THE SORPTION OF COBALT FROM AQUEOUS SOLUTIONS BY POTASSIUM NICKEL HEXACYANOFERRATE COMPLEX

ABSTRACT

The inorganic complex, potassium nickel hexacyanoferrate, KNiFC, was used for the separation of cobalt from diluted nitric acid aqueous solutions using the batch technique. The effect of hydrogen ion concentration on the distribution coefficient of cobalt has been studied in the pH range 2–5.5. The effect of particle size and temperature on the sorption isotherm and rate of uptake of cobalt were investigated. The increase of temperature was found to enhance the sorption equilibrium and rate of uptake. The diffusivity of cobalt ions into different particle sizes of KNiFC was calculated. The effect of the presence of cesium ions on the rate of uptake of cobalt is presented.     

SORPTION OF CESIUM BY HEXACYANOFERRATE COMPOSITES FROM NEUTRAL AND ACIDIC MEDIA

ABSTRACT

Silica-supported copper, cobalt, nickel and zinc hexacyanoferrate(II) composites were prepared by a modified procedure and sorption of cesium by these materials from neutral and acidic media was studied. Distribution coefficient (K_d) values in the range of 10³ to 10⁵ mL/g and capacity values in the range of 1.1 to 2.5 meq/g were obtained in neutral media. A considerable increase in K_d values and capacities was observed for cobalt composites as compared to those for the corresponding unsupported material. High K_d values (10⁴ to 10⁵) were also exhibited in nitric acid media by copper, cobalt and nickel composites but only in the presence of low concentration of hydrazine. The underlying mechanism of the sorption of trace cesium by these composites was found to be true ion exchange. Of all the composites studied, nickel-based materials were found to be most attrition-resistant in agitated test solutions. The behaviour of composites observed in this work is explained from a knowledge of known crystal structure and surface properties of pure compounds.     

EXTRACTION OF CESIUM NITRATE FROM CONCENTRATED SODIUM NITRATE SOLUTIONS WITH 21-CROWN-7 ETHERS: SELECnVITY AND EQUILIBRIUM MODELING

ABSTRACT

The extraction of cesium nitrate from a high concentration of sodium nitrate by a family of 21-crown-7 ethers in 1,2-dichloroethane has been investigated. Dibenzo-21-crown-7 (DB21C7) and bis[4(5),4′(5′)-rm-butylbenzo]-21-crown-7 (BtBB21C7) ethers have higher selectivity for cesium but lower extraction efficiency than dicyclohexano-21-crown-7 (DC21C7) ether. As measured by the distribution coefficient ratio D_cs/D_Na, the cesium selectivity averaged 78 and 93 for DB21C7 and BtBB21C7, respectively. However, in the case of DC21C7, the cesium selectivity was lower and decreased approximately three-fold from 10 to 3 as cesiüm loading increased. Alkyl substitution on the benzo group has only a small effect on the extraction behavior. It was shown by use of the equilibrium modeling program SXLSQI that the extraction of sodium and cesium could be adequately modeled by augmenting the previously determined cesium nitrate equilibrium model with a 1:1 Na⁺:crown organic-phase complex. No evidence for a mixed-metal species was found. In accord with our previous study, cesium nitrate extraction entails formation of a 1:1 Cs⁺:crown complex, but a minor 1:2 complex also forms in the case of DC21C7. Although the sodium and cesium made possible by the U. S. Department of Energy Postgraduate Research Program administered by the Oak Ridge Associated Universities.     

ION-EXCHANGE PROPERTIES OF POTASSIUM NICKEL HEXACYANOFERRATE(II) COMPOUNDS

ABSTRACT

A series of nonstoichiometric compounds K_{2 x}Ni_x/2[NiFe(CN)₆]nH₂O was prepared by varying Ni/Fe molar ratio from 0.1 to 100. The products had a face-centered cubic (fee) structure, and the lattice parameter slightly increased with decreasing K/Fe ratio. The uptake rate of Cs⁺ was enhanced at lower K/Fe ratio below 1.32 and reached equilibrium within 8 h for the products with K/Fe below 0.86. The distribution coefficients of Cs⁺ on the products were above 10⁴ cm³/g in the presence of 1 mol/dm³ Na⁺, K⁺ or H⁺ while those of other nuclides were less than 10², indicating high selectivity of the product to Cs⁺. The uptake of Cs⁺ followed a Langmuir-type isotherm and the maximum amount of Cs⁺ adsorbed was evaluated to be 1.0 to 1.5 mmol/g. Cesium nuclides were efficiently removed from a simulated high-level liquid waste.     

