摘要:

Parameters affecting extraction power of amine-based extractants for mineral acids are reviewed. Means for adjusting extractant composition for reversible extraction of mineral acids from dilute solutions are discussed. The paper also analyses process options for recovery of the extracted acid at concentrations higher than those in the original solution. Introduction of the required energy as thermal energy without resorting to evaporation of the acid or to evaporation of water is highly attractive.

ISSN:0736-6299    

DOI:10.1080/07366299108918050

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Tri(2-ethylhexyl) amine (TEHA) was found to be a considerably weaker extractant for mineral acids than straight chain aliphatic amines. It is still, however, markedly stronger than solvating extractants such as alcohols and esters. Its medium strength provides for a relatively wide range of efficient and reversible extraction. TEHA and similarly branched chain tertiary amines are therefore suitable for recovery of strong mineral acids from effluents containing them in low concentrations. Effects of diluents and modifiers and of amine concentration were found to provide a strong tool for adjusting the range of efficient and reversible extraction to characteristics of treated solutions.

ISSN:0736-6299    

DOI:10.1080/07366299108918051

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In analogy to extraction of bulky organic acids by normal amines, strong temperature effects were predicted for extraction of strong mineral acids (of small molecular size) by bulky amines. Extractants, chosen according to analysis in previous papers, were found to show the required effect and thereby provide the basis for “temperature swing” LLX process for recovery and concentration of acids from dilute solutions. Diluent/modifier effects were utilized for the adjustment of extractant properties and maximizing temperature effect.

ISSN:0736-6299    

DOI:10.1080/07366299108918052

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The solvent extraction of europium(II) from chloride media by solutions of some monobasic orcanoonosphorus and carboxvlic acids in xylene was investigated. Corresponding studies of europium(III) and of the alkaline-earth metals that most resemble europium(II) in terms of ionic radius,, calcium and strontium, were also.carried out.

ISSN:0736-6299    

DOI:10.1080/07366299108918053

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The extraction of Mo(VI) from its aqueous solutions into chloroform in the presence of 2,3-dihydroxy-naphthalene (DHN), and n-butyltriphenylphosphonium bromide (LBr), was investigated using 99-Ho tracer and the composition of the extracted compounds was studied. Mononuclear species were extracted at high DHN concentrations. The green extracts from strong acid aqueous solutions of H2SO4contained the compounds being formed from Mo, DHN and LBr in the ratio 1:2:1. Ion-pairs of the yellow anionic chelates of Mo(VI), Mo/DHN=l:l (monovalent) and 1:2, with phosphonium cations were extracted very efficiently from acid, neutral, and slightly basic media. If the DHN concentration was low, the extraction of oligonuclear (possibly complexed) species from strong acid media and oligomolybdates from slightly acid solutions was observed.

ISSN:0736-6299    

DOI:10.1080/07366299108918054

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The precipitation of fine aqueous droplets as “haze” or entrainment in dodecane solutions of di-2-ethylhexylsulfoxide (DEHSO) is demonstrated in experiments in which water-saturated dodecane solutions of DEHSO are diluted with water-saturated dodecane at 25 °C. The resulting turbidity correlates with the concentration of excess water predicted from an analysis of the water extraction behavior of DEHSO. Underlying the dilution-induced turbidity is the destabilization of dimer hydrates (DEHSO)2(H2O)n, causing the release of water to the solvent. Other neutral oxygen-donor extractants are expected to exhibit this effect, which may provide additional insight into the appearance of turbidity and associated problems in certain solvent extraction systems.

ISSN:0736-6299    

DOI:10.1080/07366299108918055

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The metal sorption properties of a series of 14 functionalised organopolysiloxanes are reported. Such materials have been synthesized at DEGUSSA by polycondensation of suitably bifunctional silane monomers. The corresponding functional groups or combination of functional groups are : -SH; -S-; -SH + -S-; -NH- + -S-; -NH-[CH2]2-NH2; -N=CH-C5H4N; -N=CH-C8H4OH; -NH-C[=S]-NH-; -NH-C[=S]-N[-]-[CH2]2-N[CH3]2; -NH-C[=S]-N[-]-C[=O]-C8H5; -NH-C[=S]-S-; -P[C8H5]-; -P[C8H5]2and -SO3H. Such materials appear as spherical or egg-shaped solid particles with a grain size of about 0.1 to 1.5 mm and surface areas up to 700 m2/ g. They are composed of a siliceous core and contain a high concentration of functional groups which, moreover, are bound to the matrix via carbon-silicon bonds which are fairly stable towards hydrolysis. They can therefore be safely used over a large range of acidities : i.e. from [HCI] > 6 mol / L up to about pH 11 or 12. The main advantages of the new functionatised organopolysiloxanes lie in the absence of swelling or shrinking during sorption operations and in their high thermal stability (up to 200 °C). The ion sorption properties of these organopolysiloxanes have been investigated by studying the fixation of a series of metal species (Ag(I), As(III), Sb(III), Bi(III). Cu(II), Ni(II). Ga(III), Fe(III), Pd(II) and Pt(IV)) representing the main families of metal ions.

ISSN:0736-6299    

DOI:10.1080/07366299108918056

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The network rigidity inherent to a polymer-supported reagent affects its ability to distinguish among a family of substrates with varying electron density at the functional group. The dimethylamine ligand is bonded to a polystyrene network whose rigidity is increased by increasing the crosslink level from 2% to 25% divinyl-benzene. The ability of the ligand to complex substituted benzoic acids of increasing acidity is correlated with the network's rigidity. The initial ratio of substrate to ligand sites is varied from 0.1 to 1.0. At the highest ratio, the amount complexed decreases with increasing network rigidity but the molecular recognition pattern remains constant. with a ten-fold excess of ligands to substrates, the polymer network plays a critical role in setting the molecular recognition pattern: as network rigidity increases, the specificity of the substrate−−ligand interaction increases. It is proposed that increasing network rigidity decreases multi-site inter actions between the substrate and two or more ligands; this decreases complexation of weakly interacting substrates while not affecting those which interact strongly.

ISSN:0736-6299    

DOI:10.1080/07366299108918057

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The sorption isotherns of boric acid on WA-21 weak-base anion exchange resin and the sorption band shape as veil as its migration velocity in a four-inch diameter ion-exchange column were studied.

ISSN:0736-6299    

DOI:10.1080/07366299108918058

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Important liquid ion exchangers and the applications of their cationic and anionic forms in the studies of separation of zirconium, niobium, molybdenum, hafnium, tantalum and tungsten through solvent extraction and RPEC systems have been reviewed.

ISSN:0736-6299    

DOI:10.1080/07366299108918059

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor