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A new zirconium oxide-based media for arsenate removal from water was fabricated and evaluated in batch and continuous flow experiments. Highly porous (epsilonp approximately 0.9) nanostructured zirconium oxide spheres were fabricated by the impregnation of macroporous ion-exchange media (CalRes 2103, Calgon) with zirconium salt; the media was then ashed at T > 750 +/- 50 degrees C to remove the organic polymer resin and obtain ZrO2 spheres. The spheres generally ranged from 200 to 800 microm in diameter, and consisted of ZrO2 nanoastructures generally ranging between 20 and 100 nm. They also exhibited monoclinic and tetragonal crystalline structures, and had an isoelectric point of 5.6. Equilibrium batch experiments were conducted in 10 mM NaHCO3 buffered nanopure water at three pH values (6.4,7.3, and 8.3) with 120 microg/L As(V). Data were fit with the Freundlich isotherm equation (q(e) = Kx CE(1/n)), resulting in an intensity parameter (1/n) of approximately 0.33 and capacity parameters (K) ranging from 115 to 400 (microg As(V) g(-1) dry media)(L microg(-1))1/n. The pore diffusion coefficient and toruosity were estimated to be 6.4 x 10(-6) cm2 s(-1) and 1.3, respectively. For a packed bed adsorbent operating at a loading rate of 11.5 m3 m(-2) hr(-1) in a realistic continuous flow experiment, the external mass transport coefficient was estimated to be kf approximately 6.3 x 10(-3) cm s(-1). The pore diffusion coefficient and the external mass transport coefficient were used with the pore surface diffusion model (PSDM) to predict the arsenate breakthrough curve. A short bed adsorbent (SBA) test was conducted under the same conditions to validate the model. In this study, surface diffusion was ignored because the particles have a very high porosity. The validated model was used to predict arsenate breakthrough in a simulated full-scale system. The overall combined use of modeling, material characterization, equilibria, and kinetics tests determined the suitability of the media for arsenate treatment cheaper, easier, faster, and with less media than a long duration pilot test would have. Although the fabricated zirconium oxide spheres exhibited adsorption capacity comparable to some commercially available media such as iron based (hydr)oxides, the high cost of fabrication may render the media not feasible for wide use in commercial applications. However, the very high porosity of this media provides for improved pore diffusion and faster overall mass transport, which may be critical for applications where mass transport is the limiting factor.

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Nitric oxide forms 1:1 low spin complexes with CruTPP, CrIMTPP(X), MnMTPP, and MnmTPP(X) species.MnTPP(X)(NO) (X-= Cl-, CH3CO2-, CN-) and CrTPP(NO) complexes have the S = 'fa ground state and EPR spectra diagnostic for the odd electron occupying a molecular orbital of predominantly metal dxy character. MnTPP(X)(NO) complexes and the isoelectronic CrTPP(NO) species are assigned the (dxzj,z)4 (dx>)1 ground configuration. Narrow lines in the isotropic EPR spectrum of CrTPP(NO) permit resolution of nitrogen-14 hyperfine from both nitric oxide (6.5 G) and the porphyrin pyrrole nitrogens (3.15 G). The metal nuclear hyperfine coupling constants in these complexes (A 55Mn) = 88.3 G and (A 53Cr> = 21.2 G are indicative of the odd electron being relatively localized on the metal. All of these nitric oxide complexes are formulated as M-NO+ species, although dir -» t* bonding substantially reduces this charge separation. Within isoelectronic sets such as (d5) MnTPP(Cl)(NO) (vno = 1830 cm-1), CrTPP(NO) (vno = 1700 cm-1), or (d6) FeTPP(CI)(NO) (mo = 1880 cm-1), MnTPP(NO) (%o = 1760 cm-1), the nitric oxide stretching frequencies are substantially smaller for the complex where the metal has the lower formal oxidation state. Electronic spectra for the chromium porphyrin species are typical for metalloporphyrins, while spectra for MnTPP(X) and MnTPP(X)(NO) complexes are highly irregular. VOTPP fails to form a nitric oxide complex even in the low temperature glass media.The coordination chemistry of diatomic molecules with metalloporphyrins is in a period of rapid development. A wide array of diatomic molecule complexes of metalloporphyrins has recently been reported.1-11 The focus of atten-

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