SEPARATION OF CESIUM FROM NUCLEAR WASTE SOLUTIONS WITH HEXACYANOFERRATE(II)S AND AMMONIUM PHOSPHOMOLYBDATE

ABSTRACT The separation of 134, 137 Cs from nuclear power plant low-level waste solutions by ion exchange with potassium cobalt hexacyano-ferrate(II), potassium copper cobalt hexacyanoferrate(II) and ammonium phosphomolybdate was studied. The pH of the waste solutions was 6-13 and the concentrations of sodium and potassium ions were 8 - 2700 and 0.5 - 240 mmol/1, respectively. The distribution coefficient of cesium was determined as a function of pH, sodium and potassium ion concentrations and of the ratio of solution volume to exchanger weight (batch factor). The ion exchange rate of cesium was determined for three exchanger grain sizes and at temperatures of 20, 40 and 60° C. A potassium copper cobalt hexacyanoferrate(II) column was tested for cesium separation from a highly alkaline (pH 13) waste solution containing high concentrations of sodium (2.7 M) and potassium (0.24 M) ions; the 1% breakthrough capacity was very high, 12800 bed volumes.     

SOLVENT EXTRACTION OF COPPER(II), NICKEL(II), AND COBALT(II) FROM SODIUM CHLORIDE SOLUTIONS BY OCTANAL OXIME

The extraction of divalent copper, nickel, and cobalt from sodium chloride solutions with octanal oxime (OCOX) was found to proceed by the following reaction:

The association of octanal oxime in toluene was taken into account in the modelling of the extraction reaction, and the formation constants for dimers and trimers were calculated using vapour-pressure osmometry. Stability constants for the formation of aqueous copper-chloro species were also calculated.     

ADSORPTION RATE OF COPPER(II) FROM AQUEOUS AMMONIUM NITRATE SOLUTION ON SILICA GEL

The adsoption rate of copper(II) from 1 mol/dm³ aqueous ammonium nitrate solution on silica gel was investigated at 303?K.At low pH, the adsorption rate was found to be proportional to copper(II) ion concentration and inversely proportional to hydrogen ion concentration and presumed to be controlled by a chemical reaction. To interpret the experimental results in this region, a simple reaction scheme where the formation of the intermediate complex of copper(II) ion with the dissociated form of silanol group is the rate-determining step was proposed. In high pH, it was found that the adsorption rate is independent of hydrogen ion concentration and proportional to copper(II) ion concentration and that it is dependent on the stirring speed. The experimental results in this region were explained by taking into account of the diffusional contribution of copper(II) ion.     

SELECTIVE EXTRACTION OF PALLADIUM(II) FROM CHLORIDE SOLUTIONS WITH NONYLTHIOUREA DISSOLVED IN CHLOROFORM

ABSTRACT

The extraction of Palladium(II) [Pd(II)] from hydrochloric acid solutions with nonylthiourea (NTH) dissolved in chloroform at a constant ionic strength of 1.0?M has been studied. The extraction of Pd(II) has been investigated as a function of the concentration of the extractant, chloride ion, and proton concentrations as well as extraction temperature. The distribution data have been treated graphically and numerically. The analysis of the experimental data has shown that Pd(II) is extracted as PdCl₂·(NTH) and PdCl₂·(NTH)₂ species with the respective extraction constants of log?K ₁₁=5.0±0.1 and log?K ₁₂=9.1±0.1. The back-extraction of Pd(II) from the organic phase using different stripping reagents has been examined. The selectivity of NTH for Pd(II) against Pt(IV), Rh(III), Cu(II), Fe(III), and Zn(II) has also been investigated.     

SELECTIVE UPTAKE OF CESIUM BY AMMONIUM TUNGSTOPHOSPHATE (AWP) - CALCIUM ALGINATE COMPOSITES

ABSTRACT

The fine crystals of ammonium tungstophosphate (AWP) exchanger were immobilized in the biopolymer consisting of calcium alginate (CaALG) gels. The uptake rate of Cs⁺ for the AWP-CaALG composite was fairly fast and the uptake percentage of Cs^? was above 90 % within 30 min even in the presence of 5 M HNO₃ In a wide HNO₃concentration region of 0.1 - 5 M, the distribution coefficient of Cs^? for the composite was about 10⁴ cm³/g, while those for other nuclides, Na⁺, Sr²⁺, Co²⁺, Eu³⁺ and Am³⁺, were less than 10 cm³/g. The uptake of Cs⁺ followed a Langmuir-type adsorption equation, and the maximum uptake capacity of Cs⁺ increased with the content of AWP immobilized in the composite. The trace amounts of ¹³⁷Cs in the presence of 5 M NaNO₃-l M HNO₃ were selectively adsorbed on the composite column. The AWP-CaALG composite proved to be effective for the selective removal of radioactive cesium from waste solutions containing HNO₃ and NaNO₃     

