ABSTRACT
Ultrasound alone is capable of killing bacteria when sufficient power is applied but ultrasound at low powers can also be used to improve the effectiveness biocides. In this paper, we explore the effect of the timing of the ultrasonic treatment at 20 and 850 kHz on the biocidal efficiency of sodium hypochlorite solution towards Escherchia coli suspensions. A remarkable frequency effect has been noted. At the lower frequency of 20 kHz the improvement in biocidal activity is greatest when the ultrasound is applied at the same time as the hypochlorite. At the higher frequency of 850 kHz the improvement is best when ultrasound is used as a pre-treatment immediately followed by hypochlorite addition under normal (silent) conditions. The kill rate achieved for pre-treatment using 850 kHz and simultaneous treatment using 20 kHz are very similar. However the former involves less acoustic energy and so is considered to be the more efficient.
Subject(s)
Disinfectants , Disinfection/methods , Escherichia coli/growth & development , Sodium Hypochlorite , Sonication , Calorimetry , Colony Count, Microbial , Time Factors , Water Purification/methodsABSTRACT
The structures of the title compounds, [PtCl(2)(C(7)H(5)N(3)O(2)S)(2)].4C(3)H(7)NO, (I), and [Pt(C(3)H(5)N(3)S)(4)][PtCl(6)].2C(3)H(7)NO, (II), respectively, comprise square-planar Pt(II) centres. In the cation and anion of (II), the Pt atoms lie on independent inversion centres. For (I), the metal atom is N-bonded to two trans organic ligands and also bonded to two Cl atoms, whereas in (II), the Pt atom is N-bonded to four organic ligands, the charge being balanced by the presence of an additional [PtCl(6)](2-) species (from the starting material). Both structures contain dimethylformamide solvate molecules, four in the asymmetric unit of (I) and one in (II), which are involved in the hydrogen-bonding network via N-H.X and C-H.X associations.
