Influence of experimental variables on decoloration of azo reactive dyes by hydrogen peroxide and UV radiation.

This paper was intended to study decoloration of azo C.I. Reactive Red 243 under UV radiation in the presence of hydrogen peroxide. The H2O2/UV oxidation process is a feasible and effective alternative in the treatment of effluents that contain such recalcitrant substances as reactive dyes. A statistical factorial design at 2n was used to evaluate how the variables pH (3 and 11), H2O2 concentration (5 and 20 mM), urea concentration (5 and 15 g l(-1)), and NaCl concentration (2.5 and 3.5 g l(-1)) affected the decoloration process efficiency. The results were expressed as percent colour removal from the solution by using absorbance measurements. The H2O2/UV process proved to be effective in degrading reactive dyes, with approximately 99% colour removal being achieved under specific conditions. Hydrogen peroxide concentration had a positive effect and influenced a great deal. Sodium chloride (NaCl) concentration presented a negative effect on the experiments in which it reduced the percent colour removal from the reactive dye solutions. Solution pH and urea concentration did not present any significant effect on the decoloration process.

Low- and high-frequency transcutaneous electrical nerve stimulation have no deleterious or teratogenic effects on pregnant mice.

OBJECTIVE: To evaluate the effects of application of transcutaneous electrical nerve stimulation (TENS) at low and high frequencies to the abdomens of Swiss mice throughout pregnancy. DESIGN: Experimental animal study. SETTING: Research laboratory. PARTICIPANTS: Thirty Swiss mice received TENS throughout pregnancy. They were divided into three groups (n=10): placebo, low-frequency TENS (LF group) and high-frequency TENS (HF group). INTERVENTIONS: In the placebo group, the electrodes were applied to the abdominal region without any electrical current. In the LF group, the frequency was 10 Hz, pulse duration was 200 µs and intensity started at 2 mA. In the HF group, the same parameters were applied and the frequency was 150 Hz. All stimulation protocols were applied for 20 min/day from Day 0 until Day 20. MAIN OUTCOME MEASURES: The pregnant mice were weighed on Days 0, 7, 14 and 20 to verify weekly weight gain by two-way analysis of variance. The numbers of fetuses, placentas, implantations, resorptions and major external fetal malformations on Day 20 were analysed using the Kruskal-Wallis test. RESULTS: No significant differences were found between the placebo and TENS groups (P>0.05). CONCLUSION: Application of low- and high-frequency TENS to the abdomens of pregnant mice did not cause any deleterious or major teratogenic effects.

Evaluation of textile dye degradation due to the combined action of enzyme horseradish peroxidase and hydrogen peroxide.

The kinetic parameters of the oxidant action of the combination of enzyme horseradish peroxidase (HRP) with hydrogen peroxide in the degradation of methylene blue dye were investigated. Twenty-one percent of color removal was obtained at pH 5.0 and temperature of 30 °C. Under these conditions, the kinetic parameters K m and V max of enzymatic reactions were determined for hydrogen peroxide in the absence of methylene blue dye (K m = 17.3 mM; V max = 1.97 mM/min) and in the presence of methylene blue dye (K m = 0.27 mM, V max = 0.29 µM/min). By means of analysis of phosphorescence, the presence of reactive oxygen species was detected in the form of singlet oxygen through the redox reaction between HRP and hydrogen peroxide. The existence of this reactive species is directly dependent on the concentration of hydrogen peroxide in the aqueous solution.