LEAD(II) EXTRACTION FROM NITRATE SOLUTIONS WITH DI(2-ETHYLHEXYL)PHOSPHORIC ACID

ABSTRACT

In this paper, equilibrium studies were carried out on the extraction of trace amounts of lead(II) from 0.2 mol/dm³ (Na,H)NO₃ aqueous solutions with di(2-ethylhexy1)phosphoric acid (HR) dissolved in n-dodecane at 298 K. The composition of the extracted species was numerically found to be and ₂. A chemical equilibrium model was developed to evaluate the thermodynamic constants for the formation of the two complexes, based on the law of mass action, which took into account the activity corrections of reactive species in the aqueous phase by employing the Bromley and the simplified Pitzer equations and those of the extractant in the organic phase.     

序批式生物膜法处理低碳城市水高效除磷的试验

针对碳、氮、磷比例失调碳源偏低城市污水,因碳源不足而降低脱氮除磷效率的难题及连续流生物膜法除磷率低的缺点,为提高生物膜的除磷效率,通过构建厌氧/好氧交替运行的序批式生物膜反应器(SBBR),合理调控厌氧和好氧段的运行时间,处理广州地区碳源偏低的城市污水,研究其生物除磷的效果和控制影响因素.结果显示,在无需额外添加碳源的条件下,当进水TP浓度为1.65～7.10mg/L,出水TP浓度可在0.085～0.5mg/L之间,去除率达到90%以上.在此基础上,对SBBR的厌氧和好氧段的工艺特性及控制影响因素进行系统分析,指出厌氧/好氧交替运行的工序是SBBR处理城市污水高效除磷的前提和基础,而确保厌氧磷的最大有效释放是SBBR系统高效除磷的关键.     

SOLVENT EXTRACTION OF COPPER(II) FROM CHLORIDE SOLUTIONS BY SOME PYRIDINE CARBOXYLATE ESTERS

n-octyl-3-pyridine carboxylate (NOPC), an analogue of the commercial reagent DS5443, was synthesized, and the stoichiometry of its reaction with copper(II) in chloride media was determined. At low metal loadings, copper(II) was extracted by the solvation reaction:

The factors affecting the separation of iron and copper from solutions containing copper(II),iron(II), and zinc(II)chlorides were determined in countercurrent extraction tests using DS5443.     

SOLVENT EXTRACTION OF ZINC(II) BY ORGANOPHOSPHORUS ACIDS COMPOUNDS FROM PERCHLORATE SOLUTIONS.

ABSTRACT

The extraction of zinc from perchlorate solutions at 0.1 mol.dm^?3 of ionic strength by di(2-ethylhexyl)phosphoric acid (HDEHP), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and di(n-octyl)phosphinic acid (H[DOP]) dissolved in toluene has been studied at 25 ° C.

The distribution coefficient was determined as a function of pH and HA concentrations and the data were analyzed both graphically and numerically using the computer program LETAGROP-DISTR.

The results showed that the data can be explained assuming the formation of ZnA₂(HA)₂ and ZnA₂HA in organic phase for all the extractants used. A correlation between extracted species and concentration of the various extractants has been found.

The predominance of the different species into the organic phase has been correlated with the difference between their extraction constants.

The anion of the ionic medium is not extracted into the organic phase.     

SOLVENT EXTRACTION OP COPPER (II), NICKEL (II) AND COBALT(II) PROM HALIDE AND THIOCYANATE SOLUTIONS BY ALDOXIMES

The extraction of divalent copper, nickel and cobalt from acidic chloride solutions with solutions of heptaloxime, nonaloxime and 2-methyldekaloxime in toluene has been studied at 18*C.

These metals were found to be extracted according to the following solvation reaction:

The influence of syn-anti isomerization of aldoximes on the extraction has been discussed. Taking into account association and syn - anti isomerization constants of aldoximes in organic phase,hydration of extracted oomplexes and activities of salts in aqueous phase, effective extraction oonstants have been calculated for chloride solutions.

Separation of nickel and cobalt from aoidic chloride, bromide and thiooyanate solutions by extraction with heptaloxime has been studied.     

