Graduate School of Environmental Studies

The purpose of E-Waste recycling is resource recovery and hazardous substances management (HSM). However, academic literature that deals with the various social aspects of HSM is limited. As such, this paper focuses on the changes for labeling method, particularly those related to hazardous substance management, and discusses how and why the current mandatory methods have been adopted. We organized the historical information related to hazardous substance management among Asian manufactures prior to the introduction of EU's RoHS Directive. In the EU, the RoHS Directive has been adopted in conjunction with the E-Waste recycling system. Initially, fulfillment of RoHS Directive requirements was confirmed through the probe assay of individual parts/products. However, Asian countries such as Japan, China and Thailand subsequently introduced product certification schemes that shared similarities with the CE mark, which had been developed as a necessary element of general supply chain management. These Asian certification schemes have played a leading role in RoHS Directive management in global manufacturing, a fact confirmed by the addition of RoHS2.0 to the EU's CE mark requirements. Thus, it can be said that HSM in Asia has contributed to the establishment of a global standard in terms of entrance control. It is important to consider the future institutional recycling design in Asian region.

In this study, we investigate the effect of new legislative requirements on industrial product development. We use the case of Restriction of Hazardous Substances (RoHS) Directive and the development of halogen-free (HF) printed circuit board (PCB) in an attempt to answer the following questions: (1) What impacts can environmental regulations – such as RoHS Directive – have on the manufacturing industry? (2) How have the manufacturers – especially those outside the European Union (EU) –responded to the RoHS Directive? (3) How has the manufacturing of HF products progressed in the wake of the directive? In order to investigate these, we focused the issue of halogen in the thermosetting resin of PCB of mobile phone. We illustrated their time trend of HF PCB labelling method and actual Br existence among many manufacturers in each milestone of the regulations. Finally, almost manufacturer complied with RoHS Directive, but each starting time was different. The results of this research a...

Thiacalix[4]arenes, in which the four methylene birdge of calix[4]arenes are replaced by sulfide linkages, were selectively oxidized to sulfinyl- or sulfonylcalix[4]arene under mild conditions with control of the stoichiometry of the oxidant. Solvent extraction of the transition and alkaline earth metal ions with these hosts showed that the metal binding ability was governed by the oxidation state of the sulfur functionalities.Thiacalix[4]arenes (2, 3) were selectively oxidized to sulfonylcalix[4]arenes (4, 5) or sulfinylcalix[4]arene (6) by controlling the stoichiometry of the oxidant, whose complexation ability to metal ions were studied by solvent extraction.

A practical method for the synthesis of p-tert-butylthiacalix[4]arene (TC4A), in which the methylene bridges of p-tert-butylcalix[4]arene (C4A) are replaced by epithio groups, is presented by heating a mixture of p-tert-butylphenol, elemental sulfur S8, and NaOH as a base catalyst in tetraethylene glycol dimethyl ether. The inclusion behavior of TC4A for a wide range of solvent molecules is examined by recrystallization, showing preference for the guests depending upon the size and/or the substituent of the guests. The X-ray structure of a 1:2 host–guest complex of TC4A with 1,2-dichloroethane reveals that one guest molecule is included in the cavity of TC4A, while the other is included in the crystal lattice to form a clathrate-type complex. It is shown that the inclusion in the cavity is attained by a cooperative deformation of both the host and the guest.

