Metallic contamination surface

Brierley, C. L. (1990). Bioremediation of metal-contaminated surface and groundwaters. Geomicrobiology Journal, 8, 201-23-... 

As indicated above, the goal in recent years in the ultra-large-scale integrated-circuit (ULSI) industry was to reduce contamination on surfaces to below the level detectable with state-of-the-art equipment. For economic and environmental reasons, this had to be replaced by one referred to as just clean enough. This requires that action-reaction-type relationships be identified between contaminants and their influence on a given surface in order to be able to fix acceptable levels of organic and metallic contamination, surface roughness, and other surface characteristics. 

Metal Preparation. Preparation of the metal surfaces to be bonded usually is required because most metals contain surface imperfections or contaminants that undesirably affect bond properties. The cladding faces usually are surface ground, using an abrasive machine, and then are degreased with a solvent to ensure consistent bond strength (26). In general, a surface finish that is >3.8 fim deep is needed to produce consistent, high quaUty bonds. 

In many of the other processes that use base metal catalysts, irreversible poisoning of the catalyst occurs as a result of deposition of metal contaminants from the process feedstock onto the catalyst surface. These catalysts are not considered to be regenerable by ordinary techniques. 

Production-Scale Processing. The tritium produced by neutron irradiation of Li must be recovered and purified after target elements are discharged from nuclear reactors. The targets contain tritium and He as direct products of the nuclear reaction, a small amount of He from decay of the tritium and a small amount of other hydrogen isotopes present as surface or metal contaminants. 

Commercial spectrometers are usually bakeable, can reach ultrahigh-vacuum pressures of better than 10" Torr, and have fast-entry load-lock systems for inserting samples. The reason for the ultrahigh-vacuum design, which increases cost considerably, is that reactive surfaces, e.g., clean metals, contaminate rapidly in poor vacuum (1 atomic layer in 1 s at 10 Torr). If the purpose of the spectrometer is to always look at as-inserted samples, which are already contaminated, or to examine rather unreactive surfaces (e.g., polymers) vacuum conditions can be relaxed considerably. 

Many applications of novolacs are found in the electronics industry. Examples include microchip module packaging, circuit board adhesives, and photoresists for microchip etching. These applications are very sensitive to trace metal contamination. Therefore the applicable novolacs have stringent metal-content specifications, often in the low ppb range. Low level restrictions may also be applied to free phenol, acid, moisture, and other monomers. There is often a strong interaction between the monomers and catalysts chosen and attainment of low metals levels. These requirements, in combination with the high temperature requirements mentioned above, often dictate special materials be used for reactor vessel construction. Whereas many resoles can be processed in mild steel reactors, novolacs require special alloys (e.g. Inconel ), titanium, or glass for contact surfaces. These materials are very expensive and most have associated maintenance problems as well. 

Since the catalyst is so important to the cracking operation, its activity, selectivity, and other important properties should be measured. A variety of fixed or fluidized bed tests have been used, in which standard feedstocks are cracked over plant catalysts and the results compared with those for standard samples. Activity is expressed as conversion, yield of gasoline, or as relative activity. Selectivity is expressed in terms of carbon producing factor (CPF) and gas producing factor (GPF). These may be related to catalyst addition rates, surface area, and metals contamination from feedstocks. 

Benson NU, Etesin UM (2008) Metal contamination of surface water, sediment and Tympa-notonus fuscatus var. radula of Iko River and environmental impact due to Utapete gas flare station, Nigeria. Environmentalist 28 195... 

HIBS is the same as RBS, except that heavy ions are used instead of He++. It is an ion beam analysis tool patented by the Sandia Corporation of the USA, and was developed to enable the measurement of trace levels of surface contamination on silicon wafers. Metal contamination present in starting material is detrimental to devices, since it results in defects which limit wafer yields and impair circuit operation. 

Before reaction, the silica is treated with acid (eg refluxed for a few hours with 0.1 mol dm-3 HC1). This treatment produces a high concentration of reactive silanol groups at the silica surface, and also removes metal contamination and fines from the pores of the material. After drying, the silica is then refluxed with the dimethylchlorosi-lane in a suitable solvent, washed free of unreacted silane and dried. This reaction produces what is called a monomeric bonded phase, as each molecule of the silylating agent can react with only one silanol group. 

