Metallic salts, adsorption reduction

Generally speaking, homogeneous nucleation needs the supersaturation level higher than heterogeneous one. In the system consisting of support solid and metal salt solution, the nucleation occurs on the surfaces of the solid. The selective reductive deposition is performed by the adsorption of metal ion or complexes on the surfaces and hereby the reduction. Namely, the initial adsorption of metal ions or complexes is the key point of this technique. Hence, key points of this method are... 

Some of the questions raised are longstanding ones in the field of colloid science, and they will not be addressed in any detail in this review. Synthesis of the colloids is generally performed (in the context of SERS) by reduction of the metal salt. Specific procedures are to be found in each of the reports which pertain to SERS on colloids. The adsorbed molecule for the SERS study can be present during the reduction stage and even participate in it (citrate on silver, for instance). Alternatively, the adsorption may be carried out after the reduction (pyridine on silver and gold, for example). The later procedure often causes noticeable changes in the colloid, such as aggregation and precipitation. 

Metal Loading and Reduction A slurry phase adsorption technique was used to impregnate the alumina powders with soluble salts of Pt, Ru and Pd. The adsorbed metals were then reduced chemically at elevated tenqjeratures. Two different methods of reduction ( methods -1 and -2) using two different chenucals were used. The temperatures of reduction remained the same. Additionally, a... 

Only few works deal with films or nanoparticles covering the surface of a Nafion membrane. In the case of metal coated Nafion membranes surface nanoparticles were deposited on the surface by in situ reduction of a metal salt precursor [21], by adsorption of a colloidal dispersion of the metal [28], or by sputtering [22, 23]. 

Microemulsions have been used as confined reaction media during the past two decades, since, due to the very small size of the droplets, they can act as microreactors capable to control the size of the particles and at the same time to inhibit the aggregation by adsorption of the surfactants on the particle surface when the particle size approaches that of the microreactor droplet. The synthesis of nanoparticles using reactions in microemulsions was first described by Boutonnet and cowoikers They synthesized monodispersed metal particles of Pt, Pd, Rh and Ir by reduction of metal salts with hydrogen or hydrazine in water in oil (w/o) microemulsions. Since then, many different types of materials have been prepared using microemulsions, including metal carbonates, metal oxides, " metal chalcogenides, "" polymers," etc. 

Toxic pollutants found in the mercury cell wastewater stream include mercury and some heavy metals like chromium and others stated in Table 22.8, some of them are corrosion products of reactions between chlorine and the plant materials of construction. Virtually, most of these pollutants are generally removed by sulfide precipitation followed by settling or filtration. Prior to treatment, sodium hydrosulfide is used to precipitate mercury sulfide, which is removed through filtration process in the wastewater stream. The tail gas scrubber water is often recycled as brine make-up water. Reduction, adsorption on activated carbon, ion exchange, and some chemical treatments are some of the processes employed in the treatment of wastewater in this cell. Sodium salts such as sodium bisulfite, sodium hydrosulfite, sodium sulfide, and sodium borohydride are also employed in the treatment of the wastewater in this cell28 (Figure 22.5). 

Adsorption inhibitors act by forming a film on the metal surface. The action of traditional oil-based red lead paint formulations presumably involves the formation of soaps and the precipitation of complex ferric salts that reinforce the oxide film. There has been substantial interest in recent years in development of replacements for lead-based and chromate-based inhibitor systems. Adsorption inhibitors based on pol3rmers have been of particular interest. In this volume, Johnson et al. and Eng and Ishida discuss inhibitors for copper 2-undecylimidazole is shown to be effective in acid media, where it suppresses the oxygen reduction reaction almost completely. Polyvlnyllmidazoles are shown to be effective oxidation inhibitors for copper at elevated temperatures. Also in this volume, Chen discusses the use of N-(hydroxyalkyl)acrylamide copolymers in conjunction with phosphate-orthophosphate inhibitor systems for cooling systems. 

The immersion of a polycrystalline gold electrode into a chloroform/methanol (2 1, v/v) solution of the tetrachloride salt of 6 (Fig. 7.4) results in the adsorption of this electroactive thiol on the metal surface.270 Consistently, the cyclic voltammogram (Fig. 7.5a), recorded after an immersion time of 24 h and extensive rinsing of the electrode surface, shows the reversible reduction of the bipyridinium dications to the corresponding radical cations. In addition, zp increases linearly with v (Fig. 7.6a),... 

Again, the precise roles of coordination-compound chemical sensitizers, in most cases, are not understood. In fact, their effects may have little to do with their own coordination chemistry. Many simple salts of gold and other noble metals are effective sensitizers. They also may be added to solutions during silver halide precipitation to produce doped emulsions that have special properties. A variety of compounds that can act as ligands to metal ions are also effective alone as chemical sensitizers, the result of complicated oxidation-reduction, ion replacement and adsorption reactions on the silver halide grain surface. These include polyamines, phosphines and thioether- or thiol-containing compounds. The chemistry of these materials with the silver halide surface is discussed in the reference literature. 

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