Pilot ion method

PUot-Ion Method. Another method, known as the quotient of two waves or pilot-ion method, is less frequently used, but offers some advantages. (This is known more generally as an internal standard method.) A known quantity of a standard pilot substance is added to each investigated solution. This pilot substance must be polarographically active and give a wave or waves in a potential region (preferably at more positive potentials) sufficiently different from that of the compound to be determined. 

To establish the well drainage boundaries and fluid flow patterns within the TFSA-waterflood pilot, an interwell chemical tracer study was conducted. Sodium thiocyanate was selected as the tracer on the basis of its low adsorption characteristics on reservoir rocks (36-38), its low and constant background concentration (0.9 mg/kg) in produced fluids and its ease and accuracy of analysis(39). On July 8, 1986, 500 lb (227 kg) of sodium thiocyanate dissolved in 500 gal (1.89 m3> of injection brine (76700 mg/kg of thiocyanate ion) were injected into Well TU-120. For the next five months, samples of produced fluids were obtained three times per week from each production well. The thiocyanate concentration in the produced brine samples were analyzed in duplicate by the standard ferric nitrate method(39) and in all cases, the precision of the thiocyanate determinations were within 0.3 mg/kg. The concentration of the ion in the produced brine returned to background levels when the sampling and analysis was concluded. 

Phase I of this project reviewed various processes to reduce, recycle and/or treat arsenic-laden wastes in a manner such that costs and disposal to the land are significantly reduced. The methods evaluated at various manufacturing stages included, buc were not limited to, separation, precipitation/fixation, ion exchange, and arsine generation. The information from Phase I was suitable for the design of a pilot scale treatment facility. 

The xanthate method has been used in the U.S. and Europe for a number of larger scale pilot plant studies. In the case of rayon, the technique has been explored for flameproofing, high water sorbency, ion exchange characteristics and bacteriostatic and fungistatic properties. Also nonwoven grafted fibers with excellent dispersibility for wet processing and improved binder affinities have been produced. It does not appear, however, that industrial exploitation of these technical successes will take place in the near future. 

Various methods for the removal of As from geothermal waste waters have been investigated at theoretical, laboratory, pilot plant and full plant scales. These include adsorption onto Fe-oxide floe and subsequent separation by dissolved air flotation (De Carlo and Thomas, 1985 Shannon et al., 1982) and co-precipitation with lime to form an As-rich calcium silicate (Rothbaum and Anderton, 1976). In both cases, effective removal was achieved only after oxidation of As" to As, For Fe-oxide floe treatment, competitive adsorption of silica inhibits As adsorption, particularly that of As" (Swedlund and Webster, 1999), suggesting that prior removal of silica would help optimise As removal efficiency. The use of ion selective chelating resins for As" removal from geothermal waters has also been successfully tried (Egawa et al, 1985). 

The applicability of the electrodialysis method was verified on a pilot scale [39]. The operating costs were found to be substantially lower than with the common process using ion-exchange and detoxification units. Considerable savings are due to the fact that almost no chemicals are consumed, and the expenses for maintenance and salaries are much lower than with the common process. 

After the first qualitative studies of lithium-, sodium-, calcium-, and silver-halides and other inorganic salts with complex anions had revealed the types of ion occurring in FD mass spectra and the high sensitivity of the method for metal cations had been demonstrated the principal question arose whether quantitative data could be obtained. If so, it was essential in the use of FDMS as an analytical technique for metals to evaluate the sensitivity, precision and accuracy for these determinations. Since pilot tests showed an extraordinary sensitivity for cesium the first approach to the quantitive determination of metals by FD was started with this alkali metal. 

Pilot plants normally are considered part of the research and development expense and usually do not represent a part of the capital of a specific plant. In some cases, especially where design letiabili is low, the pilot plant may continue to be maintained as part of the plant and us for trouble-shooting or to test proposed plant modifications. In such cases, the cost of the ot plant becomes a component of the plant capital. S ion 22.2-S discussese the need for pilot plants fw the various methods of separation. 

Purification or refining of rare earths. The separation of rare earths from thorium can be performed in different ways depending on the production scale. Small laboratory-scale methods used first the fractional crystalhzation of nitrates, followed by the fractional thermal decomposition of nitrates. Pilot-scale separation can be achieved by ion exchange. Large commercial-scale separation is based only on the solvent-extraction process of an aqueous nitrate solution with n-tributyl phosphate (TBP) dissolved in kerosene. 

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