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In this study, a natural loess soil was evaluated as an adsorbent of Li+ in seawater. Only Li+ was adsorbed preferentially by loess over other cations in seawater despite having the lowest concentration. The adsorption studies of Li+ with loess were assessed using the batch equilibration method. In batch adsorption experiment, the various factors such as agitation time, initial concentration, and amount of dose were investigated. Adsorption isotherm and kinetic studies were performed to quantify the adsorption capacity and adsorption rate of Li+ by loess from seawater. The equilibrium data of adsorption were fitted by using the Freundlich and Langmuir isotherm models. It was seen that the Langmuir isotherm is better in describing the adsorption process of Li+ by loess due to its higher correlation coefficient R2 value. The maximum adsorption capacity of loess for Li+ obtained by Langmuir isotherm was 0.193 mg/g. The pseudo-first-order, the pseudo-second-order, and the intra-particle diffusion kinetic models were employed to analyze the time-dependent adsorption rate of Li+. It was found that the adsorption of Li+ closely follows the pseudo-second-order kinetic model, from which a very accurate estimation of the equilibrium adsorption capacity (qe,cal) was achieved, as well as the higher R2. Because of its low-cost and high selectivity towards Li+, loess could be probably an applicable adsorbent for the recovery of Li+ from seawater.

We report a study on the synthesis and structural characteristics of Si/carbon nanofiber (CNF) and Si/PC/CNF composites. CNFs were synthesized by the chemical vapor deposition using Co and Cu catalysts at a Co:Cu ratio of 6:4. This study focused on the fabrication processes of Si/PC/CNF composites to confirm the contact of Si particles with CNFs. The CNF composites on Si particles were prepared on the basis of the following two processes—Sample 1: CNFs were grown on a simple mechanical mixture of Si particles and catalysts; and Sample 2: CNFs were grown on the surface of pyrolytic carbon-coated Si particles. The morphology and composition of the Si/CNF composites were analyzed by scanning electron microscope and energy dispersive spectroscopy measurements. Physical properties were investigated using X-ray diffraction, Raman, X-ray photoelectron spectroscopy, and thermogravimetric analysis, and the specific surface area was measured by Brunauer, Emmett and Teller. Consequently, pyrolytic carbon coating on the surface of Si particles showed the ability to increase the contact of CNFs to the silicon particles. The resulting pyrolytic carbon-coated Si/CNF (Si/PC/CNF) composite also demonstrated better crystallizability compared with the Si/CNF composite prepared through the first method.

The direct disposal of polychlorinated biphenyls (PCBs) in transformer oil by polyethylene glycols (PEGs) under basic condition is reported. The transformer oil containing PCBs was treated by the required amounts of PEGs and potassium hydroxide (KOH) for different reaction times and temperatures. Complete reaction produces aryl PEGs, which are the products of nucleophilic aromatic substitution. The relative efficiencies of the PCB treatment process were assessed in terms of destruction and removal efficiency (DRE, %). At the experimental conditions of 100 °C and 7 h, 125 °C and 3 h, and 150 °C and 1 h, average DREs of PCBs better than 99.9999% were attained. In studying the chemical reaction of PCBs with PEG/KOH, it was confirmed that the process led to less chlorinated PCBs through a stepwise process with the successive elimination of chlorines. Particularly, the least chlorinated PCBs such as mono- and di-PCBs were not produced in our study. Furthermore, the treated transformer oil can be reused through simple segregating procedures.

