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Salt-lake brines containing high lithium (Li) contents are highly saline solutions with total dissolved solids on the order 300 g/L with Li+ concentrations around 1 g/L only. A drastic increase in ...

The potential application of electrodialysis (ED) for arsenic (As) removal from water was investigated by evaluating the influence of operational parameters on removal efficiency of As. The applied...

Katsutoshi Inoue, May 4, 2009On behalf of the contributors and all of the colleagues and students who were touched by his teaching, we are honored to dedicate this Special Issue in celebration of E...

Separation of platinum and palladium, using solvent-impregnated resin (SIR) impregnating di-hexylamine (DHA), di-n-octylamine (DOA), or di-hexyl sulfide (DHS), coated by polyvinyl alcohol crosslink...

The adsorption equilibria of lithium from geothermal water were investigated by using both powdery and granulated forms of λ-MnO2 derived from spinel-type lithium manganese dioxide. Optimum amounts...

Separation and recovery of tetramethyl ammonium hydroxide (TMAH) was investigated using several types of MCM-41 (mesoporous silica having hexagonal structure) adsorbents. The MCM-41s were prepared by hydrothermal synthesis with structure-directing agents with different alkyl chains. The prepared MCM-41s were characterized with X-ray diffraction, transmission electron microscope, nitrogen gas adsorption, and zeta potential, and then used for adsorption of TMAH. The adsorption of TMAH with MCM-41s increased with pH up to pH ≈ 10 and then decreased as the MCM-41 dissolved. The adsorption of TMAH progressed via the Langmuir mechanism. The maximum adsorption corresponded to the pore diameter and the pore volume of the MCM-41s. MCM-41 also possesses selectivity for TMAH against phenol. The chromatographic operation was conducted using granulated MCM-41 to avoid excessive pressure-drop through the packed column and quantitative adsorption-elution processing of TMAH could be achieved.

Selective recovery of copper, cobalt, and nickel from acidic chloride media was investigated with solvent impregnated resins (SIRs) containing acidic organophosphorus extractants. The adsorption of each metal with the SIR proceeds via a cation exchange mechanism. An SIR containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC-88A) has high selectivity for Cu2+, and the order of selectivity is Cu2+ > Co2+ > Ni2+. Effective adsorption-elution can be achieved by chromatographic operation for the selective recovery of Cu2+ from a ternary metal solution. High selectivity for Co2+ was observed using a SIR comprising bis-2,4,4-trimethylpentylphosphinic acid (Cyanex 272) and can be effectively separated from a Co and Ni binary metal solution by column adsorption. A simple and effective process flow sheet is proposed for selective recovery of Cu2+, Co2+, and Ni2+ from aqueous chloride media using the two SIRs.

Recovery of Li+ from geothermal water has been investigated using a combination of adsorptive separation with magnetite and λ-MnO2 adsorbents. The inhibition of Li+ adsorption together with decomposition of λ-MnO2 was observed when geothermal water containing As was fed to the column in which λ-MnO2 was packed. Magnetite (Fe3O4) was therefore used for removal of As from the geothermal water, prior to adsorption of Li+. Using As removal from the geothermal water with magnetite, decomposition of λ-MnO2 was significantly prevented during adsorption of Li+, although a small amount of As still remained.

Batch and column mode tests were carried out to evaluate the efficiency of boron and arsenic removal from geothermal water in Kyushu Island, Japan by an ion exchange method. The geothermal water contained 34.0 mg-B/L and 3.23 mg-As/L. The sorption tests were performed using boron selective ion exchange resins (Lewatit MK 51 and Diaion CRB 03) and arsenic selective ion exchange resins (Lewatit FO 36, ArsenXnp). The optimum concentration of resin for boron removal from geothermal water was determined as 5.0 g/L-geothermal water for both Lewatit MK 51 and Diaion CRB 03 resins. On the other hand, Diaion CRB 03 performed better than Lewatit MK 51 during the column-mode study. For arsenic removal, the optimum resin amount was found as 6.0 g/L-geothermal water for both Lewatit FO 36 and ArsenXnp resins. It was observed that Lewatit FO 36 was more effective than ArsenXnp for the removal of As from geothermal water.

