Solid phase extraction of zinc(II) using a PVC-based polymer inclusion membrane with di(2-ethylhexyl)phosphoric acid (D2EHPA) as the carrier.

A polymer inclusion membrane (PIM) is reported consisting of 45% (m/m) di(2-ethylhexyl)phosphoric acid (D2EHPA) immobilized in poly(vinyl chloride) (PVC) for use as a solid phase absorbent for selectively extracting Zn(II) from aqueous solutions in the presence of Cd(II), Co(II), Cu(II), Ni(II) and Fe(II). Interference from Fe(III) in the sample is eliminated by precipitation with orthophosphate prior to the extraction of Zn(II). Studies using a dual compartment transport cell have shown that the Zn(II) flux (2.58 x 10(-6)mol m(-2)s(-1)) is comparable to that observed for supported liquid membranes. The stoichiometry of the extracted complex is shown to be ZnR(2).HR, where R is the D2EHPA anion.

Degradation of methyl orange using short-wavelength UV irradiation with oxygen microbubbles.

A novel wastewater treatment technique using 8 W low-pressure mercury lamps in the presence of uniform-sized microbubbles (diameter = 5.79 microm) was investigated for the decomposition of methyl orange as a model compound in aqueous solution. Photodegradation experiments were conducted with a BLB black light blue lamp (365 nm), a UV-C germicidal lamp (254 nm) and an ozone lamp (185 nm+254 nm) both with and without oxygen microbubbles. The results show that the oxygen microbubbles accelerated the decolorization rate of methyl orange under 185+254 nm irradiation. In contrast, the microbubbles under 365 and 254 nm irradiation were unaffected on the decolorization of methyl orange. It was found that the pseudo-zero order decolorization reaction constant in microbubble system is 2.1 times higher than that in conventional large bubble system. Total organic carbon (TOC) reduction rate of methyl orange was greatly enhanced by oxygen microbubble under 185+254 nm irradiation, however, TOC reduction rate by nitrogen microbubble was much slower than that with 185+254 nm irradiation only. Possible reaction mechanisms for the decolorization and mineralization of methyl orange both with oxygen and nitrogen mirobubbles were proposed in this study.

Selective extraction and transport of copper(II) with new alkylated pyridinecarboxylic acid derivatives.

Two kinds of N-(6-alkylamido)-2-pyridine carboxylic acid with a pyridine moiety and a carboxylic acid as chelating ligands were newly synthesized for the selective extraction and the transport of copper(II) from aqueous solution. Liquid-liquid extraction was carried out to examine the extraction ability of extractants with metal ions. The selectivity for the metal ions with N-6-(2-ethylhexylamido)-2-pyridine carboxylic acid (EHPA) was in the following order: Cu(II)>>Zn(II) approximately Pb(II) approximately Ni(II) approximately Co(II)>Cd(II)>Mn(II). All metals tested in this study were selectively extracted at a lower pH by 2-3 units compared with commercial available alkyl carboxylic acids such as naphthenic acid and Versatic 10. The extraction equilibria of copper(II) were measured by a batchwise method at 303K with EHPA and N-6-(t-dodecylamido)-2-pyridinecarboxylic acid (t-DAPA). Copper(II) was extracted as a 1:2 complex according to the following reaction: Cu(2+)+2(HR )(2)=CuR(2)2HR +2H(+). The extraction equilibrium constant, K(ex) was evaluated and the values were found to be 1.13 and 0.31 for EHPA and t-DAPA, respectively. It was demonstrated that t-DAPA was very stable to be incorporated into a polymer inclusion membrane (PIM) consisting of cellulose triacetate (CTA) as a base polymer and 2-nitrophenyl octylether (NPOE) as a plasticizer. This novel PIM containing t-DAPA as a carrier exhibited an excellent copper(II) transport characteristic and a high selectivity for copper(II) over cadmium(II) from aqueous solution.