Syouhei Nishihama

Selective Recovery Process of Lithium from Seawater Using Integrated Ion Exchange Methods

Abstract 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.

Removal of Boron and Arsenic from Geothermal Water in Kyushu Island, Japan, by Using Selective Ion Exchange Resins

Abstract 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 Platinum Group Metals from Spent Automobile Catalyst by Integrated Ion Exchange Methods

Selective recovery of platinum group metals (PGMs), such as Pd, Pt, and Rh, from spent automobile catalyst has been investigated by integrated ion exchange method using dihexyl sulfide (DHS) impregnated resin and commercial weak anion exchange resin (Diaion WA-21) as adsorbents. Batchwise adsorption revealed that the DHS impregnated resin possesses the selective adsorption ability for Pd and WA-21 possesses selectivity for all PGMs, especially Rh. Chromatographic separation of Pd with column packed with DHS impregnated resin can be selectively achieved. The chromatographic separation of Pd and Pt with a column packed with WA-21 is effectively progressed, while that of Rh is insufficient yield due to a slow adsorption rate. Separation of Rh from other two PGMs can therefore be achieved by switching the eluent. Both adsorbents show almost no adsorption abilities for other heavy metals containing in the spent automobile catalyst. Sequential chromatographic operation of the column packed with DHS impregnated resin followed by the column packed with WA-21 can be finally achieved to recover mutual PGM from leaching solution of spent automobile catalyst.

Lithium Recovery from Geothermal Water by Combined Adsorption Methods

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.

Solvent Extraction of Indium, Gallium, and Zinc Ions with Acidic Organophosphates having Bulky Alkyl Groups

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.

Seasonal changes in the microbial population of the water column and sediments of the Ongagawa River, northern Kyushu, Japan

The total viable count, population density of Escherichia coli and coliform bacteria, and nitrogen in the microbiomass (microbiomass-N) in sediments were monitored monthly at 12 points in the Ongagawa River basin from June 2002 to May 2006. The measurement of the sediment microbiomass-N was used for evaluation of the sediment’s microbial population in the river ecosystem. An extraordinarily high population of E. coli was observed during the season when there was stagnant water in the basin, with a high population and an insufficient drain diffusion system, and, thus hydrological water control is indispensable to prevent rapid E. coli growth. Microbiomass-N in sediments showed a negative correlation or independent fluctuation in relation to the bacterial population in the water column of the river. Seasonal changes in extracted nitrogen (N) in river sediments did not show correspondence with microbiomass-N in sediments. The microbiomass-N in sediments changed independently of the bacterial population in the river water, indicating that the high population of bacteria in the water does not lead to a high microbial population in river sediments. Ordination of the microbial parameters by canonical correspondence analysis (CCA) showed that microbiomass-N in sediments was quite different from other parameters. Relatively higher H+ (lower pH), PO43− concentration and dissolved oxygen (DO) were the determinant parameters of higher microbiomass-N in sediments. A relative microbial abundance between the water column and sediments as well as each of the microbial populations in the water column and sediments could be a quantitative parameter for evaluating the biochemical processes of stream water.

Separation and Recovery of Tetramethyl Ammonium Hydroxide with Mesoporous Silica Having a Hexagonal Structure (MCM-41)

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 Aqueous Chloride Media using Solvent Impregnated Resins

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.

Micro-flow injection system for the urinary protein assay

A urinary protein assay has been investigated, employing a micro-flow injection analysis (muFIA) combined with an adsorptive separation of protein from analyte. The adsorptive separation part of protein in the artificial urine with ceramic hydroxyapatite is integrated on the muFIA chip, since the interference of other components coexisting in urine occurs in the conventional FIA system. The typical FI peak can be obtained following the adsorption-elution process of the protein prior to the detection, and the protein concentration in artificial urine can be quantitatively determined.

Equilibrium and Kinetic Studies on Lithium Adsorption from Geothermal Water by λ-MnO2

ABSTRACT 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 of adsorbents were 1.0 g adsorbent/L-geothermal water for powdery λ-MnO2 and 6.0 g adsorbent/L-geothermal water for granulated λ-MnO2. The adsorbents exhibited the promising adsorption capacities and their adsorption equilibria of lithium agreed well with the Langmuir adsorption isotherm model. The kinetic data of lithium adsorption have been evaluated using pseudo-first-order, pseudo-second-order kinetics models, as well as Elovich kinetic model. In addition, intra-particle diffusion model has been used for evaluating the kinetic data to evaluate the adsorption mechanism. The adsorption kinetic process was attributed to the gradual adsorption stage where intra-particle diffusion was found as the rate-controlling step.