Degradation of microcystins in aqueous solution with in situ electrogenerated active chlorine.

A new and efficient method for the degradation of microcystins (one family of blue algal toxins) was developed and studied. Microcystins (MCs) in water were directly and effectively removed by active chlorine transformed in situ from the naturally existing Cl- in water resource using electrochemical method. Titanium coated with RuO2 and TiO2 was used as the anode. Microcystin-RR (MCRR) and Microcystin-LR (MCLR) were chosen as the model compounds of MCs. The results suggested that 20.87 mgl(-1) MCs (12.58 mgl(-1) MCRR and 8.29 mgl(-1) MCLR) in aqueous solution with 1.85 mM Cl- could be synchronously decomposed within 15 min electrolysis under the condition of the current density 8.89 mAcm(-2), 20 degrees C and pH 7.00. The qualitative analysis showed that the heptapetide ring and the Adda group of both treated MCs were changed. The results also indicated that the removal rates of both MCs increased with the increasing of chloride concentration and applied current density, but decreased with the increasing of initial concentration of MCs and initial pH of electrolyte. In the absence of Cl-, only a small fraction of both MCs were decomposed by direct anodic oxidation, while their almost complete removals could be obtained in the case of indirect electrooxidation with in situ electrogenerated active chlorine from Cl- in water.

[Fe(II) enhanced sonochemical degradation of azo dye Acid Red B (ARB)].

Sonochemical degradation of azo dye Acid Red B (ARB) was studied in this paper. The effect of pH and ferrous ion concentrations on the process was investigated. The results show that decolorization of ARB proceeds faster in acidic medium. The production of H2O2 is proportional to sonication time. The presence of Fe(II), which could react with H2O2 to produce *OH, enhances the sonochemical decolorizatio and degradation of the dye. The decolorization rates of ARB are 2.17 and 2.75 times faster, respectively, when Fe(II) concentrations are 1.43 mg/L and 2.85 mg/L. The UV absorptions at 322 nm and 254 nm also reduce ARB dramatically.