Cobalt-platinum units

Koyuncu et al. [56] presented pilot-scale studies on the treatment of pulp and paper mill effluents using two-stage membrane filtrations, ultrafiltration and reverse osmosis [56]. The combination of UF and RO resulted in very high removals of COD, color, and conductivity from the effluents. At the end of a single pass with seawater membrane, the initial COD, color and conductivity values were reduced to 10-20 mg/L, 0-100 PCCU (platinum cobalt color units) and 200-300 ps/cm, respectively. Nearly complete color removals were achieved in the RO experiments with seawater membranes. 

In the chemical process industries, nickel, cobalt, platinum, palladium, and mixtures containing potassium, chromium, copper, aluminum, and other metals are used in very large-scale dehydrogenation processes. For example, acetone (6 billion pounds per year) is made from isopropyl alcohol styrene (over 2 billion pounds per year) is made from ethylbenzene. The dehydrogenation of n-paraffins yields detergent alkylates and n-olefins. The catalytic use of rhenium for selective dehydrogenation has increased in recent years. Dehydrogenation is one of the most commonly practiced of ihe chemical unit processes. 

Color. Many water samples have a yellow to brownish-yeUow color which is caused by natural substances, eg, leaves, bark, humus, and peat material. Turbidity in a sample can make the measurement of color uncertain and is usually removed by centrifiigation prior to analysis. The color is usually measured by comparison of the sample with known concentrations of colored solutions. A platinum—cobalt solution is used as the standard, and the unit of color is that produced by 1 mg/L platinum as chloroplatinate ion. The standard is prepared from potassium chloroplatinate (K PtCl ) and cobalt chloride (C0CI26H2O). The sample may also be compared to suitably caUbrated special glass color disks. 

Silver-containing catalysts are used exclusively in all commercial ethylene oxide units, although the catalyst composition may vary considerably (129). Nonsdver-based catalysts such as platinum, palladium, chromium, nickel, cobalt, copper ketenide, gold, thorium, and antimony have been investigated, but are only of academic interest (98,130—135). Catalysts using any of the above metals either have very poor selectivities for ethylene oxide production at the conversion levels required for commercial operation, or combust ethylene completely at useful operating temperatures. 

Ammonia unites readily with iridium salts, giving rise to complex ammino-derivatives. The first compounds described appear to be ammines analogous to those of palladium and platinum, to which they were compared by Berzelius 8 and Skoblikoff.4 A further series were described by Claus 5 wliich he represented like those of ammino-rhodium salts, as they bore a marked resemblance to these. After Jorgensen had established the constitution of the ammines of rhodium, cobalt, and chromium salts, Palmaer gave similar constitution to the iridium compounds. 

Platinum forms both platinous and platinie salts, in which the metal is divalent and tetravalent respectively. Both series of salts are capable of uniting with ammonia, forming complex ammines. The co-ordination number in the platinous series is four and in the platinie series six. The latter series correspond in many respects to the chromic and cobaltic ammino-salts, but as the metal is tetravalent, the maximum number of radicles outside the complex is four instead of three. Also, the ammino-bases from which the salts are derived are much more stable than those of chromium or cobalt. 

Phosphorus unites with most of the metals, forming phosphides. Phosphorus is electronegative towards hydrogen, and its affinity for the metals is rather less than that of sulphur. The phosphides are made by the direct union of the two elements usually assisted by heat, and in an atmosphere of an inert gas to prevent undue oxidation. In this way, at a dull red-heat, the metals iron, nickel, cobalt, copper, manganese, palladium, platinum, and iridium united with phosphorus with incandescence and gold, silver, tin, and zinc without incandescence. Phosphides VOL. VIII. 3 B... 

Color is measured in color units and based on platinum cobalt units (PCU) for comparative purposes. Odor is measured by the threshold odor number (TON), based on the number of dilutions with odor-firee water necessary to cause the odor to be nondiscemible in warmed water under prescribed conditions. 

Readily Carbonizable Substances Determine as directed under Readily Carbonizable Substances, Appendix IIB. A mixture of 25 mL of 95% sulfuric acid (cooled to 10°) and 25 mL of sample has no more color than 3.5 mL of platinum-cobalt CS, diluted to 50 mL with water (equivalent to not more than 35 APHA color units). 

Platinum-Cobalt CS Transfer 1.246 g of potassium chlo-roplatinate (K PtClg) and 1.00 g of crystallized cobaltous chloride (CoCl2-6H20) into a 1000-mL volumetric flask, dissolve in about 200 mL of water and 100 mL of hydrochloric acid, dilute to volume with water, and mix. This solution has a color of 500 APHA units. 

Complex oxides of the perovskite structure containing rare earths like lanthanum have proved effective for oxidation of CO and hydrocarbons and for the decomposition of nitrogen oxides. These catalysts are cheaper alternatives than noble metals like platinum and rhodium which are used in automotive catalytic converters. The most effective catalysts are systems of the type Lai vSrvM03, where M = cobalt, manganese, iron, chromium, copper. Further, perovskites used as active phases in catalytic converters have to be stabilized on the rare earth containing washcoat layers. This then leads to an increase in rare earth content of a catalytic converter unit by factors up to ten compared to the three way catalyst. 

One indication of the importance of transition metals is the great concern shown by the U.S. government for continuing the supply of these elements. The United States is a net importer of more than 60 strategic and critical minerals, including cobalt, manganese, platinum, palladium, and chromium. All these metals play a vital role in the U.S. economy and defense, but about 90% of the required amounts must be imported (see Table 20.1). 

For the complexes which have been measured, the corresponding iridium (III) and platinum (IV) complexes have A values approximately double the cobalt (III) values, whereas the iron (II) species have slightly lower A values than the cobalt (III species. A Values are in kK units of 1000 cm. i, edta = ethylenedinitrilotetraacetate anion. 

Transition metals play a vital role in the economy of many countries because they have a wide variety of uses. As the uses of transition metals increase, so does the demand for these valuable materials. Ores that contain transition metals are located throughout the world, as shown in Figure 7-26. The United States now imports more than 60 materials that are classified as strategic and critical because the economy and the military are dependent on these materials. The list includes platinum, chromium, cobalt, manganese, and tungsten. 

Although there has been a great deal of research concerning how plahnum(II) complexes bind to biological molecules and the hkely mechanism of antitumor activity of these platinum-containing species, far less attention has been paid to the properties of other metal complexes in this arena. Recent attention has fallen on cobalt(II)-Schiff base complexes, as several have been discovered to have promise as antiviral agents. A review of recent work has appeared elsewhere [64], so the topic will not be covered here however, in addition to focusing on recent developments, emphasis is placed on the introduction of the new head unit, 3,6-diformylpyridazine (13), into Schiff-base macrocyclic electrochemistry. 

This hydrocarboration method is a valuable tool in industrial and laboratory synthesis, since it allows introduction of the one-carbon unit of carbon monoxide into unsaturated substrates and construction of new carbon skeletons with aldehyde functions or derivatives thereof formed by reduction, oxidation, condensation and other conversions. Hydroformylation, mainly catalyzed by cobalt, rhodium, or platinum complexes is an unsymmetrical 1,2-addition leading to linear and branched products if terminal olefins are used as the substrate. Since linear products are normally the industrial products wanted54, considerable efforts have concentrated on the control of regiochemistry. Other problems of the hydroformylation method arise from side reactions such as hydrogenation, double bond migration, and subsequent reactions of the products (e.g., condensation, reduction, dccarbonylation)54. 

BS 5339-76. Method of measurement of color in Hazen units (platinum-cobalt scale) of hquid chemical products (ISO 2211). 

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