THERMODYNAMIC STUDY OF THE EXTRACTION OF INDIUM(III) AND CADMIUM(II) BY CYANEX 301 FROM CONCENTRATED HCl MEDIA

ABSTRACT

The distribution equilibria of In(III) and Cd(II) between aqueous HCl solutions and kerosene containing Cyanex 301 (bis(2,4,4-trimethylpentyl) dithiophosphinic acid denoted hereafter HL) and 10 % (V/V) of n-decanol are investigated. In(III) and Cd(II) are extracted as InL₃ and CdL₂, respectively and a physico-chemical model is proposed for modelling the distribution data. In the final part of the paper, this, model is used to discuss the optimal conditions for separating indium and cadmium, previously co-extracted with Cyanex 301, by stripping in HCl media.     

EXTRACTION OF COPPER(II) FROM ACID CHLORIDE SOLUTIONS BY N-DODECYL- AND N.N-DIHEXYLPYRIDINECARBOXAMIDES

ABSTRACT

N-dodecyl- and N,N-dihexylpyridinecarboxamides with amide group at 2, 3 or 4 position were synthesized. Model individual amides were used to recover copper(II) from chloride solutions at constant water activity and constant total concentration of dissolved species in aqueous solution. It was found, that pyridine-2-carboxamide forms with copper complexes (CuCl₂)_x (Ext)₂. Remaining amides form with copper complexes CuCl₂(Ext)₂. Monoalkylamides are not suitable for extraction because they and their complexes are slightly soluble in the hydrocarbon diluents. N,N-dialkylpyridinecarboxamides and their copper complexes are sufficiently soluble in the hydrocarbon phase to carry out extraction. However, they are strong extractants and extract efficiently copper already from dilute chloride solutions ([Cl] = 0.1 M). They extract also significant amounts of copper from concentrated (3-4M) nitrate solutions.     

实验条件对减压膜蒸馏法脱除水溶液中MIBK的影响

本文采用平板式减压膜蒸馏技术对水溶液中MIBK的脱除进行了研究，分别考察了料液温度、料液流量及减压侧压力对MIBK的脱除及效率的影响。     

IMPREGNATED RESINS CONTAINING DI-(2-ETHYLHEXYL) THIOPHOSPHORIC ACID FOR THE EXTRACTION OF PALLADIUM(H). II. SELECTIVE PALLADIUM(II) RECOVERY FROM HYDROCHLORIC ACID SOLUTIONS

ABSTRACT

The extraction of Pd(II) from HC1 solutions by impregnated resins containing di-(2-ethylhexyl) thiophosphoric acid (DEHTPA or HL) on the Amberlite XAD2 polymeric support has been studied. Graphical and computer analysis with the program LETAGROP-DISTR demonstrated that the Pd(II) extraction can be explained by the formation of metal complexes in the resin phase having the composition PdL₂(HL)₂. DEHTPA/XAD2 resins extracted Pd(II) in the presence of other metals: Pt(IV), Rh(III), Cu(II), Fe(III) as well as Zn(II). The stripping of Pd(II) loaded on the organic phase and the lifetime of the resins were also investigated.     

SOLVENT EXTRACTION OF COBALT(II) WITH TRI-n-BUTYL PHOSPHATE FROM AQUEOUS-ORGANIC SOLUTIONS

Cobalt(II) has been extracted by 50% (v/v) TBP solution in benzene from HC1, HBr, and LiC1 solutions containing water miscible alcohols and nonbesic and basic aprotic solvents. All solvents used caused the distribution ratio of Co(II) to increase due to diminished water activity and shifts in equilibria of cobalt(II) complexes in solutions. Hexamethylphosphor-triamide (HMPTA) has been found to behave exceptionally in that it extracted Co(II) from LiC1 solutions into neat benzene and in the presence of TBP induced a weak synergism caused by extraction of at least two mixed solvates.     

REMOVAL OF TOLUENE AND DICHLOROMETHANE FROM AQUEOUS PHASE BY GRANULAR ACTIVATED CARBON (GAC)

Chlorinated hydrocarbons and aromatics constitute the major class of volatile organic compounds that contaminate groundwater. In this study, the equilibrium uptake and column dynamics for the adsorption of dichloromethane (as a typical chlorinated hydrocarbon) and toluene (as a representative of aromatic compounds) from aqueous phase on coal-based granular activated carbon (GAC) were investigated. The adsorption isotherms were measured in a temperature range of 20–40°C. The experimental data obtained were correlated with several adsorption isotherm models. The Langmuir model was well adapted to describe the dichloromethane adsorption on GAC, while the adsorption of toluene on GAC was found to be well described by the Langmuir-BET hybrid model in the stated temperature range with R-squared value of about 0.99. The variations in adsorption breakthrough curves of toluene and dichloromethane with respect to operational parameters such as initial concentration, flow rate, column length, and temperature were investigated. The experimental breakthrough curves of both adsorbates are well fitted by Yan's model with high accuracy (R-squared value of 0.98–99) in most cases.