Practical methods for the synthesis of sulfinyl-(5,6) and sulfonylcalix[4]arenes (7,8) were provided by the selective oxidation of thiacalix[4]arenes (3,4) with controlled amounts of an oxidant such as NaBO3 or hydrogen peroxide under mild conditions. The coordination ability of thiacalix[4]arene 4 and the sulfinyl and sulfonyl analogs (6,8) toward a wide variety of metal ions was investigated by solvent extraction and compared to that of the conventional methylene-bridged calix[4]arene 2. It was shown that the metal-ion selectivities of the sulfur-containing ligands 4, 6, and 8 were controlled by the oxidation state of the bridging sulfur moiety, which was best understood based on the hard and soft acid–base (HSAB) principle by assuming the critical role of the bridging groups in coordination to the metal center. Thus, 4 preferred soft metal ions by binding with S, while 8 did hard ones by ligating with sulfonyl O in addition to the adjacent two phenoxide oxygens, respectively. In good accordance with this hypothesis, 6 could bind to both hard and soft metal ions by using sulfinyl O and S, respectively. These made sharp contrast to the parent methylene-bridged 2, which could not essentially extract any metal ions at all, lacking lone pair electrons on the methylene bridge for coordination.The binding selectivity of thiacalix[4]arene (TCA) and the sulfinyl and sulfonyl analogs, prepared by the oxidation of TCA, toward metal ions depended upon the oxidation state of the bridging sulfur.

A simple method to coat a non-ionic hydrophilic polymer onto the inner wall of a bare fused-silica capillary is established. The capillary is first filled with l M HCl solution, then flushed with 0.2% poly(ethylene oxide) solution containing 0.1 M HCl, and finally rinsed with the electrophoretic buffer. Each step takes only 5 min. For regeneration of the coating, this procedure is repeated. Four basic proteins were separated by this method around pH 3–7 with phosphate buffer. The separation efficiency in terms of peak shape was excellent compared to bare fused-silica capillaries and comparable to many other more sophisticated column-treatment methods. The reproducibility of migration times of proteins was less than 3% R.S.D. at pH 6 by manual operation of the coating process. Titration of the fused-silica surface with acid and the structure of poly(ethylene oxide) are important factors to form a stable coating via hydrogen bonding to the surface silanol groups.

Novel molecular receptors, cone- and 1,3-alternate-tetracarboxylic acid (3) and syn-A,C-dicarboxylic acid (5), were prepared by hydrolysis of the ester moiety of the tetra- (2) and di-ethers (4), which had been synthesized by regio- and conformation-selective O-alkylation of the phenolic oxygens of thiacalix[4]arene (1) with ethyl bromoacetate. The binding ability of cone- and 1,3-alternate-3, syn-5, as well as cone-shaped, methylene-bridged tetracarboxylic acid (9) toward transition metal ions was investigated by solvent extraction to show that the selectivity for the ions depends upon the bridging sulfur, carboxylate group, and the conformation.Molecular receptors, cone- and 1,3-alternate-3 and syn-5, were prepared from 1via2 or 4, which showed selective binding abilities towards transition metal ions.

A new separation method for highly charged metal chelates based on ion association in capillary zone electrophoresis (CZE) has been developed. Metal chelates of AI(III), Co(III), CR(III) and FE(III) ions with 2,2′-dihydroxyazobenzene-5,5′-disulphonate could not be separated by a conventional CZE system (electrophoretic buffer: [NaH2PO4]T = 0.02 M, pH 7.0, V = 21.7 kV, i = 20 μgA, l = 50 cm), because they have fixed and identical (−5) charges. However, when 25 mM tetrabutylammonium bromide was added to the same electrophoretic buffer, each of the four chelates was well resolved and migrated in the order Fe(III), Co(III), Cr(III) and Al(III) with theoretical plate numbers of 210 000–250 000 per 50 cm within 11 min (V= 21.3 kV, I = 40 μA). The detection limits (S/N = 3) as determined by spectrophotometric detection (λ = 494 nm, I.D. = 50 μm) were 1.00, 1.89 and 3.11 fmol for Al, Co and Fe, respectively, in 6.0 · 10−9 dm3 of sample solution injected. The effect on the separation of the sizes, types and the concentrations of quaternary ammonium ions added to the electrophoretic buffer was also investigated. As a result, some evidence was obtained that the ion-association reaction between the chelates and ammonium ions probably took the major role in the separation mechanism.