Selective recovery of lithium from seawater was conducted by using two successive processes of ion exchange methods. The preliminary concentration process of lithium from seawater, using the benchmark-scale chromatographic operation with a granulated λ-MnO2 adsorbent, showed the recovery efficiency of lithium at ca. 33%. The purification of lithium from concentrated liquor from the benchmark plant was then conducted with a novel separation process which was developed by a combination of ion exchange methods using cation exchange resin and solvent impregnated resin. The purification process of lithium consists of the removal of divalent metal ions in the liquor with strongly acidic cation exchange resin; the removal of Na+ and K+ with the β-diketone/TOPO impregnated resin; and lastly the recovery of Li+ as precipitates of Li2CO3 using (NH4)2CO3 saturated solution. The yield of recovered Li2CO3 with the present recovery process was 56% with more than 99.9% purity.

The extraction equilibria of In3+, Ga3, and Zn2+ with bis(4‐ethylcyclohexyl)phosphoric acid (D4ECHPA), bis(4‐cyclohexylcyclohexyl)phosphoric acid (D4DCHPA), and bis(2‐ethylhexyl)phosphoric acid (D2EHPA) were investigated in acidic aqueous sulfate media. The order of extractability of metal ions is D4DCHPA > D2EHPA > D4ECHPA, which corresponds to the lipophilicity (log P) of the extractants. The separation factors, β(In/Ga) and β(Ga/Zn), of D4ECHPA and D4DCHPA are greater or comparable than that of D2EHPA, because of the steric hindrance of the bulky cyclohexyl groups. In3+ can be therefore separated from simulated liquor containing a high concentration of Zn2+ by D4DCHPA.

O,O′‐decanoyl chitosan and O,O′‐decanoyl N,N‐didecanoyl chitosan, the lipophilic chitosans, as well as O,O′‐decanoyl chitin, the lipophilic chitin, were prepared from chitosan and chitin, respectively. All of these were soluble in chloroform, and the lipophilic chitosans were also soluble in toluene while O,O′‐decanoyl N,N‐didecanoyl chitosan was soluble also in hexane and kerosene. Solvent extraction of some selected metals, Cu(II), Ni(II), Co(II), Zn(II), Fe(III) and Pb(II), were tested using these lipophilic polysaccharides in chloroform. For extraction with O,O′‐decanoyl N,N‐didecanoyl chitosan, tests were also carried out using kerosene as the diluent. With O,O′‐decanoyl chitin, none of the metals tested were appreciably extracted. With O,O′‐decanoyl chitosan, copper(II) was highly selectively extracted over the other metals, while iron(III) was not appreciably extracted. On the other hand, iron(III) and copper(II) were selectively extracted over the other metals with O,O′‐decanoyl N,N‐didec...

p-(l,l,3,3-Tetramethylbutyl)phenyl hydrogen[N,N-di(2-ethylhexyl)amino-methylphosphonate was synthesized as a novel type of extractant to investigate the extraction behavior of base metals as well as of precious metals from aqueous chloride media into toluene. This reagent exhibited high selectivity for platinum (IV) and palladium (II) ions in the low acidic region (0·01 - 6 mol dm−3) / over base metal ions except for trivalent iron over the whole concentration region under the present experimental conditions. The extraction of platinum and palladium with p-( 1,1,3,3-tetramethylbutyl)phenyl hydrogen[N,N-di(2-ethylhexyl)aminomethyl-phosphonate was higher than that with N,N-di(2-ethylhexyl)aminomethyl-phosphonic acid due to its high lipophilicity. Stripping of the loaded palladium was achieved with an aqueous mixture of I mol dm−3 thiourea in combination with I mol dm−3 hydrochloric acid. The extraction reaction of palladium from aqueous chloride media into toluene was found by slope analysis to be ...

