Wladyslaw Walkowiak

Removal of chromium(VI) from aqueous solutions by polymer inclusion membranes

The transport through polymer inclusion membranes (PIMs) was found as the effective and selective method of chromium(VI) anions removal from chloride acidic aqueous solutions. The optimal PIMs content was as follows: 41 wt% of cellulose triacetate as the support, 23 wt% of tri-n-octylamine as the ionic carrier, and 36 wt% of o-nitrophenyl pentyl ether as the plasticizer. The results obtained show a linear decrease of permeability coefficient and initial flux values with source phase pH increase. Also linear decrease of initial flux in log-log scale with chromium(VI) concentration increase was observed. Value of slope of this relationship was found to be 0.96 which indicates a first order of chromium(VI) reaction with tri-n-octylamine at membrane/aqueous source interface. Transport of chromium(VI) through PIMs reduces the concentration of chromium(VI) in source aqueous phase from 1.0 to 0.0028 ppm, which is below permissible limit in drinking water in Poland. Competitive transport of chromium(VI), cadmium(II), zinc(II), and iron(III) from acidic aqueous solution across PIMs was found to be efficient for chromium(VI) (99%), and cadmium(II) (99%).

Separation of Co(II) and Ni(II) ions by supported and hybrid liquid membranes

Abstract In this work a competitive transport of an equimolar mixture of cobalt(II) and nickel(II) across supported and hybrid liquid membranes is presented. In both types of membranes di-2-ethylhexylphosphoric acid (D2EHPA) as well as commercial extractants, i.e. Cyanex® 272, 301, and 302 were used as ion carriers. In experiments with the supported liquid membranes, the support applied for the liquid membrane was microporous, hydrophobic polypropylene Celgard® 2500. This film was soaked in 0.1 M organic solution of an ionic carrier in kerosene. The hybrid liquid membranes were made by composition of the cation-exchange membranes (CEM) with bulk liquid membrane in the system: CEM–organic phase–CEM. The source aqueous phase was composed of an equimolar mixture of Co(II) and Ni(II) ions in sulfuric acid aqueous solutions. As receiving phase, sulfuric acid solutions of higher concentration than the source phase were utilized. The influence of several factors on cation transport selectivity and effectiveness has been explored. These factors include the effect of (a) acidity of the source and receiving phases, (b) initial concentration of metal ions in the source phase and (c) concentration of ion carrier in membranes. It is shown that supported and hybrid liquid membranes, containing phosphoorganic acids allow to separate a Co(II)/Ni(II) equimolar mixture. The separation of Co(II)/Ni(II) was found to be governed by the ionic carrier used as well as the acidity of the aqueous source phase. In the hybrid liquid membrane processes lower metal ion fluxes than in supported liquid membranes processes were observed. On the other hand, higher separation coefficients for Co(II)/Ni(II) were found for hybrid than for supported liquid membrane processes.

Separation and Removal of Metal Ionic Species by Polymer Inclusion Membranes

Competitive alkali metal cation transport across polymer inclusion membranes (PIMs) containing sym-(alkyl)dibenzo-16-crown-5-oxyacetic acid carriers provides excellent selectivity for Na+ transport with the total fluxes being strongly influenced by the length of the alkyl chain that is attached geminal to the functional side arm in the lariat ether. Removal of chromium(VI) anions by PIMs from acidic aqueous phases was also investigated. Using tri-n-octylamine (TOA) as the ion carrier, Cr(VI) was removed by a PIM to decrease the source phase metal concentration from 1.0 to 0.010 ppm after 30 hours of transport. Competitive transport of Cr(VI) and Cr(III) ions from acidic source phases through PIMs and supported liquid membranes (SLMs) containing TOA and tri-n-octylphosphine oxide (TOPO) as carriers was evaluated and a very high Cr(VI)/Cr(III) separation ratio of 4800 was achieved with a PIM containing TOA. Competitive transport of Zn(II), Cd(II), and Cr(VI) from acidic aqueous solutions through PIMs containing TOA was investigated. The selectivity order for metal ion transport was: HCrO4−>CdCl42−+CdCl3−>ZnCl42−+ ZnCl3−. Non-contact atomic force microscopy was used to obtain images of the pores in cellulose triacetate membranes containing a plasticizer.

Selective Transport of Alkali Metal Cations in Solvent Extraction by Proton-Ionizable Dibenzocrown Ethers

Abstract Lipophilic crown ethers with pendant proton-ionizable groups are novel metal complexing agents for use in solvent extraction of alkali metal cations. A variety of dibenzocrown ether carboxylic acids and dibenzo crown phosphonic acid monoesters have been examined to probe the effect of structural variation within the complexing agent upon selectivity and efficiency in solvent extraction. Results from competitive solvent extractions of alkali metal cations from aqueous solutions into chloroform are summarized.

Transport of Cr(VI), Zn(II), and Cd(II) Ions Across Polymer Inclusion Membranes with Tridecyl(pyridine) Oxide and Tri-n-Octylamine

ABSTRACT An experimental investigation of chromium(VI), zinc(II), and cadmium(II) ions removal from acidic chloride aqueous solutions by transport through polymer inclusion membrane (PIM) with basic ion carriers [i.e., 4-(l′-n-tridecyl)pyridine N-oxide (TDPNO) and tri-n-octylamine (TOA)] is presented. The initial fluxes of all metal ions are higher for the less basic carrier (i.e., TDPNO). On the other hand, the more basic carrier (i.e., TOA) gives higher Cr(VI)/Cd(II) and Cr(VI)/Zn(II) selectivity coefficients. In long-term chromium(VI) transport experiments, the aqueous source and receiving phase were renewed every day, whereas the PIM remained the same as in the first run: the small decrease of permeability coefficient was observed, which can be explained by the partitioning of the carrier between the membrane and the aqueous solutions. A long-term experiment was conducted out to demonstrate the durability of PIMs. The application of PIM transport process for 99% removal of chromium(VI) from galvanic wastewaters is also shown.

