Orthophosphate adsorption

The pH of a 1% solution of pure sodium tripolyphosphate is 9.9 and that of commercial samples may vary between 9.5 and 10.1. The pH of a given sample of solid STP drops slowly with age because of water adsorption and partial reversion to orthophosphate and pyrophosphate. The pH of solutions varies with concentration because the sodium ion is bound in the complex form NaP O o higher concentrations maximum pH is reached at between 1—2% solution. 

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. 

It is interesting to note that the uptake patterns found for Mn2+ on the surface of calcite are similar to those observed for orthophosphate uptake on calcite. Stumm and Leckie (1970) observed a three-stage process for phosphate uptake on calcite surfaces from dilute solutions, representing adsorption, nucleation, and apatite growth. However, deKanel and Morse (1978) found a two-stage pattern of phosphate uptake on calcite from seawater, with an initial rapid adsorption phase followed by slow but steady uptake. 

VanBerkel, J. and Beckett, R., Estimating the effect of particle surface coatings on the adsorption of orthophosphate using sedimentation field-flow fractionation, J. Liq. Chrom. Rel. Technol., 20, 2647, 1997. 

This approach was first outlined by Beckett et al. [6], where radiolabelled pollutants as orthophosphate, in atrazine, and glyphosate) were adsorbed to two Australian river colloid samples. Sedimentation FFF was used to fractionate the samples and the radioactivity of each fraction was measured. From this, it was possible to generate a surface adsorption density distribution (SADD) across the size range of the sample. The SADD is a plot of the amount of compound adsorbed per unit particle surface area as a... 

Application of bis-(2-ethylhexyl) orthophosphate as a liquid ion exchanger in the complete or selective extraction of alkaloids from a buffered aqueous phase has been described. The behaviour of the salts of various alkaloids upon titration with base has been compared.Correlations have been made between the Rf of a number of alkaloids and the pH of an aqueous buffer solution which extracts half of the alkaloid from an aqueous solution. The stabilization of alkaloid solutions has been discussed. " Chromatographic separations of alkaloids by ion-exchange, adsorption, thin-layer, paper, and liquid chromatography have been reviewed. Reference lists have been compiled for methods and applications published in 1970—73 of chromatography and of electrophoresis of alkaloids on paper and thin layers. The optimum composition of Dragendorff s reagent for efficient alkaloid precipitation has been examined. ... 

The retention model developed by Eon and Guiochon [7,8] to describe the adsorption effects at both gas-liquid and liquid-solid interfaces, which was later modified by Mdckel et al. [6] to account for the retention at chemically bonded reversed-phase materials in HPLC, is not applicable to ion chromatography. But if the dependence of the capacity factors of various inorganic anions on the column temperature is studied, certain parallels with HPLC are observed. The linear dependences shown in Fig. 3-2 are obtained for the ions bromide and nitrate when the In k values are plotted versus the reciprocal temperature (van t Hoff plot). However, in the case of fluoride, chloride, nitrite, orthophosphate, and sulfate, the k values were found to be constant within experimental error limits in the temperature range investigated. Upon linear regression of the values in Table 3-1, the following relations are derived for bromide and nitrate ... 

In this problem we use the diffuse-layer model to compute the adsorption of orthophosphate species by goethite between pH 3 and 10. Intrinsic constants for the adsorption reactions are available in the MINTF.QA2 file,/ o-d/w.f/6r. Similar calculations have been discussed and performed by Hohl etal. (1980). (a) Assume 0.6 g/L of goethite in suspension, with a surface-site density of 1.35 x 10 moles of sites per... 

Kim, M.S. and Chung, J.G., A study on the adsorption characteristics of orthophosphates on rutile-type titanium dioxide in aqueous solutions, J. Colloid Interf. Sci., 233,31,2001. 

Reduces surfactant adsorption on rock surfaces Changes oil wettability Hydrolyzes over time to orthophosphate... 

Salts of Al, Fe and Mg " " are also capable of forming precipitates with phosphate. Phosphate can be removed from solution by adsorption on some solids, particularly activated alumina, AI2O3. Removals of up to 99.9% of orthophosphate have been achieved with this method. 

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