Jinhui L, Huabo D, Pixing S (2011) Heavy metal contamination of surface soil in electronic waste dismantling area site investigation and source-apportionment analysis. Waste Manag... 

Variation of the content of impurities in the different CNT preparations [21] offers additional challenges in the accurate and consistent assessment of CNT toxicity. As-produced CNTs generally contain high amounts of catalytic metal particles, such as iron and nickel, used as precursors in their synthesis. The cytotoxicity of high concentrations of these metals is well known [35, 36], mainly due to oxidative stress and induction of inflammatory processes generated by catalytic reactions at the metal particle surface [37]. Another very important contaminant is amorphous carbon, which exhibits comparable biological effects to carbon black or relevant ambient air particles. 

In summary, intratracheal instillation of CNTs has shown that their potential in eliciting adverse pulmonary effects is influenced by exposure time, CNT dose, CNT biopersistence, surface defects, and metal contamination [71, 72]. Despite the use of surfactants, all studies showed that intratracheal instillation caused major difficulties due to the agglomerative nature of CNTs in a biological environment. More realistic exposure methods, namely inhalation rather than intratracheal administration, are therefore needed for determining the pulmonary toxicity [59, 65, 73]. Several investigations have been performed by using administration different from intra-... 

Bacteria and their composites with soil minerals or organic matter are capable of taking up a wide range and variety of toxic metals in soil environments. Research done over the last decade or so has greatly improved our understanding of the mechanisms on biosorption of metals and bacte-ria-metal-soil component interactions. However, more studies from molecular level are needed in order to enhance the ability of bacteria and their association with soil components to remediate toxic metals-contaminated soils. The focus of future investigations should be on the mechanisms by which metals are sorbed and bound by bacterial cell surfaces and bacteria-soil/mineral composites. In this connection, X-ray absorption spectroscopy (XAS) is a promising technique because it can provide information about... 

Surface-water samples are usually collected manually in precleaned polyethylene bottles (from a rubber or plastic boat) from the sea, lakes, and rivers. Sample collection is performed in the front of the bow of boats, against the wind. In the sea, or in larger inland lakes, sufficient distance (about 500 m) in an appropriate wind direction has to be kept between the boat and the research vessel to avoid contamination. The collection of surface water samples from the vessel itself is impossible, considering the heavy metal contamination plume surrounding each ship. Surface water samples are usually taken at 0.3-1 m depth, in order to be representive and to avoid interference by the air/water interfacial layer in which organics and consequently bound heavy metals accumulate. Usually, sample volumes between 0.5 and 21 are collected. Substantially larger volumes could not be handled in a sufficiently contamination-free manner in subsequent sample pretreatment steps. 

Sorption can significantly diminish the mobility of certain dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill (see Chapters 21 and 32). In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 31). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. 

Fig. 32.4. Chromatographic separation of metal contaminants in a groundwater flow at 25 °C, due to differential sorption. According to the surface complexation model used, Hg++ in the simulation sorbs more strongly to the ferric surface in the aquifer than Pb++, which sorbs more strongly than Zn++. Plot at top shows concentrations of the metal ions in groundwater, and bottom plot shows sorbed metal concentrations.

To study the effect of contaminants (chlorides and sulphates) at the interface metal/coating, a set of panels (surface A Sa 3) was prepared and dosed with solutions of NaCl and FeSO in distilled water and methanol. Subsequently, two paint systems (chlorinated rubber and polyurethane) were applied on these contaminated surfaces. 

Competitive adsorption on clay and soils surfaces between a heavy metal contaminant (Cu) and a cationic herbicide (chlordimeform) was reported by Maqueda... 

Dissolved metals and metal-containing surfaces play an important role in the transformation of organic contaminants in the subsurface environment. Metal ions can catalyze hydrolysis in a way similar to acid catalysis. Organic hydrolyzable compounds susceptible to metal ion catalysis include carboxylic acids, esters, amides, anilides, and phosphate-containing esters. Metal ions and protons... 

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