Platinum Metals Review - Volume 49, Issue 2, 2005

The function of stirring in glass making is to create uniform, homogeneous glass. Stirring equipment operates at high temperatures and under high mechanical stresses, so stirring devices have to be robust and often involve large amounts of platinum or platinum alloys. The stirrers, stirrer bars, blenders, homogenisers, screw plungers and plunging stirrers currently used are generally effective in operation, reliable and with predictable lifetimes. Thus there has been no incentive to improve the technology, and stirrer designs have changed little in the last twenty or thirty years. However, the current economic climate in the glass industry demands lower costs, improved operational efficiency, and reduced platinum inventories – glass making uses large quantities of platinum, with stirring devices taking a large part of it. To help reduce these amounts work has been undertaken on stirrer technology. and recent developments have resulted in lower platinum requirements (in some cases by over 90 per cent) without jeopardising stirring effectiveness or stirrer longevity. Different types of glass stirrers are examined here and a new concept in stirrer design, a ‘diffusion choke’, is described.

Iridium/carbon (Ir/C) films were prepared by MOCVD using iridium acetylacetonate as the precursor and some electrochemical properties were studied, in particular the effects of oxygen on the carbon content of the Ir/C films. Small additions of oxygen (4 ml min^–1) to the source gas drastically decrease the carbon content of the films. Ir grains are formed, up to ~ 3 nm in diameter, in the amorphous carbon. It was found that Ir/C films with higher carbon content have better catalytic performance – for measuring the oxygen concentration – than Ir/C films with lower carbon content. The Ir/C films were used as electrodes in an oxygen concentration cell, and the sensitivity of the cell to oxygen was recorded. The Nernstian electromotive force of the cell is almost the same as that of a similar type of commercial oxygen concentration sensor from Bosch, but the response time is faster.

Amounts of fission-generated platinoids, as recovered from high-level liquid radioactive wastes, could considerably supplement amounts of metals claimed from natural sources. Of particular interest are fission palladium and rhodium, which can be decontaminated from other fission products to a non-hazardous level. What remains is intrinsic radioactivity which is weak in fission palladium, and which in fission rhodium decays to an acceptable level after 30 years. The intrinsic radioactivity should not play a negative role when fission platinoids are applied to nuclear technology. Some non-nuclear applications of fission platinoids may be possible, if irradiation and contamination of personnel as well as uncontrolled release of the platinoids, are avoided.

The catalytic wet oxidation process (CWOP) is a promising technique for the treatment of highly concentrated organic wastewater that is difficult to degrade biochemically. This technique is based on the wet air oxidation (WAO) method of treating industrial effluent – in use for many years. WAO is a thermal liquid-phase process whereby organic substances in highly concentrated wastewater are oxidised by air at high temperatures and pressures, for long periods of time. Removal of ammonic nitrogen and cyanide is, however, difficult. The CWOP aims to improve on the disadvantages of the WAO method. Tests were conducted to find the best catalysts. Catalyst CWO-11 reduced the severity of the reaction required and improved the chemical oxygen demand and the total nitrogen conversion of organic wastewater.