Mercury-free cells

Amalgamated zinc powder has been used as the negative material to prevent zinc corrosion and zinc passivation. Recently, from the viewpoint of environmental problems, mercury-free alkaline-manganese batteries were developed by using zinc powder with indium, bismuth and other additives [2-4]. Adding indium to zinc powder is the most effective way to improve the characteristics of the cells [3]. Figure 3 shows the variation in the internal impedance of the cells according to the additive content of the zinc powder. 

Some battery-producing companies prefer purchasing pure, nonamalgamated zinc powder to apply their own proprietary corrosion protection system. The general trend is to keep the anodes of all the consumer cells mercury-free (usually indicated by a "green label) and to make them disposable with the regular household trash. The exceptions to this rule are those cells where this makes no sense, such as cells with a mercuric oxide cathode. 

Malvern Sysmex CDA 500 employs a mercury-free vacuum pump and is designed for counting and sizing cells and particles in the size range 1 pm to 60 pm. 

Since the synthetic membrane of membrane cells replaces the older asbestos fiber diaphragm cells, no control precautions are necessary. Graphite (or later, titanium) cathodes avoid the use of mercury eliminating the need for mercury control. However, if membrane cells are operated on the same site as mercury cells, they do require a separate brine circuit from the mercury cells to maintain their mercury-free status. 

Cyclohexane and benzene (Fisher spectranalyzed grade) and nitrous oxide and sulfur hexafluoride (Matheson) were used as supplied. The samples were thoroughly freed from dissolved air and frozen into the cells on a grease and mercury-free vacuum line. Hydrogen and nitrogen were measured using conventional vacuum line techniques and a mass spectrometer. Cyclohexene and bicyclohexyl were determined by gas liquid chromatography (16). 

VOLATILIZATION OF MERCURY IN FLUIDIZED BED REACTOR USING IMMOBILIZED AND FREE CELLS... 

Klebsiella pneumoniae was entrapped on both alginate and polyacrylamide gels and physically adsorbed on vermiculite and particles wood. The concentrations of mercury were measured in both mercurial and oxidizing solutions according times for all immobilized Klebsiella pneumoniae, as well as for free cells. 

Accurate sorting relies on the identification of a number of different properties of a battery. These include the physical size and shape, the weight, the electromagnet properties and any surface identifiers such as colour or unique markings. These properties can be analysed in a number of different combinations in order to sort batteries into nickel cadmium, nickel metal hydride, lithium, lead acid, mercuric oxide, alkaline and zinc carbon batteries. Due to an voluntary marking initiative introduced by the european battery industry, it is now also possible to separate the alkaline and zinc carbon cells further into mercury free and mercury containing streams. 

Mercury-free cylindrical alkaline Mn02-Zn primary cells are produced in a pilot production [25]. In Figure 8 a discharge comparison between cells containing 250 ppm Hg and 0 ppm Hg is shown. In all important modes of discharge the curves are very similar and the cells exhibit good gassing properties and load capabilities. 

The best developed types of RAM cells are cylindrical cells using sleeve electrode construction, which are simply discribed as cylindrical cells. They are produced in AA, C and D size types with a typical trend to small sizes. In the Figures 15 and 16 of chapter 3.1. the design changes of the different cell sizes are shown. The principal construction of the cylindrical RAM cell is identical with the equivalent PAM cell design consisting of the same cell components. Differencies between these systems exist mainly in the capacity limitation of the anode to approximatly 1/3 of the cathode capacity, the application of improved separators and better anode and cathode formulations as already mentioned in the above citied chapter. A lot of experimental data exist for low-mercury (0.025 wt % Hg) as well as for mercury-free (0 % Hg) RAM cells. They are summarized in Chapter 3.6.. 

Electrical performance of Mercury-Free and Low-Mercury AA RAM cells (service hours)... 

The development of new products with less or without dangerous substances must be a future goal of priority to avoid hazards to the environment. Good examples are lithium primary and secondary cells and the mercury-free rechargeable alkaline manganese dioxide cell, which is produced at a pilot plant in Canada [57]. But also the nickel-metalhydride cell will be a favourite to supplement and partly substitute nickel-cadmium cells. 

As discussed above, for the measurement of atomic absorbance free ground-state atoms must be present in the sample cell. With the exception of mercury, free atoms do not exist in a stable form at room temperature. The atomizer is the place where free atoms of the analyte are created. The number of free atoms depends on the dynamic equilibrium between the number created and the number lost, e.g., by compound formation and ionization. The bond dissociation energy of the corresponding monoxide Dq and the first ionization energy i (shown in Table 1) are among the factors affecting this equilibrium. 

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