Amine-selective adsorbents

Fig. 4 Effects of ionic strength on selective adsorption of EPS from a BSA solution containing EPS by the various aminated cellulose adsorbents reported in Pig. 2. The selective adsorption of EPS was determined by a batchwise method with 0.2 g of the wet adsorbent and 2 mL of a sample solution [BSA 500 pg/mL, EPS E. coli 0111 B4) 100 ng/mL, pH 7.0, and ionic strength of p=0.05-0.8].

Collectors The principle role of the collector is to selectively adsorb and impart hydrophobicity to the mineral particles to be floated. These can be cationic in nature, such as amines, or anionic in nature, such as carboxylates, sulfonates, xanthates, or alkyl sulfates. Fatty acids, such as oleic and stearic, are also commonly used. 

Degradation of 7/-nitrosodimethylamine (NDMA) and A -nitrosopyrrolidine (NPYR) on zeolites was investigated by use of temperature programmed surface reaction and GC-MS. Activation of zeolite had almost no effect on TPSR of NPYR, because zeolite could selectively adsorb A-nitrosamines. Cyano derivative appeared as the main product on NaZSM-5 or NaY zeolites similar to that in pyrolysis while DNA became the dominant one on HZSM-5 or HY. On the latter the Bronsted acid sites probably play the role of main catalytic sites, hence N-nitrosamines degrades to amines on Bronsted acid sites while on the former A-nitrosamines might decompose through radical reaction process, similar as pyrolysis. No desorption of the A -nitrosamines occurs on zeolites even at elevated temperature, and protonation of zeolite... 

Figure 9.2 Using different chemical functionalities, pSi surfaces can be tailored to selectively adsorb and efficiently ionize analytes. Left to right DIOS-MS spectra of 500fmol of BSA digest analyzed on 8-month-old TMS-derivatized DIOS chip, carbohydrate mix containing sucrose (MNa 365) and maltotriose (M Na 527) on amine-silylated pSi surface, and small-mole-...

A study by Comyn et al. [8] indicated that low (or no) cure took place in the interphase between an amine cured epoxy and aluminum because the amine was preferentially adsorbed onto the aluminum oxide on the aluminum. Garton et al. [9] showed that the acidic surface of a carbon fiber selectively adsorbed amine and catalyzed the reaction between the amine and an epoxy resin. Nigro and Ishida [10] found that homopolymerization of epoxy resin was catalyzed by a steel surface. Zukas et al. [11] discovered, in a model system of an amine cured epoxy resin and an activated aluminum oxide, a change in the relative rates of the reactions leading to crosslinking of the epoxy, so that the material in the interphase was structurally different from that in the bulk. 

Zeolite A is extensively used as selective adsorbent in several purification and separation processes [9]. The most prominent examples are the enrichment of oxygen from air [e.g. 9,10] and the separation of linear and branched alkanes [e.g. 9,1 Ij. Among others, zeolites Rho and ZK-5 have been studied in detail as catalysts for the selective amination of methanol with ammonia to dimethyl-amine [e. g. 12,13 ]. Also, the potential of small pore zeolites for the conversion of methanol to lower olefins has been explored [e.g. 14,15]. 

For selective LPS removal, it is necessary not only to select the ligand of the adsorbent, but also to control the conditions of the buffer (pH and ionic strength). The effect of ionic strength on the selective adsorption of LPS from a BSA-containing solution by various aminated cellulose adsorbents 2x10 ) was examined (results are... 

Typical nonsieve, polar adsorbents are siUca gel and activated alumina. Kquilihrium data have been pubUshed on many systems (11—16,46,47). The order of affinity for various chemical species is saturated hydrocarbons < aromatic hydrocarbons = halogenated hydrocarbons < ethers = esters = ketones < amines = alcohols < carboxylic acids. In general, the selectivities are parallel to those obtained by the use of selective polar solvents in hydrocarbon systems, even the magnitudes are similar. Consequendy, the commercial use of these adsorbents must compete with solvent-extraction techniques. 

Rust inhibitors usually are corrosion inhibitors that have a high polar attraction toward metal surfaces and that form a tenacious, continuous film which prevents water from reaching the metal surface. Typical mst inhibitors are amine succinates and alkaline-earth sulfonates. Rust inhibitors can be used in most types of lubricating oils, but factors of selection include possible corrosion of nonferrous metals or formation of emulsions with water. Because mst inhibitors are adsorbed on metal surfaces, an oil can be depleted of its mst inhibitor. In certain cases, it is possible to correct the depletion by adding more inhibitor. 

An alternative approach to increase the oxidation rate is the use of alkaline solutions, because bases enhance the reactivity of L-sorbose and weaken the adsorption strength of 2-KLG. Unfortunately, the rate enhancement at higher pH is accompanied by a drop in selectivity due to the poor stability of 2-KLG in alkaline solutions. To circumvent this problem, we have modified the platinum catalysts by adsorbed tertiary amines and carried out the oxidation in neutral aqueous solution [57], This allowed to enhance the rate without increasing the pH of the bulk liquid, which leads to detrimental product decomposition. Small quantities of amines (molar ratio of amine sorbose = 1 1700, and amine Pts = 0.1) are sufficient for modification. Using amines of pKa a 10 for modification, resulted in a considerable rate enhancement (up to a factor of 4.6) with only a moderate loss of selectivity to 2-KLG. The rate enhancement caused by the adsorbed amines is mainly determined by their basicity (pKa). In contrast, the selectivity of the oxidation was found to depend strongly on the structure of the amine. 

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