Chromium(III) determination with 1,5-diphenylcarbazide based on the oxidative effect of chlorine radicals generated from CCl4 sonolysis in aqueous solution

Oxidation of Cr(III) during sonication in carbonated aqueous solutions saturated with CCl4 leads to the quantitative formation of Cr(VI) and provides a simple and rapid method for spectrophotometric chromium determination with 1,5-diphenylcarbazide. The key to this method is the production of chlorine radicals when aqueous solution saturated with CCl4 is exposed to ultrasonic waves of 40 kHz. The effects of sonication period, CCl4 solution volume, acidity, and interferences were discussed. The time required for a single determination is lower than 2 min. The relative standard deviation obtained for aqueous solutions with 1 microg of Cr was < 2% (N = 10) and the calculated detection limit (3sigma) was 5 ng of Cr.

Sonochemical synthesis and mechanistic study of copper selenides Cu(2-x)Se, beta-CuSe, and Cu(3)Se(2)

Nanocrystallites of nonstoichiometric copper selenide (Cu(2-x)Se) and stoichiometric copper selenides (beta-CuSe and Cu(3)Se(2)) were synthesized in different solutions via sonochemical irradiation at room temperature. The influence of solvents, surfactants, and ultrasonic irradiation on the morphology and phase of products has been investigated. The morphological difference of the products was mainly affected by the solvents and surfactants, which can self-aggregate into lamellar structures or microemulsions, and then these unique structures can act as both supramolecular template and microreactor to direct the growth of copper selenides. On the other hand, it was also found that the sonochemical irradiation and solvents played an important role in the formation of different phases of copper selenides. The proposed formation mechanism of copper selenides is discussed.

Ultrasonication of aqueous and micellar suspensions of anthracene fixed on silica

Degradation under ultrasound irradiation of silica supported anthracene (Ant) in aqueous suspension is studied. The initial degradation rate of Ant on silica is 28- and 6-fold lower than the degradation rate in water alone, at 506 and 20 kHz, respectively. Analysis of emission and excitation spectra demonstrates the presence of two kinds of adsorbed Ant species: a molecular form and crystals. The former species is assumed to be initially degraded at 506 kHz, while the latter species is more difficult to decompose. Specific irradiation of micro-crystals of Ant in aqueous/methanolic solution leads to the formation of CO and CO2. A pyrolytic mechanism is expected to occur on the surface of silica and the kinetic rates would depend on the chemical nature of Ant at the surface. Added surfactants decrease dramatically the degradation rates on silica, but solubilizes Ant in larger amounts than in pure water. Surfactants are pyrolysed in water with and without silica and act more as degradation inhibitors than as Ant extracting agents.