The solvolytic dissociation rate constants of 1:2 complexes of Al 3+ and Ga 3+ with an azo dye ligand, 2,2′-dihydroxyazobenzene-5,5′-disulfonate (DHABS, H 2 L 2-), have been evaluated with a capillary electrophoretic reactor (CER) system. This CER system is based on the fact that metal complexes encounter an overwhelming force to dissociate when apart from the ligand by CE resolution. Treatment of a capillary with a slightly acidic buffer solution, e.g., pH 5, reduces the double-layer potential ( ) of the inner silica wall. Owing to slow relaxation of the deprotonation equilibria of superficial silanol groups known as the pH hysteresis, this potential can be actually retained during the electrophoresis of the metal complexes in question with a neutral buffer at pH 7.0. This method enables one to manipulate migration times, namely, residence times in a capillary tube, from 5 to 90 min, depending on the prescribed conditioning pH, without changing any other operation conditions such as buffer composition and electric field strength. The excellent performance of the CER is exemplified by the accurate estimation of the dissociation degree of the complexes. The dissociation degree-time profiles for the complexes are quantitatively described using both internal and external standards; the very inert complex of [Co III L 2 ] 5for the peak signal standardization and methyl orange for the injection volume correction. The solvolytic dissociation rate constants of the 1:2 complexes of Al 3+ and Ga 3+ ions with DHABS [AlL 2 ] 5and [GaL 2 ] 5into the 1:1 ones have been determined as (4.9 ( 1.0) × 10 -4 and (3.7 ( 0.3) × 10 -3 s -1 at 303 K, respectively.

Synthetic strategies to produce nanosized metal complexes often employ large macrocyclic ligands with the ability to coordinate to several metal ions. 1 L. K. Thompson and co-workers reported octaand dodecacopper(II) complexes 1a which consist of µ 3 -oxo-bridged subunits each containing a tetra-or hexanucleating macrocyclic ligand. Calixarenes with heteroatoms on the rims and in the body are excellent candidates as ligands for making multinuclear metal complexes. 2-6 Recently, we reported several complexes having p-tert-butylthia-, 3 p-tert-butylsulfinyl-, 5 and p-tert-butylsulfonylcalix-[4]arenes 6 (X ) S, SO, and SO 2 , respectively; n ) 4) as multidentate ligands coordinated to first-and second-row transition metal ion-(s).

The solvent-extraction behavior of 2,8,14,20-tetrathiacalix[4]arene 2 was compared with those of 2-monothiacalix [4]arene 3 as well as linear tetramer (4) and dimer (5) of p-tert-butylphenol linked by sulfide bonds at the ortho positions in order to clarify the effect of the cyclic and acyclic structure and the number of sulfide bonds. The linear tetramer 4 showed almost the same extraction behavior as that of the cyclic counterpart 2, showing the dependence on the pH for the extraction of Co(b), Ni(b), Cu(b), and Zn(b) ions. On the other hand, monothiacalix[4]arene 3 and acyclic dimer 5 showed far inferior extractability as compared to the former two, suggesting that the number of sulfide linkages, rather than the cyclic/acyclic structure, is predominant to determine the extractability. An equilibrium study on the extraction behavior of open-chain 4 (H 4 L) toward Co(b), Cu(b), and Zn(b) ions revealed that the composition of the extracted species can be written as [M i (H 2 L) i ] (i: integer), as was the case obtained by cyclic 2. Furthermore, the extraction constants of 4 for those metal ions were almost the same as those obtained by 2. The similarity of the extraction behavior between 2 and 4 suggests that the acyclic tetramer 4 may act as a pseudo-thiacalix[4]arene to have the same complexation manner as cyclic 2 by the O À ,S,O À -donor set, in which the presence of a phenol unit flanked by sulfide bonds at the both ortho positions is essential. In other words, the effect of the bridging sulfide in the phenol oligomers may be reasonably explained by the electron-withdrawing effect of the sulfide moiety to provide the phenol unit with a higher acidity to form [M 2 (H 2 L) 2 ]-type complexes having a double-cone structure stabilized by two sets of O À ,S,O Àligated metal bridges. Recently, an X-ray structural analysis of Zn(b) complexes of tetrathiacalix[4]arene 2 has revealed the coordination manner via ligation of the bridging sulfur with cooperative binding of the adjacent phenolic oxygens (Scheme 2). 10a,b Notably, the same coordination manner was found in the Co(b), 10b Cu(b), 10c Hg(b), 10e and Nd(c) 10f complexes. The universality of the coordination manner of 2 by the O À ,S,O À donor set, 11 in turn, poses questions concerning the design of an extractant consist-Scheme 1. Calix[4]arene (1) and the analogues with sulfur bridge(s) (2, 3). Small numbers indicate the numbering system of calix-ring.

