Selective separation of rare earth elements by ion exchange in an iminodiacetic resin
A method is disclosed to separate the heavy rare earth elements Lu through Sm plus Y by an ion-exchange process called selective elution. Mixed rare earths are saturated onto a loading column containing sulfonic resin. Iminodiacetic resin in a separation column is conditioned into the hydrogen and ammonium form before it is saturated with rare earth retaining ion. The rare-earth retaining ion has an atomic weight at least as heavy as the heaviest rare earth element being separated. The hydrogen form section is positioned down stream of the ammonium form resin. Chelating solutions like ammonium EDTA are put through the loading and then the separation column to separate the rare earth elements. The hydrogen form iminodiacetic resin is very selective for separating rare earth elements. By using an ammonium EDTA solution with pH 8.2 to 8.6, the iminodiacetic resin in separation column is returned to the proper ratio of ammonium and hydrogen form resin. The process uses a solution velocity of 1-10 cm/min through the columns. The separation column contains about half as many moles of retaining ion as the loading column contains mixed rare earth. EDTA solution containing impure rare earth from previous runs is recycled and increases rare earth recovery. These aspects singularly and in combination are an improvement over prior art.
US Patent 6093376 Selective removal of phosphates and chromates from contaminated water by ion exchange
Phosphates and chromates are selectively removed from contaminated water by a new class of sorbent, referred to as a Polymeric Ligand Exchanger (PLE). The exchanger bed comprising a styrene-divinylbenzene or polymethacrylate matrix having an electrically neutral chelating functional group with nitrogen or oxygen donor atoms, and a Lewis-acid type metal cation, such as copper, bonded to the chelating functional group in a manner that the positive charges of the metal cation are not neutralized. PLEs are very selective toward phosphates and chromates, chemically stable, and also amenable to efficient regeneration.
United States Patent 6136199 Ion-exchange supports for facilitated transport membranes with enhanced selectivity
This invention relates to a method for effectively separating an unsaturated hydrocarbon from a feedstock containing at least two similar unsaturated hydrocarbons comprising passing the feedstock over one side of an ionopore membrane charged with a facilitator having an affinity for each of the at least two similar unsaturated hydrocarbons and recovering from a second side of the membrane permeate containing predominantly one of the at least two similar unsaturated hydrocarbons, the similar unsaturated hydrocarbons being selected from the group consisting essentially of aromatic, alkene, and diene hydrocarbons.This invention further relates to a method for achieving liquid phase separation of at least two competing components from a feedstock containing the components such that the separation factor for the competing components is at least about 4 times the separation factor calculated when permeating single components using the same membrane and under the same conditions.
United States Patent 5498823 Thermally-driven ion-exchange process for lithium recovery
Ions (e.g. lithium) can be removed or recovered from brines containing those ions and optionally one or more other ions (e.g. other alkali metal ions) by the use of a temperature-swing, ion-exchange process and apparatus employing an ion-exchange material. The process and apparatus depends on a change in the selectivity coefficient of an ion exchange material for the ions desired to be recovered with a change in temperature, resulting in desirable ions being relatively selectively released at one temperature and undesirable ions being relatively selectively released at another temperature. The process of the invention can be used to effect the separation of any ion (or set of ions) from another ion or from a set of ions wherein the selectivity coefficient for one ion (or set of ions) has a substantial temperature dependence, compared to that for the other ion (or set of ions).
Patent number: 5833844 High-purity water producing apparatus utilizing boron-selective ion exchange resin
A high-purity water producing apparatus has an excellent effect of environmental protection and is also capable of effectively removing boron. It comprises a pretreatment unit, and a double pass RO unit an EDI unit or a distillation unit or any combination thereof as principal deionization unit(s) but does not comprise any chemical-regeneration type ion exchanger. It further comprises a boron removing unit and the water treated by the principal deionization unit(s) is brought into contact with a boron-selective ion exchange resin.
United States Patent 5833846 Process for selective removal and recovery of cyanide values by ion exchange
This invention relates to the purification of industrial effluents containing cyanide ions, and cyanide precursors like acetone-cyanohydrin. More particularly, the invention relates to the purification of such effluents by utilizing a complexing compound followed by treatment with an anion exchange resin and optionally cation exchange resin to remove the cyanide complexes. The cyanide values are recovered from the resin by acid regeneration.
Patent number: 3984314 Decontamination of water using nitrate selective ion exchange resin
A method for nitrate decontamination of water which involves passing the water through a bed of alkyl phosphonium anion exchange resin which has pendant alkyl groups of C.sub.3 or larger.
Patent number: 4944878 Selective ion exchange resins with pyridyl-imidazolyl chelating functional groups
An ion exchange resin having functional groups of the formula :- ##STR1## wherein :- A and B, independently of each other, represent groups forming together with the attached carbon and nitrogen atoms, an optionally substituted five or six membered heterocyclic ring which may embody a further heteroatom and wherein at least one of such heterocyclic rings is an aromatic ring; R* may be totally absent or it may represent an optionally substituted alkyl radical and Z represents a resin to which the functional groups are attached.
United States Patent 4202944 Selective imidazole ion exchange resins
A polymeric ion exchange resin of the cross-linked type in which the active groups may be constituted either wholly or in part by an imidazole group which is, in turn, attached directly to a cross-linked, polymerized vinyl backbone. The optional substituents on the imidazole ring include optionally substituted pyridyl, imidazolyl or amino groups which can be substantially known type. A method of preparation of such resins includes the provision of at least the imidazole ring on the vinyl monomer before polymerization thereof. The active groups may be added or modified after polymerization with a cross-linking agent.
Patent number: 4401629 Nitrate selective amidine ion exchange resins
Water swellable ion exchange resins comprising a polymeric matrix and amidine groups are described together with their synthesis. The preferred amidine groups are nitrate selective and methods of selectively removing nitrate from water are also described.
Patent number: 4134861
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