ADSORPTION OF COBALT ONTO GRAPHITE NANOCARBON–IMPREGNATED ALGINATE BEADS: EQUILIBRIUM,KINETICS, AND THERMODYNAMICS STUDIES

A novel adsorbent was developed impregnating graphite nanocarbon (GNC) into alginate beads (AB) for efficient cobalt (Co(II)) removal from an aqueous solution. Physicochemical and spectroscopic properties of graphite nanocarbon–impregnated alginate beads (ABGNC) were characterized and compared with those of AB. Co(II) adsorption on ABGNC was quantitatively evaluated by determining kinetics and thermodynamics parameters. The Co(II) adsorption capacity onto ABGNC was highest at neutral pH condition. Increasing the temperature from 288 to 318 K resulted in a 2.5-fold higher Co(II) adsorption onto AB, while thermal dependence of Co(II) adsorption on ABGNC was not found. Kinetic studies showed an applicability of the pseudo-second-order kinetic model for both AB and ABGNC. Monolayer adsorption was the dominant mechanism of Co(II) adsorption on both AB and ABGNC. Thermodynamic studies revealed that Co(II) adsorption was an endothermic and spontaneous process. Positive values of entropy indicate randomness in solid/aqueous phases, and mean free energy (E _a ) fits in the range of chemisorption.     

SEPARATION OF COBALT(II) AND NICKEL(II) IONS FROM ACID AQUEOUS SOLUTIONS BY Co IT ION-EXCHANGE INTO γ-TITANIUM PHOSPHATE

ABSTRACT

The Co²⁺-2H⁺, Ni²⁺-2H⁺, and Co²⁺-Ni²⁺-2H⁺ ion exchange processes into γ-Ti(H₂PO₄)(PO₄)2H₂O were studied. Exchange isothenns and titration curves were obtained. Monometallic half ion exchange phases were formed by using MC₂+HCl (M=Co,Ni) solutions. Equilibrium constants, free energy, enthalpy, and entropy of the Co²⁺-2H²⁺ ion exchange reaction were determined. In (Co,Ni)Cl₂ solutions, bimetallic a half ion exchange substitution solid solution is detected. Equilibrium constant of the Co²⁺-Ni²⁺ substitution process in the γ-Ti(Co_xNi_0.5?x.HPO₄)(PO₄)nH₂O phase at 85°C was determined. In (Co,Ni)Cl₂+HCl solutions, total separation of Co²⁺ and Ni²⁺ is obtained.     

ω-THIOCAPROLACTAM AS AN EXTRACTING REAGENT FOR Hg(II) FROM CHLORIDE,NITRATE, AND PERCHLORATE MEDIA.

ABSTRACT

Solvent extraction of Hg(II) from chloride, nitrate, and perchlorate media using ω-thiocaprolactam (R) dissolved in chloroform was studied. In all media the extraction equilibria are reached very fast, less than a 5 minute period of shaking time is needed. At high metal: extractant ratio (1:10) the percent of extraction of Hg(II) decreases in the order chloride > nitrate = perchlorate and in the pH range studied ( 0-3 ) is independent of this variable. At low metahextractant ratios (1:50, 1:100) the percent of extraction does not depend on the media used. In the latter case a dependence with the acidity in the chloride media is observed. The dimerization constant of the extractant in CHCI₃ was determined to be 109±15 by UV measurements. Graphical and numerical analysis of the data with the LETAGROP-DISTR program allowed to propose the extraction reactions involved and evaluate their equilibrium constants. Organic phase species of the type HgX₂R and HgX₂R₂ ( where X = CI, NO₃, or CIO₄) were found to explain better the experimental results obtained. However, in concentrated HCI the extraction of Hg(II) is explained by the formation of HgCI₃RH and HgCI₄(RH)₂ species.     

THE EXTRACTION OF CATIONIC RUTHENIUM COMPLEXES FROM AQUEOUS MEDIA BY α-TIN(IV) HYDROGEN PHOSPHATE

ABSTRACT

The ruthenium species [Ru(NH₃)₆]³⁺ was adsorbed by the surface of (α-Sn(HPO₄)₂.2H₂O [SnP]) α-tin(IV) hydrogen phosphate. The ruthenium(II)-containing cation [Ru(NH₃)₆]²⁺, however, has been directly intercalated into (SnP). Since the corresponding ruthenium(III) complex cation was not so intercalated, a new self-catalysed intercalation mechanism involving labile ammonia ligands from the ruthenium(II) has been proposed. At high loadings, guest ruthenium(II) species were oxidised to ruthenium(III).     

