Electrodeposited lead dioxide coatings

Lead dioxide coatings on inert substrates such as titanium and carbon now offer new opportunities for a material known for 150 years. It is now recognised that electrodeposition allows the preparation of stable coatings with different phase structures and a wide range of surface morphologies. In addition, substantial modification to the physical properties and catalytic activities of the coatings are possible through doping and the fabrication of nanostructured deposits or composites. In addition to applications as a cheap anode material in electrochemical technology, lead dioxide coatings provide unique possibilities for probing the dependence of catalytic activity on layer composition and structure (critical review, 256 references)

Electrochemical oxidation of phenol for waste water treatment

The electrochemical oxidation of phenol for waste treatment applications was investigated on lead dioxide packed-bed anodes. The electrolytic cell was operated in both batch and continuous modes with feed streams up to 1100 mg/l phenol dissolved in aqueous solutions of Na₂SO₄ and H₂SO₄ or NaOH. Electrodeposited lead dioxide was found to be a better anode for phenol oxidation, than the lead dioxide obtained by anodizing lead shot. Results showed that all the phenol in solution could be readily oxidized but complete total organic carbon (T.O.C.) removal was more difficult. Rates of phenol oxidation were similar in divided and undivided cells. The oxidation of phenol was favoured by an acidic pH, but an alkaline pH improved the further oxidation of intermediate products. In divided cells, an anionic membrane, which allowed migration of hydroxyl ions, proved to be superior than a cationic membrane for T.O.C. removal. The percent of phenol oxidized increased with increasing current density, and decreased as initial phenol concentration, electrolyte flow rate, and anode particle size were increased. Comparisons of the experimental results with a mass transfer model are presented for the batch experiments, and a simplified model is proposed to interpret the results from continuous experiments in terms of relative mass transfer and electrochemical reaction resistances.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat

A família Rubiaceae na Reserva Biológica Guaribas, Paraíba, Brasil: subfamília Rubioideae The family Rubiaceae in the Guaribas Biological Reserve, Paraíba State, Brazil: subfamily Rubioideae

Este trabalho consiste no levantamento dos representantes de Rubiaceae subfamília Rubioideae na Reserva Biológica Guaribas, Estado da Paraíba, Brasil. Foram realizadas coletas intensivas no período de outubro/2000 a outubro/2001, as quais resultaram em 17 espécies e nove gêneros de Rubioideae. Os gêneros com maior número de espécies foram Psychotria L. (seis) e BorreriaG. Mey. (quatro). Coccocypselum P. Browne, Declieuxia Kunth, Diodia L., Mitracarpus Zucc. ex Roem. & Schult., PalicoureaAubl., RichardiaL. e Staelia Cham. & Schltdl. apresentaram uma única espécie cada. Perama hirsuta Aubl., de posição taxonômica incerta na família, também foi tratada neste trabalho. São apresentados chave, descrições, comentários e ilustrações dos táxons.<br>This paper describes the results of a survey of the Rubiaceae subfamily Rubioideae in the Guaribas Biological Reserve, State of Paraíba, Brazil. Intensive collections were made from October/2000 to October/2001, revealing 17 species and nine genera of Rubioideae. The most diverse genera were Psychotria L. (six species) and Borreria G. Mey. (four species). Coccocypselum P. Browne, Declieuxia Kunth, Diodia L., Mitracarpus Zucc. ex Roem. & Schult., Palicourea Aubl., Richardia L. and Staelia Cham. & Schltdl. were each represented by a single species. Perama hirsuta Aubl., of uncertain position within the family, is also treated in this paper. A key, descriptions, notes, and illustrations of the taxa are provided