Phosphates cycling behavior

Vanadium is present as V " in stoichiometric VPP however, the latter can host V " or V species as defects, without undergoing substantial structural changes (5,6). Therefore, the role of the different V species in the catalytic behavior of VPP in n-butane oxidation has been the object of debate for many years (7-9). Moreover, the catalyst may contain crystalline and amorphous vanadium phosphates other than (VO)2P207 (10) for instance, outer surface layers of V phosphates may develop in the reaction environment, and play active roles in the catalytic cycle. This is particularly true in the case of the fresh catalyst, while the equilibrated system (that one which has been kept under reaction conditions for 100 hours at least) contains only minor amounts of compounds with V species other than V. ... 

Tri-n-butyl phosphate and di-2-ethyIhexyl phosphoric acid (HDEHP) have been mainly used as extractants in several hydrometallurgical operations in the nuclear fuel cycle. Shukla and Mishra [27] have studied the extraction as well as transport behavior of uranium through BLM using 40% TBP in dodecane. The transport of by TBP at the feed-membrane... 

Cyclic Voltammetry—5 V/min. Figures la-e present the j-U behavior for the first cycle of copper-2% zinc in phosphated saline and in protein solutions. The corrosion potentials (ia—ic) during the forward scans were between -0.35 to -0.40 V in all cases. Two anodic peaks were observed for all protein solutions at —0.25 to —0.10 V and +0.10 to +0.30 V. The first peak in the supporting electrolyte was also observed, whereas j continued to increase, never reaching a peak up to the reversal potential of +0.5 V. Two main cathodic peaks were observed at —0.30 to —0.45 V and —0.65 to —0.75 V in all cases. A prepeak inflection also occurred at -0.2 to -0.3 V for both the albumin and globulin systems, and a small peak at —1.1 to —1.2 V for most systems. Cathodic currents increase sharply below about —1.5 V. Figures 2a-b represent the surface appearances after the first cycle of polar-... 

Silicate is a very important nutrient in the ocean. Unlike other major nutrients such as phosphate and nitrate or ammonium, which are needed by almost all marine plankton, silicate is an essential chemical only for certain biota such as diatoms, radiolarian, sihcoflageUates, and siliceous sponges. However, this biology is one of the most important producers in marine. The estimation shows that diatoms contribute more than 40% of the entire primary production. Therefore, silicate cycling has received significant scientific attention in recent years and many scientists have studied silicate behavior in marine environments. Biogenic silicate is the amorphous content extracted by chemical methods, which is named as biogenic opal or opal in brief. The concentration of dissolved silicate in the world ocean is about 70.6 pmol/L and the net input of dissolved silicate from land to ocean is (6.1 2.0)x 10 mol (calculated by Si) every year, and the primary contribution (about 80%) comes from river. 

Mixtures of hydrocarbons with calcium alkyl phosphate particles are known to be effective antifoams in the context of domestic textile machine washing where wash cycles can last for up to 1 h and involve temperature ranges from 30°C to 95°C (see Section 8.2.4.1) [43, 44]. Under these circumstances, little or no deactivation of antifoam effectiveness is apparent. Mixtures of hydrocarbons with alkyl phosphoric acid esters also function as antifoams in this context provided the aqueous phase has a high enough pH and calcium ions are present [43, 44] so that the calcium salts can precipitate as particles in situ at the relevant hydrocarbon-water interface. This behavior is of course analogous to that shown by mixtures of oleic acid and hexadecane when dispersed in an aqueous phase under similar conditions [45]. As with the preformed calcium alkyl phosphate particles, no deactivation of antifoam effectiveness is observed in the case of in situ formation of the precipitates. Indeed, it has been observed that continuous aeration for several hours, using a circulating Ross-Miles apparatus at 90°C (see Section 2.2.3), of an aqueous solution of a blend of a commercial sodium dodecylbenzene sulfonate and an ethoxylated alcohol in the presence of mixtures of a hydrocarbon and an alkyl phosphoric acid ester (dispersed... 

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