Chromium is the seventh most abundant element on earth. 1 It occurs in various oxidation states ranging from Cr(II) to Cr(VI) with trivalent and hexavalent states being the most stable and common in terrestrial environments. The coordination chemistry of chromium(III) complexes is relevant to third generation solar photoconversion scheme. 2 The geometrical isomerism and conformation in transition metal complexes with mixed ligands are very important in the medical application, and likely to be a major factor in determining the antiviral activity and its side-effect. 3,4 2,2Dimethyl-1,3-propanediamine (Me2tn, Fig. 1) is a bidentate ligand that can coordinate to the central metal ion by forming six-membered chelate ring with a chair conformation. The trans-[Cr(Me2tn)2(OH)(H2O)] 2+ can adopt either the trans or cis geometric isomer. In addition, two different kinds of conformation with respect to the chelate rings of Me2tn occur in the trans isomer, as shown in the bottom of Figure 1. The carbon atoms of the two chelate rings of the two conformers may be on the same side (syn conformer) or on the opposite side (anti conformer) of the coordination plane. In the case of trans-anti/syn-[Cr(Me2tn)2Cl2]Cl, trans-anti/ syn-[Cr(Me2tn)2Br2]2Br2·HClO4·H2O and trans-anti/syn[Cr(Me2tn)2Br2]Br, independent syn and anti conformational isomers were found within the same crystals. 5-7 However, structural analyses of trans-anti-[Cr(Me2tn)2(NCS)2]NCS·1/2H2O, trans-anti-[Cr(Me2tn)2Cl2]ClO4, and trans-anti-[Cr(Me2tn)2Cl2]2ZnCl4 indicated that two chelate rings of Me2tn ligands were only in the anti chair-chair conformation. 6-9 The different conformations of the two sixmembered chelate rings of Me2tn ligands may be dependent on the crystallographic disorder, packing forces, hydrated molecules and counter anions in the crystals. The factors which determine the stability of these geometric conformations are subtle and complicated. 5-9 X-ray crystallography is generally used to establish the presence of either conformation but the syn or anti conformer of the six-membered chelate rings cannot be readily discriminated by infrared and visible absorption spectroscopy. The elucidation of the factors that stabilize the either the syn- or anti-conformation in these complex cations continues to be of interest. Here we report the synthesis, crystal structure and spectroscopic properties of the trans-anti-[Cr(Me2tn)2(OH)(H2O)](ClO4)2 with the purpose of elucidating the influence of Odonor ligands occupying the axial positions and counter anions, on the geometry and the conformation referring to the position of the carbon atoms of the Me2tn chelate rings with respect to the equatorial coordination plane.

The aim of the present study is to explore the possibility of utilizing loess for the adsorption of total phosphorous (T-P) and total nitrogen (T-N) in water. Batch adsorption studies were performed to evaluate the influences of various factors like initial concentration, contact time and temperature on the adsorption of T-P and T-N. The adsorption data showed that loess is not effective for the adsorption of T-N. However, loess exhibited much higher adsorption capacity for T-P. At concentration of 1.0 mg L �1 , approximately 97% of TP adsorption was achieved by loess. The equilibrium data were fitted well to the Langmuir isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher R 2 compared with the pseudo-first-order and intra-particle kinetic model. The theoretical adsorption equilibrium qe,cal from pseudo-second-order kinetic model was relatively similar to the experimental adsorption equilibrium qe,exp. The thermodynamic parameters such as free energy ΔG, the enthalpy ΔH and the entropy ΔS were also calculated.

The aim of the present study is to explore the possibility of utilizing fly ash and loess, as alternative to activated carbon, for the adsorption of diazinon in water. Batch adsorption experiment was performed to evaluate the influences of various factors like initial concentration, contact time and temperature on the adsorption of diazinon. The adsorption data shows that fly ash is not effective for the adsorption of diazinon. The equilibrium data for both activated carbon and loess were fitted well to the Freundlich isotherm model. The pseudo-secondorder kinetic model appeared to be the better-fitting model because it has higher R 2 compared to the pseudofirst-order kinetic model. The thermodynamic parameters such as free energy (ΔG), the enthalpy (ΔH) and the entropy (ΔS) were calculated. Contrary to loess, the ΔG values of activated carbon were negative at the studied temperatures. It indicates that the adsorption of diazinon by activated carbon is a favorable and spontaneous process. The positive ΔH values of activated carbon and loess suggest that the diazinon adsorption process is endothermic in nature. In addition, the positive ΔS values show that increased randomness occurs at the solid/ solution surface during the adsorption of diazinon.

