Kazuharu Yoshizuka

Adsorptive separation of some metal ions by complexing agent types of chemically modified chitosan

Two kinds of chemically modified chitosan immobilizing the ligands of ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) or diethylenetriamine-N,N,N′,N″,Ni″- pentaacetic acid (DTPA) onto polymer matrices of chitosan (EDTA– and DTPA–chitosan) were prepared by interacting the anhydrides of these complexing agents with chitosan. By incorporating these ligands, the adsorption of metal ions are much enhanced compared with original chitosan. For example, adsorption of Cu(II) takes place at pH=0–1 on these chemically modified chitosan, while it takes place at pH=4–6 on original chitosan. The observed order of selectivity for some metal ions are nearly the same for both of EDTA– and DTPA–chitosan in the adsorption from sulfuric acid solution: Ga(III)=In(III)=Fe(III)>Cu(II)=Mo(VI)>Ni(II)>V(IV)≫Zn(II)=Co(II)≫Al(III)≫Mn(II). This is nearly the same as the order of the stability of these metal chelates with these complexing agents, suggesting that the chelating ability of these ligands is still maintained after immobilizing these on polymer matrices of chitosan. Based on these basic data obtained in batchwise experiments, breakthrough and elution tests were carried out using a column packed with the EDTA– or DTPA–chitosan together with glass beads for some pairs of metal ions: e.g. same dilute concentrations of Co(II) and Ni(II) as well as small amounts of Co(II) together with a large excess of Al(III). These tests demonstrated that very clear-cut mutual separations between these pairs of metal ions can be successfully achieved by these complexing agent types of chemically modified chitosan.

Extraction and selective stripping of molybdenum(VI) and vanadium(IV) from sulfuric acid solution containing aluminum(III), cobalt( II), nickel(II) and iron(III) by LIX 63 in Exxsol D80

Abstract 5,8-diethyl-7-hydroxydodecane-6-oxime (LIX 63), a commercially available reagent, has been used in this work to investigate the extraction of molybdenum(VI) and vanadium(IV) from sulfuric acid solution in the presence of various other metals, such as aluminum(III), cobalt(H), nickel(II) and iron(III). Molybdenum(VI) and vanadium(IV) were extracted preferentially and separated completely from the coexisting metals involved at low pH (e.g., around 1.5) with LIX 63 dissolved in Exxsol D80. Vanadium(IV) in the loaded organic phase was selectively stripped by contacting with a 2 M sulfuric acid solution and isolated from molybdenum(VI). Molybdenum(VI) in the organic solvent, after the removal of vanadium(IV), was easily stripped by employing an aqueous ammonia solution as stripping agent and excellent phase separation performance (rapid phase separation, no formation of a second organic phase and no generation of an emulsion) in the stripping process was observed in all cases. A special emphasis, at least as an example of potential application, has been put on the extraction recovery of molybdenum(VI) and vanadium(IV) with LIX 63 extractant from the acidic sulfate liquor containing a sufficient quantity of aluminum(III), an appreciable amount of cobalt(II) and nickel(II), as well as a small amount of iron(III), resulting from the sulfuric acid leaching of spent hydrodesulfurization catalysts. The results obtained using the synthetic solution are in good agreement with those using the real leach liquor.

Silver-complexed chitosan microparticles for pesticide removal

Two types of chitosan microparticles (CMs) and their silver-complexes CMs (SCMs) were prepared using different crosslinking agents, i.e. glutaraldehyde and epichlorohydrin, in order to investigate the adsorption and release behaviors of a typical pesticide, methyl parathion (MP). The pH and concentration dependencies on Ag(I) and MP adsorptions on both the CMs and SCMs were studied. The epichlorohydrin-crosslinked CM apparently showed the superiority of Ag(I) adsorption over the glutaraldehyde-crosslinked CM, nevertheless, adsorption behavior of MP on SCM derived from each CM was observed vice versa. Release behavior of MP from the MP-loaded SCMs was also observed in aqueous acetic acid and sodium acetate buffer solutions at low pH as well as in those containing two kinds of ammonium reagents. The aqueous solutions containing ammonium thiocyanide and ammonia could be applied for MP release from the MP-loaded SCMs without Ag(I) leakage from the particles. Furthermore, from the iteration of adsorption and release experiments of MP, glutaraldehyde-crosslinked SCM provides good reusability for MP removal.