Even though it was obtained in poor yield, p-tert-butylthiacalix[8]arene (TC8A) has been synthesized as a new member of thiacalix[n]arenes by the terephthalate-induced cyclization of a mixture of acyclic oligomers, which was obtained by the reaction between p-tert-butylphenol and sulfur with CaO in ethylene glycol/diphenyl ether system. Slow evaporation of the chloroform solution of TC8A afforded guest-free crystals consisting of TC8A itself. The close-packed crystal structure of TC8A resembles that of p-tert-butylcalix[8]arene (C8A) closely, containing a plated loop molecular structure.

Amberlite XAD-7 resin was impregnated with p-tert-butylsulfinylcalix[4]arene. Niobium(V) was collected on the impregnated resin in yields of more than 90% around pH 5.4, whereas tantalum(V) was negligibly collected. The collected niobium(V) was desorbed with 9 M sulfuric acid nearly quantitatively, hence the separation of niobium(V) from tantalum(V) was successfully achieved.

Treatment of calix[4]arenes with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane using imidazole as a base yielded O,O′-bridged calixarenes in excellent yields, which were subsequently treated with an alkyl halide/base to give O″,O‴-dialkylated products in high yields. These were, in turn, amenable to fluoride-promoted quantitative desilylation, thus providing an efficient method for the net proximal dialkylation of calix[4]arenes at the lower rim.Graphic

The first chiral disulfinyldithiacalix[4]arenes have been obtained by oxidation of two adjacent epithio groups of the tetramethyl ether of tetra(p-tert-butyl)tetrathiacalix[4]arene. The chiral resolution was achieved by HPLC using Chiralpak AD as a stationary phase. Furthermore, the absolute configuration of these compounds was determined by X-ray crystallography.

The selective de-tert-butylation of p-tert-butyl thiacalix[4]arene (p-tert-butyl TCA) with AlCl3 at 80°C has been investigated. Mono-, di-, and tri-p-tert-butyl thiacalix[4]arene (mono-, di- and tri-TCA, respectively) were obtained in yields of 6.5, 20 and 21%, respectively, when p-tert-butyl TCA was treated with 7.1 equiv. of AlCl3 for 30 min. De-tert-butyl TCA (TCA) was exclusively obtained when 10.5 equiv. of AlCl3 was used. These derivatives are converted to fluorescent active derivatives by modification with dansyl moiety at the lower rim, which are used as metal sensors in aqueous solution. The extent of the fluorescent variations with the metal cations was used to display the sensing factors, ΔI/I0. These hosts show much higher sensitivity for transition metal cations such as Co2+, Ni2+, and Cd2+ than those of alkali metal cations such as Li+, Na+, and K+. The effect of p-tert-butyl groups on metal sensing ability of these hosts was studied. It was found that p-tert-butyl groups decrease the sensing ability of these hosts. It is the first example to show that water soluble TCA derivatives can detect metal cations directly in aqueous solution by variation of fluorescence intensity upon addition of a metal cation.