Selective adsorption of lead(II) from aqueous solution.

Adsorptive separation of Pb(II) from aqueous solution containing Pb(II) and other heavy metals (Cu(II), Zn(II) and Cd(II)) has been investigated, using three adsorbents, such as an iminodiacetic acid-chelating resin (CR11) and Fe-based adsorbents (goethite and magnetite). Batchwise adsorption of Pb(II) and other metal ions in single metal system and multi-components system was carried out with varying parameters, such as pH, time and initial concentrations of metals. CR11 possesses the highest adsorption ability for these metals, while the selectivity of individual metal is little. Goethite possesses selectivity for Pb(II) and Cu(II), and magnetite possesses selectivity for Pb(II), though the adsorption capacity for the metals is less than those with CR11. The kinetics of the adsorption of metals with all adsorbents is of pseudo-second-order, and the magnetite is revealed to have the fastest adsorption kinetics. The three adsorbents can be applied for chromatographic separation for these metals. The magnetite is feasible for selective separation of Pb(II), although complete elution cannot be achieved.

Toxicity of tetramethylammonium hydroxide to aquatic organisms and its synergistic action with potassium iodide.

The aquatic ecotoxicity of chemicals involved in the manufacturing process of thin film transistor liquid crystal displays was assessed with a battery of four selected acute toxicity bioassays. We focused on tetramethylammonium hydroxide (TMAH, CAS No. 75-59-2), a widely utilized etchant. The toxicity of TMAH was low when tested in the 72 h-algal growth inhibition test (Pseudokirchneriellia subcapitata, EC50=360 mg L(-1)) and the Microtox® test (Vibrio fischeri, IC50=6.4 g L(-1)). In contrast, the 24h-microcrustacean immobilization and the 96 h-fish mortality tests showed relatively higher toxicity (Daphnia magna, EC50=32 mg L(-1) and Oryzias latipes, LC50=154 mg L(-1)). Isobologram and mixture toxicity index analyses revealed apparent synergism of the mixture of TMAH and potassium iodide when examined with the D. magna immobilization test. The synergistic action was unique to iodide over other halide salts i.e. fluoride, chloride and bromide. Quaternary ammonium ions with longer alkyl chains such as tetraethylammonium and tetrabutylammonium were more toxic than TMAH in the D. magna immobilization test.

Selective recovery of valuable metals from spent Li-ion batteries using solvent-impregnated resins.

Selective recovery of valuable metals (Cu(2+), Co(2+) and Li(+)) from leachate of spent lithium-ion (Li-ion) batteries was investigated in acidic chloride media using solvent impregnated resins (SIRs). An SIR containing bis(2-ethylhexyl) phosphoric acid (D2EHPA) had high selectivity for Fe(3+) and Al(3+), with an order of selectivity Fe(3+) > Al(3+) > Cu(2+) > Co(2+). Fe(3+) and Al(3+) could be removed from synthetic leachate by precipitation, followed by column adsorption with the SIR containing D2EHPA. The synthetic leachate was then applied to chromatography for selective recovery of Cu(2+), Co(2+) and Li(+). The solution was first fed upward to a column packed with an SIR containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC-88A) for selective separation of Cu(2+), followed by upward feed to another column packed with an SIR comprising PC-88A and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) for selective recovery of Co(2+). Finally, a column packed with a synergistic SIR containing both 1-phenyl-1,3-tetradecanedione (C11phbetaDK) and tri-n-octylphosphine oxide (TOPO) was used for selective recovery of Li(+). A process flowsheet is proposed for selective recovery of Cu(2+), Co(2+) and Li(+) using several SIRs. This process was found to be simple and efficient for selective recovery of valuable metals from leachate of spent Li-ion batteries. Pure copper, cobalt and lithium products were obtained, with high elution yields.

Analytical survey of arsenic in geothermal waters from sites in Kyushu, Japan, and a method for removing arsenic using magnetite.

The objective of this study was to survey the cation and anion contents of geothermal waters to gather fundamental information on geographical variations. Sixteen sites in hot spring areas on the island of Kyushu in Japan were studied. The study focused on the arsenic content of the samples. Very high arsenic concentrations (more than 0.1 mg/l) were detected in most of the geothermal waters sampled. High contents of boron and fluoride (more than 1.0 mg/l) were also detected in some samples. Arsenic removal was performed on a laboratory scale using columns packed with a magnetite-type adsorbent. The reduction of arsenic contamination to a concentration of less than 0.01 mg/l could be achieved in the early stages of adsorption (bed volume = 200).