THE SEPARATION OF NEPTUNIUM AND PLUTONIUM FROM NITRIC ACID USING n-OCTYL(PHENYL)-N,N DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE EXTRACTION AND SELECTIVE STRIPPING†

The extraction of neptunium and plutonium in several oxidation states was studied as a function of nitric acid concentration for 0.1M n-octyl(phenyl)-N, N-diisobutylcarbamoyl -methylphosphine oxide in 1.4M tributylphosphate with dodecane diluent. Np(V) is only weakly extractable over the range of acid concentrations studied while Np(IV) and Np(VI) are highly extractable. Pu(IV) and Pu(VI) are also highly extractable while Pu(III) was extracted but with lower efficiency. An Fe(II) reductant was used to reduce neptunium to Np(IV) and plutonium to Pu(III) for the initial extraction. Pu(III) was then stripped with dilute HNO₃ in the presence of a holding reductant leaving the Np(IV) in the organic phase. Neptunium may then be recovered to an aqueous phase with one of a number of complexing agents.     

SYNERGISM IN THE EXTRACTION OF ZINC(II)AND CADMIUM(II) WITH SOME LOWER FATTY ACIDS IN THE PRESENCE OF AMINES AND THEIR SEPARATIONS∗

Abstract

Synergism in the extraction of Zn(Il) and Cd(II)with chloroform solution of propionic, butyric and valeric acids in the presence of n-butylamine, dibutylamine, tributylamine, β-picoline, pyridine and quinoline is reported The effect of various parameters affecting extractions has been investigated The compositions of synergistic adduct extracted into the organic phase have been proposed on the basis of slope analysis method. In general the species have been represented as MA2.2HA.B (aliphatic amine system and MA₂.2HA.2B (heterocyclic amine system), where M = zn(Il)/CdII), HA = acid and B = amine. On the basis of extraction constant (K_ex) values the relative effectiveness of different amines as synergists has been compared. Based on the extraction data some separations of metal ions have also been reported with fairly high separation factor (β).     

MODELING OF ELEMENTARY PROCESS KINETICS FOR METHANOL SYNTHESIS (Ⅱ )A TRANSIENT KINETIC MODEL OF METHANOL SYNTHESIS FROM CO/CO_2/H_2

在基元过程序列结构判识的基础上,以傅立叶变换红外光谱仪(FTIR)气体池作为检测器,采用动态响应技术,进行了合成甲醇过程瞬态动力学的实验研究,得到了微型反应器尾气中各主要物种的浓度对反应器进料浓度阶跃变化的动态响应数据。基于瞬态速率模型对实验数据的拟合,得到了由H_2/CO/CO_2合成甲醇初步的瞬态动力学关系。     

THE KINETICS OF COBALT(II) EXTRACTION WITH EHEHPA IN HEPTANE FROM ACETATE SYSTEM USING AN IMPROVED LEWIS CELL TECHNIQUE†

ABSTRACT

The cobalt(II) extraction kinetics and mechanism with EHEHPA (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) were investigated by an improved constant interfacial area stirred cell. The effects of the buffer species, stirring rate, temperature, specific interfacial area and surfactants on the extraction rate showed that the extraction regime was dependent on the extraction conditions and the most probable reaction zone was at the liquid-liquid interface. This extraction process was reaction controlled at lower concentration of the reactants, while it was mixed chemical reaction-diffusion or diffusion controlled only for higher concentration of the reactants. An interfacial extraction reaction model with diffusion was derived. The kinetics of the extraction process was simulated with this model.     

KINETIC MODELING OF HYDROISOMERIZATION OF C-8AROMATICS(Ⅰ)MODELING AND ESTIMATION OF RELATIVE RATE CONSTANTS BY THE WEI-PRATER METHOD

1 Introduetlon To date,most kinetie investigations ofC一aromaties hydroisomerization over bifunetionaleatalysts have been eoneerned with reaetjon meehanisms.R6bsehl巨ger et al.[,]studied thehydroisomerization kineties under sPecifie eonditions,and ProPose…     

STUDIES ON THE RELATIONSHIP BETWEEN THE NETWORK STRUCTURE AND THE MECHANICAL PROPERTIES OF RUBBER VULCANIZATES (Ⅰ) THEORY OF ELASTICITY FOR RUBBER VULCANIZATES WITH CARBON BLACK FILLERS IN LARGE DEFORMATION

