R.A. Bailey

The earth's crust

The present structure of the earth consists of a largely molten core composed chiefly of iron and nickel, surrounded by lighter rocks. The outer few miles, the crust, is the only portion of the earth that is accessible, and is the source of most of the substances used in a technological society. This chapter describes the structure, composition, and evolution of earth crust, and the processes that take place in it. The volume of material to be mined and processed, the energy requirements, and the waste disposal problems clearly set economic and environmental restrictions on the minimum concentration that can be employed for large-scale use of any substance but the society generally uses atypical, high concentration sources for most of its mineral needs. Bacteria can also be used for recovery of metals from low-grade sources in an economical way through microbial mining. Surface rocks are subject to breakup and chemical change by several weathering processes including physical disintegration, chemical reactions, and biological effects that lead to soil formation. Soil is a vital substance but its degradation is of serious concern in terms of its impact on future food needs. Human activity frequently causes degradation of soil in ways that range from loss of nutrients to changes in physical character of the soil to contamination with toxic materials to loss of the soil itself. Different types of soils, their composition and process of formation, soil contamination, and methods of decontamination such as bioremediation, are also presented in the chapter.

Electrochemical Studies of Chromium in Molten LiF ‐ NaF ‐ KF (FLINAK)

The mechanism of the reduction of Cr(III) in molten FLINAK was studied using cyclic voltammetry and chronopotentiometry over a temperature range of 612°–983°C and a Cr(III) concentration of 0.07 to 0.13 mol/l. Two reduction and two oxidation steps were observed, but extensive differences in the electrochemistry were seen over the measured temperature range. Cr(III) is reduced to Cr(II) followed by a two‐electron reduction of Cr(II) to Cr metal and both reduction processes are quasi‐reversible. The product of the first reduction process is soluble at 983°C, but is insoluble at lower temperatures.

Complex hexacyanates of rhenium and molybdenum

Abstract The complex hexacyanates of Re(IV), Re(V), and Mo(III) have been prepared using molten dimethylsulfone as the reaction medium. These were isolated and characterized as the cesium or tetraphenylarsonium salts. Infrared spectra indicate these to be the first examples of oxygen-bonded cyanate complexes.

Dehydration and decomposition of divalent metal squarates

Abstract Divalent metal squarate complexes (MC4O4·2H2O where M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) were shown by thermogravimetric analysis to decompose in vacuum according to the reaction MC 4 O 4 · 2H 2 O ⇄ 2H 2 O + MC 4 O 4 → M+ (4−2x) CO +x CO 2+x C . The order of stability with respect to water loss is close to the Irving-Williams series, but the final decomposition order is quite different. In air, the solid product is partially or completely metal oxide. Anhydrous squarate compounds were isolated and their ligand field spectra characterized; those of iron, cobalt and nickel are tetrahedral.

Thermal decomposition of metal complexes with thioureas

Abstract Thermal decomposition of methyl and dimethylthiourea complexes of several transition metals and of cadmium complexes with several thioureas and ureas were studied by thermogravimetric analysis in air and vacuum and stability relations established. In vacuum, dimethylthiourea complexes decompose to a mixture of metal chloride and sulfide; the organic products include dimethylthiourea, methylisothiocyanate, HCl and polymerized material. In air, intermediates are formed in which part of the organic ligand is retained followed by complete decomposition to inorganic salts at higher temperatures. The intermediate contains little sulfur and appears to be a substituted urea compound.

High-temperature electroplating of chromium from molten FLINAK

Electroplating of chromium has been investigated in molten FLINAK (46.5 LiF-11.5 NaF-42.0 KF; mol %) over a temperature range of 600 to 1000°C. When Cr(III) is the electroactive species employed, a considerable amount of Cr(II) must be generated before chromium metal is deposited. Various parameters were tested to establish the optimum conditions for obtaining a smooth and thick chromium plating. Bath temperature was found to be a most important parameter; at temperatures above 870°C a smooth plate can be obtained, while at lower temperatures the deposits consist of extensive dendrites embedded in the salt which is the first reduction product of Cr(III).

The anodization products of tantalum in the fused LiClKCl eutectic

Abstract Voltammetry, cyclic voltammetry and chronopotentiometry of Ta in the LiClKCl eutectic melt showed that anodization of Ta metal produces Ta(V), Ta(IV) and a lower state (probably Ta(II)). Ta(V) slowly volatilized from the melt at 450°C. The Ta(V) ⇌ Ta(IV) redox reaction is reversible with an approximate E ° = −0·67V. Both Ta(IV) and Ta(II) are reduced to solid products, probably to the metal, in the vicinity of −1·7 and −2·2 volts (all potentials vs standard Pt(II) Pt/(0)). Spectra show that Ta(V) in the melt is present as [TaCl 6 ] − .

I.R. studies on the formation of basic nickelous nitrate

Abstract I.R. absorption studies were conducted on the formation of basic nickelous nitrate. It was found that the basic salt precipitate contains free nitrate ions balanced by unreacted nickel ions. As water is rejected from the precipitate the nitrate ions coordinate with the nickel. At a high pH these nitrato groups are eventually replaced by hydroxide ions.

Soaps, synthetic surfactants, and polymers

This chapter reviews the chemical nature, synthesis, and environmental problems associated with biodegradable and nonbiodegradable organic compounds. Most of the polymers and surfactants in the detergents are made mainly from the chemicals derived from petroleum, and contain segments of linear or lightly branched hydrocarbon chains. Both soaps and synthetic detergents have similar structures, and their mechanisms of cleansing are also similar; however, zeolites of the detergents have environmental problems and they promote surface algal blooms. Microorganisms in the environment can utilize the energy of oxidation released by some hydrocarbons, soaps, and surfactants through β-oxidation. The chapter illustrates the microbial metabolism of hydrocarbons, soaps and synthetic detergents, and proposes guidelines to facilitate the understanding of microbial degradation of detergents. Although progress has been made in the synthesis of biodegradable polymers, these materials cost more, and in general, their properties are not as useful as those prepared from petroleum feedstock. A potential problem associated with biodegradable surfactants is the eutrophication of lakes that results from microbial degradation. The biodegradable replacements have solved the environmental problems associated with nonbiodegradable surfactants, and it is likely that biodegradable polymers assume an increasingly larger percentage of the polymer market.

Water systems and water treatment

This chapter discusses the major water systems, composition of various water bodies, factors that influence the composition and properties of water, and methods of water treatment. The composition of natural water bodies depends upon the gain, and loss of solutes through both chemical reactions and physical processes. The oxides of sulfur, and nitrogen that enters into the atmosphere from automobiles, other combustion sources, smelting, and some natural sources dissolve in raindrops and decrease the pH of rain water; resulting in acid rain. It affects the weathering reactions, solubility, and biological processes in lakes, rivers, and soils whose pH values are reduced as a consequence. The ecological effects of acid deposition include disruption of species distribution and food chains in lakes, as lower organisms disappear, and potential toxic effects on vegetation. Large scale water treatment is necessary in two general circumstances; for water taken into distribution systems for household or industrial use, and for wastewater that must meet particular standards for pollution control. Industrial waste water may require specialized treatments that depend on contaminants while treatment of domestic waste involves more general procedures. Several methods of water treatment for domestic waste water for household use like chlorination, use of activated charcoal, irradiation with ultraviolet light, are discussed in the chapter. Depending upon the final water-quality desired, treatment may be at the primary, secondary, or tertiary level. Clean water is a vital commodity, and the usage now is so extensive that waste-waters must be repurified to avoid destruction of aquatic ecosystems and because, often, the water will be reused.