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.

Effects of fifteen rare-earth metals on Ca2+ influx in tobacco cells.

Effects of naturally existing rare-earth metals (REMs; atomic numbers, 39, 57-60, 62-71; Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), added as chloride salts, on Ca2+ influx induced by two different stimuli, namely hypoosmotic shock and hydrogen peroxide, were examined in a suspension-cultured transgenic cell line of BY-2 tobacco cells expressing aequorin, a Ca(2+)-sensitive luminescent protein in cytosol. Most REM salts used here showed inhibitory effect against Ca2+ influx. Especially NdCl3, SmCl3, EuCl3, GdCl3 and TbCl3 showed the most robust inhibitory action. In contrast, LuCl3, YbCl3, ErCl3 and YCl3 were shown to be poor inhibitors of Ca2+ influx. Since REMs tested here form a sequential range of ionic radii from 86.1 to 103.2 pm and the optimal range of ionic radii required for blocking the flux of Ca2+ was determined for each stimulus. The hydrogen peroxide-induced Ca2+ influx was optimally blocked by REMs with a broad range of ionic radii (93.8-101 pm) which is slightly smaller than or similar to that of Ca2+ (100 pm), while the hypoosmotically induced flux of Ca2+ was inhibited optimally by few REMs with a narrower range of relatively smaller ionic radii around that of Gd3+ (93.8 pm) a well known inhibitor of stretch-activated channels. Possible applications of such series of channel blockers in elucidation of plant signal transduction pathways are encouraged.

Micro flow injection analysis combined with a separation technique for the urinary glucose assay.

A urinary glucose assay has been investigated, employing a micro flow injection analysis (microFIA) combined with a separation technique of glucose from the analyte. The adsorption part using activated alumina for the glucose in the analyte can be successively integrated onto a microFI chip. The selective adsorption-desorption of glucose in the artificial urine can progress on the adsorption part. Along with this selective preconcentration of glucose, the typical FI peak of glucose can be obtained just by feeding the sample and deionized water as an elutant sandwiched with the reagent on the carrier stream. The glucose concentration in artificial urine can be quantitatively determined with the present microFIA system, while the interference of other components coexisting in urine occurs in the case of the conventional FIA system without any separation part. The described method serves as a template for improving the selectivity for the analyte in the multi-component system.

Action of aluminum, novel TPC1-type channel inhibitor, against salicylate-induced and cold-shock-induced calcium influx in tobacco BY-2 cells.

Previously, effect of Al ions on calcium signaling was assessed in tobacco cells expressing a Ca2+-monitoring luminescent protein, aequorin and a newly isolated putative plant Ca2+ channel protein from Arabidopsis thaliana, AtTPC1 (two-pore channel 1). TPC1 channels were shown to be the only channel known to be sensitive to Al and they are responsive to reactive oxygen species and cryptogein, a fungal elicitor protein. Thus, involvement of TPC1 channels in calcium signaling leading to development of plant defense mechanism has been suggested. Then, the use of Al as a specific inhibitor of TPC1-type plant calcium channels has been proposed. Here, using transgenic tobacco BY-2 cells expressing aequorin, we report on the evidence in support of the involvement of Al-sensitive signaling pathway requiring TPC1-type channel-dependent Ca2+ influx in response to salicylic acid, a key plant defense-inducing agent, but not to an elicitor prepared from the cell wall of rice blast disease fungus Magnaporthe grisea. In addition, involvement of Al-sensitive Ca2+ channels in response to cold shock was also tested. The data suggested that the elicitor used here induces the Ca2+ influx via Al-insensitive path, while salicylic acid and cold-shock-stimulate the influx of Ca2+ via Al-sensitive mechanism.

Advance of computational technology for simulating solvent extraction.

Due to recent significant enhancement of computer performance as well as computational techniques, molecular modeling and molecular simulations using computational chemistry can be achieved at the level of practical applications. Even in solvent extraction, the application of computational chemistry to simulations of extraction processes and the molecular design of high-performance extracting agents have gradually been increasing during the last decade. With combining the quantitative structure-property relationship between the molecule properties calculated by the computational chemistry methods and the thermodynamic properties obtained from experiments, researchers can precisely predict the next-generation of extracting agents and novel extraction processes. In this review, the concept of computational chemistry, such as molecular mechanics, molecular orbitals and molecular dynamics calculations, frequently used in the filed of solvent extraction, are outlined. Our systematic research on the solvent-extraction process utilizing MM, MO and MD calculations is also presented.