Metal factors affecting activity

P.O. Nelson, A.K. Chung, M.C. Hudson, Factors affecting the fate of heavy metals in the activated sludge process, J. WPCF 53 (1981) 1323-1333. 

A wide variety of organic and inorganic compounds inhibit microbial activity by interfering with the uptake of metabolites and enzymic reactions (Davis and Feingold, 1962 Pelczar and Reid, 1958). In particular, the heavy metals are extremely toxic to the heterotrophs but are tolerated at higher levels by Desulfovibrio spp. due to their precipitation as metal sulphides (see p. 343). Other factors affecting the activity of sulfate-reducers are discussed in Chapter 6.1. 

Figure 9 suggests that careful control of conditions of activation would be needed for good reproducibility. The level of reproducibility which we secured was fair (see Table IV) but there are factors affecting catalytic activity which we have not identified. We have established that the activity of our samples of chromia did not depend upon trace impurities of other metals nor upon surface oxidation during drying the gel at 110° in the course of preparation of the catalyst. 

Research on supported Ni catalysts, used for steam reforming and other applications " , has dealt with factors affecting their activity and stability. Catalyst formulation and the extent to which interaction occurs between NiO and the support are important factors influencing the reduction of NiO to Ni in the catalyst and the catalysts subsequent behavior. The influence of the support on the metal is illustrated by NiO on AI2O3 or MgO. It is well known that NiO deposited on oxide supports is less readily reduced than bulk NiO. Furthermore, growth of crystallites of the metal oxide can be retarded by a suitable support. For instance, the presence of MgO retards the growth of NiO. When NiO is calcined at 500°C for 4 h, NiO crystallites increase to about 30 nm, whereas in a NiO/40% MgO solid solution, the crystallites grow to only 8 nm (Fig. 1). ... 

This book describes the transport of metals to ground water from activities such as agriculture, mining, and the disposal of municipal waste and fly ash. Topics Include analytical techniques, environmental chemistry, speciation and distribution, fate and transport, and environmental factors affecting transport... 

It is well known that the catalytic activity and selectivity of a metal for a certain reaction may be substantially altered by the presence of a second metal in the system (25). In the present work, although Pt has been the metal of primary interest, two experiments were done with the bimetallic Pt-Ru/Al-A system in order to get an idea about the effect of a second metal on the activity and selectivity of Pt. From Table 3 it is observed that an equimolar amount of Ru, when combined with 1.5% Pt, does not affect the activity and selectivity of the Pt-alone catalyst. When the amount of Ru is doubled (see item 2 in Table 3), however, the activity increases by a factor of about 5, while the selectivity for various products remains virtually unchanged. This dramatic increase in activity is probably due to the formation of new, highly active sites at the bimetallic interface. The selectivity patterns of the two bimetallic catalysts are very similar to that of the Pt-alone catalyst. This implies that the new sites on the bimetallic and those on Pt-alone catalysts are of same nature as far as the selectivity is concerned. 

Hence, the dominant factors affecting the wear rate of metals during friction in electrolytes are the corrosion activity of the medium, the pressure in the friction pair and the properties of the counterbody. 

Abstract The factors controlling the transition metal catalyzed a-bond (including H-H, C-H and C-C) activation and formation, the fundamental steps of many chemical transformations, were analyzed. It was demonstrated that in the mono-nuclear transition metal systems the (1) availability of the lower lying s d and s d" states of the transition metal atoms, and (2) nature of the ligands facilitating the reduction of the energy gap between the different oxidative states of the transition metal centers are very crucial. Meanwhile, in the transition metal clusters the cooperative (or cluster ) effects play important roles in the catalytic activities of these clusters. Another important factor affecting the catalytic activity of the transition metal systems shown to be their redox activity. 

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