Zinc Resistance

Table 6-2. Enzymes of the intermediary metabolism induced after application of toxic concentrations of metals. Most of the experiments were performed on Phaseolus vulgaris cultivars, except those who are specially marked, which were performed on Glycine max (1) and on a zinc resistant (2) and a zinc sensitive (3) clone of Silene cucubalus (after Van Assche and Clijsters, 1990b, adapted).

Brasses Extreme sensitivity to SCC brasses containing <15% zinc resistant to SCC SCC increases with Zn content up to 40%... 

Mathys, W., 1977, The role of malate, oxalate, and mustard oil glucosides in the evolution of zinc-resistance in herbage plants, Physiol. Plant. 40 130-136. 

Blue-green algae are among the most zinc-resistant aquatic plants. Algae are classified as very resistant (can tolerate >10.0 mg Zn/L), resistant (2.0-0.0 mg/L), moderately resistant (0.5-2.0mg/L), low resistance (0.lA).5 mg/L Navicula, Synedra), and very low resistance (<0.1mg Zn/L Diatoma, Tabellaria, Microspora, Ulothrix). 

The Blue Ridge Mountain next to Palmerton, Pennsylvania, was decimated by SO2 pollution from the zinc refinery located there. The roasting of the ZnS ore to produce ZnO (used to produce Zn metal] also made SO2 most of which was captured to generate sulfuric acid. But cumulative SO2 releases over many years killed most of the vegetation on the mountain next to the refinery. The refinery is now shut down, and the Environmental Protection Agency (EPA) is doing extensive remediation of the mountain with acid- and zinc-resistant plants. 

Collard J-M, Provoost A, Taghavi S, Mergeay M (1993) A new type of Alcaligenes eutrophus CH34 zinc resistance generated by mutations affecting regulation of the cnr cobalt-nickel resistance system. J Bacteriol 175 779-784... 

The mechanisms of cadmium, cobalt, and zinc resistance were characterized in Gluconacetobacter diazotrophicus PAL5 by Intome et al. (2012). They found that this bacterium was resistant to high concentrations of Cd, Co, and Zn, with minimum inhibitory concentrations of 1.2,20, and 20 mM, respectively. Therefore, they provided evidence for the high tolerance of Ga. diazotrophicus PAL5 to heavy metals and that the czc gene (which encodes a protein involved in metal efflux) is a determinant for metal resistance in this bacterium. 

For example,copper has relatively good corrosion resistance under non-oxidizing conditions. It can be alloyed with zinc to yield a stronger material (brass), but with lowered corrosion resistance. Flowever, by alloying copper with a passivating metal such as nickel, both mechanical and corrosion properties are improved. Another important alloy is steel, which is an alloy between iron (>50%) and other alloying elements such as carbon. 

The formation of silicon carbide, SiC (carborundum), is prevented by the addition of a little iron as much of the silicon is added to steel to increase its resistance to attack by acids, the presence of a trace of iron does not matter. (Addition of silicon to bronze is found to increase both the strength and the hardness of the bronze.) Silicon is also manufactured by the reaction between silicon tetrachloride and zinc at 1300 K and by the reduction of trichlorosilane with hydrogen. 

It catalyses the decomposition of potassium chlorate(V). Mixed with zinc oxide, it is used as a catalyst in the manufacture of methanol. It is used as a pigment, being very resistant to weathering. 

Because of its resistance to corrosion, zinc may be used to coat iron. This may be done by dipping the iron into molten zinc or by spraying zinc on the iron articles, for example iron sheets. This is known as galvanising. Smaller iron articles may be coated by heating with zinc dust, a process known as sherardising, or suspensions of zinc may be used in paints. 

It is used as a protective agent, particularly for iron, and is more resistant to corrosion by sea water than, for example, zinc or nickel. 

Reactor-grade zirconium is essentially free of hafnium. Zircaloy(R) is an important alloy developed specifically for nuclear applications. Zirconium is exceptionally resistant to corrosion by many common acids and alkalis, by sea water, and by other agents. Alloyed with zinc, zirconium becomes magnetic at temperatures below 35oK. 

Nylon 6 and 6/6 possess the maximum stiffness, strength, and heat resistance of all the types of nylon. Type 6/6 has a higher melt temperature, whereas type 6 has a higher impact resistance and better processibility. At a sacrifice in stiffness and heat resistance, the higher analogs of nylon are useful primarily for improved chemical resistance in certain environments (acids, bases, and zinc chloride solutions) and for lower moisture absorption. 

Polymer compositions containing pentaerythritol are also used as secondary heat-, light-, and weather-resistant stabilizers with calcium, zinc, or barium salts, usually as the stearate, as the prime stabilizer. The polymers may be in plastic or fiber form (87—89). 

Molybdenum Oxides. Molybdenum was one of the first elements used to retard the flames of ceUulosics (2). Mote recently it has been used to impart flame resistance and smoke suppression to plastics (26). Molybdic oxide, ammonium octamolybdate, and zinc molybdate ate the most widely used molybdenum flame retardants. Properties ate given in Table 5. These materials ate recommended almost exclusively for poly(vinyl chloride), its alloys, and unsaturated polyesters (qv). 

Zinc Borate. Zinc borate is also effective in enhancing the flame-inhibiting powers of chlorine. Although zinc borate increases flame resistance, it is not as effective as antimony oxide, as is illustrated in Figure 3. However, zinc borate can be used in combination with antimony oxide to obtain equivalent and in some instances enhanced effects over what can be obtained using either of the two synergists alone (Table 9). 

Textile Finishing. Polyethyleneimine-A/-methylolurea derivatives improve the crease and wear resistance of cotton (429,430). The adhesion between individual wool fibers is improved by pretreatment with amines, which leads to improved shrink resistance (431). An antimicrobial finish can be appHed to cotton by using a combination of PEI and ureas to bind zinc pyrithione to the fabric (432). After wool has been provided with a flameproof finish using fluorozirconate or fluorotitanate, the wool can be neutralized with PEI (433). Conventional neutralizing agents caimot be used for this purpose since they impair the flameproof characteristics of the impregnated fabric. 

Ziac foil coated with a conductive, pressure-sensitive adhesive is used for repair of other ziac coatings or for imparting corrosion resistance at field sites. The 0.08-mm ziac tape or sheet has a 0.025-mm coaductive adhesive. The laminate is cut to size and pressed tightly to activate the adhesive. Conductive tape can be wrapped around pipe, especially around welds or connections. The corrosion resistance of this material is iatermediate between galvanized or thermally sprayed coatings and zinc-filled paints (21,50). 

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