Effect of solvent in competitive alkali metal cation transport across bulk liquid membranes by a lipophilic lariat ether carboxylic acid carrier

Abstract Fluxes and selectivities for competitive alkali metal cation transport across bulk liquid membranes by the lipophilic crown ether carboxylic acid carrier sym -(octyl)dibenzo-16-crown-5-oxyacetic acid have been determined in a variety of chlorinated hydrocarbon and aromatic hydrocarbon solvents. The membrane solvents include: dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, o -dichlorobenzene, toluene and p -xylene. The total alkali metal cation and Na + fluxes, as well as the Na + /K + and Na + /Li + transport selectivity ratios, are compared with selected properties of these organic solvents using the Schmidt, Swain, Koppel–Palm and Kamlet–Taft models. The best correlations are obtained for the Na + flux and the Na + /K + transport selectivity.

Competitive transport of toxic metal ions by polymer inclusion membranes

The paper gives a short overview of application of polymer inclusion membranes (PIMs) for separation and removal of metal ions. Investigation of the selective removal of toxic metal ions, i.e. Cr(VI), Cd(II), Zn(II) from acidic chloride aqueous solutions, as well as trace radionuclides, i.e., 137Cs, 90Sr and 60Co from wastewaters using transport across polymer inclusion membranes was studied. The carriers, i.e., tri-n-octylamine for anionic metal species, as well as dibenzo-21-crown-7, tertbutyl-dibenzo-21-crown-7, and dinonylnaphtalenesulfonic acid for metal cations were incorporated into polymer inclusion membranes composed of cellulose triacetate as a support and o-nitrophenyl pentyl ether as a plasticizer. Selective transport of chromium(VI) over zinc(II) and cadmium(II) chloride complexes through PIMs was observed. Competitive transport of trace radionuclide ions, i.e., 137Cs, 90Sr, and 60Co from NaNO3 aqueous solutions across polymer inclusion membranes containing a mixture of dinonylnaphtalenesulfonic acid, and dibenzo-21-crown-7 as the carrier provide the selectivity order Cs(I)>Sr(II)>Co(II).

Mechanism of Selective Ion Flotation. 1. Selective Flotation of Transition Metal Cations

Abstract An experimental investigation is presented of the batch ion flotation of the transition metal cations Cr3-, Fe3+, Mn2+, Co2+, Zn2+, Ag+, Cd2+, and In3+ from acidic aqueous solutions with sodium dodecylsulfonate and sodium dodecylben-zenesulfonate as anionic surfactants. The selectivity sequences Mn2+ < Zn2+ < Co2+ < Fe3+ < Cr3+ and Ag+ < Cd2+ < In3+ are established, both from data for single and multi-ion metal cations solutions, where sublate was not formed in the bulk solution. Good agreement between the selectivity sequences and the values of ionic potential of metal cations was found. An experimental investigation was also performed on the solubility of sublates. The sublates solubility values are discussed in terms of ionic potentials of metal cations as well as of the surfactant size.

Selective separation of alkali metal cations by bulk chloroform membranes containing lipophilic crown ether phosphonic acid monoethyl esters

Abstract A series of crown ether phosphonic acid monoethyl esters with crown ether ring size variation from 12-crown-4 to 24-crown-8 is used in bulk chloroform membranes to separate alkali metal cations from mixtures. Selective proton-coupled transport of alkali metal cations from weakly alkaline aqueous phases is achieved. With individual ionizable crown ether carriers, transport selectivity for Li+, Na+, K+, and Rb+-Cs+ is achieved. A closely related lipophilic phosphonic acid monoethyl ester derivative with a cyclohexyl unit in place of the crown ether exhibits transport selectivity for Li+. However, the corresponding phosphonic acid diethyl ester is devoid of transport activity. Effects of structural variation within the carrier upon the selectivity and efficiency of competitive alkali metal cation transport are assessed.

Ion Flotation of Zinc(II) and Cadmium(II) in the Presence of Side-Armed Diphosphaza-16-Crown-6 Ethers

Competitive flotation of zinc(II) and cadmium(II) ions from dilute aqueous solutions by side-armed lariat ether-type derivatives of diphosphaza-16-crown-6 ethers in the presence of nonylphenol nonylethylene glycol ether as the non-ionic foaming agent has been investigated. The influence of the type of group attached to the PNP-lariat ether molecule on the selectivity and efficiency of Zn(II) and Cd(II) ion flotation is studied. An effect of alkali metal cations, i.e., Li+ and Na+, on Cd(II) ion-flotation removal is also reported. It was shown that the removal of Cd2+ increases with increase of pH values and decreases with alkali metal cations concentration increase in aqueous solutions. The correlation between selectivity coefficients of Cd(II)/Zn(II) and pH of aqueous solution as well as molar intrinsic volume and hydrophilic–lipophilic balance of studied ethers was found.