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Novel, efficient and magnetically recyclable calcium substituted copper ferrite photocatalysts were synthesized via a facile green approach. As prepared Cu1-xCaxFe2O4 composites were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electronic microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS) and UV–Vis spectrophotometer. The result shows that there is an enhancement in electron transfer and charge separation efficiency of calcium substituted copper ferrites leading to a significant improvement in photocatalytic efficiency. As prepared samples shows high visible light absorption which favors catalytic activity and also shows good magnetic separation for reuse. UV–Vis spectrophotometer was used for the destruction of model organic pollutant. Under natural sun light irradiation the as prepared samples exhibit superior photocatalytic activity toward malachite green (MG). The model organic pollutant inactivation mechanism was investigated in a scavenger study, and •O2, H2O2, and h+ were identified as the major reactive species for organic pollutant inactivation. The calcium substituted copper ferrite exhibit excellent stability and reusability. The experimental results indicate that calcium substituted copper ferrites have great potential in large scale photocatalytic disinfection operations.

The kinetics of oxidative decolorization of acid orange 8 (AO8) by chloramine-T and bromamine-T in HClO4 medium has been investigated spectrophotometrically (λmax = 490 nm) at 298 K. Kinetic runs were executed under pretend first-order conditions of (oxidant)o >> (AO8)o. Under identical experimental conditions, reactions with both the oxidants follow identical kinetics with a first-order dependence on each (oxidant)o and (AO8) and a fractional-order dependence on (HClO4). Stoichiometry of the reaction was found to be 1:1 and the oxidation products were identified. The reaction was studied at dissimilar temperatures and activation parameters have been computed. Effects of p-toluenesulfonamide, halide ions, ionic strength and dielectric constant of the medium have been investigated. Reaction mixture fails to induce polymerization of acrylonitrile. The rate of oxidation of AO8 is about two-fold faster with BAT as compared to CAT. This may be endorsed to the diversity in electrophilicities of Cl + and Br + ions and also the van der Waal's radii of chlorine

Hydroxide precursors to perovskite oxides of the formula, LnMO3 (Ln = La, Pr, Nd; M = Al, Mn, Fe) and LaMO3 (M = Co and Ni) were synthesized by electrogeneration of base by cathodic reduction of the appropriate mixed-metal nitrate solution. The precursors were heat treated at different temperatures to obtain the perovskite oxides. The bath composition for various systems was optimized to get a single-phase oxide product. This method can be adapted as a simple route to the synthesis of perovskite oxide coatings on conducting substrates.

Cathodic reduction of aqueous solutions of Mg(NO3)2 results in the deposition of Mg(OH)2 coatings on stainless steel cathodes. The coating growth is controlled by varying the deposition time, current density and the bath concentration. The coatings comprise thin scaly particles having sub-micron dimensions. DIFFaX simulations of the X-ray line broadening indicate the formation of small anisotropic particles having a thickness 134 A measured along the [0 0 1] direction.

We report the use of electrogeneration of acid to electrochemically precipitate crystalline strontium sulfate coatings from EDTA stabilized solutions onto stainless steel anodes. This is the first report of the electrodeposition of strontium sulfate. A study of the deposited SrSO4 by microscopy and diffraction suggests that by changingn conditions of current and time, control over crystallite habit and crystallite orientation with respect to the substrate can be achieved.

While cathodic deposits of BaCO3 obtained from a dilute barium bicarbonate bath are unoriented, those obtained from EDTA-stabilized baths have a (200) orientation with respect to the substrate; thick coatings obtained at longer deposition times have a stronger orientation compared to thin coatings. The orienting influence is shown to be due to the combined effect of EDTA and the use of electrochemistry.

Adherent BaSO4 coatings have been electrochemically deposited on anode substrates from aqueous solution for the first time by electrogeneration of acid. At low current densities, thick, nearly continuous coatings comprising unoriented crystallites are obtained. At higher current densities, the coatings are not as continuous but the crystallites are oriented. At short deposition times and under high current densities, the crystallites are oriented with the a axis perpendicular to the substrate. At long deposition times, the orientation switches to the c axis. Electroless deposition under similar conditions yields crystallites that are neither oriented nor facetted.

Acidified aqueous metal nitrate solutions containing dissolved phosphate ions yield the corresponding metal phosphates upon cathodic reduction. In alkaline earth metal containing electrolytes [phosphate source, (NH 4 ) 2 HPO 4 ], the phase obtained is MHPO 4 (M = Sr, Ba). Controlled growth of adherent micrometer-thick coatings of SrHPO 4 could be achieved on the cathode substrate. In Mg, Co, and Ni containing electrolytes, electrosynthesis yields the hydrates of the corresponding NH 4 MPO 4 (M = Mg, Co, Ni) at low (25 mA cm −2 ) current densities, while at high (60 mA cm −2 ) current densities, X-ray amorphous metal orthophosphates are obtained. The use of Na 3 PO 4 as the phosphate source also yielded X-ray amorphous products. In the Co system, the electrosynthesized phase, NH 4 CoPO 4 ·H 2 O was different from that obtained by chemical precipitation. This study demonstrates the versatility of electrosynthesis.

Controlled growth of cobalt hydroxide coatings (1–2 μm thick) on stainless steel electrodes was achieved by electrogeneration of base by cathodic reduction of aqueous cobalt nitrate solutions. These coatings catalyse the oxygen evolution reaction in alkaline medium (1 M KOH) by as much as 100 mV, making cobalt hydroxide a candidate catalyst for these applications.

Hexacyanoferrate on intercalation within the interlayer region of the layered double hydroxide (LDH) of Mg with Al retains its electroactivity. Within the confined region of the interlayer, the redox potential of the intercalated ion, as estimated from cyclic voltammetric studies, is shifted by almost 126 mV higher than that of the free ion in solution. We attribute this to the activity of hydroxyl ions in the interlayer. By comparing the shifts of the redox potential of the free ion in solutions containing different concentrations of hydroxyl ions, we estimate the concentration of hydroxyl ions in the interlayer to be in the vicinity of approximately 11.8M. This corresponds to 20% of the crystallographically defined number density of hydroxyl ions (equilibrium dissociation constant approximately 0.2) and shows that the chemical environment of the interlayer is very similar to that in solution. The LDH of Mg with Al thereby behaves like a strong base.

Calcite CaCO3 has been electrocrystallized on stainless steel substrates by the galvano-static cathodic reduction of aqueous calcium bicarbonate solutions. The deposition is controlled by pH changes occurring close to the cathode due to electrogeneration of base. The deposit morphology varies from facetted rhombs observed at low (1-20 mA cm(-2)) current densities to corner-rounded particles observed at high (40 mA cm(-2)) current densities. (C) 2002 Elsevier Science Ltd. All rights reserved.