Distribution equilibria in the adsorption of cobalt(II) and nickel(II) on Levextrel resin containing Cyanex 272

Abstract Equilibrium distributions of cobalt(II) and nickel(II) were measured in the adsorption on Levextrel resin containing Cyanex 272 as extractant from aqueous ammonium nitrate and sulfate solutions. It was inferred that the extractant in the resin behaves in the same manner as in the solvent extraction. The distribution data were analyzed quantitatively by taking account of the extraction reaction described below to evaluate the apparent equilibrium constants of the extraction reactions for each metal and each aqueous medium as well as the apparent stability constants of cobalt(II)- and nickel(II)-amine complexes. M 2+ +(2+x) H 2 R 2 ⇌ MR 2 ·(2+2x) HR +2 h + where x =0 for cobalt(II) and x =1 for nickel(II). Cobalt(II) is more selectively adsorbed over nickel(II) from sulfate media than from nitrate media though the adsorption itself is suppressed by sulfate anion owing to the formation of metal-sulfato complexes.

Adsorption of Some Platinum Group Metals on Some Complexane Types of Chemically Modified Chitosan

Abstract A few kinds of complexane types of chemically modified chitosan, i.e., monocarboxymethylated chitosan (MCM-chitosan) and IDA- and DTPA-types of chitosan (IDA- and DTPA-chitosan) were synthesized to examine the adsorption of palladium(II), platinum(IV), and iridium(III) from hydrochloric acid solution as well as the elution of palladium and platinum and compared with those by crosslinked copper(II)-complexed chitosan (crosslinked chitosan). The adsorption of palladium(II) monotonously decreased with increasing hydrochloric acid concentration with all kinds of adsorbents. The adsorption of platinum(IV) also decreased with increasing hydrochloric acid concentration with all kinds of adsorbents except for DTPA-chitosan, with which it decreased in the low concentration region and increased in the high concentration region. The adsorption of iridium(III) also decreased with increasing concentration of hydrochloric acid with all kinds of adsorbents except for IDA-chitosan, but that on DTPA-chitosan was ...

Ion exchange/adsorption of rhodium(III) from chloride media on some anion exchangers

Abstract Ion exchange/adsorption of rhodium(III) from chloride media was investigated with some commercial anion exchange resins like Sumichelate MC-10 resin, and Diaion WA10, WA21, SA20A and SA21A resins as well as crosslinked Cu(II)-templated chitosan and compared with Fe(III)-templated oxine type of chemically modified chitosan (Fe-oxine-chitosan) studied in previous work. A significant amount of rhodium is adsorbed from low acidic solution and better distribution ratios of rhodium adsorption on these commercial resins were found in all cases when tin is present in the solution. However, some amount of Rh(III) is also adsorbed in all cases except for Diaion WA10 even in the absence of tin. Rhodium is hardly adsorbed on crosslinked Cu(II)-templated chitosan (Cu-chitosan) when tin is absent in the feed solution. However, in the presence of tin, an appreciable amount of rhodium is adsorbed at low acidity while the distribution ratio decreases with the increase in hydrochloric acid concentration. When tin is present in the solution, the order of adsorption ability of the resins was found to be: WA21>SA21A>MC-10>Fe-oxine-chitosan>WA10>SA20A≈Cu-chitosan at low acidity (about 3 mol/dm 3 HCl), and MC-10>WA21>SA21A>SA20A>Fe-oxine-chitosan>WA10>Cu-chitosan at high acidity (about 9 mol/dm 3 HCl). On the other hand, when tin is absent, the order of adsorption ability was found to be: MC-10>WA21>SA20A>SA21A>WA10>Fe-oxine-chitosan>Cu-chitosan. It is obvious that MC-10 resin possesses the highest adsorption ability where 66.0% rhodium was adsorbed at 3 mol/dm 3 HCl even when tin is absent in the feed solution. The maximum rhodium adsorption capacity of Diaion WA21 was evaluated to be 0.59 and 0.9 mol/kg dry adsorbent when tin is absent and present in the solution, respectively, while the maximum rhodium adsorption capacity of MC-10 resin was evaluated to be 1.4 mol/kg dry adsorbent in both cases whether tin is absent or present in the solution. The adsorption mechanism, in which resin is first protonated on contact with hydrochloric acid and subsequently adsorbs rhodium as an ion-pair complex is proposed. Stripping of rhodium from loaded adsorbents was carried out using some mineral acids accompanied by some oxidizing agents like H 2 O 2 , HNO 3 , NaClO 3 and NaClO. A significant amount of rhodium was stripped by a single contact with these stripping agents. However, the best stripping was accomplished with hydrochloric acid containing sodium chlorate.