A model structure formed by the combination of crosslinked, trapped entanglement and carbon black-polymer chain networks has been developed for rubber vulcanizates with carbon black fillers. Based on thisstructure and the proposed mechanism of large deformation, the elastic free energy     

STUDIES ON VAPOR-LIQUID AND LIQUID-LIQUIDVAPOR EQUILIBRIA FOR THE TERNARY SYSTEM METHANOL-METHYL METHACRYLATEWATER (Ⅱ) TERNARY SYSTEM

Isothermal P-x data for homogeneous, and P-x'-x\" data for partially miscible mixtures for the ternary system methanol-methyl methacrylate-water have been determined at 25, 35, 45, 55 and 60℃. By using a modified UNIQUAC model and binary parameters only, the predicted ternary phase equilibrium data were found to be in good agreement with the experimental results, indicating the adequacy of using binary model parameters in computing vapor-liquid and liquid-liquid-vapor equilibria covering pressures ranging from reduced to atmospheric.     

THE SWELLING BEHAVIOR OF (W/O)/W LIQUID SURFACTANT MEMBRANE (Ⅰ) ADSORPTION OF SURFACTANT AT THE INTERFACE AND THE SWELLING CAUSED BY EMULSIFICATION

The concept of effective concentration of surfaetant in membrane phase has been proposed,considering the high ad-sorption density of the surfactant at the droplet interfaces in LSM system.The effective concentration of surfactant,C_2,can be estimated by Eq.(7)—(9).The swelling caused by emulsification during the initial dispersion process was investigated.The swelling rate wasmeasured by a density method.A model for estimating the“Emulsification”swelling rate,F_(se),has been proposed,basedon a mechanism of swelling due to the entrainment of water resulted from the interracial turbulence and emulsification inthe initial dispersion process.It has been found that Eq.(26)gives excellent fit to the experimental data of Fujinawa,etal.and of the authors.     

STUDIES ON VAPOR-LIQUID AND LIQUID-LIQUID-VAPOR EQUILIBRIA FOR THE TERNARY SYSTEM METHANOL-METHYL METHACRYLATEWATER (Ⅰ) THREE BINARY SYSTEMS

Isothermal P-x data tor the binary systems methanol-methyl methacrylate and methanol-water, and isothermal P-x'-x\" data for the binary system methyl methacrylate-water have been determined at 25, 35, 45, 55 and 60℃. Based on the maximum likelihood principle, the modified UNIQUAC model pa rameters for these binary systems were obtained by fitting the experimental data. Vapor compositions were then calculated, and the results were compared with literature data.     

PREPARATION AND ADSORPTION PROPERTIES OF THE POLYSTYRENE RESIN HAVING DIETHYLENETRIAMINE-N,N′- BIS(METHYLENEPHOSPHONATE) GROUP

Styrene-divinylbenzene copolymer beads containing diethylenetriamine-N,N′-bis(methylenephosphonate) group have been synthesized. The adsorption properties, of the present resin for some trivalent and bivalent metal ions have been examined. The selectivity sequence of the present resin at pH lower than 2.0 is as follows: Ga(III)> A1(III)> Sm(III)>Cu(II)>Co(II)>Zn(II)>Ca(II). The present resin reveals remarkable selectivity for the trivalent metal ions. The selective concentration of In(III) Ga(III) and Sm(III) from an acidic aqueous solution has been demonstrated by using a column of the present resin.     

COBALT–NICKEL SEPARATION: THE EXTRACTION OF COBALT(II) AND NICKEL(II) WITH BIS(2-ETHYLHEXYL) PHOSPHINIC ACID (PIA-8) IN TOLUENE

The extraction behaviour of cobalt(II) and nickel(II) from sulfate solutions with bis(2-ethylhexyl) phosphinic acid (PIA-8) in toluene has been studied. Quantitative extraction of Co(II) was observed at pH 5.0–5.9 while that of Ni(II) at pH 6.8–7.0 with 0.03 M PIA-8 in toluene. The difference in pH_0.5 for Co(II) and Ni(II) was 1.9. The stoichiometry of the extracted species were determined by slope analysis method. The extraction reaction proceeds by cation exchange mechanism and the extracted species were Co · R₂(HR)₂ and Ni · R₂ · 2(HR)₂. Temperature dependance of the extraction equilibrium constants were determined to estimate the apparent thermodynamic functions (ΔG, ΔS and ΔH). The method was used for separation of cobalt(II) and nickel(II). Cobalt(II) was separated from nickel even at 1:20 (Co:Ni) ratio. The separation of cobalt(II) from nickel(II) was favoured with the increase in temperature.