A facile approach for synthesis of BiVO4 nano‐particles possessing high surface area and various morphologies

BiVO₄ with dominant monoclinic structure and relatively high surface area has been prepared by a simple precipitation method. Smaller particle size and new morphologies were observed while using non‐toxic and common organic additives including ethylene diamine tetra acetic acid (EDTA) as the synthesis constituents. The prepared materials were characterized using structural, textural and microscopic techniques. The photocatalytic activities of the samples were checked using methylene blue, phenol and 2,4,6‐trichlorophenol as probe molecules and visible light as irradiation source. Also, hydrothermally‐ synthesized counterparts of the catalysts were prepared and their structure and photocatalytic efficiency were compared. The recovery of the catalysts after successive uses was also examined.     

Preparation and Spectral Analysis of Nickel-containing Aluminophosphate Molecular Sieves of Type-5

Diffuse reflectance spectroscopy was used to studynickel ion positions in the aluminophosphate molecularsieves of the AlPO-5 type. Nickel ions wereintroduced into the reactant mixture of thealuminophosphate and the synthesis carried outhydrothermally through various methods of gel, clearsolution and diluted suspension. The visibleabsorption spectra obtained of the dried, hydrated andcalcined materials were studied. A distinct andwell-defined triplet absorption band observed at about625, 580 and 540 nm was assigned to tetrahedralframework-substituted nickel(II) ions. A relativelystrong band at about 400 nm and two broad bands withsimilar intensity at 730 and 660 nm were assigned tooctahedral nickel species. These 730 and 660 nm bandsare observable only in the sample where nickel cationswere incorporated merely in the octahedralextra-framework sites by ion-exchange treatment ofSAPO-5. According to the synthesis procedure used,the amount of tetrahedral framework-substituted nickelions in comparison with octahedral ones can beevaluated from the intensities of the characteristicbands of the 4- and 6-coordinated nickel ions. Thereis much more octahedral nickel compared with thetetrahedral ones estimated in the light of theintensity data taking into account the absorptivitiesof nickel (II) symmetries. This work showed thatusing our synthesis procedure of a dilutedsuspension will result in preparing NiAPO-5 molecular sieve with more nickel cationsincorporated in the framework sites ofthe aluminophosphate. A very small quantity of thesecations remain in their sites at temperatures as highas 550°C.     

BiVO4‐Silica Composites Containing Cobalt Phthalocyanine Groups: Synthesis,Characterization and Application in Photodegradation of 2,4,6‐Trichlorophenol

BiVO₄‐Silica composites were prepared and grafted with sulfonated cobalt phthalocyanine. The structural and chemical properties including crystalline phase, specific surface area, UV–Visible diffuse reflectance behavior, morphology and photocatalytic activity were investigated. Depending on the silica content and subsequently amounts of loaded phthalocyanine, various catalytic activities were observed. The sample containing nominal 15% silica and grafted with phthalocyanine showed less aggregated form of this organic dye, smaller and nanometric particles, and higher photocatalytic activity in degradation of 2,4,6‐trichlorophenol.     

Voltammetric characteristics of diazinon on carbon paste electrode modified with tris(ethylenediamine) cobalt(II) iodide

In this study, cyclic and differential pulse voltammetric methods were used to investigate the electrochemical behavior of diazinon at carbon paste electrode modified with tris(ethylenediamine) cobalt(II) iodide ([Co(en)₃]I₂). Cobalt complex showed an anodic peak at 620 mV (vs. Ag/AgCl, in KNO₃ 0.1 M as supporting electrolyte) at carbon paste modified electrode. In the presence of diazinon, anodic peak intensity increased with increasing concentration of diazinon that confirmed electrocatalytic activity of cobalt complex for oxidation of diazinon (EC’ mechanism). Under optimized conditions, a linear calibration curve for diazinon was obtained in the range from 0.05 to 27 mg/L with detection limit 0.0075 mg/L (3S _b /m). Applications of the modified electrode to the determination of diazinon in different water samples were also tested. The results showed a very good precision (RSD < 0.04%) and very stable voltammetric response towards diazinon.