Aluminum complexes arsenates

Aluminum l,l -bi-2-naphthol complex phthalocyanine complexes Arsenic Hu96 Lez93... 

Many studies on the direct reaction of methyl chloride with silicon-copper contact mass and other metal promoters added to the silicon-copper contact mass have focused on the reaction mechanisms.7,8 The reaction rate and the selectivity for dimethyldichlorosilane in this direct synthesis are influenced by metal additives, known as promoters, in low concentration. Aluminum, antimony, arsenic, bismuth, mercury, phosphorus, phosphine compounds34 and their metal complexes,35,36 Zinc,37 39 tin38-40 etc. are known to have beneficial effects as promoters for dimethyldichlorosilane formation.7,8 Promoters are not themselves good catalysts for the direct reaction at temperatures < 350 °C,6,8 but require the presence of copper to be effective. When zinc metal or zinc compounds (0.03-0.75 wt%) were added to silicon-copper contact mass, the reaction rate was potentiated and the selectivity of dimethyldichlorosilane was enhanced further.34 These materials are described as structural promoters because they alter the surface enrichment of silicon, increase the electron density of the surface of the catalyst modify the crystal structure of the copper-silicon solid phase, and affect the absorption of methyl chloride on the catalyst surface and the activation energy for the formation of dimethyldichlorosilane.38,39 Cadmium is also a structural promoter for this reaction, but cadmium presents serious toxicity problems in industrial use on a large scale.41,42 Other metals such as arsenic, mercury, etc. are also restricted because of such toxicity problems. In the direct reaction of methyl chloride, tin in... 

Within the context of toxicological and clinical importance, speciation studies have been focused on relatively few elements, mainly aluminum, antimony, arsenic, chromium, iodine, lead, mercury, platinum, selenium and tin. However, coupled HPLC-ICP-MS has most often been used for speciation of arsenic, selenium, iodine and, to a lesser extent, mercury. The primary species of these elements include different oxidation states, alkylated metal and/or metalloid compounds, selenoamino acids and selenopeptides.In addition, applications in smdies on the pharmacokinetics of metal-based drugs (mainly platinum complexes) and metalloproteins should be included. " In the following sections, the advances in speciation smdies of individual elements are reviewed. 

Once they have reached higher pH, reducing conditions of the intestinal tract (Davis et al, 1992), sulhdes should be more stable, and may actually precipitate if reduced sulfur is present. Other solids, such as hydroxides or hydroxy-sulfates of aluminum, and possibly iron, may also precipitate. The increased pH should also lead to the increased sorption onto particulates of various metals and metalloids such as lead and copper (Smith, 1999). However, in vitro tests (Ruby et al, 1993) indicate that the increased complexing with unprotonated organic acids and enzymes helps offset the pH-driven precipitation and sorption of the base metals that were dominantly chloride-complexed in the stomach fluids. Arsenic and other oxyanionic species are likely to be sorbed as the stomach acids are neutralized, but may be partially desorbed once higher pH values are reached in the intestine (Ruby et al, 1996). 

Diverse chemicals have been reported to affect measured endpoints of fish thyroidal status. These chemicals include aromatic hydrocarbons, planar halogenated aromatic hydrocarbons (dioxans, furans, coplanar PCBs), organochlorine, organophosphorus and carbamate pesticides, chlorinated paraffins, cyanide compounds, methyl bromide, phenol, ammonia, metals (aluminum, arsenic, cadmium, lead and mercury), low pH conditions, environmental steroids and a variety of pharmaceutical agents. For the following reasons their modes of action appear complex and are poorly understood16. 

VIBRATIONAL SPECTROSCOPY Infrared and Raman spectroscopies have proven to be useful techniques for studying the interactions of ions with surfaces. Direct evidence for inner-sphere surface complex formation of metal and metalloid anions has come from vibrational spectroscopic characterization. Both Raman and Fourier transform infrared (FTIR) spectroscopies are capable of examining ion adsorption in wet systems. Chromate (Hsia et al., 1993) and arsenate (Hsia et al., 1994) were found to adsorb specifically on hydrous iron oxide using FTIR spectroscopy. Raman and FTIR spectroscopic studies of arsenic adsorption indicated inner-sphere surface complexes for arsenate and arsenite on amorphous iron oxide, inner-sphere and outer-sphere surface complexes for arsenite on amorphous iron oxide, and outer-sphere surface complexes for arsenite on amorphous aluminum oxide (Goldberg and Johnston, 2001). These surface configurations were used to constrain the surface complexes in application of the constant capacitance and triple layer models (Goldberg and Johnston, 2001). 

He has contributed to research on the interface between soil chemistry and mineralogy and soil biology. His special areas of research include the formation mechanisms of aluminum hydroxides and oxyhydroxides, the surface chemistry and reactivities of short-range-ordered precipitation products of Al and Fe, the influence of biomolecules on the sorption and desorption of nutrients and xenobiotics on and from variable charge minerals and soils, the factors that influence the sorption and residual activity of enzymes on phyllosilicates, variable charge minerals, organomineral complexes, and soils and the chemistry of arsenic in soil environments. 

Apted MJ, Waychunas GA, Brown GE Jr (1985) Structure and speciation of iron complexes in aqueous solutions determined by X-ray absorption spectroscopy. Geochim Cosmochim Acta 492081-2089 Arai Y, Elzinga EJ, Sparks DL (2001) X-ray absorption spectroscopic investigation of arsenite and arsenate adsorption at the aluminum oxide-water interface. J Colloid Interface Sci 235 80-88. 

Electrolytes which do not afford ionic complexes with common hexitols and reducing sugars are aqueous solutions of lead acetate, copper sulfate, zinc sulfate, ferrous ammonium sulfate, calcium chloride, potassium dichromate, ferric chloride (pH 3), aluminum sulfate, magnesium sulfate, sodium sulfate, potassium antimonyl tartrate, sodium arsenate or arsenic acid, sodium phosphate, and hydrochloric acid. It is not certain whether sodium aluminate (in 0.1 N sodium hydroxide) affords ionic complexes with carbohydrates, as aqueous alkali, alone, permits their migration during electrophoresis. 

---