A novel sulfur-containing solvent extraction reagent, 3,3-diethylthietane (DETE) was synthesized and its extraction mechanism of platinum (IV) from aqueous hydrochloric acid solution was investigated at 30 °C in terms of the equilibrium distribution and extraction kinetics as well as its aqueous distribution and inter-facial adsorption equilibrium. Toluene was used as a diluent. It was elucidated that platinum(IV) is extracted as a solvated complex of the type, PtCl4-4DETE. DETE was found to have no inter-facial activity and the aqueous partition coefficient as high as 8.17xl0-4. Extraction rate was measured by using a vigorously stirred cell. It was of the first order with respect to DETE while it is 0th and inversely first order with respect to chloride ion in its low and high concentration region; this result was interpreted in terms of the classical hetero-phase homogeneous reaction model.

A few novel kinds of sulfur-containing extracting reagents, i.e. 2-ethyl-2-(isobutylthiomethyl)butanethiol (EIBTMBT), 3,3-diethylthietane (DETE) and 3,3-di-butylthietane (DBTE), were synthesized to investigate their extraction behaviors for mercury(II) from acidic chloride media at 303 K and compared with that of di-hexylsulfide (DHS), a conventional sulfur-containing extracting reagent. 1,2-dichloroethane was used as a diluent for all reagents. Mercury(II) was found to be extracted with DETE and DBTE according to solvation reaction mechanism as 1:2:2 metahchloride ion:reagent complexes as well as with DHS as follows: The evaluated extraction equilibrium constants for DETE and DBTE were virtually the same, i.e. Kc = 2.3, regardless of the Length of the alkyl radicals and, surprisingly, less than that for DHS (Kc =7.3). On the other hand, it was found to be extracted with EIBTMBT as a 1:2 metal:reagent chelate according to the following extraction reaction

Distribution equilibria were investigated for the adsorption of metal ions and acids on Sumichelate MC-10 resin, a polyethylene polyamine type of novel chelating resin. The total exchange capacitie...

The equilibrium distribution of platinum(IV) between hydrochloric acid and trioctylphosphine oxide (T0P0) in toluene at 303 K was examined. From the concentration dependencies of the distribution ratio, it was determined that platinum(IV) is extracted as follows: The extraction.equilibrium constant was found to be Ke = 3.6×103.

Equilibrium distribution of palladium(II) was investigated in the solvent extraction with tri-octylmethylammonium chloride (QC1) in toluene from hydrochloric acid solutions at 303 K. The title extracting reagent extracted hydrochloric acid as the species of the types, QC1(HC1) (n(n= 1,2), according to the similar extraction reactions as observed in the extraction of organic acids such as acetic acid and phenol with high-molecular-weight amines in the previous works. From the concentration dependencies of the reactant species on the distribution ratio and from the result of loading test, it was elucidated that palladium(II) is extracted as a mononuclear ion pair complex of the type, Q+;[PdCl]3 (HCl)] in the very high concentration region of hydrochloric acid. The equilibrium constant of the extraction reaction was evaluated.

A comparative investigation on the solvent extraction equilibria of gallium(III) from aqueous nitrate media was conducted with three kinds of acidic organophosphorus compounds, di (2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethylhexyl 2-ethyl-hexylphosphonic acid (EHEHPA) and di (2,4,4'-trimethylpentyl) phosphinic acid (DTMPPA), in toluene at 303 K. It was found that gallium(III) is extracted as 1:4 metal:reagent complexes with D2EHPA and EHEHPA and as a 1:3 complex with DTMPPA in the region of low loading ratio while it is extracted as 1:3 complexes with all reagents at high loading ratio. The extraction equilibrium constants with these extractants were evaluated for the former complexes as follows: Ke = 2.3xl0-2, 8.5xl0-3 and 1.3xl0-4 for D2EHPA, EHEHPA and DTMPPA respectively.