Solvent extraction of silver from chloride media with some commercial sulfur-containing extractants

Abstract Different kinds of commercial sulfur-containing extractants (SFI-6R, MSP-8, Cyanex 302 and Cyanex 301 in EXXSOL D-80) were examined to extract silver from chloride media. The aggregation of MSP-8 was analyzed quantitatively by means of vapor-pressure osmometry and it was found that this extractant exists as a dimeric species in aliphatic organic diluents. Extractants containing P = S and P(S)SH functional groups strongly extract silver in the whole concentration range of hydrochloric acid except for the very high concentration region, while SFI-6R only weakly extracts silver in the low concentration region and no extraction was observed in the high concentration region. Extraction equilibrium of silver with SFI-6R was measured by the slope analysis method, while for MSP-8, Cyanex 302 and Cyanex 301 the complex stoichiometries were inferred using Jobs method. It was elucidated that silver is extracted as 1:2 metal:reagent complex with extractants containing one donor atom of sulfur, while the ratio becomes to 1:1 for an extractant having two sulfur donor atoms.

Hydrolysis of triolein by lipase in a hollow fiber reactor

Abstract Hydrolysis of triolein by lipase was carried out in a hollow fiber membrane reactor, oleic acid and glycerol being formed as products. It was found that hydrolysis of triolein by lipase in the hollow fiber reactor can be quantitatively explained by a Michaelis-Menten mechanism at the interface, together with competitive inhibition by oleic acid, diffusion of all chemical species and adsorption of lipase at the interface between the aqueous and organic phases. The reaction model could be applied to a wide range of conversions in the membrane reactor.

Adsorption of Metal Ions on Gallium(III)-Templated Oxine Type of Chemically Modified Chitosan

Abstract The oxine type of chemically modified chitosan was prepared by the template crosslinking method employing gallium(III) ion as a template ion. The functional groups of oxine were found to be incorporated into the polymer chain of chitosan at a oxine/glucosamine unit ratio of 1/3. This value agrees with that expected from molecular modeling computation by the molecular mechanics method. Adsorption of molybdenum(VI), vanadium(IV), indium(III), aluminum(III), zinc(II), iron(II), and cadmium(II) together with gallium(III) on this chemically modified chitosan from dilute sulfuric acid solution was compared with that on the original chitosan. It was found that the pH at which the adsorption of these metals takes place on this chemically modified chitosan shifted to a lower pH than that on the original chitosan. The shift was the greatest for gallium(III) among the metal ions examined, which might be attributable to the template effect of gallium(III) ion. The maximum adsorption capacity of gallium(III) ...

Equilibria of solvent extraction of copper(II) with 5-dodecylsalicylaldoxime

Abstract The equilibrium studies on the solvent extraction of copper(II) with 5-dodecylsalicylaldoxime, the active component of LIX 860, were carried out at 303 K to clarify the effects of the organic diluent and the aqueous media, together with measurements of the apparent molecular weight and aqueous solubility of the extractant. It was found that the title extractant exists as a monomeric species in the organic diluents, i.e., hexane, cyclohexane and toluene and is sparingly soluble in the aqueous solutions as well as other commercial hydroxyoximes. Copper(II) was extracted as a chelate of the type CuR2 in the organic solution and the extraction equilibrium constant in hexane is about five times and twice greater than those in toluene and cyclohexane respectively, and further, the extraction equilibrium constant with 5-dodecylsalicylaldoxime was several times greater than those with other commercial hydroxyoximes. The effect of 1-tridecanol as a modifier on the extraction equilibrium was quantitatively clarified by taking account of the formation of the hydrogen bond between the extractant and 1-tridecanol.