrates and other acidic substances with a negative charge at higher pH levels. The tightness of the binding between the substance and the resin is based on the strength of the negative charge of the substance.
An ion-exchange membrane is a semi-permeable membrane that transports certain dissolved ions, while blocking other ions or neutral molecules.
