It is used in industrial process to remove arsenic from copper solutions. It is proposed as a suitable extractant for zinc from acid solution.
Ion Exchange Materials: Properties and Applications - eBook - aginanglobal.ga
As a general rule, the extractive power of phosphorous containing extractants increases with an increase in the number of carbon-phosphorous bonds over the series, phosphate- phosphonate-phosphine oxide. This is as a result of the increasingly polar nature of the phosphonyl group. It should be noted that in acid solutions these extractants have low solubility, but as the pH increases, so solubility increases. Dialkyl phosphorodithioioic acids, phosphonates, dialkylthiophosphate, sulphur-containing methyl phosphonates and ketophosphonates and the trialkyl thiophosphates have been shown to be highly selective for gold, silver and mercury.
The semipolar sulphur atom is the sole structural difference between the two types. Handley and Dean proposed that the trialkyl thiophosphates probably act by solvating an electrically neutral ion association complex. The semipolar sulphur atom has very little electron donating ability, and will bond only to ions of high field strength. Silver and mercury fit this criteria and also are amongst those metals which prefer sulphur- containing ligands.
Extraction of cadmium, zinc, and mercury have been demonstrated to be possible with thiophosphorus compounds containing a P-SH group. It has been reported that mercury and gold III chloride are extracted from hydrochloric acid solutions with triisobutylphosphine sulphide Cyanex 47 IX. This extractant is particularly selective for silver and for the separation of palladium and platinum.
In extraction of metal ions from acidic media generally two molecules of TBP are involved in the extracted species. Furthermore, as the acid concentration increases so extraction of metal increases until a maximum is reached above which extraction decreases. DBBP has a high selectivity and loading capacity for zinc in chloride solutions resulting from ferric chloride leaching of a complex sulphide ore.
Extraction was found to be independent of pH. He reported that two moles of DBBP react with one mole of zinc.
As a solvating extractant, extraction occurs as the extractant molecules replace water molecules in the primary hydration sheath of the extracted species. From the determination of free activities of water and free chloride ions it was shown that four water molecules and two chloride ions are involved for each extracted zinc species.
The extraction reaction may be written as follows:. DBBP may form dimers at concentrations higher than 3. At concentrations higher than 3. Industrial applications of ion exchange resins are many, particularly in the treatment of boiler feedwater. Patent 4,, which is incorporated here by reference, describes the application of ion exchange resins to recover copper from dilute solutions emanating from vat leaching of copper ores. This patent describes the beneficial effect of recovery from solutions containing significant levels of dissolved silica.
This patent describes ion exchange resins in bead form, including polyurethane foams and porous beads impregnated with conventional organic solvent extraction agents to produce materials which may be employed as ion exchange beads in this application. Other methods for the preparation or application of these polymers are typically describes in US Patent Numbers 3,,; 3,,; 3,,; 3,,; 3,,; 3,, 3,,; 4,,; 4,,; 4,,; 4,,; 4,,; 4,,; 4,, 4,,; 4,,; 4,,; 4,,; 4,,; 4,,; 4,,; 4,, 4,,; 4,,; 4,,; 4,,; 4,,; 5,,; 5,,; 5,, and 5,,, incorporated herein by reference.
Ion Exchange Technology I
The procedure for the manufacture of the prepolymers described in the above patents is either given within the description, or can be produced according to typical procedures as described in various publications relating to polyurethane chemistry, or as disclosed in US Patent Nos. Advantageously the ability to incorporate large volumes of water into the formulation provides an opportunity to incorporate water-based polymer emulsions directly into the polymer. This cannot generally be achieved by the application of conventional polyurethane foams.
Water- based polymers eliminate the requirement for solvents in the polymer preparation and therefore eliminate the need to remove and capture environmentally undesirable solvents. Typically, such emulsions may be water-based emulsion resulting from the reaction of vinylidene diphosphonic acid with polyvinylpyridine.
Such a product, when incorporated into the superhydrophilic polyurethane foam, any offer exceptional selectivity for FE III in the presence of Cu II in acid solutions commonly encountered in copper electrowinning tankhouse bleed streams. The present invention will now be further described by the following non-limiting examples.
A hydrophilic prepolymer "Prepolymer" was prepared by reacting together a MW poly oxyethylene glycol with toluene diisocyanate to produce an isocyanate-terminated prepolymer and then adjusted by the addition of MDI to produce a finished product with a free NCO content of 9. The ingredients were thoroughly mixed together and then poured into a second container containing 50 grams of the following mixture:.
The mixture was allowed to rise to form a foam. Pieces were then cut from this foam for metal ion loading. Alternatively, the mixture was allowed to react and cure between two sheets of waxed paper and constrained in such a manner that a sheet of about 5 mm in thickness was obtained. This sheet was cut to size.
The polymer produced was used to remove gold cyanide and copper apinade from aqueous solutions and slurries. In the examples in which a liquid organic extract was used, the following procedure was adopted:. Once the extractant was fully imbibed into the resin, the PEG was added and stirring continued.
A dry powder was obtained. Isonate L 5g The mixture was allowed to rise to form a foam.
- Ion Exchange Technology I?
- 1. Introduction.
- ISBN 10: 0080445527!
At the specified time intervals, samples of the aqueous solution were withdrawn and analysed by AAS technique. The results obtained are given in Figure 1. The experiments conducted in Example 4 were repeated but in this case, the gold cyanide was replaced with 5 ppm of copper as copper cyanide.
The results obtained are give in Figure 2. Once the extractant was fully imbibed into the resin, a dry powder was obtained. The LIX syperhydrophilic foams prepared as described in Examples 2, 6 and 7 were compared with equivalent weights of commercially available copper-selective ion exchange resins as follows: A feed solution containing 77 ppm copper, ppm iron as Fe III at pH 2 was contacted with each of the polymers, the experiments being conducted at room temperature.
The results given in Examples 1, 3, 4 and 8 indicate that on a ligand functional basis, the superhydrophilic foams show faster loading kinetics and improved loading when compared with the unmodified and commercially available ion exchange resins. The results given in Examples 2, 6, 7 and 8 clearly show that the amidoxime-based LIX superhydrophilic polymers showed significantly better loading of copper and exceptional rejection of iron.
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