The2,3,2-tet ligand is a structural isomer of 1,4,7,11-tetra-azaundecane (2,2,3-tet). The linear tetradentate with fournitrogen atoms as donors can adopt three different configu-rations in chromium(III) complexes with two chloro ligandsas shown in Figure 1. Generally, the chromium(III) tetra-dentate complexes have been shown to have a diversestereochemistry. It is not possible from the CD spectrum toassign the

A practical and efficient disposal of PCBs (polychlorinated biphenyls) in waste transformer oil by a chemical dechlorination process has been reported. The transformer oil containing commercial PCB mixtures (Aroclor 1242, 1254 and 1260) was treated by the required amounts of PEG 600 (polyethylene glycol 600), potassium hydroxide (KOH) and aluminum (Al), along with different reaction temperatures and times. The reaction of PEG with PCBs under basic condition produces arylpolyglycols, the products of nucleophilic aromatic substitution. The relative efficiencies of PCB treatment process were assessed in terms of destruction and removal efficiency (DRE, %). Under the experimental conditions of PEG600/KOH/Al/100 o C/2hr, average DRE of PCBs was approximately 78%, showing completely removal of PCBs containing 7-9 chlorines on two rings of biphenyl which appear later than PCB no. 183 (2,2',3,4,4',5',6-heptaCB) in retention time of GC/ECD. However, when increasing the reaction temperature and time to 150 o C and 240 min, average DRE of PCBs including the most toxic PCBs (PCB no. 77, 105, 118, 123 and 169) in PCB family reached 99.99% or better, with the exception of PCB no. 5 and 8 (2,3-diCB and 2,4'-diCB). In studying the reaction of PEG with PCBs, it confirmed that the process led to less chlorinated PCBs through a stepwise process with the successive elimination of chlorines. The process also permits complete recovery of treated transformer oil through simple segregating procedures.

The proposed head-space supercritical fluid extraction (SFE) methodology as an alternative to an existing conventional procedure was explored for the determination of organochlorine compounds in aqueous matrix. In this study, polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were utilized as target analytes. To enhance the recovery efficiency, the factors such as the CO 2 density, the extraction time, and the extraction mode were investigated. Furthermore, the analytical procedures and the results obtained were compared with those provided by the conventional method (the U.S. EPA method 8680). Under the optimized conditions, i.e., a combination of static with dynamic SFE mode at 2,000 psi and 40 °C, the head-space SFE methodology gave equivalent or better to the conventional method in recovery efficiencies with clear advantages such as simple sample treatment and fast analysis time as well as reduced solvent and reagent consumption.

The sharp-line absorption and emission spectra of(H 1 3 O 6 ){trans-[Cr(Me 2 tn) 2 Br 2 ]} 2 Br 2 (Cl0 4 ) (Me 2 tn = 2,2-dimethyl-l,3-diaminopropane) have been measured between 13000 cm - 1 and 16000 cm - 1 at 5 K. The 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex ion. The zero-phonon line in the sharp-line absorption spectrum splits into two components by 286 cm - 1 , and the large ""Eg splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the Me 2 tn ligand have a strong cr-donor character, but the bromide has weak σ- and π-donor properties toward chromium(III) ion.

Department of Chemistry, Andong National University, Andong 760-749, KoreaReceived November 18, 2003Key Words : Free ligand, Molecular structure, Palladium(II) complexIt is reported that symmetrical dibenzotetraazacyclo-[14]annulene are generally complexed with a variety ofmetals such as nickel, copper and cobalt.

The preparation and characterization of novel chromium(III) complexes have received much attention because the chromium(III) materials are promising materials for tunable solid state laser in the spectral region between 600 and 1100 nm. 1 As a prerequisite for these applications, a detailed study of the spectroscopic and ligand field properties is needed. Furthermore, the geometrical and conformational isomerism in transition metal complexes has been an area of intense activity and has provided much basic structural information. 2 The 2,2-dimethylpropane-1,3-diamine (Me2tn) as a bidentate ligand can coordinate to a central metal ion forming a six-membered ring, and the spectroscopic properties of the resulting metal complexes can be compared with those of the corresponding complexes containing the unsubstituted tn diamine system. 3